Cirrus And Polar Stratospheric Cloud Studies Using CLAES Data
FinalReportfor NASACirrus and Polar StratosphericNASA/GoddardContractNAS5-98044Cloud Studies using CLAES DataPrepared for:Space Flight Center, Earth Sciences ProcurementGreenbelt, MarylandPrincipal InvestigatorLockheed Martin Advanced Technolowy CenterLockheed Martin Missiles and SpacePalo Alto, CA 94304-1187Office
Introduction:We'veconcludedFebruary28,a 3 year2001)StudyCLAESreports,data.We f Performance-cirrusand ibed the progress of this study in monthlyteam meetings,AmericanGeophysicalSocietypublicationsand collaborativepublications.of Work:1. uesof PSC andcirrus cloud-top temperature retrieval from CLAES data and examineof representingthe diurnal cycle of cloudiness in the tropics.2. Completea phereCOARE) field campaigns during a CLAES3. Comparecloud ivedOceanExperimentfrom CLAESwaysGlobal(TOGAwith data fromthe P),HighResolutionInfraredSounder (HIRS) and StratosphericAerosol and GasExperimentl-I; construct a cloud datasetall results available in numerical form.on a week by week basis and make4. Provide results from these studies to a wider communitythrouthe refereed literature and presentationsat scientific meetings.The remainderof the reportwill describeour progresspapers inin each of the fourareas.L Establishand cirrusexaminetropics.CLAEScloud detectioncloud-toptemperaturewaysof cycletechniquesof PSCCLAESdata andof cloudinessin theIce clouds are of course just a special type of aerosol. CLAES is a verysensitivedetectorof aerosol capable of detectingaerosolwith volumeabsorptioncoefficients,kabs, downto about 1.0E-06/krn.Since UARSlaunchedin October,extremelyhid1991, the entire s performedunderfrom the June 15, 199I
eruption ofMt. mMountwellPinatuboaboveAlsotropicalthe maximumin our preferredvalues can be observed(PSC)or cirrus.annualcirrustheconfinedisis abouttoconfinedlq for edbyIff km I wheremissioncycle with some deviationaerosolwhereas muchcloudwas also decliningas cirrus proceedsdue to ENSOlowerbelowin areas likely to have polar stratosphericThe backgroundduringmainlywhich12.8 grn channelhi ercontinuallywasphenomena.throughaUsing our pastexperience at discriminatingPSCs with a threshold approach [Mergenthaleret al., 1997], we establishedka 9.0E-04/kTnas a thresholdfor produceswith the ichdistributionsinthe Wang et al. (1996) cirrus climatology compiled from five years worth ofSAGE II data. At higher levels in the tropics above about 14.5 kan the vastmajorityof SAGE II observationsinvolvesubvisualcirrus. The goodagreement between CLAEScirrus observationsand SAGE II observationsindicateCLAEStoo,descriptionof thecomparisonwithdetectsestablishmentthe SAGEreprintof MergenthalerSpectrometerObservationsWe studied remotelymeasuredlimbambientthecloudII climatologydeterminedA detailedthresholdas AppendixLimbEtaIonandA, aArrco'of cirrus using the limb radiancein the 12.8 gm channel.observedcirrus.detectionis includedthe temperaturetemperaturetemperatureofof subvisualet al, 1999, Cryogenicof Tropical Cirrus.sensingby CLAESbrightnessthe majorityWe examinedbyCLAESfrom NCEPa case where thegreatlyexceededand local radiosondes.part of out TOGA COAREcase study.Figan'e 1 shows thetemperaturesat 12 UTC from the ISCCP analysis of GMS-4/R/VIStheThis ,,,,,ascloud topdata onJanuary 19, 1993. The CLAES "3at" aerosol data at 100 hPa are over plottedwith their observationtime. The s3anbols are filled according to the aerosolemissivit3; l-exp(-k b'400),where400 "krn is the CLAESLOSpaththrough a 2.5 km thick shell in the limb view. If the symbol is filled CLAEShas detected a cloud. Near Yap, CLAES detects clouds where no cold cloudtops are are2 shows that helimbfrombrightnessobserved by CLAES.In order to explain this discrepancy/nwe modeled the radiativetransfer of the thin cirrus witha
simple Monte Carlo model. Our results, show that the limb brightness can begreatly enhanced as high radiance from the warm surface and loweratmosphere are scattered into the limb by thin cirrus. The amount ofscattering is related to particle size and cloud thickness. If the particles haveradii below two micrometers they are not effective at scattering the 12.8 l,tmradiation observed by CLAES, bigger particles can enhance the limbbrightness enough to match the observations. As the cloud thickens,radiation upweHing from the surface is absorbed in the cloud and notscattered so the limb brightness temperature seeks the ambient temperature.Thus the limb brightness measurement becomes akin to cloud toptemperature measurements by operational nadir viewinginstrumentswhichroutinelyOurreport cloud top atureambientcloudbrightnessof near-tropopausetemperatureduetemperaturescloudsto scatteris that:is not a brightnesstemperaturesthat exceed the ambienttemperatureby severaldegreesevidentlyreveal thin cirrus that are exposedto high surfacetemperatures.These cloudsare more important from a radiative standpointthan cirrus that overlay cold cloud tops. The CLAES data is a unique sourceof this informationuntil new instruments like HRDLS are in 70180190Greenwich220240260ISCCP Cloud Top Temperatures280(K)300ClearNo DataFigure 1. CLAES100 hPa cloud measurementssuperposed on the ISCCP12 UTC cloud top temperaturesfor January 19, 1993. The white box showsthe area near Yap where CLAEStemperatures.detectsclouds, and high limb brightness
1.ILimb Radiance 780 cm -Leve!EquivaIerlt B',ackbodyTer 'u' , ;t -?Time Lal Lon12. 1 9.58 I12.93.12.,3.5t42,24] 2.8 !5.Q4 tL45".] . 7 L7.SQ!'Z3 .L10 .Aerosol ExliTime Lat Lon12.909.s7"t13g,tZ,gz.!2, .t , .\i\\:I . !7 5. !47,; .-',Tems rs c& SoLmd,n s1JJ:7Q.100IJ0.01I0.02II m]lOO0,! "',100Figure2. The 'de,near YapvolumeI12 UTCabsorption0.50,0.910.77iiz3OOand the localat Yap Januarycoefficients5.0, 0.43,,250by CLAESParticle20.0,T200Temperature (K)observednear.radiosonde19, 1993.Theare also shown.Radius[#m],2.0, 0.24,0.30Wo, g1.0, 0.06,0.070.8, 82132051951932021981931911.0iTable 1. The calculated1981/mb brightnesstemperature0.04of a 2.5 km thickcylindrical cloud of radius 200 km centered at 16 km altitude. Temperaturesare shown for various cloud aerosol volume absorption coefficient and meanparticleshown.size.Particlesingle scatteringalbedo and asymmetryfactor are also
The emissionintendedmeasuringto provideinstrumentsmeasurementsdiurnal cycle representationsdata in hourlyCLAES'sprevent(CLAES,throughfor tropicalISAMS,the diurnaland MLS)werecycle. We constructedcirrus by binningcloud occurrenceor 4 hourly local solar time bins. One of the peculiaritiessamplingdepletionthat CLAESof cryogendidn'tsamplenear-noondue to getting sunlightofin the tropicson the telescopetobaffles.This results in a spatially and temporally nonuniformsampling pattern in thetropics. Neverthelesswe constructed the diurnal cycle from each season ofCLAESdata availability.Figure 3 is an exampleof such a constructionwherethe 146 hPa data from summer 1992 (JJA 92) in the re,onfrom 22S to 22Nhas beenused.We added error bars based on the standard deviation of themean. There are fewer measurementsnear-noonso the en'or bars arerelatively large, but through the rest of the cycle the sampling is moreuniform and so are the error bars. We found it useful to use only areaswhere the mean (over time) cloud frequencyminimum (in this example) 0. l, this preventsareas that have no diurnal variation.The diurnalof occurrencethe cycle containingcycle sho,ana in Figxlre 3 is representedsunset and sunriseand a minimumwas at least somenear midnight.cloud freepeak cloudinessThe midnightnearminimumare about 20% less than the maxima. The near-midnightminimum is acharacteristicof all seasons.Our conclusion to this segment of work is that1) a coherentdiurnalcycle of upper troposphericcirrus can be formedfromCLAES cirrus data 2.) the interpretation of the near-noon data is complicatedby sampling considerations3.) these are publishable first-of-a- "ldnd resultsbecause they include subvisual cirrus that a largely invisible to nadir viewinginstrumentsbut comparisonswith other sources of cloud diurnal behaviorand interpretationremain.
oDciumal Cycle in Tropical Cloud, ,currence r-requency@ 146 h a0.60For JJA92A easo t,.lcanCloudinessrjt 0 100.50Id.0)l0.40tll0.30IO1G0"20 I,70"10 I0.00112NoonI8 Sunsel LocalFigure 3. The diurnaldata in the region2. CompleteAtmosphereCOARE)Solar Time(Hrs.)22S to 22N for June, July and August,duringa CLAESto using TOGA COAREglobal and seasonalto these comparisonsoverpassdata for the limb brightnessof convectionin the TOGACOAREorganizedregion.that shares the sensitivitycirrus are not practicalA majorinteractionby the MaddenThe observationfor trackingof CLAESgoal of the TOGACOAREthe atmosphereJulianof the Madden-event effecting tropicalSolar occultationfor observingsubvisualthis rather small scale event.typically gathers fewer than 4 profilesCLAES obtains 280.betweenstudyDC8 lidar data and ISCCPon a scale smaller that theJulian oscillation,the most important intraseasonalweather, is a first for a limb sounding instrument.examplewhereas1992. (JJA92)comparisons with the SAGE II climatology.In additionwe used weekly cloud frequency of occurrencestatisticsto track the progressinstrumentfrom CLA2Sa case study using data from the TropicalOcean GlobalCoupled Ocean-AtmosphereResponse Experiment(TOGAdiscussed above, we have used nearly-coincidentdata to compare the CLAES cirrus observationsoscillation12Nooncycle of cirrus at I46 hPa constructedfield campaignsIn addition06 Sunrise Midnightcampaignin the tropicsSAGE i7 for(20N-20S)was to understandand ocean to sustainthe "warmthepool" in
the western Pacific. The CLAESobservationsoccurrenceclouds throughoutstatisticsfor subvisualsupplementthe data set withthe study period.The study is discussed in some detail in AppendixB, a manuscript that willbe resubmitted to the Journal of GeophysicalResearch since the addition ofthe MaddenJulian results.3. Compare cloud occurrencestatistics derived from CLAESfrom the InternationalSatellite Cloud ClimatologyProjectwith data(ISCCP),High ResolutionInfrared Sounder(HIRS) and Stratosphericand Gas ExperimentII; construct a cloud dataset on a weekbasis and make all results available in numerical form.As discussedsuccessfullyabove and in Appendixcomparedyear climatolo :AccordingCLAEScompiledA, [Mergenthalercloud frequencyto Wang et al. (1996) the predominanceobservationsby SAGE II involve subvisualel al., 1999] we haveof occurrencefrom SAGE 17 observationscirrus.Aerosolby weekwith the 5-by Wang et al. (I 996)of near-tropopauseIn AppendixcirrusB wecompare nearly coincident DC8 lidar measurements,ISCCP cloud topanalysis and CLAES cirrus measurements.We've done similar comparisonsnot shown in AppendixB. We concludeJin et al., 1996) that ISCCP analysisseen by SAGE II and CLAES.cirrus seen by SAGE II (f lieWe:ve posted a readme.tx't,retrievestatisticsfrom these studies and others (e.g.is largely insensitiveHIRS is also insensitiveto the thin cloudsto the subvisualand Wang, 1997).an idI.sav file, and a readingand, to some extent display, week cloud frequencyfor the CLAESmission on 10 degree longitudeplotting programtoof occurrenceby 5 degreeIongitude bins for the 215, 146, 100, 68 and 46 hPa levels. The data is postedon anon3Tnous ftp at claes.spasci.comin the [anonymous.clouds]directory.4. Provideresults from thesepapers in the refereed literaturestudies to a wider communitythroughand presentationsat scientific meetings.The results from this contract have widelyfashion so that they can be used by others.papersat AmericanGeophysicaldisseminatedand in a timelyWe have presentedUnion Meetings.contractrelated
Conference Presentations:1. Spring I998 AGU, J. L. Mergenthalercirrus as observed by UARS-CLAESet. al., VariabilitT2. Spring 1999 AGU, J. L. Mergenthalerand GMS-4 measurementset. al. Comparison3. Spring 2000 AGU, J. L. Mergenthalerdiurnal cycle of near-tropopausellopicalet. al. Observationscirrusin tropicalof CLAESof thePublications:Mergenthaler,J. L., A. E. Roche,J. B. Kumer,and G.A. Ely, "Cryogeniclimb etalon array spectrometerobservationsGeophys. Res., 104, 22,183-22,194,1999.PublicationsB. J.,on the foIIowingpublicationsE. J. Jensen, E. M. Stone,that use our cirrus and PSCW. G. Read, J. W. Waters,Mergenthaler,"Upper tropospherichumidityGeop ,s. Res. Lett., 27, 2645-2648,2000.Jensen, E. J., W. G. Read, J. Mergenthaler,Tabazadeh,tropopauseTabazadehcirrus", J.(cont.):We collaboratedresults:Sandor,of tropicalrecovery",and thin cirrus",B.J. Sandor,L. Pfister,and A."High humiditiesand subvisible cirrus near the tropical", Geophys. Res. Left., 26, 2645-2648,1999.A., M. L. Santee, H. Pumphrey,Mergenthalerand J. L.et al., "QuantifyingScience,M. Y Danilin,denitrification288, 1407, 2000.P. Hamill,J. L.and its effect on ozone
10Danilin,M.Y., M. L. Santee, J. M. Rodriquez,M. E. W. Ko, J. L.Mergenthaler,J. B. Kumer, A. Tabazadeh and N. J. Liveseyhunting: A case study of rapid chlorine activation Decemberseen by UARS. J. Geopto,s.Danilin,M.Y.,J. M. Rodriquez,B. Kumer,Res., 105, 4003-4018,J. L. Mergenthaler,J. M. Russell IYI, M. Koike,"Nitrogenspeciesatmosphere: Model Analysis utilizing UARSGeophys. Res., 104, 8247-8267,1999.C. C. SmallComb,Mergenthalermeasurement,Stone, E.M.,hemispherePublicationsA. Tabazadeh,Measurements,"D. L. Wu, E. M. Stone, Z. Shippony,S. Oltmans,E. Jensen, H. C. Pumphrey,polar vortex,(cont.):(in revision forJ. Geophysto the Journal of Geophysicalin Horn, J. M. N. and Becklin,Planning for SOFIA", Proceedings of the SocietyInstrumentationEngineers (SPIE), 4014, 2000.humidity:Res).and J. L.in the southernRes).Researchc/rrus:(Dr. Jochin Horn) in the SOFIA operationsas acknowledgedA. C.M. Santee,of dehydrationMergenthaleret al., Observationsofnear-tropopausecombining UARS and TOGA COARE data.We assistedJ.D. Kley, H. G. J. Smit, J. L.The onset, ex tent and durationWe're resubmittingAppendix B,G. K. Yue,in the Post Pinatuboand M. K. Karki, UARS MLS upper troposphericmethod an validation, (in revision for J. GeophysMergenthaler,J.are being revised.Read, W. G., J. W. waters,Smedley,2000.W. Hu, M. E. W. Ko, D. K. Weisenstein,N. B. Jones, and R V. Johnston,These manuscriptsTrajectory1992 asthe manuscript,A case studywith cirrus data.E. E., "Optimizedof PhotoOpticalFlight
IIReferences:Jin, Y., W. B. Rossow,high-level1996.Mergenthaler,and D. P. Wylie, Comparisonof the climatologiesclouds from HIRS and ISCCP, J. Clim.,J. L., A. E. Roche,J. B. Kumer,Limb Etalon Array observations104, 22,183-22,194,of9, 2,850-2,879,and G. A. Ely, Cryogenicof tropicalcirrus,J. Geophys.Res.,1999.MergenthaIer, J. L., A. E. Roche, J. B. Kumer, and G. A. Ely, CryogenicLimb Etalon Array observations of tropical cirrus, J. Geophys. Res.,104, 22,183-22,194,Wang, E -H., E Minnis,Skeens,1999.M. O. McCormick,A 6-year climatologyG. S. Kent, G. K. he, and K.M.of cloud occurrencefrequencyStratospheric Aerosol and Gas ExperimentII observations1990), J. Geophys. Res., 101, 22,407- 29,429, 1996.Wylie, D. R, and R -H. Wang, meterand Gas Experimentof cloud frequencysounderII, J. Geophys.from(1985-data from theand the StratosphericRes.,102, 29,893-29,900,
AJOURNALOF GEOPHYSICA.LCryogenicLimbof tropicalcirrusJ. L. Mergenthaler,RESEARCH,Array EtalonA. E. Roche,VOL104, NO. D18. PAGES 22,183-22.194,SpectrometerJ. B. Kumer,andSEPTEMBER.' "1999observationsG. A. ElyLockheed Martin Advanced Technolo ' Center, Palo Alto, CaliforniaAbstract.The seasonal evolutionand spatial distributionof upper tropospherictropicalcirrus have been analyzed using a 19-month record of infraredaerosol volume absorptioncoefficientsobtainedby the Co, ogenic Limb Array Etalon Spectrometer(CLAES)aboardthe Upper AtmosphereResearchSatellite (UARS).An empirical method of separatingclouds from backgroundvolcanic aerosol is described.Cloud occurrencefrequenciesarecomparedwith the StratosphericAerosol and Gas Experiment(SAGE) II cloudclimatolo 'of Wang et aI. [1996]. The seasonal distributionof clouds derived fromCLAES agrees well with the SAGE II results that show predominantlysubvisual cirrus inthis region. This agreementdemonstratesthat CLAES data contain informationdescribingsubvisual cirrus in addition to thicker clouds. Examplesof interannualvariationsin cloudoccurrencefrequencyobservablein the CLM S data are discussed. The eastwardshift incloud occurrencefrequencyover the western Pacific accompanyingthe 1992 El Nifio wasobserved.Substantiallyfewer cirrus were seen at the 68-hPa level in the winter of 19911992 comparedwith 1992-1993.This variationcould be related to either El Nifio orreduced convectionduring a period when Mount Pinatubostratosphericaerosol cooledthe t in tropical cirrus clouds stems from their radiativeeffects [Ramanathan and Collins, 1991]. their links to stratospheric hydration and dehydration [Danielsen, 1993; Jensen etai. 1996: RosenfieId et al., 1998]. and their role in heterogeneous chemical reactions in the upper troposphere [Solomon etat. 1997]. The most complete data set describing the seasonalvariability and geographical distribution of high-altitude tropical cirrus has come from the limb-viewing occultation observations of the StratosphericAerosol and Gas Experiment(SAGE) II [Wang et al. 1996]. These data shou that the mostfrequently occurring cirrus are sufficiently tenuous to be invisible to ground observers and the nadir-viewing satellite-borneinstruments that gather operational meteorologicaldata. Forthis reason, data sets describing these thin cirrus are verylimited.While the SAGE II data provide a good climatological description of thin cirrus, aerosol data from the Cryogenic LimbArray Etalon Spectrometer(CLAES) instrument on the Upper AtmosphereResearch Satellite (UARS) [Roche et al.,1993] obtained in thermal emission provide an opportunity toobserve thin cirrus with much more frequent, near-global sampling.AlthoughCLAES was designed to observe the stratosphere, the lower-altitudelimit of its observations was frequently below the tropopause,particularlyin the tropics,where the tropopause is high For example, CLPd S ,picallygathered about 280 profile measurements per day' within 20 ofthe equator, while SAGE II averages fewer than four. Thisincreased data density eliminates the need to average overseveral years to examine the seasonal behavior of nearCopyright !999 by the American Geophysical Union.Paper number 1999JD900397.0148-0227 99 1999JDg00397S09.00clouds and providesvariations.a more detailed look at theirCLAE8 operated from October 1991 to May 1993. Duringthis period, volcanic aerosol loading from the Mount Pinatuboeruption (June 15. 1991) reached its maximum, and a moderately strong E1 Nifio developed in the winter of 1991-1992.Analysis of the CLAES data provides an opportuni to investigate changes in cloud occurrence associated with these phenomena.In addition to its value as a stand-alone data set. the CLAESdata complementother data sets and improve our abiliw toobtain a more complete description of the atmosphere.Forexample, CLAES data are concurrent with intensive operationperiods of the Tropical Ocean-GlobalAtmosphere CoupledOcean-AtmosphereResponse Experiment (TOGA COARE)[Webster and Lukas, 1992] and the Central Equatorial PacificExperiment (CEPEX). In addition, CLAES was coaligned withthe Microwave Limb Sounder (MLS) on UARS, which measures upper tropospheric water vapor [Read et al., 1995] butdoes not detect thin clouds.2.TheCL-kESInstrumentandDataThe instrument and operation have been described in detailby Roche et al. [1993]. In brief, CLAES acquired mediumresolutionspectra of infrared thermal emission from theEarth's limb in nine channels ranging from 3.5 to 12.8 p.m,corresponding to the altitude range of approximately 10-60kin. The viewing geomet ' of the 57" inclination UARS orbitprovides for daily coverage extending from either 34"-Sto 80 N(north-look) or 34 N to 80 S (south-look), depending on theorientation of the spacecraft, which yaws 180" approximatelyevery 36 days. With this coverage the tropics were continuouslyobserved except for short calibration periods at the beginningand middle of the 36-day yaw period. A UARS measurement22,183
MERGENTHALERET AL: CLAES(a)NDJFMA22.1850.00056/kmC T -MOBSERVATIONS OF TROPICAL CIRRUSJJASONDJFMAASONDJFMAASONDJFMA(b) CT 0.0009/kmr4668;100160146215NnDJFMAMJJ(c) Difference68NDJFMAMJJMonth (1991/92/93)Occu rrence0.00.10.20.30.40.50.60.70.80.91.0Plate I. (a) The occurrence frequency of aerosol volume absorption coefficient k (12.8tsm), in excess ofthe cloud identification threshold C r for Cr 5.6 10 - km-L (b) A similar plot with Cr raised to 9.0 x10- kin -a in which the Mount Pinatubo-relatedvariation is no longer apparent in the 68- to 215-hPa layers.(c) The difference between Plates Ia and lb shows the transient aerosol background rejected by increasingCr.
68 hPa30150-15-30MAM68 hPa30150-15-30(c) JJA68 hPaSON68 hPa3015gm. [0-15-3030150-I5-3068 hPa(e) ngitudePlate 2, The seasonal cloud occurrence frequencies at 68 hPa derived from Cryogenic Limb Array EtalonSpectrometer(CLAES) (color) compared with the Stratospheric Aerosol and Gas Experiment(SAGE) IIclimatoIogy [Wang et aI., 1996] (white overlay). (a) The CLAES observations for December,January, andFebruary (DJF) of 1991-1992 overlain with ctimatolo '. The color scale is the same as Plate 1. (b) March,April, and May (MAM) 1992. (c) June, July, and August (JJA) 1992. (d) September, October, and November(SON) 1992. (e) December, January, and Februar7 (DJF) t992-1993.180
MERGENq'HALERET AL: CLAES OBSERVATIONSOF 20-90-60100 hPa(9-30100030hPa60LongitudePlate3.Sameas Plate2 exceptat 100 hPa.90120150180
22,188MERGENTHALERET AL: CLAESOBSERVATIONSOF TROPIC.MCIRRUS146 hPa3015 ":0-15-30MAM146 hPa30150-15-30146 hPa3O15wm.i0-15.:-30d) SONiI146 hPa300-15-30146 hPa30150 .Sameas Plate2 exceptat146hPa.90120150180
MERGEN -HALERET AL:CLAESOBSERVATIONSOF TROPICAL215 hPa3O150-15-30MAM215 hPa3O150-15-30215 hPa3O.,,,/oc-15-33d) SONhPa335oPlate5.Sameas Plate2 exceptat 215hPa.CIRRUS22.189
22,190MERGEN'I'HALERET AL: CLAES OBSERVATIONS OF TROPIC.M CIRRUSbearing UARS pressure levels and consists of five panels, onefor each season of CL4,ES observations. This analysis usesC r 9.0 10 -4 kTn- and E r 30% for the CI .AES data.Sensitivity of the results to these parameters is discussed below. The color scale is the same as used in Plate 1. To make aCLAES versus SAGE II comparison without entirely reana]yzing SAGE II data to take into account differences in instrument vertical resolution, the Wang et al. [1996] statistics forvarious levels and cloud type have been combined to approximate CLAES results, which have a vertical resolution of 3.5km on the UARS pressure levels. The SAGE II results areoverlain in each panel in white contours.Plate 2a shows cloud occurrence frequencies derived fromCLAES measurementsfor the 68-hPa level from December1991 through February 1992 (labeled DJF 91/92). Since thetropical 68-hPa surface is centered near 19 km, the CLAESmeasurementsincorporate contributions down to about 17.0km. This is a region of sharply declining cloud occurrenceabove the mean tropopause.The most comparable resultsfrom the Wang et al. [1996] climatoloare the SVC data at17.5 km. Notwithstandingmagnitude differences, the spatialdistributionof cloud occurrence frequent'and its seasonalevolution agree quite well with the SAGE II results. Both datasets show similar patterns of cloud occurrence including maxima over Indonesia, equatorial .africa, the Amazon Basin, andthe western Pacific. The March, April, and May (MAM) (Plate2b) data from CLAES and SAGE II show qualitative spatialand temporal agreement. For example, both data sets revealsimilar cloud occurrence frequency increases over equatorial.Africa and reductions over the western Pacific and Indonesia.In June, July, and August (JJA) (Plate 2c), both data setsshow a minimum in tropical cloud occurrence and reasonablygood agreement in spatial distribution. In the fall, September,October,and November (SON), both data sets show theprogress of the annual cycle, with the return of higher cloudoccurrencesin the locations where high winter occurrenceswere noted.am interesting aspec of the 68-hPa level is that this is a levelwhere an interannual variation can be seen that can plausiblybe linked to the Mount Pinatubo aerosol veil. This is shown bythe increasein area exceedingthe 10% frequency-ofoccurrence level in DJ'F (1992-1993) (Plate 2e) relative to ayear earlier. A possible explanation is that less convective activin' reached this high level during DJF (1991-1992) due tothe reduced penetration of solar radiation to the tropics.Amother possible cause could be circulation changes associatedwith the 1991-1992 El Nifio. It is hard to separate the influenceof these two atmospheric perturbations based on the CLAES19-month data set.In general, the cloud occurrence frequency on this level (68hPa) is less in the CLAES data than in the climatological datachosen for comparison. This occurs because the data sets compared are mismatched in altitude in the region of particularlysharp vertical gradients in cloud occurrence frequency. Forinstance, the center of the UARS 68-hPa level is in the lowerstratosphere,but the CLAES effective field of view is wideenough to include the highest excursions of the tropopause. Abetter comparison might be attained by reanalyzing the SAGEII data on the UARS pressure grid at CLAES vertical resolution; however, data comparison could be difficult because theresults are likely to be veo' sensitive to factors that contributeo the vertical resolution of the data set. Nevertheless, it is auseful comparison because it shows the spatial distributionsimilarities in the data sets at the highest cloud-bearing levels.Plate 3 shows the seasonal cloud occurrence frequency observations for the 100-hPa level. The tropical 100-hPa surfaceis centered near 16.5 krn. and the CLAES measurementsincorporate contributions from about 14.8 to 18.2 km. To avoidcountingSAGE cloud occurrencesmore than once. theCLAES data are overlain with the climatologicalSAGE II15.5-kin SVC statistics only. Cloudiness at higher levels, notably 17.5 km, appears spatially well correlated with this level.The spatial distribution of CLa,.ES and SAGE II observationsagrees well for the 1991-1992 DJF season (Plate 31) on the100-hPa level. The geographical cloud distribution is also verysimilar in MAM (Plate 3b?. A notable area of disagreement isthe western Pacific, where the 1991-1992 CLAES data showhigher cloud occurrence in the central Pacific. (This probableE1 Nifio effect is discussed more below.) For the June-JulyAugust (JJA) period (Plate 3c), both data sets agree very well.showing, for example, the shift in the maximum from the Amazon Basin to the west coast of Me.'dco. For the SeptemberOctober-November(SON) period, the Northern Hemisphere(NH) fall (Plate 3d), both data sets show that strong maximaare reestablishedover South America and equatorial .africa.Regions of minimal cloudiness are also in substantial agreement. The similarity of the CLAES obsem'ations of DJF 19911992 (Plate 3a) and DJF 1992-1993 (Plate 3e) provide evidence that Mount Pinatubo aerosol has been rejected.In all seasons the CI. dES data appear to be more spatiallyconfined than the SAGE II observations. This may be due tothe relatively large bins used to accumulate SAGE II statisticsor it may be due to higher SAGE It sensitivity at the edges ofthe cloudy regions. Otherwise, the SAGE II and CLa.ES obser 'ations at this level are in good agreement with respect tospatial distribution.The good agreement between the CLUES cloud occurrencefrequencies and the climatolQgical SVC data, which are mostlysubvisible cirrus [Wang et aL. 1994]. is compelling evidence thatCL-XES detects subvisual cirrus in addition to thicker clouds.Plate 4 shows the seasonal progression of cloud occurrence onthe I46-hPa level centered near I4.5 kin. Comparable climatological data have been appro.'dmated on a grid-point by gridpoint basis as the maximum of either the sum of the 13.5-kmSVCs and 14.5-kin OPCs or the 15.5-krn SVCs alone. Thereare regions such as the Scinib of the Southern Pacific Convergence Zone (SPCZ) ( -135 E.25 S) where the SVC occurrence at 13.5 km is relatively high compared with the15.5-km level, so cloud occurrences at the lower level woulddominate the CLAES obse 'ations. Near the equator and theIntertropicalConvergence Zone (ITCZ) the SAGE II datashow that the 15.5-kin level dominates the cloud count. In theSAGE II analysis an OPC occurrence on the 14.5-km level isindependent of SVC occurrence at the 13.5-kin level, since anopaque cloud event at 14.5 km precludes an 5VC event belowit. We assume that an SVC at 15.5 km is highly correlated withlower level OPCs due to the similarities of their
tropopause cirrus. This threshold produces cirrus distributions which compare favorably with the near-tropopause tropical cirrus distributions in the Wang et al. (1996) cirrus climatology compiled from five years worth of SAGE II data. At higher levels in the tropics above about 14.5 kan the vast majority of SAGE II observations involve .
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STEP 3: Connecting with Lorex Cirrus Connect to your system using the free Lorex Cirrus app for smartphones and tablets (iOS and Android). To Connect with Lorex Cirrus 1. Download and install the free Lorex Cirrus app from the App Store or Google Play Store (Or scan QR code on the front page). 2. Tap the Lorex Cirrus icon to launch the app. 3.
3011 Cirrus Tile Sq LayIn DS_109:85_86 Cirrus Square LayIn 12/17/08 12:45 PM Page 85. Physical Data . CIRRUS Beveled Tegular with SUPRAFINE 9/16″ Exposed Tee grid; SOUNDSOAK . the closed-loop Armstrong Ceiling Recycling Program.
Cirrus Design, Duluth, MN 55811 1.5 Transition Training Kits To ensure successful transition of pilots into the Cirrus aircraft, each pilot will need a Cirrus aircraft transition training kit prior to the start of the transition course. This kit includes the following: 1. Training Guide (this binder) 2. Cirrus Aircraft Training Software (CATS) 3.
Importantly, Cirrus is designed to efficiently support the en-tire ML workflow. In particular,Cirrus supports fine-grain, data-intensive serverless ML training and hyperparameter optimization efficiently. Based on the parameter server model (see Figure 2), Cirrus provides an easy-to-use interface to perform scalable ML
stage of the life cycle is characterized by preconditioning of the stratospheric zonal flow and anomalous, quasi-stationary wavenumber-1 forcing in both the stratosphere and troposphere. As the life cycle intensifies, planetary wave driving gives rise to weakening of the stratospheric polar vortex and downward propagation of the attendant
describe the concept of pseudo-Polar domain, including fast forward and inverse transforms. For those interested primarily in Polar FFT’s, the pseudo-Polar FFT plays the role of a halfway point—a nearly-Polar system from which conversion to Polar coordinates uses processes
Banking on Cloud A discussion paper by the BBA and Pinsent Masons Outside of banking, public cloud computing has proven to be a driver of innovation, enabling new competitors, products and more flexible business models. By comparison, banks have been understandably slower in migrating products and services and leveraging the benefits of the public cloud, taking time first to focus on assessing .
