Regional Spectral Model Simulations of the Summertime Regional Climate over Taiwan and Adjacent Areas

The National Centers for Environmental Prediction (NCEP) regional spectral model (RSM) version 97 was used to investigate the regional summertime climate over Taiwan and adjacent areas for June-July-August of 1990 through 2000. The simulated sea-level-pressure and wind fields of RSM1 with 50-km grid space are similar to the reanalysis, but the strength of the simulated subtropical high tends to be too strong, resulting in intensified southeasterlies, instead of southwesterlies, over the region of southern to southeastern China. Generally, the simulated precipitation patterns of RSM1 followed those of NCEP reanalysis, but the large-scale southeasterly wind bias was responsible for the precipitation excess over eastern and southeastern China when compared to observations. For simulation at 15-km grid space over Taiwan (RSM2), the climatology and inter-annual variability of island-mean precipitation agreed well with station observations and were improved from the coarser forcing reanalysis and RSM1. However, the temporal correlation was seasonally and geographically dependent, presumably due to influences from the interaction of the orography and biases of the large-scale circulations. The RSM, although improved from reanalysis, still tends to produce less heavy rainfall days than observations, especially in July and August. In addition, while the typhoon-day composites of sea-level pressure and precipitation reveal poor agreement between the observations and the RSM simulations, RSM2 simulation placed the precipitation center accurately over southwestern Taiwan during non-typhoon days, albeit with weaker amplitude. These results indicate the limitations of the RSM in simulating summertime convective storms and typhoon events in this area.

並列關鍵字

Regional modeling ； Region climate ； Taiwan climatology ； Downscaling

國際替代計量

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