Towards Passive Microwave Radiance Assimilation of Clouds and Precipitation

Towards Passive Microwave Radiance Assimilation of Clouds and Precipitation

Ralf Bennartz1, Tom Greenwald2, Andrew Heidinger3,

Chris O’Dell1, Martin Stengel1, Kenneth Campana4, Peter Bauer5

1: Atmos. & Oceanic Sci.,University of Wisconsin2: CIMSS,University of Wisconsin3: NOAA/NESDIS4: NOAA/NCEP5: ECMWF

Outline

SOI model and applications

Cloud/precipitation overlap

3-year accomplishments

Further plans

SOI Radiative Transfer Model

• Hybrid multi-stream solution method (doubling plus iteration)

(Heidinger et al. 2006; O’Dell et al. 2006)

• Implementation

- Less scattering: 2-stream solution

- More scattering: 4-stream solution

• Forward, tangent linear and adjoint models integrated into CRTM

Accuracy of Results (Eddington and SOI versus Monte-

Carlo model)

Forward and adjoint simulation example

AMSR-E ObservationsGFS Simulations

Infrared Applications: MSG SEVIRI

MSG SEVIRI Comparison Results

Channel RMSE [K] Bias [K]

6.2 m 1.93 0.22

7.3 m 1.91 -1.25

8.7 m 1.54 1.17

10.8 m 1.38 0.73

12.0 m 1.37 0.64

13.4 m 1.37 1.06

Different cloud/precipitation overlap models

• Conventional approach uses cloud cover to subdivide NWP pixel in cloudy/precipitation

• New approach derives two or three optimal columns based on subscale distribution of precipitation columns with similar optical properties

• Numerically efficient (2-3 radiative transfer calculations per NWP grid point)

• Highly accurate against independent column/Max-Random-overlap reference

• Optimal approach reduces errors due to cloud overlap from maximum values of 5-10 K to values < 1K

Different cloud/precipitation overlap models

O’Dell, Bauer, Bennartz, JAS, 2006, submitted

Currently operational at

ECMWF

1Column 2Columns 3columns 3 optimal

Different cloud/precipitation overlap models

Currently operational at

ECMWF

New scheme with much better error

characteristics

O’Dell, Bauer, Bennartz, JAS, 2006, submitted

1Column 2Columns 3columns 3 optimal

3-year Accomplishments

• Fast forward RT model (SOI) developed, tested and integrated in CRTM (3 publications)

• Tangent linear and adjoint model developed, tested, and integrated in CRTM

• Bias GFS/SOI statistics for passive microwave and infrared

• Fast and accurate new cloud overlap scheme for use in NWP radiance assimilation (forward/adjoint); manuscript submitted

Further plans

• Monitor bias statistics over longer time period, especially:

– Fully include scattering (need more complete GFS input data)

– Biases in IR including scattering • Precipitation assimilation:

– Include cloud diagnostics to generate precipitation rate

– Further test and integrate cloud overlap with NCEP/GFS.