Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2 , M. Weber 2 5 , F. Dezitter 2 16506 16505 , A. Grandin 1 , and C. R. Williams 4 , A. S. Ackerman 1 , A. V. Korolev 3 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. NASA Goddard Institute for SpaceAirbus Studies, Operations 2880 S.A.S., Broadway, New 316 York, route NYMet de 10027, Analytics Bayonne, USA 31060 Inc., Toulouse Aurora, Cedex Ontario, 03,Cloud Canada France Physics and Severe Weather Research Section, Environment Canada, Toronto, Cooperative Institute for Research in Environmental Sciences, University of Colorado Received: 5 May 2015 – Accepted: 13Correspondence May to: 2015 A. – M. Published: Fridlind 17 ([email protected]) June 2015 Published by Copernicus Publications on behalf of the European Geosciences Union. J. W. Strapp High ice water content atreflectivity low near radar deep convection –Consistency Part of 1: in situ and remote-sensing observations with stratiform rain column simulations A. M. Fridlind Atmos. Chem. Phys. Discuss., 15, 16505–16550,www.atmos-chem-phys-discuss.net/15/16505/2015/ 2015 doi:10.5194/acpd-15-16505-2015 © Author(s) 2015. CC Attribution 3.0 License. 1 2 3 4 Ontario, Canada 5 Boulder, and NOAA/Earth System Research Laboratory, Boulder, Colorado, USA Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C. Power loss events commonly ◦ , mean Doppler velocity, and re- e Z 50 − , less than 20–30 dBZ) or more than e ) less than 20–30 dBZ and no more than Z e Z 10 to or more over a 10 km length scale, based on − 3 16507 16508 − ” conditions, where the IWC designation remains e regions of large, cold-topped storm systems in the Z e C over Alabama, induced by enhanced ice water con- Z ◦ 28 − C(Lawson et al., ; 1998 Mason et al. , ).2006 During these inci- ◦ 33 − 27 to − After a period of confusion regarding the potential role of supercooled liquid water to idle, commonly referredwas to automatically returned as after rollback, descentmore and through than in the trace melting occurrences most of level. casessuccessfully Crews hail reported or reproduced engine graupel. no a power In rollback 1997, authority convection industry-sponsored event at flight while tests 8.8 circling km downwind and of continental deep tent (IWC), sustained at likely 0.5–1 gm owing to the appearanceing of some events, streaming by meltwater 2003jet on the engine connection heated power between cockpit both loss windshieldstions commuter events dur- and was and large established, the transport ultimately ingestion2011). involving of As a of dozen copious 2011, engine ice aloss types under database or (Mason glaciated of damage and condi- roughly connected Grzych, 100meteorological with documented conditions the events encountered of engine (Grzych and jet core2011). Mason , engine had2010; power Namely, indicatedMason events and several occurred, Grzych patternspothesized almost in and the exclusively sometimes near unambiguouslyof deep fully pilot-reported convection, glaciated under equivalent conditions, hy- radar in reflectivity the ( absence trieved rain rate. Thethe results microphysical of pathways these that could consistency befeatures checks responsible in motivate for Part the an 2. observed examination size of distribution 1 Introduction Between 1990 and 1998, commuterengine transport power jets loss experienced at near least thunderstormsatures ten at of incidents elevations of of 8.5–9.5 km AMSL and temper- estimates obtained indirectly owing to primaryet probe al., failure2006). (Strapp On et the al., modified one1999; hand, engineMason the simultaneously flight tests experiencedbeen were no reported deemed rollback, a on success and that since particular no(Mason a et aircraft further second, al., since events2006). such have On modificationsinstruments the were other to made hand, reliably standard industry and concludedcle accurately that to the measure addressing inability such similar of high current 1999, hazards IWC2005; beingMason posed identified et a in al., other major2006). aircraft obsta- types (Strapp et al., moderate turbulence at flightical level. Hereafter conditions we as will “high referqualitative IWC–low or to relative, event-related as microphys- discussed further below. moderate turbulence, often overlying moderate2010–2012 to Airbus heavy carried rain out nearter flight the content surface. tests (IWC) During seeking in to such characterize low- the highest ice wa- dents the engines lost power slowly prior to abrupt uncommanded reduction of power Abstract Occurrences of jet enginethrough fully power glaciated loss deep convection and at occur damage during flight have through been radar reflectivity associated ( with flight vicinity of Cayenne, Darwin,tered, and at Santiago. typical Within samplingexhibit the a elevations notably circa highest narrow 11 concentration IWC km, of500 µm. regions the mass over Given measured encoun- area-equivalent substantial diameters ice and ofevaluate size 100– poorly the distributions consistency quantified of measurement the uncertainties,ing Airbus radar here in observations we situ obtained measurements underone with quasi-steady, heavy of ground-based stratiform profil- the rain Airbus-sampled conditions locations. in and mean We Doppler find velocities that at profiler-observedwith Airbus radar sampling those reflectivities temperatures calculated are generally fromcolumn consistent simulations in using situ the size inare situ distribution generally size consistent measurements. distributions with We as observed an also upper profiles find boundary of that condition 5 5 20 15 20 10 25 25 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C, with little ◦ conditions dur- cient to support 26 ciency of either e ffi − ffi Z , with an accuracy of 15 % 3 − ort to rigorously establish the con- ff c frequency, these maps generally ex- of the equator under preferentially moist ffi ◦ frequency, based on statistical comparison of 16510 16509 e Z ect, or developing, immature, continental convec- ff at flight altitude and no identification otherwise of e Z ), and modest wind shear (generally su 1 − or degree of glaciation encountered. Regions of the highest expected e Z (10 km) in length, making it impossible to rule out the su O over length scales of 10 and 100 km, respectively, and more than 5 % of all 3 − Motivated by the 1990’s commuter jet engine power loss problem, Lawson et al. Outside of these commonalities, events occupied a rather wide envelope of storm To evaluate event distribution geographically and seasonally, Grzych and Mason It is notable that the MCS class events documented (80 % of the total) occurred , Farquhar 1996; McFarquhar andof, Heymsfield IWC1996). were Since obtainedable no during data direct available. these From measurements CCOPE, campaigns, IWC ittems was (PMS) was calculated two-dimensional from calculated precipitation a from Particle (2DP)fields the Measuring probe colocated Sys- most with and flight suit- scanning tracks, radar, Palmer with reflectivity 1986; an, Heymsfield estimated1986). accuracy From CEPEX,dimensional of IWC 50 cloud % was particle (Heymsfield calculated probe and from (2DC), a with PMS an two- estimated accuracy of a factor of two, (1998) reanalyzed more limited intana situ during measurements collected CCOPE within (Knight, anvils)1982 over and Mon- near Tiwi during CEPEX ( Heymsfield and Mc- estimated at that time. reference to turbulence and water contentwere were also adjusted avoided to for find reasons andperformance. maintain of Based high safety, on water but roughly content the inpore, 200 order and flight cloud to Darwin, paths traverses challenge maximum in engine total5 the water gm vicinity contents encountered of were Entebbe, inreported Singa- excess measurements of at 6 each and location exceeded 2 gm instrumentation: use the aircraft radar’s tiltmoderate and to gain heavy to rain scan (Grzych below and the Mason, freezing2010; levelMason for and, Grzych 2011). 2 Microphysical conditions From the perspective of industry, thedensed most water recent content e possible intablishment convection in was the undertaken 1950’s by using thesate Royal a in Aircraft pitot-type a Es- tube thermostatically-controlledtem that heated inside collected tube ice the and and aircraft deliveredmade water (McNaughton, it at conden- 1959; to roughlyMason a 10 et measuring km al., sys- resolution2006). over Measurements a were temperature range of 0 to conditions: 38 % occurredwhere within pilots an typicallya oceanic flew complete directly mesoscale lack through convective of the system detectable central (MCS), and deepest clouds owing to flight-level convective cores; 34 %detected occurred within convective a cores strong atpassing tropical flight MCS, over where regions altitude, pilots of butagain heavy maneuvered detected rain; to and 8 avoid % divertedgions; them, occurred around 6 in typically cores % a at occurred continentalavoided flight in MCS, on altitude, where classical the flying pilots over continental downwinddiately heavy side anvils, below; rain of and where re- the storms, coreswarm remainder in frontal, were occurred vigorous this variously identifed winter case within lake-e and without tropical significant multicell, elevated rain imme- squall lines). When also considering flight tra reanalysis model fields with the followingdian event of conditions: 6 cm), high marginal precipitable to waterpotential modest (me- atmospheric energy instability of (median 1400 Jkg convectively available (2010) derived maps of high IWC–low tion (Mason and, Grzych 2011). plained the concentration of events within 45 ing some events hasshort suggested as that enhancedlong IWC or short regions duration might exposuretive commonly to analysis cause be such of as events conditions (Mason encounteredone et with consistently al., recommended and).2006 hazard An without detection exhaus- power action loss available events using led current to cockpit only beneath a cirrus anvilanalysis shield of of temperature at instrument errors least caused 185 km by high in IWC–low maximum dimension. However, an conditions seasonally. 5 5 25 20 10 15 10 15 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , . 3 α C − ◦ (1) max max was , the 10 to D D 3 12 − − − at flight max e D Z in fresh and aged 3 − , a vicinity commonly e Z in mm: above and below which half of max max D er an estimate of uncertainty in IWC D ff C, where convection was approached , calculated as described above). They ◦ 3 , the − 65 , the estimated saturation of that instrument max − 3 − 16511 16512 ) in mg and m (MMD 15 to − max D of 100–400 µm (Lawson et al., 2010). During both TC4 and max , with a suggested factor-of-two uncertainty, falling to well below D 3 − less than 20 dBZ if present in monomodal size distributions with e Z , with particle mass ( max 2.0 max D D at a distance of 50 km from storm locations of highest , Fig.1 illustrates that such relatively small mass median diameters would be 3 3 C). Considering this diversity of new data with strikingly similar microphysical fea- − − 0.021 ◦ = Based on measurements during the TC4 campaign over Central America (Toon In a data set compiled for development of satellite retrieval algorithms, comprising During TC4, IWC was calculated by applying the habit-independent mass-dimension In a more detailed analysis of ice properties in three CEPEX anvils at elevations 50 et al., 2010), reportedly theCEPEX most extensive tropical (Lawson anvil measurement et campaign al., since 2010), and the NAMMA campaign over West Africa (http: associated with typical assumptions regarding icelations crystal do properties depend (asidewhich strongly are we on not note directly assumed that measuredproperties). by ice such any crystal current calcu- instruments, mass-dimension as well characteristics, as size distribution mass resides) decreasing from 500in to 100 the µm mass with size increasing height.4 distribution gm Prominent were peaks found at 150–600 µm. Even if IWC were as high as as closely as thea pilots considered predominance safe, ofMcFarquhar irregular, andgates plate-like,(1996) Heymsfield in reported compact the spatial highestreported crystals IWC typical regions and mass (0.1–1 irregular median gm aggre- of 7–14 km and temperatures of calculated or measured during TC4calculated or in NAMMA. one Although convective IWC turret, exceeding maxima 2 gm were less than 1 gm thousands of 5 s-averaged aircraft data from TC4, NAMMA, and other campaigns, IWC anvil regions. hygrometer; IWC uncertainty is(Twohy et estimated al., to1997). Lawson be et 10 al.(2010) % do for not values o larger than 0.2 gm under TC4 measurement conditionsimpacted (Lawson ice et is al., evaporated into2010). a Within dry a airstream, which heated is CVI in inlet, turn sampled by a Lyman- relation derived in mountedBaker PMS and two-dimensional(2006) Lawson stereo3000 to (2DS) µm in probe measurements over from a an size range underwing of roughly 10– − and then growing by vapor deposition,evaporated while and smaller and sedimented, larger respectively. outflow ice preferentially m Calculated IWC was shown totual agree impactor with (CVI) direct inlet measurements mountedage from on at a the IWC counterflow fuselage concentrations vir- of below the 0.5 aircraft gm to within 20 % on aver- //airbornescience.nsstc.nasa.gov/namma/), the iceanvils, aged mass anvils, size andnated distributions convective by crystals turrets in with alike fresh NAMMA, were fresh consistently anvils found contained tolar columns, be crystals capped domi- columns, and relatively irregularwhereas compact aggregates turrets irregu- that contained were 1–2 generally mm smaller graupel than over 2 tures, mm aLawson et in wide al.(2010) attributed temperature theticles predominance range to of several cloud ( hundred droplets micron par- freezing heterogeneously at temperatures colder than diameter of the smallestimaged circle at enclosing random orientation two-dimensional in projections situ). of Working ice in particles the absence of recorded level from these scientificanvil IWC research of campaigns, 1–3 gm Lawson1 gm et) al.(1998 reportedreported for peak initiation of commuter2006). and Ice large size transport distribution jetthe properties engine largest were events particles (Mason not encountered, et extensively which, al. analyzed, were commonly except on to the report order of 2 mm in owing largely to sensitivity toattributed mass-dimension relationships to applied, particle plus roughly2DP counting 50 and % uncertainty 2DC probes (McFarquhar respectively30–1800 measure and µm particles, Heymsfield in that are).1996 maximum nominally dimension The 300–9600 and of randomly oriented projected area ( 5 5 25 20 25 20 15 10 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − and 94 GHz 3 − 0.5km resolution) N) from 7 July to to reflectivity for the ◦ × , cirrus formed in situ max , with a large uncertainty conditions. We compare max S–25 in clouds associated with 3 ◦ 25–100 µm (e.g., Connolly D e − . e 1.4km 3 Z and ice mass mixing ratio. Z ∼ × − , and the spread of algorithm 3 − max at 10 km in elevation (frequency of and Doppler fall speed profiles with 1.8km 3 e − cient to enhance the aggregation pro- ∼ Z ffi N, ◦ 16513 16514 S–25 ◦ derived from measurements; these are the fac- commonly less than e cult to objectively define in a mid-latitude squall line Z max ffi D are very rare (Delanoë et al., 2014). Aside, we note that no the equatorial coast of Brazil, they concluded it likely that 3 ff − , Fig.1 illustrates the relationship of MMD and, Houze 1991 ), commonly associated with a radar reflectivity ciently many such small crystals to aggregate, perhaps owing to 3 − ff ffi ) from two out of three algorithms (Wu et, al. 2009). However, a third al- 8 − conditions were not specifically avoided, to our knowledge. e Z below 18 dBZ, including 2.5 km-footprint peaks of 2–4 gm In this two-part study, we examine a set of measurements gathered by Airbus during Motivated directly by the engine power loss problem, a more recent satellite-based Comparison of IWC retrievals using CloudSat data (25 Focusing briefly on observed ice morphology, the McFarquhar and Heymsfield e that is electrically activegregates may (Stith also et al., bedroplets2004), distinguished or faceted which by crystals have a with been predominance found of to chain be composed ag- of small frozen observations. Aside, wea note region that classified althoughit as many is stratiform power not rain loss clear bycolumns events whether (Biggersta some may power measure be loss (Grzych events within are and associated Mason , with), 2010 classical stratiform rain owing to unknown ice morphologicalmixing ratio and of size 4 gm distribution properties.simplest case For of an monodisperse ice ice mass nential particles size with distributions mass with following slopes Eq. over (1), an and observation-based for range expo- of 1–1000 cm are most commonly characterized by a2010, notably larger per fraction of their rosettes Fig. (Lawson et 2)., al. Although not reported from TC4 or NAMMA, deep convection et al., ; 2005 Gayet etis al., attributed2014; toStith the et presence al., cess, of2014 ). electric as The fields well occurrence su as of su chain aggregates the McNaughton(1959) campaigns, the purposeest IWC was regions to possible, find within andIWC, the stay mass limits within size of the distribution, safety. high- tors Here and immediately in Part relevant to 1, wethe characterizing first flight high survey IWC–low test the dataa with well-observed previous MCS over literature Darwin during andnally, the we with TWP-ICE use remote-sensing campaign Airbus (May measurements observations et al. , to of stratiform).2008 initialize rain Fi- steady-state columns, column and simulations compare of predicted heavy bright band (e.g., Steinertional et regime region al. , is1995), already or di some type of transitional regime. A transi- homogeneous freezing of abundant cloudassociated droplets with in electrical the strong, activity mixed-phase (e.g., low, updrafts Connolly the et complexity al., of).2005 crystal As morphologyrelationship discussed contributes between further substantially IWC, to be- ice uncertainty mass in size the distribution, and 2010–2012 in deep convection nearGrandin Cayenne, et Darwin, al.(2014), and conditions Santiago. sampled Asmonsoonal included described oceanic and by and sea continental breeze conditions, convection, and a range of storm size extents. Similar to study aimed to establishcraft IWC flying conditions at conceivably an encounteredsurements elevation by of and commercial 10 air- retrievals km in (Gayetobserved the et tropical tropics al., MCS using2014). o CloudSat After and identifying CALIPSO mea- and analyzingZ a well- (Heymsfield et al., 2013). Holding sizewould distribution lead properties to fixed, increasing denser reflectivity ice for particles the same MMD (1996) and Lawson et(2010) al. tal studies both shapes identify seen a in sharpsitu. distinction deep Although between convection crys- both outflow vs. maycompact those contain appearing seen particles a in of mixture cirrus several of hundred that habits microns is in that formed include in irregular and rather deep convection. showed rare occurrences of greater than 2.5 gm the storm included an area wider than 55 km with IWC greater than 1 gm 16 August 2006 over the tropics (25 less than 10 gorithm showed occurrences of IWCresults exceeding diverged 10 sharply gm at IWC values greater than 1 gm values greater than 2 gm research aircraft involved encountered enginelow power loss events although high IWC– 5 5 25 20 15 25 10 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er ff ), 2.5, 1 − C, where ◦ 20 − ciency of the capture, melt- ciences of 0.2–0.3 (Grandin ffi ffi ciency. Recent flight tests have pro- ffi ciency to estimate IWC from the Robust ciency for liquid water content is close to ciency characterization in the near future ciencies owing to re-entrainment of only ffi ffi ffi ffi 16515 16516 ciency should provide an accurate lower limit on IWC), we can o ffi and , Houze 1993 ), where convective and stratiform rain regions are ff The accuracy of applying a 0.4 collection e Since about 2005, it has been realized that hot-wire devices using trapping geome- In Fig.2 the total condensed water content (CWC, liquid plus ice) reported by the liquid contributions are considered negligible. Robust probe during eachaveraging lengths: campaign 0.2 km is (1 Hz plottedand data as as 10 reported, km. a at Data function typicalDarwin airspeed include of (F1403–F1409), of eight 200 elevation and ms flights over ninethe from three flights Cayenne from Cayenne and Santiago (F1419–F1426), (F1539–F1547). Darwin sixSantiago We flights flights flights note targeted targeted from that warmer cruise temperatures;of the elevations elevation concentration circa of at IWC 10 each km, assample location a whereas frequency. function should Based the on therefore a bebust more viewed probe detailed data primarily analysis as of as a theet an continuous Cayenne al.(2014) function indication and of report of Darwin length that Ro- scalescale 99th within over percentile identified two CWC legs, orders isGrandin ofacross a magnitude all (0.2–20 surprisingly km), three weak consistent locations function with inpeak of the Fig.2. CWC pattern length They does seen also exhibit here a showbe sharper that expected decrease a within in leg a CWC with narrow with statistically updraft, averaging extreme for distance, instance. as might probe under natural iceinvestigation (Grandin particle et conditions al., 2014). remains Comparisonsnephelometer unknown with in IWC Airbus and flight estimated tests will from has the require indicated imaging smaller further e tries are subject to relatively low capture e (cf. Biggersta commonly well separated, and isthe more variety complicated of in convective large regionlations tropical are structure systems limited (e.g., owing toMapes to heavyspeed and stratiform information, Houze rain under1992). regions relevant Here inbe quiescent simu- order neglected conditions to at where make elevations mean circa use 11 vertical of km Doppler wind relative fall to can reflectivity-weighted ice fall speed. 3 Airbus in situ measurements The Airbus flight campaigns includedality two under in situ high probes IWC(SEA) intended conditions: to Robust maintain a solid function- newly hot-wireStrapp et designed probe al., Science used2005) Engineering forof and liquid Associates estimation an droplet of Airbus size imaging distribution icetion but nephelometer (Roques, mass used2007). designed here mixing for for measurement ratio estimation of (cf. ice mass size distribu- ing, and evaporation byabout the 0.4, the Robust value assumed probe here.bus for The on probe shaved the was basis ice subsequently of recommended particlessimple durability to installation, and was Air- to its estimated provide simple real-time principle at guidance of during operation, requiring flight a tests. relatively et al., 2014). Although theprimary IWC accuracy source was of initially error estimateduncorrected as to for 30 be % e (assuming the the loss of re-entrained mass, such that measurements a fraction of particles that bounceet out al., of2005; theKorolev et capture, al. volumesurrogate2013). (Emery IWC The et Robust measurements al., probe2004; for wasStrapp the developedat primarily relatively calibration high to of wind provide a speed (Strapp windable et tunnel hot-wire al., probes producing),2008 conditions were high where known IWC (Strapp essentially or all et suspected avail- al., to1999). fail owingbe In to used a particle alongside wind impact ice tunnel, ingestion damage size Robust measurements distributions. probe to During measurements deduce the were absolute course intended IWC of and to calibrations, ice the mass e no further evidence ofof accuracy two here uncertainty to owing establish to anything overall better collection than e the raw factor vided a data set that is hoped will improve e unity, such that liquid andhere ice we consider contributions only to measurements mass taken at cannot temperatures be colder than accurately determined, (Grandin et al., 2014). Because the probe’s e 5 5 10 25 20 15 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 − (2) is slightly is roughly values are 3 eq e − D Z in mm derived relation was de- eq of 2–12 mm mea- was only reported D eq 3 D eq − – (Lawson et, al. 2010 ). D m defined by Locatelli and 1 in fresh anvils, and mean − 3 eq erences may be within the − in mg to ff D erence could be explained by ff m 100 µm; such small particles do not ective density is limited to that of bulk ∼ ff size distributions at the largest particles e obtained from the measured size distribu- Z e region at circa 11 km in altitude, Fig.4 shows 0.93 (Smith, 1984). 16518 16517 Z / e Z in all three mass ranges shown, so this calculated e ), and ), defined as the diameter of a circle with area equal is smaller than Z eq eq conditions. Figure5 shows the time series of integrated eq of 1–12 mm (based on roughly fifty particles total), it is D e D Z C during the flight segment analyzed (Fig.5), the sampled eq ◦ of 1–3 mm measured). Aside, we note that this D (MMD 43 eq (1 km) in an updraft exceeding 20 ms size distributions; although they must also be truncated to some − , with the exception that e eq D e O D eq Z D 1.9 eq D are found in all three locations. At a length scale of 10 km, 2 gm 3 − 0.037 is low by an unknown amount. However, mass size distributions do not appear to erent from the average of chord lengths parallel and perpendicular to a photodiode = Here we apply this relation using the same dimension Taken together, the envelope of measurements is qualitatively similar to that reported As mentioned above, here we focus primarily on the mass and radar reflectivity that We next consider in greater detail the measurements obtained during a flight that ff e below 15 dBZ, although the sharp drop in tions. Here it isobtained shown from integration that of calculated IWC mass obtained size distributions from over roughly the 0.1–4 Robust gm probe closely tracks IWC reported, with the mass calculatedbust from probe the nephelometer by exceeding roughly that 25 from % the at Ro- thesizes highest indicates values that reported. the Calculated nephelometerticles size contributing distributions to do calculated not include the largest par- be as truncated as degree by an unknownsuggests amount, that agreement this of may integrated not IWC be with a the great Robust amount. probe We might expect a greater mass con- Z (1974)Hobbs for their single-particle measurements,densely applicable rimed both to radiating aggregates assembles of of dendrites or dendrites ( di ice, which is relevant where by )(1959 McNaughton insofar as2 10 gm km-mean condensate mixing ratios in excess of array substituted in Brown and(1995). Francis Whereas this applied here at all TC4 IWC at a 10 km length scale reached at least 0.25 gm sured) and tobullets, aggregates and of columns ( unrimed radiating assemblages of plates, side planes, rived from particles with contribute substantially to the masscertainty size distributions in shown mass here, size thoughat bin-wise distributions this un- calculated time. using Alsoice this shown mass in approach size Fig.4 is distributionsare notmultiplied as Rayleigh by quantifiable the a radar integral dielectric reflectivities of factor calculated the of from sixth 0.208 moment the of the melted diameter contribute to high IWC–low IWC, mass median at a length scale of twice the maximum value shownquhar across and the,(1996 Heymsfield three cf. CEPEX their anvils Fig. examined 3). by McFar- During TC4, 2 gm anvil IWCs reported appear, Heymsfield 1996; generallyLawson consistent et al., with2010).tically On CEPEX the inconsistent. data face However, of at (McFarquhar it, least and these some results may degree seem of statis- di the objective of the Airbusprioritize flight the tests repeated to measurement sample ofof the very such highest large, IWC measurements cold-topped found storms does there.large and A not and to large poorly currently database quantified exist. uncertainty Other of di both measured andencountered calculated relatively IWC high values. IWC. Fromspirals the in track an of identified Cayenne highice flight IWC–low F1423 particle (Fig.3), number with sizeAt distributions temperatures circa derived from the nephelometer measurements. of area-equivalent diameter ( to the two-dimensional projectionsitu, of over a an bin icetribution midpoint particle calculated range assuming imaged of a at 67.5 µm relationship random to of orientation 3 particle mm. in Also shown is the mass size dis- cloud is fully glaciated. The nephelometer size distributions are reported as a function from measurements of natural crystalston (Locatelli sampled and in, Hobbs the1974): Cascade Mountains, Washing- m 5 5 10 15 10 15 20 20 25 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) and 3 − of roughly erent parts ff eq scarcely deviates eq er the advantage of better ff measurements at relevant vol- e similar to 250 µm, although more Z eq within dense anvil regions. Ground- e Z in the densest anvil clouds in di 16520 16519 eq er stormwide ff er instantaneous stormwide coverage, for instance, but ff of roughly 250 µm in Fig.4. Although the peak is narrower eq D range in both fresh and aged anvils around Central America and max were also noted in all three of the CEPEX anvils examined by McFar- D max Encountering a consistency of MMD The most striking feature of the median size distributions shown is the consistent Within any single flight through dense anvil at circa 11 km altitude in the Cayenne spatiotemporal coverage than inthe situ various flight limitations legs associatedSatellite and infrared with in images can in part o situ becauseinclude no probes they direct are and information free measurementbased on of scanning techniques. either weather IWC radars or can o that exponential fits tointercept ice but size little distributions in exhibitedfield order-of-magnitude slope et variability within al., in individual2002). spiral loops of 5–10 km diameter (Heyms- 250 µm. Lawson et(2010) al. 100–400 µm also reported a consistentWest concentration Africa; of a mass particularly inwithin stable the turrets, peak leading of massupdrafts them that in to could that explain suggest such sizeduring a a range pattern. the was microphysical The Airbus also size flight pathway range tests observed although of of is mass also IWC ice concentration roughly was found consistent formation substantially withwithin in that graupel-containing less reported updraft throughout from turrets CEPEX, sampled. previous scientific campaigns, even 4 Profiling radar measurements Owing to the uniquenesssomehow of with the independent measurements. Airbus It flightsensing is test data also data, desirable if to it possible, make in is use part desirable of because to remote- they corroborate commonly it o of the world may alsoexpected be (e.g., surprisingVarble given et the relativelytests al., wide systematically2015). range targeted One of central updraft possiblein strengths regions explanation all of is locations the (in that some largest thecoupled cases and Airbus very dynamical coldest-topped shortly flight and clouds after microphysical electricalclouds processes activity do that ceased), lead and so that to consistently the the by highest producing IWC a in concentration such of mass at MMD peak in particle mass at tribution from unsampled largerflight. particles at lower elevations than sampled during this at higher IWC, the time series in5 Fig. show that calculated MMD then normalized by theirinsofar as total they mass exhibit for similarconcentration. width Flight Three and other 1423, shape flights they across withlocation appear roughly show the similar a roughly highest behavior, with factor IWC self-similar calculated of encountered MMD four in in each mass flight test from 200–300 µm overfurther more than demonstrates an that order whenwithin of the the three magnitude calculated mass variability ranges mass shown in size in IWC. Fig.4 distributions Figure6 (1–2, are 2–4, averaged and greater than 4 gm smaller and larger particleswhich appear sampled likely lower to elevations have (seepled been2); Fig. larger present owing particles in also contributed theomitted to more from Santiago the substantially Part flight, likelihood 2 to that of that unsam- this flight, study. Santiago resultsand are Darwin flights, a stableof self-similarity IWC of can mass be sizeprocess considered distributions of a over ice a surprising outflow wide from resulttently convective range because leads updrafts to and it subsequent preferentially is larger sedimentationsources generally particles consis- (e.g., thought andLawson more that et mass the , al. occurringand1998, (1996) Heymsfield closer2010). reported to Consistent that updraft larger with ice thatto crystals reasoning, convective were coresMcFarquhar found and preferentially nearer lowerGarrett in et the al.(2005) anvil, within consistent Floridaform with anvils. MMD size However, horizontal sorting regions documented of by relatively uni- quhar and(1996), Heymsfield leadingnot the be authors the to only dominant concludeprecipitating process that deep in size convection the sorting spanning CEPEX anvils several must they TRMM examined. field A campaigns later study also of reported 5 5 25 15 20 10 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | spectrum e . At 4.7 km, during each Z 1 − 1 − is greater than as the meltwa- below the melt- e e e , as suggested by Z e Z Z Z C, close to that during ◦ upward and exceeding 1 43 − − at relevant volumetric scales of ; omission of the full 3 e − Z m , it provides the valuable benefit of an 6 e Z 16521 16522 at this elevation nears 30 dBZ (during convective e in excess of 10 dBZ commonly still extends above in linear coordinates during each stratiform period. -weighted fall speeds of roughly 1 ms Z e e e ), but variability in ice hydrometeor single-crystal and Z Z 3 Z cult to draw conclusions owing to lack of retrieved winds in excess of 30 dBZ. ffi e Z and Doppler spectral width is less than 2.5 ms (1 km 1 O near the midpoints of the stratiform periods rather than at the − 1 − ), in addition to mean Doppler velocity (MDV). Since MDV represents a higher . At the surface, rain rates measured by disdrometer tend to read sustained downward. The strongest drafts are colocated with the strongest deep echoes 3 1 1 − − is greater than 25 dBZ. The beginning of the first period (12:17–14:07 UTC) cor- Figure9 shows time series extracted from the S-band profiles and surface rain rate Figure 10 shows MDV vs. The S-band MDV curtain in8 Fig. shows two broad periods of stratiform rain passing (100 m e periods), it does notare exceed that. the The contiguous two periods stratiform of time periods at within least dashed 15 lines min where, at 11.7 km, Cayenne flight F1423. Although 5 dBZ, MDV is 0–2 msZ responds to the21:49 earliest UTC) to panel the in lastobtained panel. Fig.7 from Also theand shown profilers in the at Fig.9 ble the end (9are highest km) retrievals elevation and of where of near-surface retrievals vertical the rain were(Williams rate wind usually second and where speed possi- retrievals, May period can2008; confidently (20:13– bandWilliams be spectral made and width (2.5 km) , Gage indicate that).2009 turbulence the Retrieved and two vertical stratiform no winds periods strong and are updrafts. quiescent, S- During with minimal each period, maximum O order moment of the ice size distribution than at 11 km, it appears possible that MDV may be a weak function of 11 km, with someheavy detectable rain echoes is extending indicated above by 15 km. Below themeasured bright by band, a colocatedDoppler NOAA spectral Joss width Waldvogel are disdrometer.able shown Reflecitivity, from MDV at Darwin and on an 23 elevation January of indicate 11.7 a km, temperature where of soundings avail- ing level exceeds 40 dBZ4 mmh and maximum rainpeaks rate circa retrieved 2–4 mh at 2.5 km reaches nearly Mean values of MDV indicate period, consistent with(Fig.5) those using calculated the from methodcoherent Cayenne of oscillations flightHeymsfield in and F1423likely retrieved(2010). indicative Westbrook measurements vertical of In gravity winds waves, the andaround at these profiler the generate mean 9 data, a km in significant Fig. component and10;of of extraction in this scatter of work. gravity MDV waves Although is at it considered is 11.7 beyond km di the scope are MDV calculated from the Airbus data,not as strongly expected dependent in the on case IWC. that Duringpear size faster the distributions where second are reflectivity period exceeds in 20–30 Fig. mm 10, fall speeds do ap- endpoints. umetric resolutions of size-distribution properties precludepointing reliable radars retrievals of can IWC also at provide this non-attenuated time. Vertically work is devoted to examinationflight of test these data. measurements in comparison with the Airbus over the profiler ontent 23 turbulence January throughout 2006, theform periods bisected observed are by column characterized a by atof a several-hour roughly sharp roughly period 23.65–23.83. decrease 5 km, in of The MDV where intermit- strati- at the melting melting ice level height also creates a bright band in independent measurement constraint thatThe is chief disadvantage also of sensitivea profiling to profile radars compared mass is with size the a scanningthe distribution. severely radar TWP-ICE reduced volume. campaign, spatial However, on the coverage 23 NOAA of ments January S-band 2006 during profiler during obtained evolution a of time a series tropical of measure- MCS near Darwin (Fig.7). The remainder of this ter undergoes conversion to faster-fallingDoppler rain. velocities During the reach turbulent10 localized ms convective period, peaks ofobserved nearly in the 10 storm ms aboveing 15 km. of Where a ice bright into band is stratiform present, rain, owing to the melt- apparent in the Airbus measurements,the as contribution discussed of above, may the substantially largest truncate particles to MDV in the Airbus data. 5 5 10 20 25 25 15 15 10 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 − under 1 − that were eq ciencies are D ffi C. This exercise therefore , we therefore assume that ◦ by definition, and the overall eq 40 D and MDV are shown with blue eq − in these regions, consistent with e D e Z legs aloft. Colocated retrievals of Z e , consistent with heavy rain expected Z 1 − 16524 16523 shown in Fig.6 represent a mean IWC of 4.3 gm 3 − frequently exceeds 30 dBZ below these stratiform regions, range at temperatures below conditions beneath low- e e Z Z max , the projected area is related to D eq can be associated with relatively stable MDV of circa 1 ms D e Z , heavy stratiform rain indicated in8 Figs. 9.and Aside we note that no e Z is equal to We initialize the column with Airbus ice size distribution measurements obtained over Overall, the S-band measurements and retrievals appear to generally confirm that We begin with an atmospheric column with 250 m vertical grid spacing that is ini- For these simulations, we adopt a steady-state simulation approach, considering max conditions similar to thosedoes sampled not on vary flight strongly with F1423. a MDV, factor which of includes four change air in motions, rough self-similarity in size distribution shapeFigure9 found inshows the in that situ Airbus measurements. consistent with high- rain rate indicate precipitation exceeding 3beneath mmh high IWC conditions. 5 Column model simulations As shown above, the iceto size be distribution generally features consistent found with in otherconvection Airbus and recent with flight in profiling tests situ radar measurements are measurements in ina found a the step large vicinity tropical further of MCS. deep Here to werain compare take regions observed one-dimensional during simulations TWP-ICE ofparison with is the the intended profiling quasi-steady to radar stratiform observations. allowhigh This an IWC com- evaluation regions of are whether consistent theshown ice with in mixing heavy Part 2, ratios rain three-dimensional measured rates simulations in retrievedice generally below, size fail for to distribution instance. reproduce As features the observed in in the deep 100–500 convection, µm withalso concentration serves of to mass test narrowly perform how when well initialized a with column theestimate observed simulation of size with distributions bin-wise size-resolved and ice microphysics an properties,processes can observation-based and of when sedimentation and limited aggregation to in the the relatively stratiform simple region. dominant tialized thermodynamically with a21:00 UTC mean on 23 of January soundings 2006, observed obtained from around a at variational analysis Darwin of at conditions over particle aspect ratio is unity. Particle fall speeds and pairwise collision e sounding is available at Darwinfailures. during The the atmospheric column second is halfabove saturated of 8 with km. 23 At respect January the to owing melting icebelow to level at relative with balloon relevant humidity respect elevations is to roughly ice 90 %, and increasing water, above respectively and (not shown). Darwin during flightreported F1405. IWC The greater mass than 4 size gm distributions averaged over regions with the TWP-ICE sounding array (Xietive et of al., high- 2010). This time is selected to be representa- calculated following (1999),Böhm with(2010)Westbrook fall as speeds described modified by following Avramov etHeymsfield al.(2011). and that large andtherefore long-lived exhibiting stratiform roughly regions equalbelow are quantities at changing of each slowly mass level.time coming over We to from hours neglect steady above in large-scale state, andobserved we time, vertical exiting initialize mass motion. all size To elevations speed distribution.represent above evaporation up Vapor the of ice exchange simulation melting and level with liquidin with in hydrometeorsFridlind the the et is unsaturated same 2012b) al.( regions, permitted and treatedand discussed as to water described further vapor in mixing Part ratios 2.melting to However, level, the we which observed fix would profile, temperatures otherwise therebystable require neglecting as application cooling of at observed. divergence the Melting termsall of to ice remain ice to is melted equivalent treated drops in when a the rudimentary column temperature fashion, allows. by transferring measured between 11 and 11.5 km. The calculated shown to agree with thethe ice Robust particles probe are measurements. spherical ForD in shape. simplicity, Given we mass assume and that asterisks in Fig. 11. Here we assume that the particles have the mass and regions of low 5 5 20 25 15 10 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 − under corre- 1 e − Z and MDV) or e Z ), defined here as i throughout a satu- E 1 − ciency ( ffi monotonically increases. In the , although higher rain rates of 4– ciency (0.01 and 0.005) and two 1 e − ffi Z band scanning polarimetric radar at Darwin 16526 16525 C , Doppler velocity, precipitation rate, and CWC e Z ers a wider view of rain rates, which are retrieved at ff and MDV represent the steady-state boundary condition. and rain rate from C-POL measurements near the time of e or the smooth increase in MDV seen in the observations. e Z e Z Z with height above the melting level also exhibit a roughly 30–50 % decrease e is similar to observed, including reproducing a reduction of MDV with distance Z e Z Unlike the constant precipitation rate profile in a saturated column at steady state, the Simulations are shown using an observed sounding (with RH of roughly 90 % at the In Fig. 11 are shown simulated MDV above the melting level is usually similar to observed or is underestimated by introduced at 11 km, with thetent ice with morphological Airbus and measurements, size corresponds distribution to properties a consis- rain rate of roughly 8 mmh (C-POL, Keenan et al., )1998 o The Australian Bureau of Meteorology saturated conditions. Figure 12 shows thatice half size as distribution much or IWC properties, aloft, corresponds without to a change roughly in 4 mmh sponds to a reduction of IWC as ice sediments faster. 6 Meteorological context 2.5 km in altitudedrometeor following classBringi aloft et, (Keenan stratiform al.(2001),2003; periods andMay identified a and in, Keenan horizontally, three-dimensional with Fig.8,2005). view higher Of the peak of rain the second hy- 2.5 rates km two turns seen cross-sections quiescent by out of disdrometer to (Fig.9).maximum be Figure stratiform rain13 far rateshows more atasterisk. the extensive S-band Areas profiler, outlined whose location inet is black al.(1995) indicated textural with are algorithm an those assified in identifiedFridlind as as et stratiform. convective al.(2012a); At surrounding usingstratiform areas the the area are where timeSteiner clas- most shown, rain the rates are S-band 2–4 is mmh embedded within an extensive a more gentle decreasetrend during in sedimentation; simulations thatin roughly IWC reproduce the between 11 and 5 km. Thus, aggregation consistent with increasing simulated CWC profile decreases monotonically andsurface. drastically Most between dramatically, 11 melting km ice and causes the with a rapid observed increase MDV), in which falla speed is (consistent accompanied uniform by (steady-state) a precipitation rapid decrease rate. in Above CWC the to melting maintain level, IWC undergoes melting level, as described above) andwith with the respect same sounding to that has iceulations been with and saturated the water saturated abovewithout sounding evaporation, and precipitation demonstrate below rate that is the in constant melting a with level, steady-state height. respectively. Thus environment Sim- an IWC of 4 gm rated column. simulations, the rate of increase scalesthe with probability the that sticking e anhere ice-ice to collision be results fixed, in althoughand it aggregation. ice may The be morphological probability a isobservationally properties substantial taken (e.g., function inKienast-Sjögren of a et environmentalthe manner conditions al., omission that2013, of and is mixed-phase referenceswhen not the particles therein). generally temperature Owing from is well warm to this enough,melting established simplified and band simulations feature model, therefore in do ice not instantly reproduce the melts towards the surface, except in oneevaporation simulation may with substantially a increase saturated MDV. However, sounding,the underestimation indicating of that melting MDV below levelprocesses in (e.g., aPhillips et simulation al., could2007), which also could enhance be aggregation. attributable to missing mixed-phase As the ice aggregates during sedimentation, the a few tenths of awhen meter per second. MDV below the melting level is similar to observed retrieved with a combination of S-band,rate UHF and and CWC). VHF The data below observed thethe and melting retrieved available level data values (rain at over each the elevationof stratiform represent the time means simulated periods of columns, shown in8 Figs. and9. At the top (liquid plus ice) for two values of ice-ice sticking e environmental conditions (the observed sounding orsteady a state. saturated Also version) shown after are reaching profiles measured by the S-band profiler ( 5 5 15 20 25 10 25 15 10 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | conditions e Z erence across ff does not exceed 30 dBZ e Z ; these areas are periodically e Z ering properties of convective and ff 16528 16527 C, the Airbus flights primarily sampled at colder ◦ 26 − were not rare at any of the three global regions sampled, and 3 and, Houze 1991). Subsequent analyses usefully extended this − ff during roughly an hour-long period containing convective cells over the 1 can be found locally roughly 50 km northwest of the profiler. Thus maximum − 1 − An examination of the Airbus nephelometer data in the regions of highest IWC at Similar to CWC measurements reported by McNaughton(1959), IWC measure- Separation of rainy areas into convective and stratiform areas has an origin in the Although convective rain areas that contain some amount of hail are found north and elevations circa 10 km indicate thatin mass size the distributions 100–500 were µm dominated range by of particles area-equivalent diameter consistently across all locations. various direct and indirect measurement approaches. is sometimes organized intocommonly linear scattered features, within but individual regionsquiescent convective identified vertical turrets winds as are and stratiform, low also consistent rain rates. with otherwise 7 Conclusions Roughly a hundred well-documentedscribed in jet the literature engine to power date have less been characterized and by high damage IWC–low events de- In addition, the factor-of-two uncertaintyany generally means, assigned in to the IWC absence2008; measurements ofBaumgardner by et past, al. test2011 ), facilities could to also provide account ground for truth some (Strapp of the et di al. , maximum IWC exceeded twiceet al., that2014). value These at IWCsurements 10 measurements km from are length similar roughly a scales cloudHowever, as factor (see regions noted of above, two also documented a greater large inGrandin than database the mea- of such scientific measurements literature is not to yet date. available. framework to consideration of tropical storms,stratiform the region di energy and waterspheric budgets, circulation and their (e.g., unique, Houze However, the consequences2004 ; structure for ofSchumacher atmo- convective regions etety within, al. a (Mapes tropical and2004; MCS, Houze presentZeng1992, a cf. et large their vari- al., Fig.2013). 15). In the system studied here, convection encountered almost exclusively inweak the vicinity to of moderate deepDarwin, turbulence. convection and During Santiago under carried conditions 2010–2012 a of elometer new Airbus SEA used flight Robust hot-wire to tests probetests report and from was an ice to imaging Cayenne, find neph- particle andin size remain a within distributions. the manner A higheststudy similar chief IWC measured regions, to objective within CWC that of the at limits described the of 0 flight by safety, to McNaughton (1959). Whereas that earlier ments of roughly 2 gm first-order division of mid-latitudevertical squall-lines winds into commonly iceto exceed particle detrainment ice source regions), crystal regions, andimentation where fall ice (Biggersta particle speeds sink (thus regions transporting dominated particles by ice particle sed- temperatures, where many such events have occurred (cf. Grzych and, Mason 2010). slightly larger duringthis some event periods (not earlier shown). Vertical4–10 and ms wind later, speeds but retrieved at areS-band, 9 km never including from extensive the the during moderate profilers time turbulence. reach of Fig. .14 These would presumably be associated with south of the stratiform rain area over the S-band in Fig. 13, 8 mmh stratiform rain rates in these observationsmeasured appear IWC roughly consistent aloft, with sedimenting thesuch maximum under rain saturated rates are conditions, not inbe widespread. our attributable The to locally calculations, enhanced stronger but precipitation stratiformelevations from rain rates mesoscale or could ascent also other concentrated at processesrather lower than that high IWC could far enhance aloft. rain rate locally by other means, at 11 km anywhere withinfields the at C-POL the domain time at of the thatS-band strongest time. is convective Figure rain now14 over embedded theshowselongated S-band, within the region by C-POL a with contrast. some Here linear amount the band of11 km hail of according there convection to remain containing C-POL only definitions. a However, several at continuous tiny areas of 30-dBZ 5 5 25 20 10 25 15 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | e is Z e Z nominally smaller ice properties, albeit . This is roughly twice size distributions from max e 1 e D Z − Z cient to explain increasing ffi . e Z at 11 km, which is consistent with self-similar e 16530 16529 Z er two indepdendent measurements sensitive to ff ce of Biological and Environmental Research, Climate and Environmental TWP-ICE soundings and S-band radar data were obtained from the Atmo- , consistent with that calculated from Airbus flight test data. MDV ap- ffi 1 − and mean Doppler velocity (MDV). We focus on regions of heavy stratiform e Z is found to correspond to a rain rate of roughly 8 mmh 3 − ce of Science, O The objective of Part 1 of this two-part study has been to vet the Airbus size distribu- Owing to the great uncertainty associated with both IWC and size distribution mea- Column model simulations initialized with ice morphological and particle size dis- ffi to extend the comparisongross by inconsistencies, relating here we IWC conclude aloftappear that with to size distribution rain give and rates a IWC below. reasonable measurements Given representation a of lack high of IWC–low Sciences Division. C-POL radarMay, measurements Centre and for retrieval Australian products WeatherThe were and authors supplied Climate thank by Research, Peter Thomas Australiansistance, Ratvasky Bureau and and of Jeanne Ron Meteorology. Mason Colantonio andported Matthew for by Grzych logistical the for and NASA valuable programmatic discussion. AviationProject. Safety This as- We Program’s thank work Atmospheric Airbus was Environment for sup- Safety providing Technologies their data to support this research. tion measurements to the degreea possible in uniquely comparison relevant with remote-sensing past data measurements set. and A simplified modeling framework served Acknowledgements. spheric Radiation Measurement (ARM) ProgramO sponsored by the U.S. Department of Energy, with decreasing elevation owing toduced aggregation IWC alone by also the exhibit melting roughlya level owing 30–50 steady-state % to column re- increasing under mass-weighted suchat fall speed. conditions, the Thus, IWC melting in is level. expecteddo In to appear summary, be the grossly higher highest consistent aloftobserved Airbus with than during IWC the the measurements highest 23 near January stratiform Darwin 2006 rain event rates over Darwin. and ice properties with large uncertainties. The objectiveby of which such Part properties 2 could is likely to be examine achieved microphysical under pathways relevant updraft conditions. event, but polarimetric retrievalslocally of within rain the rate stratiform aroundrates region. the can It profiler be is did attributed unknownpossible. report to Model whether such simulations ice such rates also aloft locally indicatein or enhanced that the some in rain vicinity a mesoscale of column the ascent,Finally, that melting steady-state which is level, 10 seems simulations precipitation % equally can with undersaturated be aggregation rapidly reduced su by evaporation. the maximum rain rate observed by disdrometer or retrieved at 2.5 km in the 23 January ice size distributions. However, gravitystratiform rain waves duration with appear periods present9 of km, in perhaps complicating vertical analysis one-half wind of speed of MDV retrievals the relationship available to up to tributions consistent with Airbusintended Robust to probe test and whether nephelometerder conditions measurements the of are properties heavy precipitationcolumn of appears is consistent a assumed with steady-state saturated the with measurements. stratiforming respect If level, rain to the respectively, ice column then and precipitation un- 4 water gm rate above is and below independent the of melt- height, and an IWC of the nephelometer data aspresent were shown not in measured Fig.4 bymake the apparent nephelometer that (limited the to largest particles pears relatively weakly correlated with The mass size distributions alsostability consistently of exhibited an shape, over unexpected large self-similarity, or changes in IWC. Calculations of less than 30 dBZ atbe roughly typical 1 Airbus ms sampling elevations of 11 km and MDV is found to surements, here we describeprofiling a radar comparison measurements of that the o measurements with ground-based than 2–3 mm), perhaps unrealistically enhancingover the the stability size of range mass seen. medianin On diameter previous the data other sets hand, and similar analyses. features have also been reported rain within an MCS observeduary with remote-sensing 2006, instruments where over large-scale Darwinwith on vertical reflectivity-weighted 23 motions Jan- ice are fall neglected speeds. to During first heavy order stratiform compared rain periods, ice morphological and size distributionserved: properties over the full atmospheric column ob- 5 5 25 15 10 20 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 16532 16531 , M. and Houze Jr., R. 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Keeler, J.,Kienast-Sjögren, and E., Spichtinger, Geophys., Lutz, P.,and J.: Gierens, The K.: Formulation BMRC/NCAR 42, and C- test of an RG4003, ice aggregation Knight, C.: The Cooperative-Convective-Precipitation-Experiment (CCOPE), 18 May–7 August Korolev, A., Strapp, J. W., Isaac, G. A.,Lawson, and R. Emery, P., Angus, E.: L. Improved J., airborne and Heymsfield, hot-wire A. mea- J.: CloudLawson, particle R. measurements in P., Jensen, thunder- E., Mitchell, D. L., Baker, B., Mo, Q., and Pilson, B.: Microphysical 5 5 20 10 15 25 30 10 15 20 25 30 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 16536 16535 intercomparison simulations using TWP-ICEGeophys. observations: Res., 2. 119, 13–919–13–945, Precipitation doi:10.1002/2013JD021371, microphysics, 2015. J. 16520 statistics, Ann. 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A., Ciesielski, P., Guy, N., Pierce, H., and Steiner, M., Houze Jr., R. A., andStith, Yuter, J. S. L., Haggerty, E.: J. A., Climatological Heymsfield, A., characterization and of Grainger, C. three- A.:Stith, Microphysical J. characteristics L., Avallone, L. M., Bansemer, A., Basarab, B., Dorsi, S. W., Fuchs, B., Lawson, R. P., Strapp, J. W., Chow, P.,Maltby, M., Bezer, A. D., Korolev, A., Stromberg, I., and Hallett, J.: Cloud Strapp, J. W., Lilie, L. E., Emery, E. E., and Miller, D.: Preliminary comparison of ice water con- Strapp, J. W., MacLeod, J., and Lilie, L.: Calibration of ice water content in a windToon, O. tunnel/engine B., Starr, D. O., Jensen, E. J., Newman, P.A., Platnick, S., Schoeberl, M. R., Wennberg, Twohy, C. H., Schanot, A. J., and Cooper, W. A.: Measurement of condensed waterVarble, content A., in Zipser, E. J., Fridlind, A. M., Zhu, P., Ackerman, A. S., Chaboureau, J.-P., Fan, J., 5 5 10 15 20 10 15 25 30 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 1 Hz 1 − ) as a function ) for ice particle e Z eq C, where liquid water ◦ 20 0 − 100 m) 800 μ ( eq max eq max eq 600 ) for ice particle properties following Eq. (1) max or MMD with a monomodal ice number size distribution that 16538 16537 max 3 − 400 MMD 200 Monodisperse MMD Monodisperse MMD Monodisperse Exponential MMD Exponential MMD 0

10 30 20

e (dBZ) Z Total condensed water content (CWC) measurements by the Robust probe during For an ice water content of 4 gm Figure 2. contributions are expected tomeasurements be corresponding negligible. Considering to a aexceed typical horizontal those air length averaged speed over scale 2.5 of of and 200 ms roughly 10 km 0.2 length km scales. (top row) slightly flight tests from CayenneMeasurements (left are column), Darwin included (middle only column), for and air Santiago temperatures (right were column). below Figure 1. is either monodisperse orof exponential in mass shape, median equivalent maximum radar reflectivity dimension ( (MMD (Baker and, Lawson )2006 andproperties mass median following area-equivalent Eq. diameter (2) (MMD (Locatelli and, Hobbs 1974). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (right 3 − 4 gm > (middle column), and 3 − 16539 16540 (left column), 2–4 gm 3 − Cayenne flight F1423 ice number size distribution (top row), mass size distribution Cayenne flight F1423 track over brightness temperature from Meteosat 9 channel 10 Figure 4. (middle row), and equivalentcontent radar (IWC) reflectivity ranges: size 1–2 gm distribution (bottom row) in three ice water Figure 3. at 12:45 UTC on 16 May 2010. column). Measurements fromduring the spirals analyzed within an time MCSbution. period (cf.3 Figs. 11:30–13:20 UTCand5). Red on line 16 indicates bin-wise May median 2010, size distri- Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ), e Z ) during Z V 13.0 13.0 13.0 13.0 13.0 -weighted fall speed ( e m m m m 1000 1000 1000 1000 μ μ μ μ Z m) ) listed for the highest concentration μ

( eq D eq Darwin F1405 MMD = 250 MMD = 260 MMD = 280 MMD = 240 Santiago F1546 Cayenne F1422 Cayenne F1423 100 100 100 100 ), and 12.5 12.5 12.5 12.5 12.5 (left panels) and normalized by IWC (right eq

3

0.04 0.02 0.00 0.08 0.06 0.04 0.02 0.00 0.08 0.06 0.04 0.02 0.00 0.08 0.06 0.04 0.02 0.00 0.08 0.06

eq eq eq eq (-) dM/dlogD (-) dM/dlogD (-) dM/dlogD (-) dM/dlogD − UTC (h) 16542 16541 1000 1000 1000 1000 m) μ

( eq D Darwin F1405 Santiago F1546 Cayenne F1422 Cayenne F1423 100 100 100 100 0 8 6 4 2 0 8 6 4 2 0 8 6 4 2 0 8 6 4 2

10 14 12 10 14 12 10 14 12 14 12 10

12.0 12.0 12.0 12.0 12.0

eq eq eq eq ) m (g dM/dlogD ) m (g dM/dlogD ) m (g dM/dlogD ) m (g dM/dlogD

-3 -3 -3 -3 Nephelometer Robust probe ). 3 − 11.5 11.5 11.5 11.5 11.5

0 8 6 4 2 0 0

30 20 10

IWC (g m (g IWC

) 2.0 1.5 1.0 0.5 0.0

-10 -55 -50 -45 -40 -35 -30

Static air temperature, ice water content (IWC), equivalent radar reflectivity (

-3 400 300 200 100

Ice mass size distributions in three ice water content (IWC) ranges (1–2, 2–4 and Z

) s (m V Reflectivity (dBZ) Reflectivity Temperature (C) Temperature eq

m) ( MMD shown in cyan, blue and red, respectively) based on bin-wise median measurements

μ -1 4 gm 3 − > 4 gm ice mass median area-equivalentCayenne flight diameter F1423. (MMD range ( > during four flights. Masspanels). Mass concentrations median in area-equivalent gm diameter (MMD Figure 6. Figure 5. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 16544 16543 ) and mean Doppler velocity curtain measured by e Z Equivalent radar reflectivity ( Cloud top temperature derived from MTSAT-1R at 12:00, 16:33 and 22:33 UTC on Figure 8. the S-band profiler onperiods 23 defined January as described 2006. in Dashed text. lines indicate duration of two stratiform rain Figure 7. 23 January 2006includes over the Darwin. Tiwi Islands Darkest in shade each image. is colder than 200 K, overlying a region that Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 40 ) -3 m 24.0 24.0 24.0 24.0 24.0 24.0 24.0 6 30 10.9 dBZ 2.5 km Surface 11.7 km 11.7 km 11.7 km 9.0 km 4.7 km 20 23.9 23.9 23.9 23.9 23.9 23.9 23.9 10 23.842-23.909 Reflectivity (mm 23.8 23.8 23.8 23.8 23.8 23.8 23.8 0

1 0 ), mean Doppler velocity (MDV; negative

-2 -3 -1

e

MDV (m s (m MDV

Z ) -1 23.7 23.7 23.7 23.7 23.7 23.7 23.7 Day of January (UTC) 40 16546 16545 ) -3 23.6 23.6 23.6 23.6 23.6 23.6 23.6 m 6 30 10.1 dBZ 20 23.5 23.5 23.5 23.5 23.5 23.5 23.5 10 23.512-23.588 0 8 6 4 2 0 0 8 6 4 2 0 8 6 4 2 0 8 6 4 2 0 5 23.4 23.4 23.4 23.4 23.4 23.4 23.4

-5 -2

50 40 30 20 10 10 10 30 20 10 10 10 10

-10 -10 -15

Rate (mm h (mm Rate h (mm Rate Width (m s (m Width s (m Wind ) ) (dBZ) Reflectivity ) )

) s (m MDV Reflectivity (dBZ) Reflectivity Reflectivity (mm

-1 -1 -1 -1

-1

Precipitation Precipitation Spectral Vertical 0

1 0

-1 -2 -3

MDV (m s (m MDV ) Mean Doppler velocity vs. equivalent radar reflectivity measured by S-band profiler

Time series of observations and retrievals from colocated S-band, UHF, and VHF just below the melting level at 4.7 km; retrieved precipitation rate at 2.5 km; and pre- -1 e Z Figure 10. during two stratiform periods showneach in sample;8 Figs. meanand 9. reflectivity Dashed reported lines in indicate dBZ mean units values within at lower left. downward), and Doppler velocity9 km; spectral width at 11.7 km; retrieved vertical wind speed at Figure 9. cipitation rate measured at thein surface. Fig.8. Vertical dashed lines indicate stratiform rain periods as profilers on 23 January 2006: radar reflectivity ( Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 5 5 4 4 ) ) -3 -3 3 3 2 2 CWC (g m CWC (g m 1 1 0 0

5 0 5 0

15 10 15 10

20 20 ) ) -1 -1 15 15 10 10 5 5 Precipitation Rate (mm h Precipitation Rate (mm h 0 0

5 0 5 0

15 10 15 10

) ) 12 12 -1 -1 16548 16547 10 10 8 8 6 6 4 4 Ei=0.005 Ei=0.01 Ei=0.005 sat. Ei=0.01 sat. Ei=0.01 Ei=0.02 Ei=0.01 sat. Ei=0.02 sat. 2 2 Mean Doppler Velocity (m s Mean Doppler Velocity (m s 0 0

0 5 0 5

15 10 15 10

50 50 40 40 30 30 20 20 10 10 Reflectivity (dBZ) Reflectivity (dBZ) 23.512-23.588 23.842-23.909 23.512-23.588 23.842-23.909 0 0 Same as Fig. 11 except that the initial ice size distribution is scaled by a factor of Profiles of reflectivity, mean Doppler velocity (positive downward), precipitation rate ciencies of 0.01 or 0.005, and the baseline sounding or a saturated sounding (see -10

-10 0 5 0 5

10 15

10 15

Altitude (km) Altitude ffi (km) Altitude Figure 12. 0.5. (liquid equivalent), and condensed watertrieved content from (CWC) S-band, observed UHF, and by VHF theand radars S-band red) during profiler are the or stratiform compared periods re- withmeasured identified steady-state in during column Fig.8 model Airbus(pink results test initializedsticking flights with e at size distributions 11–11.5 km over Darwin (blue). Simulations use ice-ice Figure 11. text). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C-POL 23.8958 C-POL 23.7639

1 = drizzle 2 = rain 3 = low-density snow 4 = high-density snow 5 = melting snow 6 = dry graupel 7 = wet graupel 8 = small hail 9 = large hail 10 = rain-hail mix 1 = drizzle 2 = rain 3 = low-density snow 4 = high-density snow 5 = melting snow 6 = dry graupel 7 = wet graupel 8 = small hail 9 = large hail 10 = rain-hail mix

at 11 km altitude, and column 9 8 7 6 5 4 3 2 1 0 8 6 4 2 0 8 6 4 2 0 9 8 7 6 5 4 3 2 1 0 e

Z ) ) 300 300 300 300 -1 -1

250 250 250 250

200 200 200 200

150 150 150 150 X (km) X (km) X (km) X (km)

100 100 100 100

50 50 50 50 2.5-km Rain Rate (mm h 2.5-km Rain Rate 16550 16549 2.5-km Rain Rate (mm h

0 0 0 0

0 0 0 0

50 50 50 50

300 250 200 150 100 300 250 200 150 100

300 250 200 150 100 300 250 200 150 100

Column Maximum Hydrometeor Class Column Maximum Hydrometeor

Column Maximum Hydrometeor Class Y (km) Y (km) Y Y (km) Y Y (km) Y

54 48 42 36 30 24 18 12 6 0 54 48 42 36 30 24 18 12 6 0 54 48 42 36 30 24 18 12 6 0 54 48 42 36 30 24 18 12 6 0

300 300 300 300

and rain rate at 2.5 km altitude,

250 250 250 250 e Z

200 200 200 200

150 150 150 150 X (km) X (km) X (km) X (km)

100 100 100 100

50 50 50 50 2.5-km Reflectivity (dBZ) 2.5-km Reflectivity 2.5-km Reflectivity (dBZ) 11.0-km Reflectivity (dBZ) 11.0-km Reflectivity (dBZ)

0 0 0 0

0 0 0 0

50 50

Cross-sections from C-POL radar fields when the S-band experienced stratiform 50 50

Same as Fig. 13 except when the S-band experienced convective rain at 23.7639.

150 100 300 250 200 150 100 300 250 200

250 200 150 100 300 250 200 150 100 300

Y (km) Y Y (km) Y Y (km) Y (km) Y field, where they enclose areas greater than 30 dBZ (only present in Fig. 14). e maximum hydrometeor class (seean legend). asterisk. The Areas location outlined ofZ in the black S-band are profiler identified is as marked convective with (see text) except in the 11 km Figure 14. Figure 13. rain at 23.8958 (cf. Fig.8):