GSI/WRF Regional Data Assimilation System and Its Application in theWeather Forecasts over Southwest Asia - Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications - page 616

a

2-m Temperature Diurnal Cycle variation

GTS

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b

10-m Wind Speed Diurnal Cycle variation

ANL

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Fig. 25.10 Diurnal cycle variation, ( a ) 2-m temperature ( ı C), ( b ) 10-m wind speed (ms 1 ).
Twenty-four-hours forecasts only (Updated from Xu et al. ( 2009 ))

variation. The magnitude of model forecasts values are fairly consistent with the
analysis values, except for the large difference on May 3. There is no evidence of a
sharp gap between the model forecasts and the analysis data.
However, the spatial domain of the SWA areas appears to cover about four
time zones. The whole domain average did not reflect significantly the diurnal
cycle of the different regions. The 30-day period mean of diurnal cycle (Fig. 25.11 )
displayed the variation by region. The results show that over regions in the
western and northeastern part of Southwest Asia, including the Saudi Arabian
desert and northern border of Afghanistan, the model forecasts of 2-m temperature
(Fig. 25.11 b) are in much better agreement with the GTS observations (Fig. 25.11 a)
than in the Zagros mountains of western Iran, and Indian northwest deserts. Note
the amplitude of the diurnal cycle in the model is much smaller than the GTS
observations.
For the diurnal cycle variation in 10-m wind speed, the model forecasts
(Fig. 25.11 d) over Southwest Asia has a similar amplitude and distribution to the
NCEP GFS analysis data (Fig. 25.11 c) except for the clear mesoscale features in the