Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ´ ere , and , , 12 11 10 Chemistry and Physics Discussions Atmospheric , X. Yang , 8 4 ´ etude de l’Atmosph , N. R. P. Harris , T. Reddmann 3 9 , O. Wild 14 , C. Chemel 6 , W. Feng 12 , J. A. Pyle 1 , S. Viciani 3 , J. Arteta 9 ´ 20356 20355 eorologiques/Groupe d ´ et , T. Peter 5,** , W. Tian , O. Dessens 11 13 , M. R. Russo 7 ´ ecal , F. D’Amato , P. J. Telford ´ 3 eo-France and CNRS, Toulouse, France 3 ´ , O. Morgenstern et , V. Mar 12,* ´ eans, France 1,2 5 ´ eans, Orl ´ eorologique, M ´ et Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology, European Ozone Research Coordinating Unit,Centre University for Atmospheric of Science, University Cambridge ofCNR-INO Cambridge, (Istituto Cambridge, Nazionale Department UK di Ottica) of Largo E. Fermi, 6 50125 Firenze, Italy now at: the National Institute of Water and Atmospheric Research, Lauder, New Zealand and Physics (ACP). Please refer to the corresponding final paper in ACP if available. This discussion paper is/has been under review for the journal Atmospheric Chemistry Lancaster Environment Centre, Lancaster University, UK NCAS climate, Centre for Atmospheric Science, Department of Chemistry, Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, CNRS and University Centre National de Recherches M Institute for Atmospheric and ClimateDepartment Science, of ETH Geosciences, Zurich, University Zurich, of Switzerland Institute Oslo, for Norway Climate and Atmospheric Science, School of EarthNCAS-Weather, and Centre Environment, for Atmospheric & Instrumentation Research, NCAS-Chemistry Climate, Department of Chemistry, Cambridge University, UK now at: British Antarctic Survey, Cambridge, UK 8 9 University of Cambridge, UK 10 Karlsruhe, Germany 11 Chemistry, Lensfield Road, Cambridge12 CB2 1EW, UK 13 ∗ ∗∗ Received: 5 July 2010 – Accepted: 24Correspondence August to: 2010 C. – R. Published: Hoyle 27 ([email protected]) August 2010 Published by Copernicus Publications on behalf of the European Geosciences Union. 7 of Orl M 6 N. A. D. Richards Tropical deep convection and itson impact composition in global andmodels mesoscale – Part 2: Tracer transport C. R. Hoyle Atmos. Chem. Phys. Discuss., 10,www.atmos-chem-phys-discuss.net/10/20355/2010/ 20355–20404, 2010 doi:10.5194/acpd-10-20355-2010 © Author(s) 2010. CC Attribution 3.0 License. M. P. Chipperfield J. S. Hosking G. Zeng 1 2 3 University of Leeds, UK 4 University of Herfordshire,5 UK Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ; , , , 2000 2009 , , Laube et al. ; 2007 , Sturges et al. Sinnhuber and Folkins Fueglistaler et al. erences are less pronounced . Their fate, once in the UT/LS, ff X Feng et al. ; 2006 , ). In addition, fast transport is important erent models, and the upper tropospheric ). Recently the issue has received greater erent models or model versions were com- ff ff 2010 20358 20357 , 2007 , ) and, by implication, NO Liang et al. ects of modelled transport could be isolated. We find large ; ff 2008 , Sinnhuber and Folkins er by up to an order of magnitude. The timing of convective ff ; 2010 , er between the models, even among those which source their forc- ff Law and Sturges 2005 , Park et al. ( 2 H 2 Hossaini et al. ). ; erences in the vertical transport of very short lived tracers (with a lifetime of 6 hours) In considering just the short-lived halocarbons such as bromoform and dibro- In the tropics there is a gradual transition from tropospheric to stratospheric be- ff upward transport to the upper tropospherethe or main lower meteorological stratosphere phenomena (UT/LS). in Inand the which larger tropics this areas occurs of are individual convection.UT/LS thunderstorms The in quantity the of tropicsmodelling short-lived is studies species not which ( known reachesattention the with as great the confidence potential fromand role either in observational of stratospheric or ozone verySalawitch depletion short-lived et has halocarbons al. been in recognised the (e.g. bromine budget The time scales for atmosphericical, transport interlinked and photochemical factors production/losssphere. in are Short-lived crit- determining chemical species the emittedlower at distribution troposphere the of Earth’s unless surface trace they are removed encounter species in meteorological the in conditions the that atmo- result in fast level where this takes place depends on the local temperature profile, the water vapour 1 Introduction momethane, which arebromine in likely the stratospheric to bromine budget, providein one needs these some, to know gases the if amount which2006 of is not bromine lofted all to of a region the of reported upwardhaviour ”missing” motion known ( as theand tropical references therein). tropopause layerheating, Net (TTL) which upward (e.g. motion is occurs where above radiative the heating level becomes of positive zero and radiative air rises. The exact in determining the atmospherichydrocarbons distributions and of their other breakdown products) natural,as as short-lived CO, well C species as (e.g. anthropogenic pollutantsis such determined to a large extent by the altitude to which they are lofted. 2008 parameterisations, and boundary layerlocation mixing of rapid parameterisations transport of intois the the mostly upper models. concentrated troposphere over is The the similarOcean. western among Pacific, the In the models, Maritime contrast, and Continent nonetransport and of over the the western Indian models Africa.in indicates the The significant mean upper enhancement in mixing tropicalratios upward ratios troposphere in of are the an found regions idealisedrectly to with modelling CO the be both like most the sensitive location tracer active to ofemission convection, convective the transport patterns. revealing and surface the the CO importance geographical pollutant mixing of cor- ing data from thefor same longer NWP lived model tracers, (ECMWF).halogen however The they burden di could of have the implicationsor lowermost for for the the stratosphere modelling transport throughmodelled of of species tracer the short profiles such are lived as found hydrocarbons to bromoform, into be strongly the influenced lowermost by stratosphere. the convective transport The (NWP), chemistry transport,used and in climate order chemistry tosubstantially, so prevent models. that the the model’s Idealised e chemistrydi tracers schemes were from influencingwithin the the results tropical troposphere.300 hPa Peak to convective almost outflowtracer altitudes 100 hPa mixing range among from ratios the around di events di is found to di The tropical transport processespared, of within 14 the di frameworkphasis of on the the SCOUT-O3 Upper (Stratospheric-Climate Troposphere andrange Links Lower from with Stratosphere) the project. Em- regional The tested to models the global scale, and include numerical weather prediction Abstract 5 5 10 25 15 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . ; , ) 3 2002 2004 ) used , , ). 2009a Folkins et al. ( 2009 ) evaluated the , ine models). All ). The results are Deng et al. ffl ; 4.4 2009b ( 2007 Sherwood and Dessler , Arteta et al. Hartmann and Larson , focusing on their concentration ort to assess the performance of 4 Fueglistaler et al. ff ; ered in one main aspect (see Sec- Arteta et al. Rind et al. ff ; 2010), we present a comparison of the 2007 , and found that the models which pro- 3 , 2006 , ). As a result, only a fraction of the air lofted 20360 20359 erence in transport to that aspect of the model and O ff 3 2000 , erences in the tracer profiles the models produce. erent models and parameterisations. ff ff ) (hereafter R Ricaud et al. ; erences but do not in themselves indicate which model’s 1999 ff O, HNO , 2 2010 , Wild and Prather 2004 ), the strength and spatial distribution of tropical convection , 4.1 Russo , as are the lessons from this first comparison of model descriptions 5 ). A typical value is 15 km (ca. 120 hPa) ( Folkins et al. of this paper, the models which took part and their set-ups for the com- 2005 Kupper et al. er among the models, as does the method used to calculate the vertical , 2 ff ) compared two convective parameterisations in a one-dimensional framework ), allowing the attribution of the di ), which is above the level of maximum convective outflow (about 12–13 km, or 2 ), and a comparison of the idealised CO with measurements ( -line chemical transport model (CTM) simulations, 4 global general circulation mod- ect of resolution on the simulated tracer distributions, showing that the higher reso- In Sect. Thus far, however, there has been no concerted e In the first paper ( A number of studies have investigated the mass transported and altitude reached ff ff 4.2 2006 A total of 14 models,o or model versions, participated in this inter-comparison: 7 global The results of the comparisons are described in Sect. ( discussed in Sect. 2 Models transport scheme is better. To shedalised light CO) on is the used latterin issue, and a the compared semi-realistic troposphere to tracer is measurements. (ide- at Since the ground, the it primary is sourceparison a of are good CO described. tracer of The upward idealised vertical tracers and transport. their rational are explained in Sect. of tracer transport in strongly convective regions. models’ meteorological parameters with satellite-basedpaper measurements. we In compare this the second resultslack of of model an tracer observational transport.emissions quantity This and which in task can chemical is degradation be hampered schemesancies by considered limit can the as the be degree “truth”: ascribed to toson which uncertainties any the is in discrep- based transport on schemes. idealisedThese Therefore, tracers reveal the which model-model core are di of prescribed our in compari- the same way for all models. profiles in the Tropics ( The resolutions, boundary layer mixing schemes and convective transport parameter- winds, even when thethese same factors meteorological contribute data toSome is the of used the di (for model thetion versions o which participated di have shown that increases inmodel horizontal in and predicting vertical tracer transport resolution by improve convection. the skill ofshort-lived the tracer transport schemes acrossIn a this range pair of of globalparticipated papers and in we mesoscale the attempt models. SCOUT-O3 project. topled These do chemistry-climate include exactly chemical models that, transport or using models, global a cou- circulation number of models models and which a mesoscale model. isations di configuration. lution versions of their modelaltitudes. produce Various more studies convective ( transport which reaches higher an online regional model, CATT-BRAMS, totransport investigate to the the sensitivity of convectivee tropical parameterisation, tracer and by convective transport, using di 2000 duce a more clearly defined265–165 hPa) convective outflow altitude layer matched in the the region measurements of best. 10–13 km (or ca. mixing ratio and whether orCorti not et clouds al. are present (e.g. 195–165 hPa) ( the distribution of convective outflow.or This modelling is studies, not wellmatter and known (e.g. there from either has observational recently been considerable controversy on this ( as well as twowith further climatologies parameterisations of in CO, the H GEOS-3 and GEOS-4 global models, up in convective flowmuch reaches of this this lofted higher air level, eventually and reaches so the stratosphere any have studies to considering consider how the tail in 5 5 25 15 10 20 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 2010 ce UM ( ffi Louis the model Feng et al. ). ce Unified Model (UM) version longitude, with 19 vertical layers ffi ◦ ), and the boundary layer is mixed 1979 ( 3.75 1990 × ( erence between cloud and environmental ff Louis levels from the surface to 10 hPa. This run 20362 20361 Louis except that the boundary layer mixing p - latitude -height coordinates. Not using the hydrostatic σ ) was used. Further investigation of the impact of ◦ σ ). The scheme does include cumulus up-drafts in 1993 ( 1999 , . The CTM, and nudged CCM model simulations were run 1 with 31 hybrid Gregory and Rowntree ◦ ). This model is non-hydrostatic and vertical velocity is calculated ). The model is forced using 6-hourly ECMWF analyses for vortic- ). Meteorological data from ECMWF operational analyses is used to 2.8 × ◦ 2005 2006 ), except mid-level convection and convective down-drafts are not in- , , 1979 R2 is based on TOMCAT ( Holtslag and Boville ). Advection is calculated using the two-step flux-corrected scheme described 1989 ◦ ( 5.6 × ◦ Zalesak erent treatments of convection with the TOMCAT CTM is given in TOMCAT The convection scheme implemented in TOMCAT is identical to that described by Two TOMCAT runs were performed. For the simulation TOMCAT ff Davies et al. Stockwell and Chipperfield Chipperfield approximation allows runs at very high resolution. To increase stability the model uses using a MOSES-1scheme Non-local version K 1). scheme Seafrom with surface the entrainment temperatures BADC and dataset (UKMO sea for surface 2005. ice exchange distribution are2.4 prescribed UKCA CCM UKCA is an Eulerian GCM( based on the “new dynamics”as version a of the diagnostic Met variable O on hybrid UMCAM is an4.5. Eulerian CCM The based horizontalbetween resolution on the is the surface 2.5 and Metmass 4.6 O hPa. flux scheme Convection of is parameterised using the penetrative used the boundary layer mixing scheme of 2.3 UMCAM CCM scheme of di drive the model, and thewinds. vertical There wind is no is convective derived transport, from and the no divergence boundary of layer the mixing horizontal scheme. cluded and there is( no organised entrainment of environmental air above cloud base KASIMA is aThe global transport CTM, is calculated5.6 with on a a lower sphericalby grid boundary with at a a T21 resolution pressure (approximately altitude of 4 km. was run at 2.8 2.2 KASIMA CTM the vertical column entrainment ofcloud environmental air air to into the thevergence cloud environment. of and moisture The detrainment below cloud of magnitudes andspecific of the humidity these di at are cloud base. relatedby Mass to including balance horizontal sub-grid within con- the subsidencethe vertical of same column environmental time is step. air maintained (induced by convection) within ity, divergence, humidity and temperature.the The large-scale vorticity horizontal and windsdivergence. divergence and fields Sub-grid vertical provide scale winds transportfrom are is the diagnosed parameterised large-scale from analyses. in the the analysed model using information Tiedtke this time period. The2005, NWP and CATT-BRAMS model was run WRF forThe was the models run Maritime are for Continent described February, area below. August for and November 2005. November 2.1 TOMCAT CTM TOMCAT is a 3-dimensional( CTM with a variable horizontal and vertical resolution prediction (NWP) models. An1 initial (R1), series and of based modellingof on experiments experiments were the was run, results carried Round of outruns Round these, is 2(R2). the provided A tracers in summary werefor Table of refined the the and configuration year a of 2005, these second the set un-nudged CCMs used boundary conditions representative of els, or coupled chemistry-climate models (GCMs, CCMs) and 3 numerical weather 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 | ) ). ), ◦ ◦ 3.8 2.8 × 1990 × ◦ ( ◦ Gregory and Gregory and ). For deep con- erence between ff 1999 ( ). erence in upward mass ) and semi-implicit time ff 1995 1993 , ). The boundary layer param- Gregory and Rowntree , 1980 ( Priestley Grant and Brown Parker et al. nud) was run at N48 resolution with 38 levels ). It also includes an explicit parameterisation 20364 20363 ), and parameterised entrainment and detrainment 2000 ( 2001 ( Fritsch and Chappell Grant Lock et al. ). coordinates) for these experiments. The mass centre of the upper longitude but the model has 64 vertical levels between the surface ◦ p ). There is no mixing of tracers in the boundary layer. - 1990 ( σ highres is a higher resolution run of the free-running UKCA model (N216, 3.75 ) with 38 levels from 0 to 39 km. The model is initialised using UKMO ), and convection with the penetrative mass flux scheme ( × ◦ 1990 , 0.56 2002 × , ◦ latitude ◦ As well as providing large-scale winds, the IFS forecasts provide archived convective Three UKCA runs were performed. Run UMUKCA-UCAM (R1) isThe nudged a model free (UMUKCA-UCAM running UM-UCAM The convective parameterisation scheme is based on the fluxes through thewithout top any and entrainment bottom or of detrainmentis of the determined tracers. by box, the The the lowest maximum level up-draftflux where height simply is either of precipitation passes zero. convection flux through is Fullmixing zero, or mixing in upward of mass the entrainedHoltslag boundary air et into al. layer the is up-draft treated core according is assumed. to the Turbulent Holtslag K-profile scheme of T319L40, which is truncated to T42 for themass simulations in fluxes. this The study. convective transportsystem”. of tracers Starting is from then the parameterisedflux as bottom between an the of “elevator top a andor model bottom column, detrainment of the to a di or model from grid the box determines grid whether box entrainment takes place. If there is no di model layer is at 10 hPa.The The horizontal model resolution used uses here iswith winds T42 the (approx from 2.8 vertical theThe wind ECMWF meteorological being Integrated input calculated Forecast datain System from were a generated (IFS) the series by divergence model, of runningEach of the forecast forecasts, the was IFS started horizontal run model fromforecasts for at fields. results the in 36 ECMWF a analysed h, continuous fields recordforecasts allowing were of every for run input 24 12 with data. h h the Data cycle of (at are 29 spin-up. sampled 12:00 version UTC). every of 3 the Linking h. IFS together The model, with all a the spectral resolution 2.6 Oslo CTM2 The Oslo CTM2 is2 hPa a (hybrid global CTM, run on 40 vertical levels between the surface and Rowntree vection, the thermodynamic closure isclosure based approach) on based the on reduction of CAPE to zero (CAPE eterisation is based on of entrainment at the boundary-layer top. version of the UKCAand at 38 the levels usual from climate 0 to horizontal 39 resolution km. of N48 (ca. 2.5 rates for shallow convection are obtained from from 0 toevery 39 km. 6 h. This Thetemperature data nudged and is horizontal model interpolated winds onto usesNewtonian are the relaxation. ECMWF constrained model operational to time-steps this and analyses levels. data available using The the model technique of 0.83 assimilated initial conditions andice is derived constrained from by the sea GISST surface 2.0 temperatures climatology and ( sea stepping. and both shallow andconvection deep is based convection on are included. Cloud base closure for shallow and 0.01 hPa. AdvectionWest is calculated with the Quintic-Mono scheme ( a two time-level, semi-Lagrangian advection ( 2.5 UMSLIMCAT CCM UMSLIMCAT is aatmosphere coupled chemistry-climate version of model2.5 based UM on version the 4.5. extended middle Like UMCAM the horizontal resolution is 5 5 15 20 10 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ). ◦ ). The Arteta 2002 ( ). The simulation uses ects of convective and ), and is therefore very ◦ ff ), as described in 1993 x 0.5 ( ◦ 2002 ( ) to specify the fraction of satu- ´ enyi Wicker and Skamarock 1996 ´ ev ( -line models of diagnosing convection ff 60 km ( 0.5 × 20366 20365 latitude) and the time step is 600 s. The model ◦ Grell and D Holtslag and Boville ), which employs a prognostic turbulent kinetic en- ). The entrainment rate is set to be half the value Rossow et al. levels from the surface to 10 hPa. This run used the 1982 2010 ( p , coordinates). The mass centre of the upper model layer ). This means there will be less stable ambient air en- − p σ - sets the problem in o σ ff 1989 R2. ( longitude by 1.25 ◦ ). The non-resolved convective transport of tracers is parameterised Barret et al. Tiedtke 2000 ). This scheme uses a multi-closure and multi-parameter ensemble ap- , and 31 hybrid ◦ Mellor and Yamada 2.8 1994 2009a × , ( ◦ In pTOMCAT-tropical, the original implementation of the convective scheme used Janjic shallow clouds were parameterised( by the Betts-Miller-Janjic (BMJ) cumulus scheme a terrain-following hydrostatic-pressure vertical coordinateolution system. is The N96 horizontal (1.875 res- uses the advective transport scheme describedinitial by state at theECMWF surface analyses at and a throughout spectralThe the resolution WRF of model model T511 physics atmosphere (horizontal does not resolution isThese predict of fields derived sea about are ice, from 0.5 updated SST, vegetation in the fraction,soil time and temperature every albedo. 6 is h updated during every the 6 model h simulation. as The well. deep Sub-grid layer scale e The model is nudged at theSea lateral surface and temperatures top are boundaries from with satellite-derived ECMWF 6-hourly weekly analyses. analyses. 2.10 WRF NWP WRF version 3.1.1 is a NWP model, run on 38 layers from the surface to 5 hPa using eterised following the formulationet of al. proach with typically 144 sub-gridprofiles members. and/or An down-draft ensemble parameters ofof entrainment/detrainment is tracers. used Turbulent to mixing inscheme determine of the the boundary vertical layer redistribution isergy. The treated horizontal according resolution to used39 the is vertical level 60 km 2.5 levels from surface to 40 km. Initial conditions are from ECMWF analyses. 2.9 CATT-BRAMS Regional Model isCATT-BRAMS a regional tracer and aerosol transportmeteorological data model, within which calculates the its model own domain. Deep and shallow convection are param- each layer’s newly formed condensed liquid water. forced using the sameof ECMWF 2.8 analysis files.boundary pTOMCAT layer has mixing a scheme horizontal of resolution of CTM2, except that thelayers. Convection lowest is parameterised 5 with layers anmass elevator of approach fluxes based the up on through net 40-layer convective thedefined output atmospheric entrainment/detrainment are column, fluxes where with combined these additional into are treatment two non-zero. of explicitly 2.8 pTOMCAT CTM pTOMCAT is a global CTMizontal originally and derived from vertical TOMCAT. It coordinates, still the uses same the same advection hor- and convection schemes and is FRSGC/UCI is a globalThe model CTM was with run at asurface T42 to similar resolution 2 configuration for hPa these (hybrid tois studies, that with at 37 of 10 vertical hPa. the layers from Oslo The the CTM2. meteorological forcing data is the same as that used by the Oslo 2.7 FRSGC/UCI CTM similar to run TOMCAT in p-TOMCAT has beenper updated troposphere to ( increase convective transport to the mid and up- trained into thealtitudes. cloud This and change thus o with positive analyses buoyancy that in have theusing already ISCCP cloud been satellite is convectively cloud retained adjusted. data to Other higher changes include layer rather than infor each tracers layer from between the cloud boundary top layer. The and deep bottom convective to precipitation is allow set a to maximum be lift from suggested by rated water vapour in each surface model grid and putting detrainment at the cloud top 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 | . , . , ), 1 3 3 (1) − − s is the 1 2003 − er. For τ ff , Sukoriansky molec cm molec Deeter et al. 3 6 10 × Sander et al. erent resolutions, and )( ff atm is the time step and P t 6 . has units of cm 0 . Being so short-lived, the T6h k + 1 (1 erent models. ∗ , where ff 1 13 − ), however it should be noted again that erences in the timing of rapid transport ff 10 × 2008 5 . , 20368 20367 1 = k erences in short-lived halogen species reaching the ff , as in CATT BRAMS). The mass flux is calculated us- Wang et al. 2002 , ´ enyi ´ ev is pressure (in atmospheres), and . The definition of the tracers, and the information that they provided is t/τ 2 atm − e ). 0 ) between the surface and 700 hPa. Everywhere else in the atmosphere the The lifetime of this tracer was 6 h. It was initialised at the beginning of the This tracer had a lifetime of 20 days. The initial concentration was 1 pptv at The idealised CO tracer was initialised from MOPITT data ( C Grell and D = 2005 the objective was tosome similarly create to a CO highly indation the of simplified atmosphere. hydrocarbons tracer are Secondary also which sourcesconcentration ignored, does of would and not CO the behave from take use with into the ofradiation account oxi- a (OH single latitudinal concentrations value or are for seasonal muchare the changes higher OH higher in during in solar the the daypressure-dependent, tropics than given than the by night, at and midwhere and P polar latitudes).The The CO reaction tracer rate was allowsisons a with measured qualitative CO validation distributions. of modelled transport via compar- tracer could beevents used between to the surface investigate andT6h di the tracer upper was troposphere, also such suitable asshort for convection. comparisons lifetime The with reduced the the limitedAdditionally, influence T6h area of required models, shorter transport as spin-up the from timesregional outside for models. the the computationally model expensive domain. CO 2007 initial mixing ratio wasprescribed, zero. constant Loss mean OH of field theThis with tracer value a is occurred concentration up only of to 0.5 OH via a concentration reaction factor (e.g. with of two a lower than recent estimates of the global mean C tracer lifetime. This tracer,can having be a used to lifetime assess similarTTL the to di and that lowermost stratosphere of between bromoform di CHBr model run with a zero mixingthe ratio surface everywhere and in 500 the atmosphere, m,loss except where between process the mass was mixing decay ratio according was to set to equation 1 ppbm. The only T20 the surface, and zero elsewhere.tration was Throughout held the constant, model in runthe the tracer the was rest surface decay of concen- according the to equation atmosphere the only loss process for T6h , – – – as well as witheven observational when data. the spacing The of models the grid have points rather is di similar, the actual positions often di 4 Results In this section, the fields of the modelled tracers are compared between the models as follows: et al. column ( ing precipitation rates anddowndraft cloud parameters properties. are used The toers determine entrainment/detrainment the are profile vertical not and redistribution chemically ofing tracers. active. the Trac- quasinormal The scale surface elimination and (QNSE) boundary parameterisation scheme layers ( are represented us- using an elevator approach based on the convective mass flux through the atmospheric 3 Methodology 3.1 Tracers The idealised tracers whichlisted were in Table used in the R1 and R2 modelling experiments are 5 5 25 15 20 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ff er in the ff 10.5 km) for ∼ erent types of ff , averaged over 1 tropical, and 190– 12.5 km) and those ∼ 2010: with the exception , the monthly mean model 4.2 erent regions, the changes in 190 hPa ( ff ∼ erences in the model’s convective ff 9 km). These two model categories ∼ 20370 20369 erences in the height of the convective outflow ff 300 hPa ( erences in the strength of the convection and the erences in the vertical extent of the convection or ∼ ff ff S, we can distinguish between two sets of models, erences between models vertical profiles of T6h are ◦ ff , the data from each model has therefore been linearly 24 h. Because of its extremely short lifetime this tracer can 180–200 hPa for most models and 250 hPa ( N–20 ∼ 14 km) for CATT-BRAMS and pTOMCAT ∼ ◦ 4.1 ∼ erent geographical locations compared to the tropical mean. erences between models are not always directly attributable to ff ff 2010 will help to attribute di 150 hPa ( ∼ 2010 for further discussion on the choice of the regions and the respective 2010, we performed a detailed comparison of modelled and observed cloud top ected by convective transport. To analyse the convective transport in the di We first analyse the height of the mean convective outflow and how it varies between 4 h and goes to zero after ff of the WA region, these two models show a consistently smaller percentage of clouds with a lower convectiveare outflow also clearly at markedspectively. for For SA, the with MC outflow regionsplit heights between the at outflow 190–200 heights hPa of200 and hPa the for 300 first hPa most re- set other ofaround models, 300 models while hPa. TOMCAT are and For further the pTOMCAT outfloware WA heights smaller, region, remain with di values of TOMCAT and The pTOMCAT. lower outflow heightsCAT displayed can by be TOMCAT and explained pTOM- by the cloud top height analysis in R transport. models and between di For the tropical region,those 20 with a mean convective outflow at a height of entrainment-detrainment rates in the convective plume,tracer can have distribution a than larger the impact on verticalsome the extent models or use frequency convective of schemesvection the while which convection. others release For distribute the example the tracerone tracer at should throughout the keep the top in convectivenot of mind column. always the that Therefore directly con- di attributable tothe di number of convective events.vective properties For in this R reason, the meteorological analysis of con- vertical transport of tracers.tive In outflow particular and we the focus tracer’s on peak the concentrations height at of the the outflow mean relative convec- to the surface the height of thein tracer’s the main vertical convective extenttion outflow of at should the the convection, be outflow while determined shouldthat the height. follow by changes changes However, changes di in in tracer’s thesuch peak number changes. concentra- of In convective fact, events the way reaching models parameterise venting of the boundary layer, and months). The monthly mean verticalSA profiles in of T6h February, are WA shownparison in in the August Fig. annual and mean MCthat tracer only in profile a November. subset averaged of over AdditionallyIn the the we R models whole show have archived tropical for theheight region com- necessary distributions (note information to for investigate this di plot). ability of convective parameterisations toof reproduce clouds. the Here observed we vertical investigate distributions how the same convective parameterisations di concentration. If one compares the same model in di models using T6h (andnamely T20 South in America, the West next Africaas section), and SA, the we WA Maritime and focus Continent MC), on (hereafter whichland 3 abbreviated have and geographical been island chosen regions, deep to convection. provideanalysed examples for The of one convective di transport month in chosen(see each so R of that these the region regions exhibits is a strong convective activity therefore some models are not included in each of4.1 the plots shown Tropical below. concentration profiles We start our analysis with∼ the T6h tracer; this tracer’sonly mixing experience ratio fast decreases transport by processes halfa and in its vertical profile will be therefore mainly data was linearly interpolated toidentical the pressure same grid levels. as the Several Oslo CTM2, of in the order to models compare did not run all of the experiments, interpolated in the necessarymore spatial finely resolved and grid temporal thanminima the dimensions. best was model By avoided. resolution, interpolating the For smoothing global to out plots, a of such peaks or as in Sect. the comparisons in Sect. 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 | nud nud, and nud for WA erent models highres. The ff 13–12 km), with ∼ 13 km. highres. The span of tropical and UMUKCA- ∼ highres have fairly similar 2010); the tracer’s convective 2010 shows that the cloud top erent domains, which show mix- ff nud and the relatively lower convec- ) produces cloud top heights which 1 tropical have the highest outflow heights 20372 20371 highres. In this case, the inconsistency between nud are similar in all regions except WA, where nud and UM-UCAM erent regions shows that for the Tropics, the tracer erent geographical locations compared to the trop- ff ff cient in these three regions at the selected times compared ffi ) starts decreasing with height above ◦ erent models shows that the short-lived tracer transport de- ff 2.5 × being WRF, CATT-BRAMS and UM-UCAM ◦ 1 14 km for the MC region), and although the cloud top height analysis in ∼ nud). The generally larger mixing ratios for these regions suggests that for most nud have smaller mixing ratios at the convective outflow than they have for the highres and UMUKCA-UCAM tropical, shown as the dashed line in Fig. 2010 does not point to them as having the highest percentage of high clouds, this While convection lifts the T6h tracer typically only to it’s convective outflow height, We now analyse the tracer mixing ratio at the convective outflow and how it varies Indeed, modifying the convective parameterisation scheme in pTOMCAT (pTOM- In general, the relative heights of the convective outflow for the di Most of the models are either forced or nudged by the ECMWF winds (the only ex- ing ratios in the range(note 1.4–5%, that 0.5–3.5%, for and WA we 1–7% haveUCAM for ignored SA, the WA, anomalously and low MCmodels value respectively under associated investigation, to convective UMUKCA- transport fromflow the height surface to level is the convective more out- e to the annual average convective transportis in West the Africa: whole for tropicalUCAM this region. region One TOMCAT, pTOMCAT, pTOMCAT exception Tropics. ties (such as surface albedothe and outflow soil height moisture). betweenmixing Comparing the the di ratios tracer at mixing the ratiosmixing at convective ratio outflow imposed at heightmixing the vary ratios surface. at within These the the convective values outflow range are for 0.9–2.5% generally the three smaller of di compared the to have the lowest. TheUCAM other models arethe generally high in resolution between. versionpeak of The in the profiles tracer model concentrations from produces than UM- a the both nudged much a model. larger, more Over and SA, pronouncedvery a the mid-tropospheric low nudged higher monthly-mean model minimum altitude has tracer thanresults mixing from UM-UCAM ratio an produced anomalously low byto number UMUKCA-UCAM of other convective events regions; for this this region is compared thought to be due to poor representation of surface proper- model gridbox (3.7 between models and betweenical di mean.ratios Generally at FRSGC/UCI, the Oslo level of CTM2 convective and outflow, while WRF TOMCAT have and/or UMUKCA-UCAM the largest mixing tive outflow height can be attributed to the fact that the cloud fraction within the large do not change significantlyand with pTOMCAT geographical which location, have with significantlyother the higher regions. exception outflow of heights CATT-BRAMS and TOMCAT for pTOMCAT WA compared to all pends more on the detailsor of the the model convective resolution. parameterisation than on the forcing data, CAT outflow for this modified versionresolution is CATT-BRAMS model, also significantly which higher, uses and itsforcing. very own similar dynamics to as the opposed high to ECMWF R apparent discrepancy can be explained bytive the detrainment fact at that the both top these of modelsOslo the have convec- cloud CTM2, rather than throughout WRF, the UMUKCA-UCAM column. FRSGC/UCI, that the vertical extent ofmight tropical be convection, and underestimated the in associated these fast models. vertical transport, ceptions in Fig. results between the di (150 hPa, reaching above 10 km compared to observations and other models. This indicates are in better agreement with observations (see also R convective outflow heights for all regionsFRSGC/UCI, (in Oslo the CTM2 range 170–200 and hPato WRF ( the being two slightly UCAM higherdistributions models. are for The highest some cloud for regions top FRSGC/UCI,slightly compared analysis Oslo lower for in CTM2, WRF R and and UMUKCA-UCAM UM-UCAM the high cloud tops produced by UMUKCA-UCAM 5 5 25 15 20 10 15 20 10 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erence ff . Due to nud pro- 2 highres, for . While the maxi- 3 ering from those of erences in both the ff ff er greatly between the ff nud and UM-UCAM nud than the other models. The free- erence between the models, considering erent rates of the stratospheric up-welling erence between TOMCAT (R2) and TOM- ff ff ff erences in the model used to generate the ff 20374 20373 ). 2007 , Louis. The di can also be viewed as a time series, as shown in Fig. nud shows greater transport to about 200hPa at days 305–308, a 1 Louis than TOMCAT (R2) up to about 100 hPa. The boundary layer ers slightly between UMUKCA-UCAM ff Monge-Sanz et al. , the lowest tracer concentrations in the lower troposphere, except in West erences in tropospheric transport are carried on into the stratosphere, where 3 ff erence between the November mean mixing ratio over the Maritime Continent ff Louis is the boundary layer mixing scheme employed in the model, the Louis erences between models in the outflow height and in the tracer mixing ratio at this The di In Fig. UMUKCA-UCAM The FRSGC/UCI and Oslo CTM2 produce similar time series, di The data in Fig. The magnitude of the daily changes in transport intensity di ff fields to calculate vertical transportestimate in the the model TOMCAT/pTOMCAT rate is known ofheating to rates vertical over- ( tracer transport, for example in compared to the use of sphere UMCAM has the largerlowermost mixing stratosphere. ratios, due On to thehas faster other greater vertical mixing hand, transport ratios in within inin the the the mixing tropical upper ratios mean troposphere continues panel, than toup-welling FRSGC/UCI pTOMCAT, in and increase FRSGC/UCI the with than di altitude, in due However, pTOMCAT. the to use a of faster analysed lower divergence stratospheric mum di of two models (UMSLIMCAT and100 hPa, FRSGC/UCI) by was 70 hPa about itcrease a is with already factor increasing more of altitude. than There three anof are at two order the around processes of contributing modelled magnitude, to and the mixinglower continues divergence stratosphere ratios, to begins, in- firstly and secondly, thebetween di the altitude models. at For whichfrom example, the UMCAM while is the slow lower upper up-welling than tropospheric of that peak of in the FRSGC/UCI mixing over ratios WA and SA, higher in the strato- duces fairly constant enhanced mixingOslo ratios CTM2 at and about FRSGC/UCI 700hPa, the whilevariable. lower tropospheric in peak CATT-BRAMS, mixing ratios are much more the spread between the models further increases, as shown in Fig. Africa, are those of TOMCAT mixing scheme therefore, has the potential to influence tracer mixing ratios throughout models have far less variability in the upper troposphere. UMUKCA-UCAM CAT scheme restricting thethan amount the of scheme tracer usedtios mixing in for TOMCAT into (R2). TOMCAT the This lower leads to troposphere significantly far smaller more mixing ra- feature which is not seen inactivity the around TOMCAT (R2) day or 320 pTOMCAT is plots. seen TheTOMCAT in (R2), lower all convective pTOMCAT of and the UMUKCA-UCAM models, howeverrunning it models starts produce 1–2 results days earlier similar for toseen the in general features the of the forcedtroposphere convective models. activity di The timing of the enhanced concentrations in the upper pTOMCAT and TOMCAT (R2) mainly by mixing ratio,of and the altitude. time At series, the both very FRSGCUCIlevels, beginning and while Oslo CTM2 pTOMCAT show and moderateperiod, transport TOMCAT apart to (R2) from higher this show the very timing in little the vertical results is transport similar. in this the models, resulting fromfrom the a surface daily to higher cycle levelsaltitude of in of the maxima maximum troposphere. outflow, and Again asous here, minima well di and in as cannot the rates always strength be ofmeteorological of attributed forcing transport the data. to vertical di A transportthat surprising are many di obvi- of themtiming use of meteorological the forcing changes in data the from intensity the of same the vertical source, transport is is that not the identical. level will also have an impacttransported on upward the amount from of the surface TTL species to which the are subsequently lower stratosphere. the short lifetime of T6h,mixing a ratios, marked and diurnal indeed, cycle there is expected is in some the periodicity upper in tropospheric the T6h mixing ratios for all of ing ratios almost completely decaying in between the convective peaks, while the other di example around day 315. models. has CATT-BRAMS the strongest daily cycle in convective activity, with T6h mix- 5 5 15 20 10 25 15 20 10 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ), nud. 2007 ( Levine et al. Holton and Gettelman should relate to the precipita- nud and UMUKCA-UCAM (R1) 6 . The 90 hPa level was chosen as 6 ). Subsequently 1981 20376 20375 ( ), the picture is similar, with most models indicating 5 2010. Over South America, all models show a marked ) found that convective transport of trace gases into the 2007 ( . This was calculated by dividing the annual mean T20 mixing ratio 4 Ricaud et al. Newell and Gould-Stewart ) pointed out that the observed stratospheric water vapour mixing ratios could The seasonal cycle of the T20 mixing ratios at 90 hPa in the three areas SA, WA, The annual mean enhancement in T20 mixing ratio at approximately 200 hPa is 2001 tion rates shown in Fig. 3 of R that the vast majorityand of the Indian upward Ocean, transportCTM2, with is TOMCAT very taking and place little pTOMCAT also over contributionand show the western from smaller Africa. western contributions No other Pacific data over areas. was South available at America the FRSGC/UCI, 90 hPa Oslo levelMC for UMUKCA-UCAM as well as a tropical mean are shown in Fig. the tropical mean. Inconcentration contrast in to the August–September other oversignificant models, the variation UMSLIMCAT MC. throughout shows the Over a year, peak exceptions WA,(R1), are in few which UMCAM T20 of and both UMUKCA-UCAM show the larger modelscal mixing average, show ratios mixing towards ratios the arefrom middle generally of November smaller the to from year. May. about In Julysponding UMSLIMCAT the has to to tropi- a October, the and peak similar larger inmixing peak mixing in ratios ratio over in in the July September,The MC, to corre- seasonal and August, cycles UMUKCA-UCAM which in (R1) T20 is has mixing related elevated ratio to shown the in Fig. similar feature seen over WA. vertical transport to this levelhigh takes convective activity place does there, not as varythe expected. greatly greatest between The the vertical width models, transport of and taking allMost the place models band of show over of the the western modelsand Pacific also and Africa. show Indian transport Ocean. At being 90 slightly hPa enhanced (Figure over South America of the models showand a larger seasonal mixing variation ratiosthe with from MC about minima with January from low to values aboutand from March. July December. about to June A The to September similarother September mixing pattern areas, and ratios which is larger leads over seen values to the in over the November MC general are cycle over also the generally MC being larger similar than to in that seen the in highest T20 mixing ratios are seen in the tropics, indicating the greatest amount of it is located wellreaching into this the level TTL will and likely is be transported above the into the level lower of stratosphere. zero Over radiative SA, heating. most Tracers at each grid point by the annual, global mean mixing ratio on the 200 hPa level. The ary of the model. Dueof to KASIMA the lack shows of a noratios convective pronounced transport than parameterisation, upper the the profiles tropospheric profile most of peak, stratosphere. the The and other profiles has models from smaller UMUKCA-UCAM in mixing the upper most troposphere and lower- stratosphere. The ideathe stratosphere of over the a westernforward “stratospheric tropical by Pacific fountain”, and with the Maritime air Continent, preferentially was put entering shown in Fig. the troposphere. The profile for KASIMA starts at 600 hPa, as this is the lower bound- mixing ratios in the middleels. troposphere, Over more WA, in the line situationratios with is than the reversed, all results with the of the other the nudged models other version between showing mod- about lower 8004.2 hPa mixing and 400 hPa. Location of convection The geographical location of convectionof is water important and as the it chemical determines species the transported mixing to ratios the upper troposphere and the lower ( also be explainedtrap”) if in air the passed upperlocation. more troposphere, but or Transport did less from notand horizontally the necessarily the tropical though enter stratosphere the boundary a during stratospherewho layer cold found at January to that area that 2001 two the (”cold thirds was tropicaloccurs of investigated the tropopause vertically transport by layer over from the theother planetary hand, Indian boundary Ocean, layer to Indonesia thelower TTL most and stratosphere the mainly takes western placeAfrica. Pacific. above land convective On regions, particularly the look very similar except over the MC, where the nudged version produces higher tracer 5 5 10 25 15 20 10 15 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ect in ff ). , these areas 5 2006 , erent models, e.g. ) show that in the ff S) CO mixing ratio 7 ◦ cients (R) as high as ), and the much larger ffi 3 N–20 ◦ where the mixing ratios are 5 Shindell et al. . For most of the models, there is 7 20378 20377 ected the results. The correlation between up- ff . In contrast, when the 153 hPa tropical mean CO is plotted 3 . There is no direct relationship between amplitude of seasonal changes in the 6 During the SCOUT-O3 measurement campaign carried out in the area of Darwin, The lower boundary condition for CO was a monthly varying, prescribed mixing ratio Over WA, there is also a seasonal cycle in precipitation rates, however, as described Australia, in November andwith December the 2005, the COLD concentration (Cryogenically of Operated CO Laser was Diode) measured instrument on board the Geo- tional sources, therefore it cannot befields expected to on exactly a reproduce the particular observedthe day. tracer model It transport, can such still asaltitude be the of representation used the of however, transport seasonal to of cyclesit’s evaluate lower relatively or general tropospheric long the features photochemical air strength of lifetime, to and the theextent distribution upper by of transport troposphere. CO processes, Because is although determined of due there to to a is the large also oxidation a of significant hydrocarbons atmospheric and source, methane (e.g. for the modelling of therapid composition vertical of transport the in tropical the tropopause models region are that correctly the4.4 located. areas of Comparison with measurements The idealised CO tracer used in the models has a uniform removal rate and no addi- are larger than theinteresting to surface note mixing that the ratioswith surface in faster CO transport the mixing to ratios convectivelyare the are active often generally upper over areas. smaller troposphere. the in ocean, As the It where areas can the is be air also seen is less inbetween the polluted. Fig. surface and 700 hPa, thereforein using the a boundary CO mixing layer ratio wouldper from not slightly tropospheric have higher tracer a mixing ratio and location of convection show that it is important most active transport regions,the a upper smaller troposphere. change The fact inshow that CO in that the can it lower lead is panelcontrol to the the the gradients a surface are UT/LS greater mixing much CO e smaller, ratio mixingconvectively in ratios. active areas, the There as is areas for however with a some the few contribution points, most from the the rapid upper less transport tropospheric that CO mixing ratios gradients in the regions with faster transport (upper panel of Fig. regions (lower panel), the correlationpoints is plotted much smaller. for The each gradient model of was a also linear calculated fit (M to in the Table a clear correlation between the0.90, two as values, shown with in correlationagainst Table coe the mean of the CO surface mixing ratios in the less active vertical transport the highest). Then,at for each 153 hPa month, is thethe plotted tropical points as mean where a (20 the153 function hPa transport tropical of mean time the CO was mixingtransport surface ratio determined regions vs. mixing is CO to shown ratio surface in be mixing of the ratio the upper CO in panel shortest. the of averaged active Fig. vertical over The plot of The dependence of uppervertical transport tropospheric in tracer the mixingthe models monthly ratios can mean on be T20 thetransport assessed mixing location using ratios time of are the between used idealised rapid mixing the to tracers. ratios, surface determine similar Firstly, the and to grid the 153 hPa boxes areas where are in the each the panel shortest of (the Fig. highest T20 above, there is no pronouncedof the seasonal models. cycle At in 200 T20 hPaWA (not mixing which shown), correlates ratios most with at of the 90 theaccording hPa models changes to for show in these most a precipitation models, seasonal throughout the cyclelinked the over vertical to year. transport convection for from Therefore, the the MC surface and to SA 90hPa but is4.3 not strongly for WA. Impact of location of rapid transport on TTL composition in Fig. precipitation and amplitude of the seasonalOslo changes in CTM2 T20 and for FRSGC/UCI the di haveand the approximately highest amplitude the changes lowest insimilar amplitude T20 over change mixing the in ratios MC. precipitation rate. The situation is seasonal cycle in precipitation rates, which is reflected in the T20 mixing ratios shown 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 | , )). . TES 9 2010 , 8.3 km footprint Osterman et al. × ; set of the models ). On the 16th of ff 2008 ). , 2009 , Hossaini et al. 2008 , , 131 hPa and 110 hPa for the ◦ Nassar et al. , 20.9 ◦ nud underestimates the measured CO Brunner et al. ected by the strong convective systems Lopez et al. ff ; ). TES is the first satellite instrument to pro- 20380 20379 ). 2007 , 2001 2008 , , nud still returning the lowest mixing ratios, which are ects of a priori information inherent in the retrieved TES Luo et al. erences between the models decrease as the lifetime of ff ff ; Beer et al. 2008 Viciani et al. , . One of the focuses of the SCOUT-O3 measurement campaign in 8 nud, overestimate the CO above 100 hPa. Some of the o Richards et al. ; In order to correctly compare TES and model profiles one must account for the limited The agreement of the models with the measurements is encouraging, but it should Measurements of CO made by the Tropospheric Emission Spectrometer (TES) in- On the less convectively active days, such as the 23rd of November, the models The modelled idealised CO fields were interpolated to the measurement times and In general, all the models produce idealised CO values which are similar to the mea- the model profile. The observation operator consists of the averaging kernels and vertical resolution and theprofiles. e This is achieved through the application of the TES observation operator to strument, averaged over an areanorthern bounded and by southern 4.2 hemispheres areis plotted along an with modelled infrared COAura Fourier in satellite Fig. transform in spectrometer 2004 which ( was launched on-board NASA towards higher COlifetime values than may CO in be thetransport due atmosphere. that to In corresponds general, more the the to models convectively idealised influenced all CO profiles. seem to tracerbe have having a kept vertical a in mind longer the that tracer increases, the and di withlived a lifetime than of many around of 3such months, the CO as halogen is bromoform considerably species longer (withactually with much a lifetimes longer of lifetime lived (with the of a order about lifetime of of 30 over days 6 days), or months, although weeks, ( dibromomethane is on a global basis.operating mode The in data whichproviding used TES near in makes global this nadirprofiles coverage study observations are approximately comes with provided from every a onextensively the 16 67 5.3 validated TES against vertical days. in-situ levels Global observations from ( Survey TES the ozone surface to and 0.1 hPa CO and have been measured between about 150 hPa andreproduce 60 hPa, the while lower on the toUCAM 25th, mid the models tropospheric generally CO mixing ratios but, except for UMUKCA- vide vertical information on tropospheric ozone whilst simultaneously measuring CO capture the lower troposphere mixing ratios, however they all overestimate the values 2008 mixing ratio in theestimates lower the -mid mixing troposphere, ratios.models while match Higher at better in about with thevalues, the 350 atmosphere, hPa, with convectively around pTOMCAT perturbed UMUKCA-UCAM over- 100 CO hPa,within values most the than of range the the of background capture the the measurements. UT/LS CO Oncontinues as the to increase. 30th well Lower of as down,the November, the however, measured there again slope values are the by substantial of all models over-estimations the models. of decay in mixing ratios as altitude locations along the Geophysica flightis track, plotted and in a comparison Fig. Darwin with the was measured to data measure(“Hector”) air which that form had been over a the Tiwi islands ( sured values. On the 16th, UMUKCA-UCAM November, air in the outflowquiescent of TTL was a sampled, Hector andobserved. was on sampled. On the On 30th 25th the of ofair November 23rd November, masses. only relatively of weak strong November convection convection the was influenced the sampled ments, an in-flight sensitivityprecision of of 1% few and ppbv anmolecular is accuracy database in achieved, ( the with range a 6–9%, mainly time due resolution to of the accuracy 4s, of a the airborne spectrometer for in-situ measurementlead-salt of diode trace gases. laser A is liquid(providing used nitrogen in an cooled combination optical with pathunder an analysis. astigmatic of Herriott A 36 m) multi-pass directcalibration, cell absorption to is detection detect employed technique, the in which conjunction does absorption not with signal need fast of in-flight sweep integration. the molecules For CO measure- physica research aircraft. The COLD instrument is a mid-infrared tunable diode laser 5 5 25 10 15 20 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 1 3 erent ff erences ff R2 in Fig. Worden et al. ). The application er between several of ine models pTOMCAT ff 2003 ffl , Louis and TOMCAT nud and the Oslo CTM2. In the southern Rodgers and Connor 20382 20381 erence is the way in which the convective trans- ff erences in their T6h and T20 profiles shown in Figs. ff Louis produced very similar T20 concentrations, smaller than highres). Better agreement with other models is achieved with nud) shows significantly lower mixing ratios for the T6h tracer over erences from the TES CO mixing ratios in the northern hemisphere ff highres). Despite the lack of an explicit boundary layer mixing scheme, ine models, i.e. those which use a pre-calculated set of meteorological ffl again illustrate the significant influence of the convective parameterisation. The ). For this study the unique TES observation operator for each TES profile was erence in the altitude at which detrainment results in peak tracer concentrations, 3 ff All of the models reproduced the observed seasonal cycles in mean upper tropo- For extremely short-lived species (with lifetimes of the order of hours to days), the All the models follow the seasonal cycle seen in the TES data, with CO values being 2007 and and it was found that the mean upper tropospheric CO mixing ratio in the tropics at port is calculated. The large di only model which does notalso contain produced a a tracer convective transport profile100 hPa. with parameterisation, Over smaller KASIMA, the concentrations middle than portionKASIMA the of and other the TOMCAT models tropical up meanthe to profile around remaining 150 models, hPa-400 hPa, furtherary under-scoring layer the mixing importance scheme,terisation, of when and the studying the tropospheric choice use(UMUKCA-UCAM tracer of transport. of bound- an The nudged accurate version convective of transport UKCA parame- between several of theshape, models. the concentrations All and aspects thethe timing models of of which the transport use tracer events thethe distribution, same di ECMWF source, i.e. data. the transport Clearly, the parameterisationsthe despite play tracer profile the a distribution. use substantial role of in forcing determining data from spheric CO well, inferences comparison in with model transport the remain TESin relatively measurements, constant the throughout suggesting geographical the that year. location the Di of dif- the most rapid vertical transport were also examined, parts of the profile forversion SA (UM-UCAM and WA, than is the case for the high resolution free running from that of the other models. influence of the models’the transport use parameterisations of are ECMWF evenof meteorological more di data obvious. to Despite drive the models, there is around 100 hPa (UM-UCAM UMSLIMCAT did not have a tropospheric tracer profile which was significantly di throughout the tracer profile, upand to pTOMCAT-tropical, the at only least 100 di hPa. For the o For the o forcing data, the shorttransport lived parameterisations tracer in distribution themixing is model. scheme influenced has Specifically, to apersive the a large schemes choice large limit influence of the extent onsphere. boundary flux by the When layer of the comparing tropospheric a the tracer profilesthe tracer profile, influence from emitted of TOMCAT as at the less boundary ground dis- layer level mixing into scheme the on a free short tropo- lived tracer can be seen FRSGC/UCI overestimate the TES values.ern The hemisphere highest are CO measured mixinghowever, ratios have by the in TES peak the in in south- October. November. All the models except pTOMCAT, 5 Discussion larger in October-December than duringmodelled the CO rest mixing of ratios the isHemisphere, year. larger with The in values spread the in between(FRSGC/UCI), Northern July the and Hemisphere ranging from than 100ppbv from in (pTOMCAT) to aroundThe the 115ppbv 75ppbv smallest (FRSGC/UCI) Southern in (pTOMCAT) di to November. 90ppbvare seen for pTOMCAT, UMUKCA-UCAM hemisphere, the TES mixingels ratios between July are and underestimated October, slightly while by in most November and of December the TOMCAT mod- (R2) and of the TES operator to aapplied comparison to profile each model is profilecomparisons. described before averaging in the detail resulting profiles in for monthly mean the a priori profile used in the retrieval( ( 5 5 25 10 15 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , - ffi ¨ en, erences ff Jacob et al. ), the feasibility of large 20380 1998 , 20366 , 120175/1. NRPH thanks NERC erent models, this may create a ff 20359 Kritz et al. 20393 , 20384 20383 20359 20365 erence between the models, as in the long term ff ` ` ere, E. D.: Regional modelling of tracer transport by tropical ere, E. D.: Regional modelling of tracer transport by tropical x production upon the upper tropospheric composition: a multi- erences in the strength of convection and detrainment alti- ff This work was supported with funding from the EU project SCOUT-O3. erence in the amount of tracer transported upwards. For the composition ´ ´ ecal, V., and Rivi ecal, V., and Rivi ff erences in concentration at these altitudes were found, with the di ff ), there is no extensive data set suitable for model evaluation. Despite the di convection - Part 2:doi:10.5194/acp-9-7101-2009, 2009b. Sensitivity to model resolutions, Atmos. Chem. Phys., 9, 7101–7114, E., Liousse, C.,Schlager, Peuch, H., V. H., Mari, Carver,transport C., G. and and lightning D., Cammas, NO Pyle,model J.-P.: J. study, Impact A., Atmos. of Sauvage, Chem.doi:10.5194/acp-10-5719-2010, 2010. West B., Phys. Discuss, African van Velthoven, 2245–2302, Monsoon P., doi:10.5194/acpd-10-2245-2010, convective ing System’s Aura Satellite, Appl. Opt., 40, 2356–2367, 2001. convection – Part7081–7100, 1: doi:10.5194/acp-9-7081-2009, 2009a. Sensitivity to convection parameterization, Atmos. Chem. Phys., 9, During the course of this study, it became clear that there is a need for measure- For tracers with a lifetime of the order of a month, a priority should be for the model to Arteta, J., Mar Barret, B., Williams, J. E., Bouarar, I., Yang, X., Josse, B., Law, K., Pham, M., Le Flochmo Beer, R., Glavich, T., and Rider, D.: Tropospheric emission spectrometer for the Earth Observ- Acknowledgements. CRH was partly funded by SNSF grant number 200021 Arteta, J., Mar scale measurements of radon throughoutfuture the – atmosphere should such be a consideredenormously. in dataset the would improve the existing possibilities for model validation References radon. Although radon has1997 been used in several studiesculties in in measuring the radon past in (e.g. the atmosphere ( for their AdvancedBRAMS Research work was Fellowship. supportedand Tropopause by 2009) NADR and the was program is performed2008- using LEFE/INSU c2008012536 funded HPC in and resources 2009 via of France -c2009015036 CINES (projectsCalcul made NERC under Intensif). by UTLS-tropicale the GENCI allocation NCEO. (Grand Equipement The National de CATT- atmospheric species and of altitude. The only tracer which really fits this profile is altitude of interest. Throughout thefered troposphere, among the the models, modelled however, profiles for altitudes oftracer of all profiles 100 tracers from hPa dif- and all higher, models thelarge were idealised di CO similar. For thebetween shorter-lived models tracers being T20 greater and for T6h, the very short-lived tracer T6hments than of T20. tracers with whichchemistry. model Such transport a can tracer bebe should validated, insoluble, have independently and relatively have of well a model short defined lifetime emissions via at a the loss surface, process which is independent of other height and vertical advectionvective rate detrainment in altitude the maythe still UT/LS lowermost have is stratosphere, larger important, because mixingoutflow. models of ratios a with The of more a impact CO, rapid low of fortude advection con- di example, of above in the convection convective between the models depends on the lifetime of the tracer and the tracers, the intensity of theof transport the also transport becomes events increasinglytios, is important. unless probably The there of timing is lesserthe a importance amount systematic for of di average tracer traceron transported mixing the into timing ra- the oflinked upper the to events. troposphere the will On stability the notsystematic other of strongly di hand, the depend if boundary the layerof timing in air of entering the the the di transport lowermost events stratosphere, is the combination of convective detrainment rapid vertical transport inareas the with greater model. concentrations of Models anthropogenicpolluted with species upper may vertical troposphere therefore transport in have a the taking more tropics. place over reproduce the observed altitude at which tracer detrainment occurs. For shorter lived 153hPa is correlated with the CO mixing ratio at the surface below the area of most 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 | 20393 20363 , 20359 , 20393 , 20364 usion in a global 20358 ff 20359 20379 20363 20362 20359 tt, M.: A barrier to vertical 20393 ffi , 20359 -line chemical transport model: ff 20365 , 20359 20358 20393 20362 20375 er, D.: Evaluation of interregional transport using 20359 20393 ff 20386 20385 , 20363 20359 ce’s global and regional modelling of the atmosphere, Q. 20362 20361 ffi 20368 ¨ omel, H., and Fu, Q.: Mean radiative energy balance and 20393 : Implications for the water vapor budget, J. Geophys. Res., 111, − 3 20363 20363 , O, and O 2 ´ enyi, D.: A generalized approach to parameterizing convection combining en- 20367 , 20362 ´ ev , CO, H 3 20366 Geophys. Res. 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Holtslag et al. Holtslag et al. Sukoriansky et al. Mellor and Yamada Holtslag and Boville Holtslag and Boville Holtslag and Boville ) no mixing N/A ) ) ) see text N/A Round 2 Round 1 20393 20394 ) ) 700 hPa is a function of pressure) 2002 ) no BL ECMWF operational 500m ) ) ) ) ) ) ( 2008 ( 1987 1995 ( ( < 1993 1993 1979 1986 1986 1986 1986 1986 1986 ( ( ( ( ( ( ( ( ( Z Z< the surface at Prather Prather Prather Prather Prather Prather Zalesak Priestley Priestley Leonard et al. Tremback et al. Skamarock et al. Gregory and West ´ eans L31 L31 L38 L64 L37 L31 L38 L38 L31 L19 L38 semi-Lagrangian L40 ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ , 750 m ◦ 2.8 2.8 3.8 3.8 2.8 2.8 1.3 0.8 2.8 3.8 3.8 2.8 60 km L39 × × × × × × × × × × × × 5.6 × ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ × ◦ Condition nud nudged GCM 2.5 Name InitialT20T6h 0CO Source 0 0 1pptv at mixing ratios prescribed 1ppbm at Lifetime 1-3 months (decay rate 20 days 6 hours The idealised tracers used in the experiments. More details are provided in the text. The models which participated in the inter-comparison. highres global NWP 0.6 University of Cambridge Louis CTM 2.8 12 , 11 , ´ eo-France and CNRS and University of Orl pTOMCAT-tropical CTM 2.8 UMUKCA-UCAM UM-UCAM WRF global NWP 1.9 CATT-BRAMS Regional NWP 60 km University of Leeds ´ 10 et pTOMCAT CTM 2.8 UMSLIMCATFRSGC/UCITOMCAT (R2) CCM 2.5 CTM CTM 2.8 2.8 TOMCAT KASIMAUMCAMUMUKCA-UCAM (R1) CCMOslo CTM2 CTM 2.5 CCM 5.6 2.5 CTM 2.8 , 9 10 5 7 8 11 12 14 Model1 2 3 4 Type6 Resolution13 Transport BL mix. Circulation Reference 9 8 M University of Herfordshire , , Karlsruhe Institute of Technology University of Oslo Lancaster University 4 5 , , 2 3 6 7 13 14 The models were run1 at the following institutions: Table 2. Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , the 7 0.1 − 0.40.4 0.00 − − Fast trans. Slow trans. 20396 20395 nud 0.80 0.4 0.05 0.02 cients (R) and the slopes (M) of lines fitting the data shown in ffi Average 0.66 0.30 0.08 0.10 UMUKCA-UCAM ModelFRSGC/UCIOslo CTM2TOMCAT (R2)pTOMCAT 0.90 0.43 R 0.27 0.90 0.59 0.07 0.44 0.30 M 0.41 0.57 0.14 0.29 R M . The column “Fast trans.” shows data from the upper panel of Fig. 7 The correlation coe The mean profile of T6h volume mixing ratios, for each model, averaged over three erent areas for particular months of 2005, as well as an annual mean for the tropical region ff (lower right panel). Fig. 1. di Table 3. column “Slow trans.” shows data from the lower panel. each panel of Fig. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 20398 20397 nud above 90 hPa. The mean profile of T20 volume mixing ratios, for each model, averaged over three Modelled profiles of mass mixing ratio as a function of time, for T6h, averaged over the erent areas for particular months of 2005, as well as an annual, tropical mean (lower right ff panel). The legendavailable is for split UMUKCA-UCAM over the lower two plots, but refers to all four plots. No data was Fig. 3. di Maritime Continent. The data2005 runs to from midnight on day the 304 30th to of 334, November i.e. 2005. midnight on the 1st of November Fig. 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | nud. 20400 20399 The fraction enhancement of the 2005 annual mean mixing ratio of the T20 tracer, for The fraction enhancement of the 2005 annual mean mixing ratio of the T20 tracer, for The enhancement was calculated byat dividing that the level. value at a particular point by the global mean Fig. 5. each model at the 90 hPa level. No data was available at this level for UMUKCA-UCAM Fig. 4. each model, at theparticular 200 hPa point level. by The the enhancement global mean was at calculated that by level. dividing the value at a Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ◦ . 3 erent models at 90 hPa ff 20402 20401 cients and the slopes of fit lines are given in Table ffi N, directly below the grid boxes at 153 hPa with the highest T20 mixing ratios ◦ N. The correlation coe ◦ The tropical mean CO mixing ratios at 153 hPa vs mean surface CO mixing ratios. The variation throughout 2005 of the T20 mixing ratio in the di S and 20 ◦ (indicating the 15% shortestratios transport in times the from lower the panelS surface and represent to 20 the 153 hPa). average of The the surface remaining mixing 85% of the area between 20 Fig. 7. Values are plotted forCO each mixing ratios model in and20 the each upper month panel were (monthly taken means) from of the 2005. 15% of The the model surface surface, between over SA, WA, the MC andapplies as to a all tropical panels. mean. The legend is split over the two lower panels, but Fig. 6. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 20404 20403 A comparison between the monthly mean modelled CO mixing ratio in the northern A comparison between modelled and measured CO mixing ratios along the Geophysica Fig. 9. (upper panel) and(Tropospheric southern Emission Spectrometer) (lower satellite panel) based measurements hemisphere of upper CO. tropical troposphere, and TES flight track for (clockwise): the 16th,were 23rd, made 25th during and 30th the of SCOUT-O3 November campaign 2005. in The Darwin. measurements Fig. 8.