Megha Tropiques Ground Validation
Megha Tropiques Ground Validation
Megha Tropiques Ground Validation
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<strong>Megha</strong> <strong>Tropiques</strong> <strong>Ground</strong> <strong>Validation</strong>Marielle Gosset(Institut de Recherche pour le Développement , IRD /LMTG)and <strong>Megha</strong>-<strong>Tropiques</strong> mission group.<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Review of Cal/Val needs per instrument SCARAB ERB TOA : satellite to satellite comparisons - other spaceborne ERB instruments. No in situ for TOA ERB SAPHIR atmospheric water profiles : direct measurements of the RH profiles from ground based Radio Sounding. Operational RS + dedicated launches (RS unbiasing - synchronisation with sat. Overpasses) Other ground based and space borne indirect measurements of IWP will provide additional datapoints with a high temporal resolution. MADRAS L2 (hydrometeor profiles, instant rain) and L4 (gridded 1°/6h) Raingages network Radars (3D, polarimetry) In situ information on ice phased hydrometeors .<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
2300 km 1700 km SAPHIRScaRaBMADRASRainfall products to be validated :Level 2 : Instant product below swath‘Instant’ Surface Rain ratesWater/Ice content and hydrometeor profilesConvective/Stratiform Flag.Level 4 : Surface Rain maps (gridded accumulations)1° x 1° - 1 Day global ( 0°5x0°5 - 6h WA Continent)<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Some GV Challenges-Sampling issues (trajectories / limited number of overpass)- -ponctual nature of ground or in situ measurements.- -limited availability/coverage of high quality ground rainfall vs rainfall variability(3D) and intermittency : at all scale !- ‘Instant’ rain from ground instruments ?- -<strong>Ground</strong> trouth quality assessment- Instrumental errors / Radar rain retrieval errors- Errors in deriving mean areal rain amounts.- -Difficulty to measure some variables :- microphysics, vertical profiles in rain.- -Sat Prods regional biases - Biases vs time of the day / system type ….. needto be investigated.- -Satellite products performances are scale dependant…….. and end users have different needs.<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Some GV Challenges-Sampling issues (trajectories / limited number of overpass)Required GV deployment :- -ponctual nature of ground or in situ measurements.-From -limited Regional availability/coverage scaleof high quality ground rainfall vsrainfall variability (3D) and intermittency : at all scale !down to smaller scale where high quality, high resolution data canbe - ‘Instant’ measured. rain from ground instruments ?- -<strong>Ground</strong> Provide information trouth quality at small assessment time steps (instant rain pdf and spatialstructure) , document the diurnal cycle,- Instrumental errors / Radar rain retrieval errorsProvide information on rain type and vertical profiles - Hydrometeor Sizedistributions - Errors in and deriving densities. mean areal rain amounts.- -Difficulty<strong>Ground</strong> truthto measurequality assesmentsome variables(or GVV)::Combine instruments for intercomparisonand document the smaller scale (to inferr sampling errors).-Combine microphysics, direct and vertical statistical profiles (distributions in rain. based) satellite-ground- -Sat comparisons. Prods regional biases - Biases vs time of the day / systemtype ….. need to be investigated.- -Satellite products performances are scale dependant…….. and end users have different needs.<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Next : Details on the West African GV activitiesFrench / CNES validation activities will focus on WestAfricaAn area well studied recently with the AMMA (africanMonsoon Multidisciplinary Analysis) Program.<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Regional scale :Operational networks (daily rain)-CILSS/AGHRYMET (regional agency fordrought alarm)-+ National weather services<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
AMMA-CATCHOuemeAMMA-CATCHNiameyseverallocations withdifferent rainfallregimes tostudy regionalvariablity.Recording rain gages 20 kmMeso scale (1°x1°) :Senegal3 high resolution research networks(tipping buckets - ‘instant’ rain)<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GVAverage density : 1 stat/200 km2
Meso scale (1°x1°) : Work with the high resolution research networks (tipping buckets -‘instant’ rain)At this scale : Rain intensities freq. distribution comparisons / diurnal cycle evaluation / rainfield structureSee posters MTCompare the Frequency distributions of the rain ratesSee poster Kirstetter< quantile-quantile comparisons of the pdf of 5 minrainrates (12x12 km2) from the Niger and Benin networks.Assess the ground truth accuracy anddocument the field structure. Variogram and map of estimationvariance for the Benin mesoscalenetwork..Evaluate the diurnal cycle rendition.< average diurnal cycle for August, inBenin, gages and 3 pdts.Courtesy Roca et al, 2009.Gauges EPSAT GSMAP TMPA<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Meteorological radars :To go down to kilometric resolution - highrepetition sampling of the rain fieldInstant products and profilesL2 validationStructure, dynamics and intermittency of the‘instant’ rainfields -> spacial variability athigher time stepsEx : Instantreflectivities fromXport andTRMM-PRHourly accumulations<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> -Gosset - GPM-GV
Meteorological radars :To analyse the hydrometeors type, size distribution and propertiesPolarimetry basedPIDHydrometeorsidentificationCourtesy Dolan >Analyse of X-bandpolarimetric Xport radarAMMA data<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Meteorological radars :To analyse 3D structure and vertical profilesRadar 3 D analysisCONV/STRAT flagCourtesy Kirstetter ^ >Analyse of C-Band AMMA dataVertical watercontent distributionstatistics<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
DensityMeteorological radars :To analyse the hydrometeors type, sizedistribution and properties1000Stratiform zone : ice particules densityVertical Profileof Reflectivitydensity (kg.m-3)8006004002000convectif 10->20 20->30 30->40 40->50distance from convective zones (km)Physicaly basedinversion of theobserved PVRKirtetter, 2009Courtesy Kirstetter ^ >Analyse of C-Band AMMA data<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Meteorological radars ->dedicated campaigns.need of a super site forAlready in Niamey :MIT C-‐Band Thanks GPM/NASA!<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV< Niamey Super site : goodfor sampling5 overpass / day.
Meteorological radars ->dedicated campaigns.need of a super site forMIT C-‐Band radar (250 km range) 2 radars : 1 long range, 1 shorter range attenuated butPOLARIMETRIC2 frequencies - dual Doppler capacity1 dual pol radar (100 km range-‐ a8enua9on)-‐ Complementaryinstruments forvalidation of QPE andprofiles + hydrometeorsinformation :.MRR -‐ profiler disdrometers <strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV16 Rain gages
Airborne validation campaign : hydrometeors type, size distribution andDENSITY -> for parameterization of BRAIN algorithm1000Stratiform zone : ice particules densitydensity (kg.m-3)8006004002000convectif 10->20 20->30 30->40 40->50distance from convective zones (km)Bouniol et al, 2009Ice density from airborneAMMA data (rasta+probes)Aout 2010 !!!combined : airborne + ground measurement<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> -Gosset - GPM-GV
Summary : a combination of approachesand scales-Satellite to satellite comparison is the only possibility to compare MTproducts to a reference data base on a global basis.-Existing ground based networks : Operational network (Nationalweather services) and research networks (Ex AMMA-CATCH).-Devoted super site : Radars for profiles validation, high resolution(both in space and time) data and focused in situ measurements.-Ponctual Airborne measurements-Data from other scientific, sea campaign (right timing/right zone….)MT life time /monitoring2011, monitorng2010-20112010 (Africa)2011/12Time frame- On going investigations on <strong>Validation</strong>/Evaluation through landsurface/hydrological models in several tropical basins …<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Summary : a combination of approachesand scales-Satellite to satellite comparison is the only possibility to compare MTproducts to a reference data base on a global basis.-Existing ground based networks : Operational network (Nationalweather services) and research networks (Ex AMMA-CATCH).-Devoted super site : Radars for profiles validation, high resolution(both in space and time) data and focused in situ measurements.-Ponctual Airborne measurementsResearch opportunities !!-Data from other scientific, sea campaign (right timing/right zone….)MT life time /monitoring2011, monitorng2010-20112010 (Africa)2011/12Time frame- On going investigations on <strong>Validation</strong>/Evaluation through landsurface/hydrological models in several tropical basins …<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Thanks for your attention !<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
I- Review of Cal/Val needs per instrument SCARAB ERB TOA : satellite to satellite comparisons - other spaceborne ERB instruments. No in situ for TOA ERB SAPHIR atmospheric water profiles : direct measurements of the RH profiles from ground based Radio Sounding. Operational RS + dedicated launches (RS unbiasing - synchronisation with sat. Overpasses) Other ground based and space borne indirect measurements of IWP will provide additional datapoints with a high temporal resolution. MADRAS L2 (hydrometeor profiles, instant rain) and L4 (gridded 1°/6h) Raingages network Radars (3D, polarimetry) In situ information on ice phased hydrometeors .<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Elements for the in flightcalibration of MEGHA-TROPIQUES microwaveradiometersL. Eymard, N. Karouche and theIndian - French project andmission teams<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> -Gosset - GPM-GV
<strong>Megha</strong>-Tropique microwaveradiometers Madras : conical scanning radiometer :18 GHz H/V24 GHz V 40 km footprint36.5 GHz H/V89 GHz H/V 10 km footprint157 GHz H/V 6 km footprint SAPHIR : transverse scanning radiometer :183.3 GHz ± 0.2, 1.1, 2.7, 4, 6.6, 11 GHz HFootprint 10 km at nadir<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV Close to existing instruments (SSMI, AMSU-B/
MADRAS and SAPHIRInsérer dessins /photos<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Specificities of MADRAS andSAPHIR wrt other radiometers No window channel on SAPHIR (but channel 6(±11GHz) far on the wing of the absorption band) difficulty to ensure footprint location? Smaller footprint, good directivity (20 cm antennadiameter) expected small « contamination » ofthe main lobe, and low side lobes Channel 157 GHz on MADRAS no overlapbetween scans; no experience of calibration ofsuch channel (H and V) Radiation protection of the instrument less« contamination <strong>Megha</strong><strong>Tropiques</strong> » of the <strong>Validation</strong> main - Gosset / - side GPM-GVlobes, betterhomogeneity of the hot load
Major steps of in-flightcalibration (both radiometers) From launch to 1 - 3 months: Instrumentchecking: Radiometric behavior (counts, gain,magnitude of Tb) : range wrt on groundcalibration Swath homogeneity : detection of majoranomalies Footprint location : detection of anomaliesdue to mechanical / engine / clock failuresEx: anomalies dans le scan TMI (Wentz et al, 2001)<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Major steps of in-flightcalibration (both radiometers)- 2 Comparisons to assess the absolute calibration Use of assimilation tools to evidence mean differencesbetween measured Tbs and model simulations (first guess),compared with other assimilated instruments (over ocean,clear air) Direct comparisons with other radiometers with similarchannels over ocean, clear air Statistical comparisons with simulations Tb from measured - modelTb simulated5analyses, radio-soundings : swath homogeneity, impacts of4unexpected « contaminations »32<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset -3 - GPM-GV10-1-2EMWR 23EMWR 36TMR 18TMR 21TMR 37SSM/I 19VSSM/I 19HEMWR - TMRSSM/I 22VSSM/I 37VSSM/I 37HSSM/I 85VSSM/ISSM/I 85HTMI 10VTMI 10HTMI 19VTMI 19HTMI 21VTMITMI 37VTMI 37HTMI 85VTMI 85H
Major steps of in-flightcalibration (both radiometers)- 31 Analysis of the radiometer performances over the0,980,960,94whole range (objective 1K) : Comparisons with simulations and other instruments0,840,82over « cold » scenes : calm sea (specular 0,80,78reflection),frequencylowest surface temperature and « hot » scenes : rainforest (near black body) If suspected to be significant : analysis of side lobecontributions (mean value, specific contaminationwithin the swath) Sensitivity to the coast approach Sun glint effects detection, flagsImpact of far side lobe contribution to the main lobe(Envisat/MWR : 4% at 23.8 GHz : up to 8K overoceans!)Method thenaplied to Topex / Jason1 radiometers0,920,90,880,86<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GVderived emissivity18 18,7 21 23,8 31,4 36,5 37AMSUATMREMWRSSM/I
Additional calibrationcorrection for retrieval Once the calibration achieved, no more change toTbs (level 1B/C products) Possible inconsistencies with simulations / otherradiometers due to different tools used Additional correction to Tbs might be requiredbefore applying retrieval methods or assimilation : Use of validation results and simulations to determinethe correction Users may apply their own corrections<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
Along life monitoring Drift survey : use of specific targets,comparisons with simulations Detection of any anomaly Use of validation comparisons toevidence any anomaly …<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
I- Review of Cal/Val needsGlobal <strong>Validation</strong> plan- must include measurements from varous climatic zone and rainfall regimes- Sample several area in the Tropical Belt- French effort : Focus on West Africa.<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
<strong>Megha</strong><strong>Tropiques</strong> <strong>Validation</strong> - Gosset - GPM-GV
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