Development of a Two-way Nested LETKF System for Cloud-resolving Model - Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications - page 496

Fig. 20.12 Horizontal distributions of 1 h rainfall ( shaded regions ) and horizontal wind at the
height of 20 m ( vectors ) reproduced by the Inner LETKF at 17 JST obtained by the assimilation
of ( a ) horizontal wind, ( b ) horizontal wind and PWV, and ( c ) radial wind. Circles and arrows
indicate the rainfall regions that were reproduced by the assimilation of wind data and of GPS
water vapor data, respectively. Circles and arrows of broken lines indicate the rainfall regions
where the rainfalls were reproduced but their intensities were weaker
conventional data from JMA was assimilated. Assimilations of GPS water vapor
data and Doppler radar data further increased the number of ensemble members in
which local heavy rainfalls were reproduced. These results indicate that the nested
LETKF system has the potential to be used as a data assimilation system for local
heavy rainfalls. In general, high-resolution ensemble forecasts using high-resolution
data (e.g. Radar data) have a huge computational cost. The nested LETKF system