Assimilation and evaluation of MISR cloud tracked winds with GEOS-5 operational data assimilation system

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Monday, 5 January 2015
Junjie Liu, JPL, Pasadena, CA; and K. Mueller

Assimilation of wind observations in global models plays an influential dynamical role by forcing adjustment of the mass field at all scales in the tropics, and at smaller scales in the extratropics. However, critical gaps remain in the coverage of wind observations typically assimilated in current forecast systems. The MISR instrument aboard EOS-Terra has observed cloud-tracked wind (CTW) since early 2000, with observations expected to continue until at least 2020. Amongst the strengths of MISR winds are wind heights at 330 m precision and global pole-to-pole coverage including the latitude gap from 50-70 N/S between traditionally assimilated geostationary and polar-orbiting instruments. In this study, we assimilate the MISR winds into GEOS-5 Data Assimilation System (DAS). We will discuss the assimilation methods, and show the impact of MISR winds on short-range weather forecast in GEOS-5 DAS. We will evaluate the impact of MISR winds on short-range weather forecasts by comparing 5-day forecast errors of geopotential height and winds between the control run, which assimilates baseline observations, and the MISR-run, which adds MISR winds to the baseline observation network. We will further evaluate the MISR winds impact on the reduction of 24-hour forecast errors as measured by global and regional energy norm calculated by the adjoint sensitivity method.