AMSU-A Radiance Assimilation becomes Operational at FNMOC
Last Updated: Tuesday, 15-Jul-2008 11:04:59 PDT
The results of medium-range forecast tests of radiance assimilation versus NESDIS ATOVS retrieval assimilation show substantial improvement in the forecasts of height, wind, and temperature in both the Northern and Southern Hemispheres. In the Tropics, the tropical cyclone track errors are smaller with radiance assimilation, even though the upper- and lower-level wind errors are essentially the same. Overall, there are fewer forecast "busts" with radiance assimilation, especially in the Southern Hemisphere.
The improvements to the forecast skill,
as measured by the 500 hPa height anomaly correlation, are shown in Figures
1 and 2.
 FIG. 1. Southern Hemisphere 500 hPa height AC vs. forecast hour for the summer 2003 case. The test run (AMSU-A) includes NAVDAS assimilation of AMSU-A radiances as described in Section 2. The control run assimilated NESDIS ATOVS retrievals with NAVDAS. |
 FIG. 2. Same as FIG. 1, but for Northern Hemisphere. |
AMSU-A Channel 10 represents stratospheric
temperatures near 20 km and shows the
cold south polar air in the So. Hemisphere winter.
AMSU-A Channel 4 represent temperature in
the lower troposphere and
can also "see" the surface for high incidence angles and high
terrain
Radgram depicting the time history of the
Observed - Computed radiances (OB-BK) from the NAVDAS assimilation run.
The radgram also depicts the time history of the Bias Corrected radiances
that NAVDAS actually assimilates.
