Spatial And Temporal Variability Of Precipitation Over The Main River Basins In The West Coast Of Taiwan Strait

The research on watershed precipitation has great significance not only for nutrients and pollutants transport in river basin but also for the study on estuary ecological effects. In this thesis, we retrieved data from TRMM (Tropical Rain Measuring Mission) rain rate available in daily and monthly temporal and25km spatial resolutions. The rainfall data from Xiamen meteorological station was used to validate the TRMM satellite rain rate and found significant correlation between them. This paper is focused on spatial and temporal variability of precipitation over the main river basins in the west coast of Taiwan Strait over the15-year period from1998to2012.In the first part, we research on the basic features of regional precipitation distribution in Taiwan Strait and its adjacent area. The climatological monthly analysis showed that April to September is rainy season. The maximum rainfall occurs in June, followed by August. The average monthly precipitation in parts of TWS and its adjacent area could exceed300mm. It was supposed that the precipitation mainly come from the frontal precipitation in spring and typhoon rainfall in summer. The result also indicated that spatial difference in precipitation is in connection with the influence of topography to a great degree. Furthermore, at inter-annual time scale, it was found that the highest rainfall appeared in1998,2006and2010, the minimum in2003. This might be attributed to the difference in rainfall intensity brought by typhoons and the El Nino effect.Then, this paper uses some statistical methods such as EOF analysis, power spectrum analysis to study on the spatial and temporal distribution of precipitation over the main river basins in the west coast of Taiwan Strait. EOF analysis results show that:the first mode reflects the overall consistent pattern in spatial distribution of precipitation in the three basins, which is influenced by East Asian monsoon; the second mode presents southeast-northwest inverting type, or South-North Inverting type, which reflects the difference of precipitation mechanism between the rainy seasons (5-6) and the summer seasons (7-9) in different river basins. Seasonal variation is the remarkable characteristic in annual and inter-annual variability of precipitation, with11-13month and2-3month periods. The spatial distribution is significantly different in every season. Precipitation in spring seasons (3-4) and rainy seasons (5-6) are concentrated in the northwestern of the three basins because of the frontal precipitation and orographic precipitation; The precipitation center transfers from the northwest inland to the southeast coast influenced by the South China Sea summer monsoon and tropical cyclones in summer. The Inter-annual variability of precipitation during the rainy season showed obvious fluctuation, and the summer precipitation is showing a steady decreasing trend. The strength of the South China Sea summer monsoon will affect the amount of summer precipitation over the main river basins in the west coast of Taiwan Strait to a certain extent. El Nino mainly affects the precipitation and its spatial distribution of dry season.At last, we analysis the extreme heavy precipitation events over the main basins in the west coast of Taiwan Strait based on the TRMM3B42from1998to2012. As for the spatial distribution, we got that the mountainous and coastal regions is the area that heavy precipitation occurs frequently. In annual variation aspect, the heavy rainfall concentrates in rainy season both in Min River basin and Han River basin. But the annual variation of heavy precipitation in Jiulong River basin has characteristic with ’double-peak’. As to the interannual variation, the heavy rainfall appears a periodic fluctuation in rainy seasons and a increasing trend in dry season all the three basins. In gernal, the heavy precipitation days increase from1998to2012both in Min River basin and Jiulong River basin, while decrease in Han River basin. There are three change cycles of heavy precipitation days in all basins; they are2-3years,5years and9-10years.