Precipitation Retrievals Precipitation Retrievals Over Land Using SSMIS Over Land Using SSMIS

Nai-Yu WangNai-Yu Wang11 and Ralph R. Ferraro and Ralph R. Ferraro22

1 1 University of Maryland/ESSIC/CICSUniversity of Maryland/ESSIC/CICS2 2 NOAA/NESDIS/STARNOAA/NESDIS/STAR

OutlineOutline

MotivationMotivation Current status of GPROF land Current status of GPROF land Profiling approachProfiling approach High frequency and temperature High frequency and temperature

sounding channels from SSMIS sounding channels from SSMIS Land precipitation retrievals in Land precipitation retrievals in

complex terrain complex terrain Conclusions and future work Conclusions and future work

MotivationMotivation

Improve current precipitation retrievals over Improve current precipitation retrievals over land (TMI GPROF 6.5 land) land (TMI GPROF 6.5 land)

Explore mid-latitude precipitation retrieval Explore mid-latitude precipitation retrieval using passive microwave radiometer high using passive microwave radiometer high frequency and sounding channels, in frequency and sounding channels, in preparations for GPM preparations for GPM High frequency bands between 150 and 183 GHzHigh frequency bands between 150 and 183 GHz

Less sensitive to surface emissivity variationsLess sensitive to surface emissivity variations Respond to thick clouds, water vapor, and precipitationRespond to thick clouds, water vapor, and precipitation

Oxygen absorption bands between 50 and 60 GHzOxygen absorption bands between 50 and 60 GHz Primarily probe atmospheric temperature and moisture Primarily probe atmospheric temperature and moisture

profiles, might be critical in classifying different climate profiles, might be critical in classifying different climate regimes (e.g., freezing height) regimes (e.g., freezing height)

Current status of GPROF Current status of GPROF LandLand

TMI GPROF 6.5 landTMI GPROF 6.5 land Ferraro’s scattering index (SI) and Ferraro’s scattering index (SI) and

rainrate algorithm for SSMI and TMI, rainrate algorithm for SSMI and TMI, utilize 22 and 85 GHzutilize 22 and 85 GHz

TRMM TMI SI and PR rainrate matchups, TRMM TMI SI and PR rainrate matchups, convective probability, separate convective probability, separate convective and stratiform in the convective and stratiform in the database; coastline improvements database; coastline improvements (McCollum and Ferraro)(McCollum and Ferraro)

Retrieve Surface rainrateRetrieve Surface rainrate

Profiling Approach Profiling Approach

Retrieve hydrometeor profiles using 150-183 Retrieve hydrometeor profiles using 150-183 GHz and 50-60 GHz brightness temperaturesGHz and 50-60 GHz brightness temperatures

Bayesian frameworkBayesian framework Employ cloud resolving models (CRM), Employ cloud resolving models (CRM),

coupling CRM outputs with radiative coupling CRM outputs with radiative transfer calculations to construct an a transfer calculations to construct an a priori database of brightness temperatures priori database of brightness temperatures and the hydrometeor profiles over land and the hydrometeor profiles over land

Profiling ApproachProfiling Approach

Use a probabilistic approach to calculate the most likely a Use a probabilistic approach to calculate the most likely a posteriori distribution constrained by actual satellite posteriori distribution constrained by actual satellite measured brightness temperatures measured brightness temperatures

Precipitation estimates are weighted averages of the mean Precipitation estimates are weighted averages of the mean precipitation values corresponding to the classes in the precipitation values corresponding to the classes in the databasedatabase

R: retrieved hydrometeor profileR: retrieved hydrometeor profile

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SurfaceScreening

HydrometeorMicrophysical

schemes

RadiativeTransferModel

TOA multichannelBrightness Temperatures/

Hydrometeor Vertical profiles

Observed Multichannel

Brightness Temperatures

Observations

ConvectiveStratiform ?

Best matchedBrightness Temperatures

Hydrometeor profiles

Surface rainrate

Generate Database

Land Database Land Database

GPROF land profiles are selected exclusively fromGPROF land profiles are selected exclusively from GPROF CRM simulations that are predominantly GPROF CRM simulations that are predominantly

from tropical oceanic systems from tropical oceanic systems Profiles tested:Profiles tested:

GCE TRMM LBA: simulations of mesoscale convective GCE TRMM LBA: simulations of mesoscale convective system during Jan-Feb in Brazilsystem during Jan-Feb in Brazil

MM5 MIDACF: mid-Atlantic ocean cold front systemMM5 MIDACF: mid-Atlantic ocean cold front system 5 classes of hydrometeor: cloud water, cloud ice, rain, 5 classes of hydrometeor: cloud water, cloud ice, rain,

ice and graupelice and graupel 1-1.5 km horizontal resolution, averaged to individual 1-1.5 km horizontal resolution, averaged to individual

SSMIS resolutions (15 km for 150, 183 GHz)SSMIS resolutions (15 km for 150, 183 GHz) Radiative transfer model: Eddington two-stream Radiative transfer model: Eddington two-stream

approximation (Kummerow)approximation (Kummerow)

Land database issuesLand database issues Bayesian approachBayesian approach

Strength : direct use Strength : direct use of explicit microphysical of explicit microphysical mechanisms in CRMmechanisms in CRM Disadvantage: Disadvantage: susceptible to errors susceptible to errors in the a priori databasein the a priori databasein terms of the accuracyin terms of the accuracyof microphysical details, of microphysical details, and the fidelity with whichand the fidelity with whichthe model outputs capturethe model outputs capturedifferences in climate differences in climate regimes. An example. regimes. An example.

Observations: SSMISObservations: SSMIS

Conical scanned passive Conical scanned passive microwave radiometer, microwave radiometer, launched in Oct 2003launched in Oct 2003

SSMI heritage channels SSMI heritage channels 19-91 GHz19-91 GHz

Air temperature Air temperature sounding channels near sounding channels near 60 GHz oxygen 60 GHz oxygen absorption bandabsorption band

150 GHz imaging 150 GHz imaging channel and three 183 channel and three 183 (+-1, +-3, +-6.6) GHz (+-1, +-3, +-6.6) GHz troposphere water vapor troposphere water vapor sounding channelssounding channels

SSMIS IFOV SSMIS IFOV

FreqFreq Footprint Sampling intervalFootprint Sampling interval GHz (km) (km)GHz (km) (km) 22 73X47 2522 73X47 25 50 38X38 37.550 38X38 37.5 54 38X38 37.554 38X38 37.5 150 150 14X13 37.514X13 37.5 183183 14X13 37.514X13 37.5

Grid all channels to 0.15 deg Grid all channels to 0.15 deg

in latitude/longitude gridsin latitude/longitude grids

Courtesy of Dr. Joe Turk

NOAA HMT 2006 siteNOAA HMT 2006 site

Complex terrainComplex terrain Off coast of CaliforniaOff coast of California American river basinAmerican river basin Sierra mountainSierra mountain Winter time floodingWinter time flooding

InstrumentationsInstrumentations Radar profilersRadar profilers X-band polarimetric X-band polarimetric radarradar GPS soundeGPS sounde DisdrometerDisdrometer Rain gaugesRain gauges

IOP4 : DEC 30-31, 2005IOP4 : DEC 30-31, 2005Cold frontal system, moist oceanic Cold frontal system, moist oceanic air mass crossed the area, air mass crossed the area, small scale rain band structure, small scale rain band structure, high snow level on the groundhigh snow level on the ground

High Frequency Precipitation signalsHigh Frequency Precipitation signals

SSMIS Dec 31, 2005 1637ZSSMIS Dec 31, 2005 1637Z

Surface ScreeningSurface Screening Surface ice and snow, Surface ice and snow, and sand yield similarand sand yield similarscattering signatures as scattering signatures as precipitationprecipitation Screening surface scatters Screening surface scatters

““scattering index” SI to locatescattering index” SI to locatehigh scattershigh scatters combinations of low/highcombinations of low/high

frequency channels to differentiatefrequency channels to differentiate

precipitation from surface scattersprecipitation from surface scatters TB(22 GHz)TB(22 GHz) TB(91 - 150 GHz)TB(91 - 150 GHz) - 150 GHz)- 150 GHz)

Preliminary Rain RetrievalPreliminary Rain RetrievalDecember 31, 2005 December 31, 2005

SSMIS retrieved rainratesfrom 50, 150, 183+-1/+-7 GHz at 1637Z

Composite radar reflectivity at 1700Z

Conclusions and Future Conclusions and Future WorkWork

A framework of land precipitation profiling retrieval A framework of land precipitation profiling retrieval algorithm using passive microwave high frequency is algorithm using passive microwave high frequency is establishedestablished

Currently, retrieval does not have the ability to locate the Currently, retrieval does not have the ability to locate the freezing level and differentiate convective and stratiform freezing level and differentiate convective and stratiform systems from brightness temperaturessystems from brightness temperatures plan to gather large number of matchups between plan to gather large number of matchups between

SSMIS, TRMM PR and CloudSat for different climate SSMIS, TRMM PR and CloudSat for different climate regimes to enhance the retrieval skillregimes to enhance the retrieval skill

Radar reflectivity/hydrometeor profiles will also used to Radar reflectivity/hydrometeor profiles will also used to build up hydrometeor database for landbuild up hydrometeor database for land

Validate radiative transfer model with HMT ground radars Validate radiative transfer model with HMT ground radars and satellite radar matchups and satellite radar matchups