Geoscience Reference
In-Depth Information
a
PWV
#001
#002
#003
#004
#005
#000
#010
#007
#008
#009
#011
#006
(mm)
(m /s)
b
SWV
#001
#002
#003
#004
#005
#000
#007
#010
#011
#006
#008
#009
(mm)
(m /s)
Fig. 20.11 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 ) PWV data and ( b ) SWV data. Arrows indicate the rainfall regions that extended northwestward
the ensemble members. It is deduced that some paths from GPS receivers to GPS
satellites penetrated the humid regions that generated the convection cells northwest
of Sakai City. The rainfall regions extending northwestward were reproduced in
9 ensemble members (#000-#007, #011) (Fig. 20.11 b). The number of ensemble
members in which the intense rainfall was reproduced was increased by assimilation
of GPS water vapor data. This means that GPS water vapor data had a strong
influence on the reproduction of the heavy rainfall. The ensemble spread is expected
to be smaller because the rainfall regions became closer to the observed ones by
data assimilation. In the case that the rainfall regions with small spreads are greatly
different from the observed ones, the ensemble spreads should be wider by removing
the causes of the small spreads before data assimilation. On the other hand, the
analyzed rainfall regions in this study were close to the observed ones. These
distributions indicate that the ensemble forecasts were performed appropriately.
20.5.2
Impact of Doppler Radar Data and the Synergistic
Effect of GPS Water Vapor Data and Radial Wind Data
As for the Doppler radar data, two kinds of data were assimilated. The first was
the horizontal wind obtained by the dual analyses of the radial wind of Kansai and
Search WWH ::




Custom Search