Cloud rain partitioning using modis and amsr e
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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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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

  • 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


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.


Optimal Estimation Retrieval

A-Priori Uncertainty

Observational Uncertainty


January 2007 Results


No Cloud Fraction


Cloud Fraction


Precipitation Water


January 2007 Statistics


Radiative Transfer Simulations

Polarization

Brightness Temperatures

Emission Signal

Scattering Signal

Depolarization Signal

There does appear to be a signal in the brightness temperatures


Land Influence?

Water Vapor?


Continued Work

  • Add a realistic DSD

  • Add rain fraction to retrieval

  • Include an optical depth constraint


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


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


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


PR-CloudSat Matchups

7 Wm-2

10%

50%

Berg et al., 2010


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