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Cloud/Rain partitioning using MODIS and AMSR-E

Cloud/Rain partitioning using MODIS and AMSR-E. Matt Lebsock. Aqua AMSR- E & MODIS. The world is a drizzly place. Drizzle defined where 750 meter reflectivity exceeds -15 dBZ Area and Low cloud fraction weighted oceanic mean is 19.2%. Physical Basis For Cloud/Rain Separation.

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Cloud/Rain partitioning using MODIS and AMSR-E

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  1. Cloud/Rain partitioning using MODIS and AMSR-E Matt Lebsock Aqua AMSR-E & MODIS

  2. The world is a drizzly place • Drizzle defined where 750 meter reflectivity exceeds -15 dBZ • Area and Low cloud fraction weighted oceanic mean is 19.2%

  3. Physical Basis For Cloud/Rain Separation • The water path can be partitioned between cloud and Precipitation • @ Visible/Near-Infrared wavelengths Qext->2 • @ Microwave frequencies • Tb are sensitive to both cloud and precipitation water Small

  4. Spatial Resolution • MODIS • 1km • AMSR-E • Use Backus-Gilbert method to resample the AMSR-E footprints to a common resolution @ 23 GHz (31km x 18km) • Average the MODIS cloud products to the 23 Ghz resolution with the antenna gain function as a weighting parameter.

  5. Optimal Estimation Retrieval A-Priori Uncertainty Observational Uncertainty

  6. January 2007 Results

  7. No Cloud Fraction

  8. Cloud Fraction

  9. Precipitation Water

  10. January 2007 Statistics

  11. Radiative Transfer Simulations Polarization Brightness Temperatures Emission Signal Scattering Signal Depolarization Signal There does appear to be a signal in the brightness temperatures

  12. Land Influence? Water Vapor?

  13. Continued Work • Add a realistic DSD • Add rain fraction to retrieval • Include an optical depth constraint

  14. Summary • It appears possible to place bounds on the ratio of precipitation water to cloud water in liquid clouds. • Critical assumptions • Precipitation DSD • Insensitivity of MODIS to precipitation • Applications • Improved GPROF database • Studies on the control of precipitation production • Aerosol indirect effects • Thermo-dynamical controls

  15. Radiometer Obs TMI, AMSR-E, SSM/I Background retrieval SST, TPW Radiometer Appropriate Database Compare Tb with a-priori database Rainfall Product GPROF Algorithm Does the A-priori database contain The correct statistics of rain/no-rain

  16. TRMM Radiometer Obs TRMM Radar Obs Background Retrieval SST, Wind, TPW, CLW Rain? No Yes Radar Rain Profile CompareTb to Obs Combine & Compute Tb Agreement ? Make Database Make Database Yes No Add rain below sensitivity of PR & Recombine and Compute Tb CompareTb to Obs Agreement ? Yes No Modify DSD in PR pixels w/o PIA information & Recombine and Compute Tb CompareTb to Obs Yes GPROF 2008 Database Generation Make Database

  17. PR-CloudSat Matchups 7 Wm-2 10% 50% Berg et al., 2010

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