Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − ¨ are, Chemistry and Physics Discussions Atmospheric 1 ¨ ur Physik der Atmosph , and H. Volkert 2 ´ e de Toulouse III, Toulouse, France 9718 9717 , E. Richard 1 , the latter collocated with lightning strokes. Reflectivity ¨ oller 1 − , H. H 1 ¨ ur Luft- und Raumfahrt (DLR), Institut f ´ erologie, CNRS and Universit , M. Hagen 1 enhofen, Germany ff The study embarks from two multi-channel time-lapse movie-loops from geosta- Inner cloud flow fields are available from radar multiple Doppler analyses, gridded on This discussion paper is/has beenand under Physics review (ACP). for Please the refer journal to Atmospheric the Chemistry corresponding final paper in ACP if available. Laboratoire d’A Deutsches Zentrum f ity experiments in the modelling community. runs in research mode. tionary satellite imagery (asphases Supplement), making which up provide the animage-loop, entire juxtaposing intuitive a life-cycle distinction close-up of of of the thebrightness six cloud thunderstorm. temperature motion as (as It seen a by concludesand Meteosat, proxy with simulated a for a perspective clouds triple view seenthe on by motion-geared the the human model infrared satellite generated visualand channel), system as system, yet of such hardly cloud utilised multiple cells. potential image By for a loops employing well-grounded provide specification a of further high, sensitiv- and polarimetric dataFurthermore, indicate polarimetric the and existencevariability Doppler of and radar hail cloud dynamics variables at corresponding indicate3-D the to wind intense an fields. 2 enhanced km Profiles hydrometeor variance of level ofprovide flow the and around reference retrieved hydrometeor data 14:40. statistics for over the high-resolution, entire episode-type cloud numerical volume weather prediction locity retrievals from updrometeors to and four spatio-temporal Doppler-radars, occurrencesrive of the at lightning polarimetric a strokes determination are synopticperiod, of employed quantification rare to hy- event. of ar- the physical parameters of this,a 500 during m-mesh, the at four COPS 15:05, consecutive 15:20; times all separated times byand are 15 updrafts min-intervals in exceeding (14:35, UTC). 5 14:50, m They s contain horizontal winds of around 15 m s The three-hour life-cycle of thevective isolated and thunderstorm Orographically-induced on Precipitation 15 Studytail, July 2007 (COPS) with during is a the documented Con- specialsensing in emphasis techniques de- on as the 5-min rapid rapid scans development from and geostationary mature satellites, phases. combined Remote ve- Abstract Detailed flow, hydrometeor and lightning characteristics of an isolated thunderstorm during COPS K. Schmidt 2 Atmos. Chem. Phys. Discuss., 12, 9717–9769,www.atmos-chem-phys-discuss.net/12/9717/2012/ 2012 doi:10.5194/acpd-12-9717-2012 © Author(s) 2012. CC Attribution 3.0 License. 1 Oberpfa Received: 2 March 2012 – Accepted: 2Correspondence April to: 2012 K. – Schmidt Published: ([email protected]) 16 AprilPublished 2012 by Copernicus Publications on behalf of the European Geosciences Union. 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) ). 2000 ) or to ( Brown- 2011 , 2008 Cotton and , Dolan and Rut- ). ) mapped a highly Chong et al. ) and constitutes an ) extended the analy- 2010 Richard et al. , 1988 ( 2002 1989 Deierling et al. , ( ; ). Others relate observations 2005 2006 by surface heating and horizontal , , Lim and Sun ; Tuttle et al. ). 2009 , Fehr et al. 9719 9720 ) had investigated the accuracy of vertical mo- 2008 , Wakimoto and Bringi Lang and Rutledge ; Kuhlman et al. 1998 ( – often attains similar magnitudes as the horizontal 1994 , downdrafts prevail in the storm’s lower part and block ), dedicated experimental campaigns, like COPS, are still Shapiro et al. initiation of convection ¨ oller ). The sound produced by the sudden reversal of the previ- H 2008 convection ; ), which had its field phase from June to August 2007 over the , 1921 , ) combine Doppler- and polarimetric analyses for a supercell thun- sees the merger of several cumulus elements into a large convec- , rather than remaining two orders of magnitude smaller as under 1962 2011 , , Deierling and Petersen 2009 , p. 456): the ( Matejka and Barthels Wilson ) presented an integrative tool for the analysis and display of multivariate dissipating phase cient backscattering particles are available. Additionally, independent polar- 1989 ffi advection 2007 , Bousquet et al. ( mature stage Multiple-Doppler-analyses integrate data from several Doppler-radars and reveal The quantitative documentation of a thunderstorm’s life cycle was among the ob- Lightning strokes are among the most spectacular meteorological phenomena of the flow components during the mature phase after the onset of precipitation, i.e. important ingredient for the ongoingprediction development models of and high resolution quantitative numerical precipitation weather forecasts (e.g. ization measurements in twohydrometeors. perpendicular In planes allow a the pioneering discrimination study, of various ing and Ludlam when su jectives of theWulfmeyer et Convective al. and Orographically-inducedVosges-Rhine valley-Black Precipitation Forest-region in Study centralconcerning Europe. (COPS; the The airflow, the provision hydrometeor ofpropriate distribution datasets spatial and lightning and locations temporal with resolution an complements ap- previous surveys (e.g. sis to polarimetric parametersFrame and et comparisons al. with a two-dimensional cloud model. tive system with thedischarges compensating formation previous of charge separations,during various and hydrometeors, the the onset the of occurrenceconvective precipitation; energy of being further lightning fed into the storm. dynamical thunderstorm and the(USA), induced inter microburst alia on by(photos) superposing 20 with the July its visual 1986 internal external over reflectivity appearance Alabama structure. of the cloud system convergence at a varietythe of locations becomes marked by towering cumulus clouds; derstorm on 23 May 2002 during the IHOP campaign, whereas technique are more recent ( ledge wind or typical circumstances. In mid-latitudes, thunderstormsical are active often frontal connectedconditions to zones dynam- favour of their cyclones initiation,exhibits or especially a they on typical develop hot lifeAnthes in summer cycle, days. isolation for The which when three latter atmospheric phases category can be distinguished ( systematically retrieved from dual-Doppler radarthe data orographically southern disturbed flank flows at ofAlpine Programme the in Alps autumn 1999 duringmotion. including the Also an special adequate determination observing oftion period the obtained vertical of from the radar Mesoscale measurements, while variational refinements of the retrieval radar data. As itsgions operational ( application in Europe is currently limited to special re- local extent and, asgation a (e.g. physical process,ously possess attained a charge long separationand tradition by makes of fast also detailed moving inSpecialized investi- hydrometeors studies plain cannot deal language be with a correlationsvolume overheard “thunderstorm” between and flash updraft distinct rate, mass from graupel flux an volume, (e.g. updraft ordinary storm. Thunderstorms constitute an archetype ofby a a fierce fleet meteorological of eventand accompanied potential lightning. Within dangers, thunderstorms e.g. thesumed vertical severe under motion gusts, the – high updrafts term and precipitation downdrafts rates, sub- large hail, necessary for principal case studies. 1 Introduction of lightning rate to hydrometeorupdraft content motion ( ( 5 5 25 15 20 15 10 10 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 6 Aminou convective ). Section 5 ). On this day the erent perspectives, ff 2008 ( Kottmeier et al. 9722 9721 ), followed by the description of the applied methods 3 . Then the various data sources for our synoptic per- 2 east as vertical meridian). Two loops are provided as a Sup- ◦ , p. 168). Let us first seek an overview of the overall development through 1900 ). The evolving characteristics of the mature and decaying thunderstorm, re- , 4 ), the update rate of one image every 15 min in normal mode and every 5 min The paper is structured as follows: the single isolated “text-book case” of a thun- With an entire lifetime of hardly more than 3 h, the “golden thunderstorm” of COPS These are considered as the overall features of the event, which provide the frame for Since the launch of the Meteosat Second Generation geostationary satellite series in During the three months of the COPS field phase it was only during IOP8b on 15 atmosphere over central Europethe was COPS essentially area. cloud free Radiosoundings and in stably the stratified COPS over area indicated moderate garding the combined determinationtribution of and horizontal lightning positions and makediscusses vertical the the flow, core findings hydrometeor of and dis- points the to investigation future (Sect. applications of the results provided. 2 Previous studies concerning IOP8b ofFollowing COPS a categorization ofIOP8b trigger was mechanisms classified for as deep “locally convection initiated” during by COPS, derstorm during the COPS periodwhich induced are several studies reviewed from inspective di are Sect. introduced (Sect. (Sect. as well as reliableThe simulation aim of of precipitation this complexesthunderstorms in study flow, a is hydrometeor quasi-operational to and mode. provideto lightning an its characteristics rapid as with development completefindings and special as are mature emphasis possible to phase documentation be between combined ofmid-level 14:20 to flow the and a structures conceptual 15:20. as picture At inferredby of the a from the end four-fold the event. nested the A combined simulation juxtaposition observations withsensitivity of 500 and studies the m based as resolution on provided points this the exemplary direction event. to a series of its detachment as well asat north-eastern low progression levels. relative to a few remaining cumuli clearly lies close tothe the spatio-temporal border resolution of of what both can multi-parameter be and hoped multiple-radar for monitoring the coming decades to be shadow to its east; (v) the formation of a wide and curved anvil around 15:00, and (vi) sudden vertical development at the middle location at 14:30, which induces a dark speed of 14 frames perCOPS second region (4200-fold consisting speed-up), of and 97the (ii) speed images a (7 between fps; close 10:00 2100-fold up and speed for 18:00 up). the (movie2.mpg) wider at half the detailed data analysesFrance of small this study: cumulus (i) cloudsVosges, well the develop ahead Black around of Forest 12:00 a andkm-long cloud frontal only the line cloud Alps; over over the band (ii) the easternenhancements across the slopes mountains formation of of of the of the Black a the cloud Forest by nearly line’s 13:00; contiguous, southern (iii) 100- the and gradual northern portions until 14:00; (iv) the map-projection (with 10 plement to give anof intuitive the awareness thundercloud of development the as15 horizontal well July dimensions as 2007: and its (i)ages the relation an (movie1.mpg) to duration between overview other 06:00 for cloud and western 18:00 systems (all during and times central in UTC) Europe with concatenating a nominal 145 display im- Jerome a movie-loop obtained from satellite imagery. 2004 with its multi-channel “spinning2002 enhanced visible and infra-redin imager” rapid ( scantime-lapse mode movie-loops. provides From the dataCOPS, of opportunity three the channel to experimental overview inspect rapid images in scans were executed detail produced during cloud on motions a stereographic as weather- July 2007 that an isolated,developed just strong east and of high the crest reaching,of line the though of large short-lived international the thunderstorm Black team Forest inas – the well much field as that in they contrast very can to pronouncedof probe the systems, a the hopes number and region of to such (“... old isolated popular but wisdom a about Black the Forest peculiarity thunderstorm is not an ordinary circumstance”; 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Richard Barthlott Behrendt Kirshbaum ). (CIN) values 2009 , ). A convergence line et al. ff 2008 , Kaltho convective inhibition Aoshima et al. 9724 9723 ). for geographical location). Here cloud bases were erent data sources are introduced. 1 ff culties to realistically simulate the quickly evolving and 2011 ffi , cient updraft velocities to overcome the convective inhi- ffi (CAPE) and relative high ). Sensitivity experiments including variations in the prescribed ). These observations, however, were not obtained in the vicin- Hanley et al. 2011 2009 , , ). In a following model-comparison study, no less than eight mesoscale ) scanned for IOP8b the broad variety of in-situ and remote sensing data ). Also, an entire ensemble of detailed hind-casts with a research version et al. ce’s Unified Model only produced deep convection after manually adjusting the ff 2010 2011 2011 ( ) conducted semi-idealized, two-dimensional numerical experiments in ensemble ffi , , Considering the apparent di The brief survey of previous studies clearly shows that a consistent combination of Besides observational studies, the isolated thunderstorm of IOP8b also attracted 2011 Kaltho Barthlott et al. ning strokes. In this section the di data with good spatial and temporal resolution. 3 Data sources This study takes a synopticof view the on the IOP8b-thunderstorm. rapidzontal The development, mature winds key and and physical decay their phases quantitiesupdraft vertical and are shear; downdraft; cloud vertical hydrometeor top motion, types especially heights; and pronounced hori- concentrations; cores and of positions of light- over, the low level convergence linealready had by noon to ( lie to the east of the Black Forest crest-line ascended up to the tropopause level. the available remote sensing perspectives duringphases the of developing, mature the and deep decaying realistic convection NWP event as is well still as lacking. the Both partly numerical conceptions, idealized the cloud resolving models, need reference moisture content in the boundary layer closer to the non-routine COPS data. More- ( mode with a cloud-resolving modeltion. tailored They for were the inspired explicitalized by simulation the profiles of isolated obtained moist COPS convec- fromlee thunderstorm the and side upstream initialized of by radiosounding ament, gener- station which symmetric was Burnhaupt. generally mountain hostile On of toa the the gradual Black development removal Forest of of deep CIN dimensions convection,domly and experienced the moistening varied through low-level background shallow environ- cumuli. windthe For convective conditions some core of a provided the rapid ran- a favourable succession environment of for subsequent updrafts updrafts ejected which by short life cycle of the IOP8b-storm with state-of-the-art mesoscale models, MetO anism triggering the development of low-level clouds ( modulate the moisture supply of the atmospheric boundary layer significantly ( ( ity to the developing thunderstorm.through The a convection series initiation of process MSGtion was satellite precipitation documented images scans (infrared from and Feldberg visible radarwas channels) ( detected and in low eleva- the radial velocity field of the Feldberg radar and identified as a mech- soil moisture content demonstrated how this seemingly remote quantity can indeed available potential energy et al. simulations with the regional forecasting modelresolutions) COSMO-DE resulted (at in 2.8 a and capturing 1 of kmconvection, the horizontal indicating that convergence line, the but atmosphere a above the completeto Black lack thunderstorm Forest of was deep development, generally as hostile et indicated by al. the values of CAPE and CIN ( et al. regarding convection initiation processes.version Over topped the boundary Rhine layerby valley did 11:30 the at not depth supersite exceed M ofdetermined 1 km, (see at the Fig. 3 while km in- it above sea rose level to after 13:00. moreconsiderable than interest 2 km of the mesoscale modelling community. Realistic episode-type models attempted to reproducethree the of thunderstorm which in produced anbition. su realistic But episode-type matters are setting, moreNH complex model, and contain for manycontents instance subtleties. compared produced The French to deep Meso- those( convection, retrieved but air exhibited the too airborne high water-vapour moisture lidar LEANDRE 5 5 25 15 20 10 25 15 10 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2 ◦ , 2 ◦ erent ). The ff full vol- are rgb- 2002 13 , Mecikalski et al. and 4 (RHI) scans as well ¨ urkheim, the Doppler-radar Schmetz et al. ) every 5 min and a ). Following erent elevations downwards ◦ ff ) and the highest unambiguous 2006 , max r ) [p. 34]. During COPS, the European C of the brightness temperature derived ◦ range height indicator 2006 anging) emits microwave pulses and de- ( r are obtained with larger range, but lower ve- 9726 9725 . ◦ ¨ urkheim are operated routinely in two di 4 nd ). Established empirical relationships and thresh- at low elevation (0.8 a Krebs ) every 10 min containing 13 elevations in ascend- 2003 , Mecikalski and Bedka (PPI) sector scans with more than three elevations. ). Radar data from Karlsruhe are available from the CERA etection 2 d dio ). In this study we use data of five radars, namely two Doppler- ). Details of the multiple-Doppler analysis, which combines data ). The findings are cross-validated with analogous deductions from ra precipitation scan 1 max with a better velocity resolution but shorter maximal range, while five v 2003 ◦ ( http://cera-www.dkrz.de every 15 min. The latter mainly includes 18 di to 0.5 Roberts and Rutledge ◦ plan position indicator ) four indicators are used to specify time and location of the onset of deep con- ). They are augmented by high resolving Meischner ◦ The mentioned observation details indicate that the consistent scanning of the The DWD-radars at Feldberg and T While the visible channels clearly map the horizontal extent of isolated clouds and 2010 RHI-slices moving with the strongest cell were undertaken. The DOW position from the wheels (DoW) positioned at Fessenheim on(Poldirad) 15 of July, DLR, and the which polarimetric wasDoW Doppler deployed radar operates at in Waltenheim the during X-bandband. the frequency A entire band, number COPS the of period. other installationetition four dependent frequency in radar (PRF), the parameters, and further as single range reaching step, or C- pulse dual rep- PRF-operation mode are given in Table locity resolution (cf. Table database ( ing order. Poldirad repeated regular scans20 every 10 min but onlyas at by 3 elevations (1 quickly evolving deep convection event ofthe short fixed duration is routine (i) schedule anoperators of extra challenge who DWD, during and work (ii) long a hours sort in of the reactivity field test for for research weeks. radar From 14:43 several series of radars of Deutscher Wetterdienst (DWD)at at Feldberg the and T Karlsruhe Institute of Technology (KIT), the truck-mounted Doppler-radar on scan strategies: a ume scan from 37 additional scans upward from 0.5 to 4.5 Doppler-capability additionally measure the relativeline velocity of of hydrometeors along the the by radar pulse. An overview of modern weather radar applications is given hydrometeorological targets, e.g. raindrops, snowflakes, ice particles. Radars with along with derived quantitiesradial as maximum velocity range ( ( from several radars, are given in Sect. from the 10.8 µm radiancestion, is whereas related an equality to of vertically brightnessa growing temperatures cloud at cumuli top 10.8 with µm at and ongoing the at tropopause glacia- 6.2 ( µm indicates movie-loops depict their advection, cloud topdiances heights ( can be estimated fromolds infrared ra- in local timeseriesment with of short convective clouds. update The intervals drop allow below 0 to infer the vertical develop- verted infrared channel at 10.8 µmof (blue). 3 All km. three have The a imagehigh nominal horizontal resolution resolution resolution is visible enhanced channelfollowing by (HRV the adding with technique the 1 km defined betterOrganisation nominal by resolved resolution) for broad to band the the Exploitationthe former standby of two, spacecraft Meteorological Meteosat-8 in Satellitesbetween experimental scans (EUMETSAT) rapid operated reduced scan to modeare 5 with min used the here. (instead intervals of 15 min for the full disc). The rapid scans As stated in theteosat introduction, Second several Generation channels (MSG)images of satellite used are the used for SEVIRI here the instrumentcomposited ( movie-loops on from and the the Me- displayed visible as channels parts at of 0.6 µm Figs. (red), at 0.8 µm (green), and the in- A weather radartects ( the small fraction of pulse energy which is backscattered to the antenna by 3.1 Spectral channels of SEVIRI on Meteosat ( vection (see Table radar measurements and lightning positions. 3.2 Radar observations 5 5 10 25 15 20 15 20 10 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , right 1 Schmidt azimuth. ◦ ) and E (Fig. ◦ 2004 30 km and a height ( × ). After systematic tests, a . Observations from Poldirad N and 8.3335 4 Betz et al. ◦ 1986 , Mohr et al. 9728 9727 ), both developed at NCAR with a special emphasis ) in close combination with the mapping programme erences in wavelength, detection capabilities and scan- ff 1995 were undertaken. , 1998 , max v ). Interpolation details are given in Sect. 3 Oye and Case ). 2005 ( Miller and Fredrick The synthesis of multiple-Doppler winds is achieved by the CEDRIC software pack- Compared with satellite or radar measurements, the temporal and spatial resolutions The derivation of a consistent spatio-temporal allocation of unambiguous Doppler- ¨ urkheim and Karlsruhe are used for a series of triple-Doppler analyses at 15 min in- on observations from field experiments ( age ( REORDER ( a Cartesian grid waspanel). defined This with point its coincides with originThe the at size 70 km 48.3329 of distance the fromof Poldirad retrieval at 14 km. domain the Distances 130 has of135 an km. the horizontal grid extent points of to 55 the four C-band radars range from 25 km to some scans obtained bywe the document X-band how DoW thetemporal grid were flow and used characteristics how for weresurements hydrometeor obtained consistency retrieved by content for checks. Poldirad. was Here an determined appropriate from spatio- polarimetric4.1 mea- Doppler-wind retrievals Observational radar datasetsarchives (except at from CERA Poldirad) and were converted obtained to from a the common COPS format. As region of special interest, Data from five radarsning with patterns di were used innation a of the coherent storm’s fashion transient incontent. three-dimensional order Up flow to to characteristics four obtain C-band and a radars hydrometeor consistent were determi- combined to multiple Doppler-syntheses, while tions are synthesized by CEDRICunfolding to of consistent radial Doppler-winds velocities in was all altitude not levels. necessary, An as the Nyquist-velocity proved to be 4 Radar retrieval methods constant grid size ofapplications 0.5 of km REORDER was map chosenonto the the in Cartesian radial all grid, radar separately three velocities forof spatial each from influence of dimensions. the spherical in radars Subsequent the coordinates with Cressman-type grid point interpolation dependent scheme. radii These independent observa- of lightning observations are accurateas indeed. In an this indirect study indicator lightningparticular locations for, are during e.g. used updraft the strength, earlyupdrafts. turbulence mature or state type of hydrometeors, the in thunderstorm and within the strongest additional sensors were installed inSource the locations COPS region can for be thecloud-to-ground duration determined lightning of with from the campaign. an intra-cloudemission height lightning accuracy for and of intra-cloud events. provides 50 All m.with technical an other features LINET estimates of lightning discriminates LINET detection of and systemset the comparisons are al. described in and DoW are used for cross-checks at intermediate times. 3.3 Lightning location The location and time ofdetection lightning Network discharges (LINET), is obtained whichwhen from the is the same in European electromagnetic Lightning operation pulsenetwork, is since which observed 2004. covers at central a Lightning Europe minimum is with of a registered four an sensors average of displacement the of 100 km. Four far-field scans with low observations forms theT core oftervals (Table this study. Data from the three radars Feldberg, storm proofed to be beyond the range of near-field operation; from 14:30 to 14:47 three 5 5 20 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- . ff 1 − erent classes ff Chong and Testud erent elevations were ff . For radar pulses emit- 3 30 dB serves as an indicator )). LDR is typically found to be > HH Z / HV ). Systematic variations regarding grid Z erential reflectivity (ZDR) and linear de- ff 1998 ) is used to infer the presence of hail below , 9729 9730 10 log( 1986 = , was determined by a vertical integration of the continu- erent radars. For the statistical sampling of grid points and ff w Aydin et al. ). Standard procedures were applied for data filling and hori- Miller and Fredrick 2 ) provided a semi-empirical scheme for the classification of hy- )). Spherical particles as small raindrops produce ZDR values near 1994 ( V Z / H Z 0. The typical orientation and fall characteristics of ice particles induce ZDR ), a variance of vertical velocity was specified at the upper and lower bound- > ¨ ciently large (Table oller et al. 10 log( ffi H ZDR is used to infer the particle shape, i.e. the ratio of mean upward to sidewards Finally, the vertical wind For all grid points an average reflectivity field was obtained, taking into account di To account for the fast development and the progression of the disturbed wind field 1983 After data and methodsobservational have findings of been the introduced, thunderstorm’s we characteristics. The present documentation in of a the synoptic fashion the ZDR values near zero or below.ferential A hail signal combination (HDR; of ZDR and ordinary reflectivity, termed dif- of rain (small andphase large constituents. drops), For the ices short-livedscheme particles is summer (snow, applied thunderstorm graupel, here under in hail) apel investigation, as compact and the version, well hail which as as just distinguishesof distinct mixed- rain, enhanced classes. snow, cloud Furthermore grau- dynamics by can using be Doppler identified. spectral width, regions 5 Detailed flow, hydrometeor and lightning characteristics extent of the particles withinted a with sampling volume alternating of horizontalthe about 1 and km ten-fold vertical logarithmic planes= ratio of polarization, of ZDR thezero, is while return defined large signals as raindrops induce with larger the horizontal than same vertical orientation reflectivity and, (ZDR thus, tends to be very smallvalue for increases sampling when melting volumes snow, composed waterTherefore of coated it hail only serves or rain graupel as or are an ice within indicator particles. the for volume. Its ice above therometeors melting solely layer. based on ZDR and LDR measurements, containing di the melting layer. Abovefor the hail. melting For layer, pulses(LDR) only emitted is HDR with defined horizontal asthe the polarization horizontal tenfold the or logarithmic linear co-polar ratio return depolarization ofmore (LDR sensitive the ratio to vertical hydrometeor or variability cross-polar within return the to measuring volume than ZDR. LDR polarization ratio (LDR) areazimuth-intervals moving used with in the strongest five cell adjacent of cross-sections the thunderstorm. (RHIs) at 2 degree masks contain all points withmarks region average reflectivity outside of above 0 the dBZ, cloud while edge, the but with updraft4.2 vertical mask velocity exceeding Hydrometeor 2 m retrievals s Beside ordinary radar reflectivity andwidth, Doppler-quantities the as radial polarimetric velocity quantities andregarding spectral obtained the by hydrometeor Poldirad typestudy during in the COPS categories linear allow as estimates polarization rain, snow, parameters graupel di and hail. In this resolution, setting of filterconditions parameters proved the and vertical details velocities in to the be robust, prescription particularly ofing at the observations mid-levels. from boundary the di the fine-scale display of the results, two horizontal masks were determined. The cloud the REORDER-CEDRIC-sequence untilmined at consistent four independent in-cloud nominal observing15:05, flow times 15:20). separated fields by 15 were min (14:35, deter- 14:50, ity equation using a( variational method. Following thearies. approach of Technically, this wasthe realized command within INTEGR ( CEDRIC via the parameter FRACT inside zontal smoothing. within the storm, the scanningobserved schedules as of well the as radarsnisgrinde. at the Radial the background velocities di wind got profile adjusted from for the each 14:00 radar site sounding and from iteratively Hor- underwent su 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 3 et al. , lower ff 2 in order 2 Kaltho ). A further 30 min (11–8 km)/(14:30– . Already by 14:35 1 erence of the bright- = − ff t 2011 ∆ / , 10 km)). It is there where z − ∆ ¨ urkheim radar-data provide ). This proxy for fully developed (15 km, = 2009 ) Behrendt et al. ). The pixel-wise, parallax-corrected lo- , y , ; x 2010 et al. ) coincided with maximum reflectivity in the 2009 , 9731 9732 1 ) is attained from 14:40 onwards (Fig. ff , − C) relative of the Black Forest topography are given 2010 et al. ◦ , Kaltho 5 ff 10.5 m s < = Siewert et al. Kaltho max w ). 1 erent overall characteristics of the passive (10.8 µm-channel) and ff Mecikalski et al. C, equivalent to cloud tops growing from 4 to 12 km (assuming a wet ◦ 50 for six times during the 80-min-period before the rapid development. Whereas − 1 ), the first 3 km by 3 km SEVIRI pixel fell below the threshold at 13:05 over the C to Putting these overall indicators together, we set the begin of rapid development Time series of di ◦ Triple-Doppler syntheses of the Feldberg,a Karlsruhe closer and inspection T of the flow within the mature storm at 15 min intervals. Figure panel). After 14:30lightning maximum strokes reflectivity were recorded values during from the Poldirad 11 min exceed period 40 betweenat dBZ, 14:34 14:20. and while From 14:45. the14:25)) temporal the gradient vertical of motion cloud ofthe the thunderstorm top cloud attained height top its ( is mature phase. estimated as 10 m5.2 s Three-dimensional flow within the mature storm active (radar reflectivity) remote sensing information are combined in Fig. adiabatic lapse rate).well The until independent 14:40. Later cloud the top thunderstorm’s anvil, estimates consisting of from small four ice particles, radars keeps agree detectable clouds tops decrease to aboutness 10 km. temperatures The from vanishing di waterthat vapour the and infrared clouda channels top tropopause (6.2–10.8 µm) reaches just indicates the belowdeep convection 13 tropopause ( km; region (sounding data at 11:00 exhibit ably. The cloud-mask region, wherefilled the high-resolution box flow along determination its 60 is km meaningful, long diagonal. Patches of upward and downward motions deep incision of the Kinzigthe valley. definition The of gradual the movement region ofthe of “cool-BT-pixels” motivated right special interest panel for of the Fig. multiple-Doppler syntheses (box in to check the consistencycal of development. Between the 14:00 data and0 sources 14:40 and the to brightness obtain temperature dropped estimates from for rapid verti- its brightness temperature (and height of 12 km) in the satellite data, while the radar- allows for the 5-km-level aarrows), compact depiction its of horizontal the structure storm’sinner-cloud extent of (regions horizontal two with motion dense moving anda reflectivity the strong cores, patterns the updraft of highly coresouthern updrafts perturbed part ( and of the downdrafts. northernthe At horizontal cell 14:35 (position: flow ( directionssecond, deviated smaller most updraft was from situated the attivity the general cell’s core motion northern at flank. towards the At NNE. 14:50grown southern A the in edge low reflec- extent of in theincreased, a box while had north-easterly upward increased, motion direction. is while Areaswere sustained the of still at northern the downward two cells cell motion separate southern had (blue reflectivity flank. tones) At cells 15:05 which there perturbed the horizontal flow consider- later the development areasmulus moved generation towards NNE also covering startedhigher more terrain above pixels. of the southern At elevated and 14:05 saddle northern cu- Black area, Forest which and lies separates directly the to the east of the velopment also startednorthern above Black the Forest. high Theseof terrain positions low-level to convergence coincide ( the with the east previously of documented the line Murg valley in the Brightness temperatures from theidentify developing 10.8 µm-infrared-channel cumuli ( of Meteosat are used to 2009 northernmost extent of the southern Black Forest. 20 min later significant cumulus de- namical features including lightningteor activity. distribution After during analyzing the the storm, theresolved evolution observation hindcasts of results of hydrome- are a juxtaposed numerical to weather comparably prediction model. 5.1 Location and vertical development of convection spatio-temporal development is followed by a description of flow characteristics and dy- cations of cloud formation (BT in Fig. a first ground based photo of a small cloud was reported for 11:15 UTC ( 5 5 10 25 15 25 15 20 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ◦ at ◦ 10 > (at 2 km) 1 − azimuth. The ◦ ) and juxtaposed 5 elevation and 133 ◦ , augmented by the plan ). The averaged profiles 4 1 , which is consistent to the 1 − at all levels with standard de- 1 − merely covers a small part of the ◦ and lightning strokes, both in-cloud and contains the region of most active devel- ◦ 1 − azimuth remains stationary through several ◦ 9734 9733 and 132 , which appears to be consistent with the storm’s , p. 206). Analogous statistics for the vertical wind 1 ◦ − 2010 , erence at the trailing (right) side. Otherwise, the high lateral , separately sampled over all valid data points (red), as well as ff elevation and 134 6 . The area of imminent vertical growth at 3 ◦ di 3 ) and gradually increasing with height from below 5 m s ◦ ◦ were confined to the 4 km level, while mean vertical velocities were 1 − (at 12 km). At 14:35 the fluctuations were largest at the highest levels, 1 − azimuth) is situated directly above the strongest updraft. Areas of downward mo- ◦ Following the spatial depiction of the radar-retrieved flow structure and a plausibility The azimuth band between 126 In order to obtain a clearer appreciation of the strongest cell’s rapid development, a Markowski and Richardson exceeding 2 m s wind shear below the 6empirical km threshold level value amounted which to distinguishes about( single-cell 8 m from s multi-cell thunderstorms are assembled in Fig. most active phase. During thethe updraft-strength following and 45 min the the variability downdraft-strength shrinks was from exceeding the top. At 15:20 vertical velocities (southerly from 200 to 15 m s while the standard deviation diminishedvalues somewhat were at found the at later mid-levels. instants Meaningfulwhere when retrievals radar its were beams largest only are possible unblocked above by 1.7 orography km from all radar-sites. At 14:35 the mean over those exhibiting risingwere (green) more or intense sinking than downdraftsviations (blue) and motion. around exceed At and 2 m 14:35 above s mean 4 m s updrafts check against the visible appearanceflow’s of vertical the profile thunder-cloud, provides a additionalzontal statistical information. wind analysis speed Four and consecutive of direction profiles the arein of determined account hori- as all mean cloud-mask and points standardto deviation of taking the the triple-Doppler 14:00 analyses soundingwere (Fig. at smoother Hornisgrinde than supersite theheight (H sounding dependence was at in consistent a Fig. with a single rather (and uniform direction drifting) between location, 4 and while 12 km the overall rated cumulus complexes. The (not corrected)the parallax elevated of anvil the too viewingstationary) geometry far places satellite north imagery relative is tocloud-system’s most its extent valuable and shadow for qualitative it on estimatesof progression the timing of with ground. and a time, Therefore location convective- while (geo- necessitates more remote sensing a equipment precise in assessment closer proximity. perspective from some 36 000 km, while the side view from about 80 km reveals sepa- gradient of reflectivity at mid-levelsary is composed consistent with of the thecloud visually convex tail distinct elements cloud around of bound- 2.5 aphotographs cumulus (not congestus displayed); it at appearsthe 132 to flow be field a in region Fig. of entrainment, consistent with entire elongated cloud system; (ii) the shadow throwing anvil dominates the satellite parameters in the photographer’s perspective isview given of in three Fig. MSG rapidtaken scans from at 5 the min-intervals. The Poldiradand photograph site, elevation stems some angles from were 80 a km uniquely series the determined away Black by from Forest recovering the from the this cloud.cal distinct location extent silhouette The in of of axes a the of multiple high-resolutionthe azimuth radar topographic photo reflectivity dataset. of contours The 14:42, at verti- evident 14:35 while from (black the lines) the cloud’s coincide 2 progression with to the north-east (i.e. to the left) is azimuth is too small to be properly resolved in theopment, multiple-Doppler where analysis. updrafts exceedingcloud-to-ground 11 ones, m s are collocated. The128 highest part of thetion lie cloud mostly (elevation at thealong edge the of the lines cloud. ofappear Note sight to that all overlap (i.e. retrieved in into parameters places.lateral are the The view sampled in three cloud); perspective: small (i) therefore satellite the upward viewing scenes angle and at of 5 downward 18 min motion intervals put the united with shrinking extent.cept The within densely the resolved downdraft flow athad appeared begun. the less southern perturbed, flank of ex- the system. Thecomposite decay of of the a storm rectified lateral photograph, lightning locations and synthesized radar alternated. By 15:20 the north-easterly progression had continued, reflectivity cells got 5 5 15 20 25 10 15 10 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − c). The locations 8 ) emphasized as black ) and appear plausible 1 a. Coloured contours in 6 − 8 b) essentially confirm the 8 and ). For the early mature phase c), which generally serves as 2 m s 5 7 8 at 14:35 and decreases to 2.5 at w > 1 . First, the RHI-reflectivity is overlaid (Fig. er from Poldirad radial velocities by − at the presumed cloud-top height of erences are positive/negative within 8 ff ff 1 1 − − a. 8 c and with the updraft tube – indicated by the 9736 9735 8 , indicating a compliance of the retrieved wind vec- 1 − ect of strong dynamic and turbulence in more detail, special ff (retrieved minus measured di 1 b). Details are juxtaposed in Fig. − ). The distinct convective event was about to be over. 3 1 a). A consistent updraft tube is evident between distances 81 and 85 km − 8 ¨ b surround areas where retrieved winds di urkheim taken during the 14:45-to-14:52-interval and with the Karlsruhe data from b. For the current retrieval these data are blended with the radar data of Feldberg 8 3 Because of the low time resolution of 15 min interval from the triple-Doppler analysis For the rapid development phase of the thunderstorm, the multiple-Doppler retrievals To investigate the e compared to only 12 min of lightning occurrences, no statistical correlation could be Corresponding to the intenselightning cloud dynamics flashes, documented divided byand into the 14:42 radar eight analysis, inside lightning two theof strokes ground 1 and km were cloud range lightning detectedfrom of strokes between Poldirad are the at concentrated 14:40 selected near thecomplete the RHI-plane the south-east 82 (Fig. km dynamic flank range picture distance ofregion of of the the higher thundercloud. current cloud dynamics state, Theseblack in because arrows lightning Fig. and of the positions matching reflectivity well tower in with Fig. the ning routines). Nevertheless, thevealed a presented consistent combination picture of of theturbulence various predominant within regions the data of storm. sources vigorous cloud re- dynamics and 5.4 Relationship between lightning and updraft Fig. more than 4 m s the red/blue contour line).between Finally, 6 these and areas 8 km“spectral of altitude width enhanced and of discrepancy coincide radial velocity” arean with exceeds indicator regions located 4 for where m enhanced s the turbulence within Poldirad parameter the measurement volume. operated near the limit of meaningful temporal resolution (imposed by the fixed scan- with retrieved winds along the section with updrafts ( (from Poldirad), collocated with a11 “tower” km. of Second, high radial Doppler-velocities reflectivity fromretrieved between Poldirad wind altitudes (Fig. directions of for 7 the and tudes selected between section; 7 the and blue 12 regionwith km part the and bounded predominant by by wind horizontal alti- direction ranges towards of Poldirad 73 in to Fig. 80 km corresponds well fourfold-Doppler retrievals were performed, includingpared RHI with scans additional of Poldirad, radar-parameters andselected available between com- from 14:35 Poldirad. and A 14:50,resolution reference when the time RHI-scans cloud was was are fullyFig. developed. available The at first high- 14:43;and their T positions are14:40 marked to 14:44. as Most lines(red revealing line is in in a Fig. section through the region of maximum reflectivity arrows (Fig. 14:50. Furthermore, at 14:35,linearly the with rms-trend height, for attaining altitudes12 a higher km. value than Apparently, of 10 the 6.5 km m enhancedcloud increases s during rms-values the are 15-min-retrieval-interval. A inducedsumable shorter provide by radar retrievals observation the with cycle rapid smaller would rms-deviations, pre- growth also of for rapid the developments. at 14:35, the rms-valuestrend are of horizontal significantly and enhanced. verticalbecause They profile of are statistics more (in in Figs. vigorous agreementrms-maximum cloud with at dynamics the 8 km during altitude this amounts phase. to For 3.5 m instance, s the local sured radial velocities weremarized compared as a with root retrieved mean square valueswithin (rms) for a deviation. From each range 14:50 of radar onwards 0.5 alltors and rms-values and with sum- are the 2.5 m original s measured radial components (Fig. found to be about twoversus orders 10 m of s magnitude smaller than the horizontal ones5.3 (0.1 m s Uncertainty of wind retrieval resultsFor due evaluating to enhanced the cloud uncertainty dynamics of the derived three-dimensional wind field, the mea- 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , ) 3 1994 ( and 16 km 3 , the updraft vol- ¨ oller et al. 1 H − c. However besides 8 60 dBZ) at the distance of ) which determined an up- > and 10 m s is denoted by labels with two- 1 2011 ( 9 − . For this, the 69 lightning strokes 9 b. A first indicator for the presence of hail in 5 km) was estimated to 210 km 9737 9738 3 Palucki et al. a) due to unresolved multiple scattering waves. > erential reflectivity (HDR) over 32 dB at around 8 ff for a less active, two-flash-producing thunderstorm, 3 a, the melting layer is identified between 2 and 3 km a shows the cloud during the early phase of the mature 10 b mark the region of mixed hydrometeors, which is inter- 11 ). The advantage of using number of volume bins instead of scan) in Fig. 10 ◦ 11 c) in this area and point to tight link between microphysical de- 10 ) volume of 25 km 1 − 30 dB) in Fig. − d, below the melting layer, (strong) rain was found in some regions mixed with > 5 m s ) was compared to lightning locations in Fig. erent azimuth angles with an increment of two degrees. In detail, the hydrom- 10 which demonstrates the relationship between high vertical motion and lightning 1 ff > − 4 To document the life cycle of convection, hydrometeor types are evaluated in a sta- By analyzing ZDR in Fig. The temporal evolution of lightning flashes in Fig. 5.5 Classification of hydrometeors The evolution of distribution ofis hydrometeor evaluated content by during using thefrom polarimetric thunderstorm’s POLDRIAD. lifetime radar Up data from from 14:43,five vertically these di high RHI resolved scanseteor RHI were content taken scans every is teen estimateddenoted minutes for for as the red south-easterly line flank during (130 the early mature phase, draft ( this result is interpretedthe as updraft a volume. further indicator, that the number of flashes is related to the lower part of82 the km and thundercloud a is “hail the spike” at high 86 reflectivity km (Fig. ( part collocated with highspectral ZDR width spreading (Fig. are in agreement with an enhanced Doppler maximum at lower altitudes. The fraction of rain within the whole volume increased hail stones) below. The3 strong km hail documents di thelocal evidence maximum of at large the icedicator HDR for particles, signal the typically exceeding probability hailradar 10 that dB parameters in hail by at this could using 1.5 region. hydrometeor km reachin classification The Fig. altitude the according ground. is to Summarizing ahail. polarimetric further Furthermore, the in- upper leftthe part centre of wet the ice cloud crystals consists known of as dry graupel ice dominates. particles The (snow), rain at “outliers” in the upper velopment and turbulent cloud dynamics. tistical manner. For all available RHIclasses scans were determined. in They every were 10-min-intervals, countedby four dividing for hydrometeor by each all altitude used and points finallyof in standardized all the altitude volume. The levels (Fig. result isaltitude a bins volume for fraction standardizing for lies eachnot type in the be fact emphasized. that Figure altitudestate, levels with in only which a hail fewexhibited bins was the are highest classified volume fraction in at aing an altitude cloud fraction of top of 10 km. height 3 Corresponding %by the to 15:13. decreas- maximum of The of total shape snow volume. of occurrences At the decreased 14:43 graupel-profile to snow was the similar 5 km-height to the snow-profile but with the ume at 14:35 aboverespectively. the Together melting with zone results ( from altitude. While below 3 km,the upper positive part ZDR is values dominatedrain (between by drops ZDR 3 below values and around and 4 zero.values dB) the These ( presence are are indicators of prevailing, for ice large preted particles as above wet the melting ice level. particles High above LDR the melting layer, and a rain-ice mixture (up to wet minute time intervals starting withlocation first at flash at 14:45 14:39.lightning (mark Besides positions the as match latest well number lightning withinflashes, flash 6) the marked area and as of number the extended 4, updraft. single are Note, displayed point both at lightning (marked RHI as scan in number Fig. 1), as well. By summarizing all updrafts exceeding 5 m s lightning strokes belonging toFig. flash number 6, all strokes positions are displayed in were grouped into 22(Note, lightning grouping flashes result by summarizing doesresults were strokes not achieved within by depend 2 changing s on the and parameters choose by 30 of km. a factor parameters; of in 2.) fact the same draft depth from triple-Doppler5 m analysis s at 14:35 (considering only updraft exceeding composed for an updraft-lightning relationship. However the spatial distribution of up- 5 5 25 20 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ◦ as well as Volkert and 2 ). At 14:35 two small 14 ) blew from the south-west at b and c cold MSG pixels are 1 190 grid points over the central − 12 × , and references therein). The large ). A detailed view of the location accu- ) of observation and simulation, as both 2011 , 2008 ( 9740 9739 1994 d. A possible reason for this phenomenon could , , lower brightness temperatures correspond well 12 2 ) the simulated cells are at about the same location, ) allow to depict the calculated mid-level flow analo- 3 er from radar derived one, as seen in Fig. ff erent altitude levels. While infrared and visible channel ff Richard et al. 2003 , Aoshima et al. Hollingsworth ), Fig. 2d). These smaller ice particles could only be detected by ) and ). In this section we exemplify how a tight combination of satellite and ) from south occurred at the northern upper part (30–50 km range and , radar derived cloud-top heights reached its maximum approximately 1 2 ). As shown in Fig. 2009 − 2009 ( ( 12 Richard et al. 2007 , 20 m s et al. et al. > , the cloud at 15:20 was stretched over a range of more than 50 km while strong ff ff 13 erent wind directions in di The mesoscale non-hydrostatic modelling system MesoNH is applied for 15 July The satellite images of visible high resolution channel, infrared red channel and ff eteors, while the algorithm extrapolates the flow outside of the reflectivity zones to the but smaller in horizontalthe extent multiple and Doppler embedded flow in analysis a mainly more relies northerly on flow. the We relative note movements that of hydrom- reflectivity fields, obtained through theappendix application of of a forwardgously operator to the (details multiple-Doppler in analysis the reflectivity at cores 15 min are intervals evident (Fig. whichPronounced progress with updrafts the and rather uniform downdraftscells flow where are towards the NNE. located horizontal at flowsgrated becomes observational the severely result southern disturbed. (Fig. Compared side with of the the inte- united 2007 in episode-modescale (cf. initialisation stems fromzontal ECMWF grid-spacing analyses in at the 00:00 4thportion UTC embedded of the , nest Black of while Forest 180 was, the for finest this study, hori- reduced to 500 m. Model generated radar standing of physical processes actingidation during process the of sampled appropriate episodeserational and simulation forecasts. to models, They aid assist which the to ultimately val- of establish aim a the close at atmosphere link reliable and between op- Gutermann the the numerical natural laboratory laboratory of the modelling system ( domains contain inevitable uncertainties. 8-12 km altitude) and slowthe to central medium bottom winds part (5–10 (10–15 m km s range, 2 km5.7 altitude). Cross-validation with simulated flow structure Data from atmospheric field experiments are regularly used to increase the under- radar data retrievals withto results the from cross-validation non-hydrostatic nested ( simulations contributes bins decreased. 5.6 Time evolution of cloud topAs height seen in Fig. during the dissipation of the thunderstorm, while the absolute number of classified rain at 14:40. Finally, after lastThe lightning accurate flash extend at of cloud-tops 14:45, waspixel the evaluated decay positions by process using from was parallax corrected in MSGresults cloud-top progress. infrared (Fig. channel (10.8 µm) and radar based triple-Doppler winds ( with higher radar cloud-topinside heights. the As 12 or seenfrom 13 in km brightness Fig. temperature contour di linepixel from pattern radar. and But contour lines at in 15:20, Fig. cloud-top height derived racy shows that the first radarlow reflectivity brightness area at temperature 14:30 from matchedvisible well infrared with channel channel the of and location MSG of reflectivity satellite.wards, from While the high the radar resolution cell cell seendi moves by slowly the in satellite more movesobserved easterly northeast- the direction. top The of reason theelevation is cloud, detected the given approximately 5 by min theFig. precipitation 1 radar to scan 2 from km Feldberg altitude at 0.8 level at this area. As seen in be the ice shield locatedKaltho at the upper partinfrared data of from the MSG cloud satellite (e.g. but seen not at by visible the channel radar. low-level in radar reflectivity ofKaltho this COPS case were displayed and compared e.g. by 5 5 25 15 20 10 10 25 15 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) will C and ◦ 11 5 < east in accord ◦ ) depicts the double- the the cloud feeding 15 ff 9742 9741 as a proxy for developing cumuli, the white towering volumes con- 1 as a proxy for anvil cirrus. Around 13:00 cool spots of BT − 1 − 1 mg kg 1 mg kg > > 95 km (south-to-north) extents. More simulation information is contained in a per- The detailed observational results presented in this section began to serve as start- A loop through 48 triple images at 5-min-intervals between 12:05 and 16:00 classification between single andcloud multi-cell dynamics are deep necessary convection, by further reducing the investigations gap of between high resolved models and the high resolution simulationseparated indicates by (figure 5 not min shown). fromjection Animated both, as loops multi-channel well of satellite as images put imagery simulation generated on the brightness a deep temperatures weather convectionupdrafts and map event reflectivity cores pro- at cores and the athunderstorm’s threshold multi-cell life between systems time a composed coulddrafts single of are be storm a generated caused with few toomechanisms several by smaller close for too cells. the to low current The the cell wind short main as shear, well updraft so as and for that cut-o all the further ones. down- To overcome the rough energy (CAPE) and of convectiveues, inhibition respectively. Upward (CIN) forcing attained near only the ground, moderatenoon however, and triggered along small high cumuli a val- after contiguous convergenceDeeper line development only along happened the in easternmesoscale its part flow middle, of at apparently the low instigated Black levels by along Forest. channelled the western edge of the southern Black Forest, as 6 Discussion and conclusion The synoptic combinationstationary of satellite diverse observations, data calibratedmeasurements, ground sources lightning based location) (as photography, provides multiple images importanties radar extensions and regarding to the data the short-lived, previousparticular from stud- isolated for geo- thunderstorm the of phases 15vection of was July rapid 2007 not development during favoured and on COPS, maturation. that in Generally, day deep as con- the indices of convective available potential ern Black Forest. Details of theof simulated microphysical storm scheme. depend In to theover-represented. a present high Model run degree generated for on instance, average the the profilesbe details role used of of to hydrometeors hail adjust (cf. appears microphysical Fig. to parameters. be of the Kinzig valley and between the still higher crest regions of the northern and south- however, was restricted to the much smaller region above the elevated plain to the east 1 h later. Theof vertical about steps 500 m in at thereflectivity-tower high with elevations. reflectivity a The common volume base snapshot above depict of thecirrus upper 14:55 the anvil Kinzig (Fig. valley, was vertical while the already grid-spacing observed terest. reaching the norther-eastern corner of the area ofing special point in- for aclude that series the of initiation of sensitivitymesoscale deep experiments convection convergence on line using 15 along Meso-NH. July the 2007 So was Black-Forest only crest. far possible The we along eventual the can development, con- red cloud spots are alignedwith over the the observation. eastern First heights13:20. reflectivity roughly The along cores latter 8.4 appear move over northwardsabove the along mid-tropospheric southern the levels Black apparent by Forest convergencethe by line 14:00. convective and The system, shoot which most up reaches active up part to remains 13 km in by the 15:00 and rear has of nearly collapsed blow-up of the cloudbrightness extent temperature as (BT) seen within× by the MSG complete is fourthspective juxtaposed view nest from to of the the 90of NW km model onto (west-to-east) the generated the Black simulationratio domain Forest above and the its surfacetain topography valleys: reflectivities red above cells 0.1tio dBZ, enclose and values blue of surfaces cloud stand for water an mixing ice water mixing ra- ground flow is providedthrough the from four the computational nests larger while scale the spatial initial resolution fields gets(movie3.mpg finer and from and “handed the finer. downwards” Supplement)tween observation exemplifies both and simulation the as remarkable well agreement as be- apparent discrepancies. In plan view, a prescribed background profile. In the simulation, however, the slowly evolving back- 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 80 km ∼ ), reveals at the 14 ciently strong and lasting ffi ). Within the growing and north- 3 9744 9743 at 9 km. During the next 10 min in-cloud activity was 1 − together with the typical locations of important detected features as 16 36 000 km away) and lateral, ground-based cloud photography ( ∼ A central result of the study is the fine scale determination (500 m resolution in all The overall value of this study is regarded to be fourfold: first, previous investiga- Only the largest cell above the elevated, almost level ground, which separates the The collage-style combination of three consecutive satellite scenes from geostation- dent of the north-eastward progressing anvil and diminishing convective cellsthree behind. directions) of airflow15-min-intervals from within a the triple-Doppler thundercloud’s analysis radar (Fig. reflectivity as retrieved at simulation; the motivation to further sensitivities studies, e.g. regarding variants in the multi-radar retrieved reflectivity and horizontal flow. A distinct separation becomes evi- storm during COPS were extendeddecaying by phase, detailed not glimpses into thescenes; the second, least systems the through mature synoptic and time perspectivemote based sensing laps on systems movie a and variety loopshuman ground of observer) from based passive clearly showed and MSG photography that active (approximating deep rapidconfined re- the convection area scan was vision eventually at sparked of the in saddle a aparisons very point between with the a Black Forest’smode high highest provided parts; resolution third, valuable numerical com- cross-validationalso weather between exemplified prediction both the narrowed, independent simulation yet approaches, in still but evident research gap between details in observation and and lightning datasets appear tositivity be simulations of particular can value be whenelectrification displayed results were is of started systematic the using sen- this same IOP-8b fashion. case Modelling of studies COPStions as including a about reference. the initiation and overall nature of the only isolated and strong thunder- ative to the rather uniform flowat of the their right environment. rear-side The of strongestfor the updrafts the cores. are same The located one-hour-period display ofsame on the a time simulated similarly (i) winds dense field, acells, fourth determined remarkable which grid were agreement (Fig. solely in generatedby location, by the timing the numerical and evolving weather larger prediction overallin scale analysis strength cell environment some of size, initialized 14 size the htial and earlier, distribution strength and of of (ii) distinct the updraft discrepancies and horizontal downdrafts. flow The disturbance, observational plus flow, hydrometeor extent and spa- eastward progressing reflectivity cores, horizontal winds are significantly disturbed rel- position of wide-angle lateral photography, satellite view and an along cloud section of available for four instantsdirection separated above by 3 km 15 min.the and first They updrafts quarter reveal of over-compensating an the downward-motionwere hour. rather Vertical used only RHI-slices to uniform during of put various wind distribution radar-quantities the of from mentioned Poldirad the statistics hydrometeor in classesslicing perspective rain, of snow, and graupel the to and obtain moving hail.to a A core derive five-fold range-height cell vertical vertical during profilesonly for at of four the consecutive volume first 10-min-intervals fraction instancewith was (14:43), of time. used while Finally, the the the hydrometeors. maxima strom’s Hail of dissipation the was phase other detected is categories compactly descended documented by a juxta- given in Fig. ary orbit ( away) with multi-radar retrievalstency and checks lightning between locations thestructive provides observing visualization (i) of systems the valuable and system’stemporal consis- retrieval transient limits. algorithms nature and Vertical and of profiles (ii) the of an observations’ kinematic in- spatio- quantities over the entire main cell are convenient multi-device observations. A schematic lateral viewupdraft and of downdraft the cores, lightning, main turbulence, cloud graupel and is hail. southern Black Forest from itsupdraft northern volume, part, contained so a that su two numerous dozens lightning flashes. strokes Its vertical werewith development generated was upward making most motion rapid up of between about found 14:20 10 to m and be s 14:35 strongest comprisingning pronounced positions. updrafts An collocated with empirical registeredvolume linear light- of relationship, from updrafts New exceedingcase. Mexico a At cases, the specified between same threshold the timeof was and hail. location confirmed polarimetric for measurements our indicate the European existence 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 9731 , N., Khodayar, , ff Gramelsberger 9723 http://www.esa.int/esapub/ , 2011. 9739 , 9720 9723 9729 9730 9721 9723 doi:10.1002/qj.758 , 2008. 9746 9745 . , 2002. 9723 , 2010. ˆ 9727 atelet, J.: Operational Multiple-Doppler Wind Retrieval , N., Adler, B., Kottmeier, C., Blyth, A., and Mobbs, ff , 2011. , 2004. bul111.pdf ¨ aumner, K., Wieser, A., and Wulfmeyer, V.: Observation of convection This work was supported by the Deutsche Forschungsgemeinschaft doi:10.1175/2008JAMC1878.1 9719 doi:10.1002/qj.707 ). Sophisticated algorithms have to be applied and a lot of purpose-built computing Inferred from Long-Range Radial2929–2945, Velocity Measurements, J. Appl. Meteorol. Climatol., 47, Gouget, V., Houze Jr., R., James, C., Prieur, S., Rotunno, R., Roux, F., Vivekanandan, J., Dorninger, M., Flamant, C.,S., Di Mannstein, Girolamo, H., P., Tr Gorgas,initiation T., processes Huang, with Y., Kaltho a8b, suite Q. J. of Roy. state-of-the-art Meteorol. Soc., research 137, instruments 81–100, during COPS IOP doi:10.1029/2004GL019821 Part III: the boundaryJ. condition: Clim. An Appl. optimum Meteorol., determination 22, 1227–1241, based 1983. on a variational concept, J., Kern, B., Bauer, H.-S.,Flamant, Schwitalla, C., T., and Keil, C., Handwerker,ensemble Seity, J.: of Y., Gadian, Initiation mesoscale A., of models: Blyth,118–136, deep a A., convection case-study Mobbs, at from S., marginal COPS, Q. instability J. in Roy. an Meteorol. Soc., 137, nation of intracloud and cloud-to-ground discharges, Geophys. Res. Lett., 31, L11108, 135, 1962. tion overdoi:10.1016/j.atmosres.2009.09.010 complex terrain: A case study from COPS, Atmos. Res., 95, 172–185, S.: Model representation of boundary-layer convergence triggering deep convec- of Meteosat rapid scan dataStudy during (COPS), the Meteorol. Convective Z., and 17, Orographically-induced 921–930, Precipitation 2008. J. Clim. Appl. Meteorol., 25, 1475–1484, 1986. bulletin/bullet111/chapter4 Bousquet, O., Tabary, P., and du Ch Chong, M., Georgis, J., Bousquet, O., Brodzik, S., Burghart, C., Cosma, S., Germann, U., Behrendt, A., Pal, S., Aoshima, F., Bender, M., Blyth, A., Corsmeier, U., Cuesta, J., Dick, G., Chong, M. and Testud, J.: Three-dimensional wind field analysis from dual-doppler radar data. Barthlott, C., Burton, R., Kirshbaum, D., Hanley, K., Richard, E., Chaboureau, J.-P., Trentmann, Betz, H., Schmidt, K., Oettinger, P., and Wirz, M.: Lightning detection with 3-D discrimi- Browning, K. and Ludlam, F.: Airflow in convective storms, Q. J. Roy. Meteorol. Soc., 88, 117– Barthlott, C., Schipper, J., Kaltho Aydin, K., Seliga, T., and Balaji, V.: Remote sensing of hail with a dual linear polarization radar, Aoshima, F., Behrendt, A., Bauer, H., and Wulfmeyer, V.: Statistics of convection initiation by use Acknowledgements. (DFG) in the Priority Programterdienst SSP (DWD), 1167 the “Quantitative Precipitationradar Karlsruhe Forecast”. and Deutscher Institute lightning Wet- for dataDLR) Technology via processed (KIT) the the COPS and MSG database.Houze Nowcast images, Kaspar (University Winfried GmbH Graf of Beer Washington) and provided pointed (DLR) Hermannbaum to helped Mannstein references (University to of (both of level previous Reading), case theon studies, Peter photographs, earlier Daniel Meischner Bob versions Kirsh- of and the Caroline manuscript. Forster All (both this DLR) assistance is commented acknowledged with gratitude. References Aminou, D.: MSG’s SEVIRI instrument, ESA Bulletin, 111, 15–17, Supplementary material related to this article is available online at: acpd-12-9717-2012-supplement.zip value dynamical simulations withtions. grid-nesting Though and modest a in full sizeBlack fleet Forest and of will duration, continue physical the to parametriza- isolatedof play its deep thunderstorm role convection. over as the benchmark central case for the realistic simulation http://www.atmos-chem-phys-discuss.net/12/9717/2012/ case study can alsocomputational tools serve in as the an2011 knowledge instructive generating process example of forhas science the to ( be growing undertaken importancetrievals in using of both distributed areas sensors, which wavelengths, are and independent polarizations as from well another: as the the data initial- re- microphysical scheme or lightning parametrizations became evident; and finally, this 5 5 30 15 10 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 9720 ¨ aumner, K., , 2007. ¨ olkung in Eu- 9721 9725 9720 9719 9745 doi:10.1127/0941- , 1900. 9720 ¨ 9724 9739 unchen, 2006. , ¨ urliche Zirrusbew , 2008. doi:10.1175/2009JAMC2344.1 9724 9719 9732 doi:10.1175/JAM2524.1 , , 2011. 9720 9719 9720 , 2011. 9763 9731 , , , 2010. 9738 9723 9720 , 9748 9747 9720 9751 9730 , www.gutenberg.org/ebooks/2183 , 2009. , 2005. 9720 9740 ¨ doi:10.1002/qj.877 onig, M., and Muller, S.: Cloud-Top Properties of Growing 9725 doi:10.1029/2007JD009598 ¨ oller, H.: Comparion of lightning activity and radar- ¨ oller, H., Konow, H., Kunz, M., Mahlke, H., Mobbs, S., Richard, , 2008. doi:10.1175/2010JAS3642.1 , 2006. 9722 9720 , N., Barthlott, C., Corsmeier, U., Van Baelen, J., Behrendt, A., Behrendt, ff , 2008. 9732 doi:10.1175/2010JTECHA1300.1 , 9725 9726 9734 , N., Adler, B., Barthlott, C., Corsmeier, U., Mobbs, S., Crewell, S., Tr ff Cumulus prior to ConvectiveI: Initiation Infrared as Fields, Measured J.2010. 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A Program for Gridding Radar Data, Installation Mohr, C., Miller, J., Vaughan, R., and Frank, H.: The merger of mesoscale datasets into a Palucki, J., Biggersta Richard, E., Cosma, S., Tabary, P., Pinty, J.-P., and Hagen, M.: High-resolution numerical simu- Shapiro, A., Potvin, C., and Gao, J.: Use of a vertical vorticity equation in vari- Roberts, R. and Rutledge, S.: Nowcasting storm initiation and growth using GOES-8 and WSR- Richard, E., Chaboureau, J.-P., Flamant, C., Champollion, C., Hagen, M., Schmidt, K., Kiemle, Schmetz, J., Pili, P.,Tjemkes, S., Just, D., Kerkmann, J., Rota, S., andSchmidt, Ratier, A.: K., An introduction Betz, H., Oettinger, W., Wirz, M., Pinto Jr., O., Naccarato, K., H 5 5 10 20 15 10 15 30 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | repetition rate [min] Mecikalski and Bedka step [m] [km] range max r 30 K 14:10 UTC − ] 1 3 K/15 min 14:10 UTC − > [m s C over 15 min 14:15 UTC ◦ max v 32 125 100045 15 120 500 10 4 K/15 min 14:10 UTC 9752 9751 < C 14:00 UTC ◦ 0 < erent channels after criteria from ff erent radars during IOP8b; DWD comprises Feldberg and ff rate (6.2 µm–10.8 µm) (6.2 µm–10.8 µm) exceed ) of di B B rate (10.8 µm) (10.8) drop below 0 (10.8 µm) B T T T B B B ∆ T T ∆ T PRF [Hz] dual mode (3:2) 1200, 800 500600 6.71153, 864 8.0 300 1000 250 15 1000 5 Specific properties of di Selected indicators for identifying convection initiation on 15th July 2007 by using MSG ). updraft strength cloud-top glaciation updraft strength cloud depth Indicatorcloud depth Criteria Attained on 15 July by radar/ scan modus DWD volume downwards DWD volume upwards DWD precipitation KarlsruheDOW near dual modeDOW (4:3) farPoldirad 2000 1000 1150 15.88 7.92 51 15.67 144 150 130 240 ca. 3 300 ca. 3 10 ¨ urkheim. 2006 T Table 2. Table 1. brightness temperatures ( ( Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ” marks + 9754 9753 ¨ urkheim), course of rivers (1: Kinzig, 2: Murg). The ) of detailed multiple-Doppler analyses (“ 2 ¨ urkheim Karlsruhe analysis time 55 km × Feldberg T ). 14:30–14:37 14:30–14:3714:45–14:52 14:30–14:3415:00–15:07 14:45–14:52 14:50–14:5415:15–15:22 15:00–15:07 15:00–15:04 15:15–15:22 14:35 15:20–15:24 14:50 15:05 15:20 3 C) relative to the topography of the Black Forest during the 80 min period of the ◦ Scan time intervals for the radars of the triple-Doppler analysis. Origin and north-easterly propagation of cool cloud tops (10.8 µm brightness tempera- Fig. 1. origin within Fig. ture below 5 thunderstorm cumulus and early mature(A: state. COPS Achern, supersites H: are markedF: Hornisgrinde, by Feldberg, gray M: P: diamonds Murg-Valley), Poldirad, K: radarrectangle Karlsruhe, sites indicates T: by T the circles area (D: (30 Doppler on wheels, Table 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ◦ 10 m/s 10 7.5 5 2.5 0 -2.5 -5 -7.5 -10 10 w [m/s] lightning rate [ stroke / min ] north, 8.3335 20 20 15 10 5 0 ◦ . erence between 9 ff [km][km] 15:20

height [ km ] radar reflectivity [ dBZ ] 10 10 10 0 16 14 12 10 8 6 4 2 70 60 50 40 30 20 0 0 d) , respectively; the rectangle in m) with corresponding cloud top 13 denote vertical cross sections µ (d) and

20 20 10 15:20 and [km][km] 15:05 (b) 10 10 radar P denotes the edge of Fig. lightning MSG 10.8 (a)

0 0 c) 36 cloud height F cloud height P cloud height T MSG 6.2−10.8 15:00 37 9756 9755

130° ¨ urkheim, P: Poldirad). Lower panel: di elevation), and lightning rate detected by LINET. 20 20

◦ time [UTC] 14:40 [km][km] m) channels, maximum radar reflectivity measured by Poldirad (at 14:50 µ 10 10

0 0 . b) mark available azimuth angles for Poldirad RHI scans from 14:43 to 9 14:20 (c) , respectively; the rectangle in and 20 20 m) and IR (10.8

µ ¨ urkheim, P: Poldirad). Lower panel: difference between minimum brightness temper- 13 [km][km] 14:00 (b) 0 0 14:35

10 20 10

−40 −10 −20 −30 −70 −60 −50 −40 −30 −20 −10

B B 10 10 [ ° C ] C ° [ T ] C ° [ T ∆ and 10 Temporal evolution of cloud system characteristics derived from remote sensing instru- Mid-cloud flow structures from triple-Doppler analyses at 5 km (m.s.l.) in 15 min intervals: 0 0 Temporal evolution of cloud system characteristics derived from remote sensing instruments. a) Mid-cloud flow structures from triple-Doppler analyses at 5 km (msl) in 15 min intervals: hori-

0 0

[km] 10 10 [km] 20 20 -10-10 -20-20 -30-30 in Figs. Fig. 3. horizontal wind vectors every 3coded km vertical outside velocity and 1 (positive(10 km dBZ values inside intervals, for or starting upward near from the motion), 10 cloud dBZ). and structure, The averaged colour origin reflectivity (0,0) isolines is located at 48.3329 east. Lines in 14:53, and 15:03 to 15:23, respectively. Red Lines in Fig. 2. ments. Upper panel: minimum brightness temperatureing of cloud IR top channel (10.8 height µm) (assuming withPPI wet correspond- scans adiabatic of lapse 3 rate), radarsminimum and (F: brightness estimated Feldberg, cloud temperatures T: T top of heights WVreflectivity from (6.2 measured µm) by and Poldirad IR (at (10.8 2 µm) channels, maximum radar 2° elevation), and lightning rate detected by LINET. Upper panel: minimum brightness temperature of IR channel (10.8 atures of WV (6.2 Fig. 2. height (assuming wet adiabatic lapse(F: Feldberg, rate), T: and T estimated cloud top heights from PPI scans of 3 radars a) denotes the edge of Figure Fig. 3. zontal wind vectors every 3 kmvelocity outside (positive and values 1 for km upward insideing or motion), near from and the 10 averaged cloud reflectivity dBZ). structure, isolines The colouravailable (10 coded azimuth origin vertical dBZ angles (0,0) intervals, for is start- Poldirad locatedRed RHI at Lines scans in 48.3329° from b) north, 14:43 and 8.3335° to d) east. denote 14:53, vertical and Lines cross 15:03 in sections to b) in 15:23, and Figures respectively. c) mark Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 280 4 20 260 2 15 240 ; downdraft: 10 1 0 220 − direction [°] 15:20 w [m/s] 5 wind speed [m/s] 200 −2 triple Doppler: 15:20 0 erent perspectives ff −4 280 20 260 15 4 240 10 220 2 direction [°] 5 wind speed [m/s] 200 0 triple Doppler: 15:05 0 15:05 w [m/s] −2 280 20 −4 260 15 240 10 220 38 39 direction [°] 4 5 9758 9757 wind speed [m/s] 200 triple Doppler: 14:50 2 0 0 280 14:50 w [m/s] 20 −2 260 15 240 −4 10 220 direction [°] ) from triple-Doppler analysis at 14:35; positions of intra-cloud and 5 wind speed [m/s] 1 200 triple Doppler: 14:35 − 0 4 2 4 m s 280 20 − 0 260 14:35 15 w [m/s] 240 −2 10 220 direction [°] −4 5 sounding: 14:00 wind speed [m/s] Visual appearance of the early mature state cumulonimbus from different perspectives in com- 200 Temporal development of profiles of horizontal wind speed (red) and direction (blue) Temporal development of profiles of horizontal wind speed (red) and direction (blue) measured Visual appearance of the early mature state cumulonimbus from di Temporal development of profile statistics of mean vertical velocity (w) from triple-Doppler anal- 0 2 8 6 4

8 6 4 2 0 14 12 10

12 10

altitude [km] altitude -wide-viewing angle. [km] altitude ◦ Fig. 4. bination with various retrieved14:42 physical UTC parameters. (Black Forest Right: silhouettevalues recovered along levelled from lines photograph digital of sight elevation from for model:motion Poldirad reflectivity green (black (updraft: site line) contours from red at with 0 maximum contours dBZanalysis at with at 10 4, 14:35; dBZ 11 positions intervals) and m/s; ofmonds. vertical intra-cloud downdraft: Left: and blue ground position dotted lightning ofrelative line until cloud to 14:45 at Poldirad system are -4 (red with indicated square) m/s) shadow by and from as yellow 18°-wide-viewing triple-Doppler seen dia- angle. from Meteosat for three consecutive times Fig. 6. yses: average of all values(blue). with standard deviation (red), average of updrafts (green), and of downdrafts Fig. 5. by sounding at supersite ’Hornisgrinde’ atError 14:00 bars and retrieved display mean the values standard from triple-Doppler deviation analyses. of mean wind speed for triple-Doppler retrievals. measured by sounding attriple-Doppler analyses. supersite Error “Hornisgrinde” bars display at theDoppler standard 14:00 retrievals. deviation of and mean retrieved wind speed mean for values triple- from Fig. 5. in combination withPoldirad various site retrieved at physicalgreen 14:42 line) parameters. UTC with Right: maximum (Black values levelled Forestwith along photograph lines silhouette 10 dBZ of from recovered sight intervals) from for and reflectivity digital (black vertical contours elevation from motion model: 0 dBZ (updraft: red contours at 4, 11 m s ground lightning until 14:45 are indicatedshadow by as yellow diamonds. seen Left: from position Meteosat of for18 cloud three system consecutive with times relative to Poldirad (red square) and Fig. 4. blue dotted line at ). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper3 | 280 4 20 260 2 15 240 ) from triple- 10 0 220 direction [°] direction w 7 15:20 w [m/s] 5 wind speed [m/s] 200 −2 triple Doppler: 15:20 triple Doppler: 0 −4 6 280 20 260 15 4 240 10 5 220 2 direction [°] direction 5 wind speed [m/s] 200 0 triple Doppler: 15:05 triple Doppler: 14:35 14:50 15:05 15:20 0 15:05 w [m/s] −2 4 280 [m/s] 20 −4 260 3D 15 240 10 3 40 220 39 direction [°] direction 4 9760 9759 5 wind speed [m/s] 200 triple Doppler: 14:50 triple Doppler: rms v 2 0 2 0 280 14:50 w [m/s] 20 −2 260 15 240 −4 1 10 220 direction [°] direction 5 wind speed [m/s] 200 triple Doppler: 14:35 triple Doppler: 0 4 0 ). 2 280 3 8 6 4 2 20 14 12 10 0 260

14:35 15 w [m/s] 240 [km] altitude −2 10 220 direction [°] direction −4 5 sounding: 14:00 sounding: wind speed [m/s] 200 Temporal development of profile statistics of mean vertical velocity ( Temporal development of profiles of horizontal wind speed (red) and direction (blue) measured Consistency check for triple-Doppler results expressed by root mean square deviation Temporal development of profile statistics of mean vertical velocity (w) from triple-Doppler anal- 0 8 6 4 2

8 6 4 2 0 14 12 10

12 10

altitude [km] altitude altitude [km] altitude Fig. 6. yses: average of all values(blue). with standard deviation (red), average of updrafts (green), and of downdrafts Fig. 5. by sounding at supersite ’Hornisgrinde’ atError 14:00 bars and retrieved display mean the values standard from triple-Doppler deviation analyses. of mean wind speed for triple-Doppler retrievals. Fig. 7. comparing observed radial velocitiescalculation, from elevation, each azimuth, individual and radar locationaccount with of (see retrieved Table radars values. for For all the four retrieval runs were taken into Doppler analyses: average(green), of and of all downdrafts values (blue). with standard deviation (red), average of updrafts Fig. 6. Consistency check for triple-Doppler results expressed by root mean square deviation comparing observed radial velocities from each individualazimuth, radar with and retrieved location values. of For radars the for calculation, elevation, all four retrieval runs was taken into account (see Table Fig. 7. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | −10 −15 −20 20 15 10 5 0 −5 reflectivity with

86 (a) 7 6 5 4 3 2 1

84 a). Lightning flashes 3

82 radial velocity [m/s] radial velocity

80

depth [km]depth [km]depth [km] 78 a). Lightning flashes are labelled range [km] 2 1 0 7 6 5 4 3 3

15 15 76

6 86 ) from fourfold-Doppler analysis pro-

1 74 b) −

84

72

2 8 6 4 2 0

12 10 14 2 82 2 m s height [km] height > 3

spectral width [m/s] 1 80 42 3 41 measured radial velocity by Poldirad with marked 2 3 10 10 9762 9761

3 1 70 60 50 40 30 20 10 0 −10 78 4 5 3 3 range [km] (b) 5 3 4 2

1 2 m/s) from fourfold-Doppler analysis projected onto RHI- 76

b), 86 86 2 > 3

1 74

c) 84 84 .

72

8 6 4 2 0 82 82 10 reflectivity [dBZ] reflectivity

14 12 10

3 height [km] height 5 5

80 80 b), b) measured radial velocity by Poldirad with marked areas of retrieval and 3

8 78 78 range [km]range [km]

76 76 .

m/s 5 74 74 10 5 5 0 0 -5-5 a) 5 -10-10 -15-15

and 72 72

6 6 4 4 2 2 0 0 8 8 8

14 14 12 12 10 10

Collocation of lightning positions and depth of vertical updraft columns (with threshold of 5 m/s)

Detailed wind field parameters of RHI scan from Poldirad at 14:43: a) reflectivity with overlaid height [km] [km] height height Detailed wind field parameters of RHI scan from Poldirad at 14:43: ) from triple-Doppler analysis at 14:35 UTC (see rectangle in Fig. Collocation of lightning positions and depth of vertical updraft columns (with threshold of 1 by two-minute intervals, with ’1’Figures starting at 14:39 UTC; red line denotes position of RHI scan shown in Fig. 9. from triple-Doppler analysis at 14:35 UTC (see rectangle in Figure − Fig. 8. wind field (black arrowsplane mark (red updrafts line indiscrepancies (see Figure text for details), andcircles c) within Doppler less spectral than width with 1 overlaid km lightning from positions RHI-plane). (black are labelled by two-minute intervals,RHI with scan “1” shown starting in at Figs. 14:39 UTC; red line denotes position of Fig. 9. 5 m s overlaid wind field (black arrows mark updrafts jected onto RHI-plane (red line in Fig. Fig. 8. areas of retrieval discrepancies (see textlightning for positions details), (black and circles c) within Doppler spectral less width than with 1 overlaid km from RHI-plane). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 20 erential ff 15 di hail rain snow 10 −45 −50 −55 hail graupel snow rain −10 −15 −20 −25 −30 −35 −40 (a) graupel denote ordinary 5

86 86 d) fraction of volume [%] (c) LDR [dB]

0 84 84 to hydrometeor

82 82 (a) 20

80 80

15 78 78 range [km] range [km] hail rain

snow 76 76 10 graupel

74 74 15:13 UTC. erential reflectivity hail signal HDR, and b) d) 5 ff ). Black lines in

c) fraction of volume [%] di 72 72

(d)

8 6 4 2 0 8 6 4 2 0

0 14 12 10 14 12 10

height [km] height height [km] height (c) 1994 ( 44 43 20 9764 9763 4 3 2 1 0 −1 −2 −3 −4 35 30 25 20 15 10 5 0 15 15:03, and

hail rain 86 86 ¨ snow oller et al. (c) 10 ZDR [dB] HDR [dB] graupel H

). Black lines in a) to c) denote ordinary reflectivity contours from 84 84 5

1994 82 82 b) ( fraction of volume [%] 14:53, 0

80 80 (b)

78 78 20 range [km] range [km] ¨ oller et al.

76 76 H linear polarization ratio LDR, 14:43, 15

74 74 (b) a) c) (a) hail rain snow 10

72 72

graupel 0 6 4 2 0 8 6 4 2 8

14 12 10 14 12 10 Polarimetric radar parameters within RHI scan from Poldirad at 14:43: a) differential reflectivity

5 height [km] height height [km] height a) Time evolution of hydrometeor profiles obtained from adjacent RHIs of Poldirad for reference Time evolution of hydrometeor profiles obtained from adjacent RHIs of Poldirad for Polarimetric radar parameters within RHI scan from Poldirad at 14:43: fraction of volume [%] 0 8 6 4 2 0

Fig. 10. ZDR, b) linear polarization ratioclassification after LDR, c) differential reflectivity10 hail dBZ in signal intervals HDR, of and 10 d) dBZ. hydrometeor 14 12 10 hydrometeor classification after [km] altitude times a) 14:43, b) 14:53, c) 15:03, and d) 15:13 UTC. Fig. 11. Fig. 11. reference times reflectivity ZDR, (d) Fig. 10. reflectivity contours from 10 dBZ in intervals of 10 dBZ. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − −20 −25 −30 −35 −40 −45 −50 −55 −20 −25 −30 −35 −40 −45 −50 −55 BT [°C] BT [°C] marks vertical cross 14:50 15:20 (d) d) b) ). Top-left: Meteosat visible channel with 8˚00' 8˚30' 9˚00' 9˚30' 8˚00' 8˚30' 9˚00' 9˚30' 3 49˚00' 48˚30' 48˚00' 49˚00' 48˚30' 48˚00' 45 46 9766 9765 −20 −25 −30 −35 −40 −45 −50 −55 −20 −25 −30 −35 −40 −45 −50 −55 (blue) along lines of sight. 1 BT [°C] BT [°C] − ). Top-left: Meteosat visible channel with Poldirad location (red 3 2 m s 15:05 14:35 − . 13 c) a) . Location and extend of cloud-top structure using parallax corrected cloud-top positions from 13 8˚00' 8˚30' 9˚00' 9˚30' 8˚00' 8˚30' 9˚00' 9˚30' Dissipation of thundercloud at 15:20 UTC. Top-right: vertical cross section from triple-Doppler 49˚00' 48˚30' 48˚00' 49˚00' 48˚30' 48˚00' Dissipation of thundercloud at 15:20 UTC. Top-right: vertical cross section from triple- Fig. 12. Meteosat (dots with color codedcontours IR (black: brightness temperature) 8 and km, triple-radar red:Figure derived 12 cloud-top km height and as 13 km). Red line in d) marks vertical cross section displayed in Location and extent of cloud-top structure using parallax corrected cloud-top positions Fig. 13. analysis with averaged reflectivity anddotted horizontal line wind marks vectors the (only levelsquare), every of position fourth Figure of vector cross is sectionphoto. (black plotted, line), the Bottom: and viewing levelled directionsdashed photograph (yellow green lines) taken line), of from overlayed cross Poldirad section withand and site maximum 30 triple-Doppler at dBZ), radar 15:24 updrafts reflectivity (recoveredsight. higher (black terrain than contours silhouette 2 at as m/s 10, (red), 20 and downdrafts lower than -2 m/s (blue) along lines of Doppler analysis with averaged reflectivity andis horizontal plotted, wind vectors the (only every dotted fourth line vector marks the level of Fig. Fig. 13. Poldirad location (red(yellow square), lines) position of cross of sectionat cross and 15:24 section photo. (recovered Bottom: (black terrain levelledDoppler photograph line), silhouette taken radar and as from reflectivity dashed Poldirad viewing (black site green directions contours line), at overlayed 10, with 20 maximum and triple- 30 dBZ), updrafts higher than 2 m s (red), and downdrafts lower than Fig. 12. from Meteosat (dots with color codedtop IR height brightness as temperature) contours and triple-radar (black:section derived 8 km, displayed cloud- in red: Fig. 12 km and 13 km). Red line in Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 10 m/s 10 7.5 5 2.5 0 -2.5 -5 -7.5 -10 10 w [m/s] 20 20 [km][km] 15:20 10 10 0 0 d) 20 20 [km][km] 15:05 10 10 0 0 c) 48 47 9768 9767 20 20 [km][km] 14:50 10 10 0 0 b) C in white. Bottom left: three-channel MSG composite with Vosges, Rhine ◦ 20 20 Observation versus simulation at 14:55. Top left: model generated brightness temperature; [km][km] 14:35 10 10 Fig. 15. values below 5°C inand white. elongated cloud system Bottomthe above left: nested the simulation three-channel eastern domain. part MSGbox of above composite the the Right: with model Black Vosges,reflectivity topography; perspective Forest; (white), Rhine thresholds view and red for valley, from ice crosses iso-surfaces water NW denote (blue). are on corners indicated of the for cloud 15-km-high water computational (red), radar Simulated cloud characteristics: reflectivity as black isolines (10 dBZ intervals, starting Observation versus simulation at 14:55. Top left: model generated brightness tempera- 0 0 Simulated cloud characteristics: reflectivity as black isolines (10 dBZ intervals, strating from a)

0 0

[km] 20 20 10 10 [km] -20-20 -30-30 -10-10 valley, and elongated cloud system abovenote the corners eastern of part the of nestedhigh the simulation computational Black domain. box Forest; Right: above red perspective the crossesfor view de- model cloud from topography; water NW thresholds (red), on for radar the iso-surfaces reflectivity 15-km- are (white), indicated and ice water (blue). Fig. 15. ture; values below 5 Fig. 14. from 10 dBZ), horizontal wind (arrows)episode and simulation vertical nested motion down (color to coded) 0.5 at km 5 horizontal km resolution. from Meso-NH Fig. 14. 10 dBZ), horizontal windsimulation (arrows) nested and down to vertical 0.5 motion km (color horizontal coded) resolution. at 5 km from Meso-NH episode Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | hail lightning turbulence graupel low level convergence line low level convergence 49 9769 Schematic view of main processes during mature state: downdrafts were generated Schematic view of main processes during mature state: downdrafts were generated close to the Fig. 16. close to the updrafts so that further updrafts were suppressed. updrafts so that the resulting cut-off further updrafts Fig. 16.