Ecmwf

Figure 8. Ten day mean wind vector and isotachs (ms 1) at 850 mb for the first 10 days of June, July, and August of 1998 (Sun and Chern, 1999).

850 hPa subtropical high, (2) a stronger barocli-nicity around 40° N over eastern Asia and a low pressure located to the north of the front, and (3) excessive evaporation from the abnormally wet, warm land (Sun, 2002). The precipitation ended on 18 August, when the subtropical high retreated and the low pressure in Manchuria moved away from the Asian continent. The model reproduced well the observed baroclinic waves to the north, the subtropical high and low-level jet to the south, and the front with heavy precipitation extending from southern China and the Korean peninsula to Japan. High correlations (Table 2) were also found for most variables between the model simulation and the ECMWF reanalysis for the 20-day means. However, it is also noted that the simulated low pressure in Manchuria, which was to the north of the Mei-yu front, propagated more slowly than observed, which may be responsible for the deepening of this low as well as for excessive heavy precipitation in the area (Fig. 9). It is also noted that the model generated a wet bias of precipitation in mountainous areas and a too strong subtropical high in the Pacific.

The PRCM also reproduced well the spatial distribution of mean surface temperature and mean sea level pressure during ten summers over East Asia as well as the temporal variation of mean vorticity over the South China Sea (Fig. 10; Yu et al., 2004a,b; Hsu et al., 2004).

2.5. Simulations of dust and ozone

Regional models coupling atmospheric chemistry have been applied with the PRCM to predict the transport and dispersion of trace gases and aerosols. Yang (2004a) has coupled the

Table 2.

Purdue Atmospheric Models and Applications 20-day mean statistics of PRCM compared with ECMWF (Sun 2002).

FIELD LEVEL BIAS RMS COR

Mean Sea Level Pressure

0 0

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