[10-2]

Assimilation experiments of bright band heights

T. Enomoto and Munehisa Yamamoto (Kyoto University)

Bright bands are strong echo from the melting layer and their heights represent several hundred m below the freezing level (Harris et al. 2000). Bright band heights, not typically used operationally, convey valuable information on a key height in cloudy areas over ocean. The bright bands heights in TRMM PR 2A23 (Awaka et al. 2009) are assimilated as 0C temperature observations at the respective heights with a statistically obtained difference from the freezing level into an atmospheric general circulation model using the local ensemble transform Kalman filter. With the bright band heights, the tropical troposphere near the freezing level is warmed by O(0.1) K and the ensemble spread is reduce by O(0.01)K. Comparisons against ERA-Interim and radio-sonde observations as well as the change in analysis increment imply the improvement of analysis with bright band heights. Although our results may be exaggerated by the lack of the assimilation of satellite radiances, the bright band heights may be complementary to the conventional and remotely sensed observation because it provides global information on the lower tropospheric temperature in the cloudy areas, where other observations do not typically cover, and has a potential impact on hydrological cycle through cloud microphysics.