The Contribution Of Different Synoptic Systems To The Precipitation And Its Change Over Hainan Island

The data used in this study include daily precipitation dataset of 18 stations in Hainan Island from 1966 to 2005, the Northwest Pacific tropical cyclone dataset from 1949 to 2005 developed by the Shanghai Typhoon Institute of China Meteorological Administration, dataset of daily rainfall weather system influencing Hainan from 1966 to 2005, NCAR/NCEP reanalysis data from 1966 to 2005. The railfall is categorized into TC rainfall and non-TC rainfall two main groups, and non-TC rainfall is sub-categorized under four kinds of influcing weather systems. All groups and sub-groups are further categorized into several ranks basing on the amount of daily rainfall. The distribution characteritics, the trend and their influenced factors of Hainan Island's annual and seasonal rainfall under different weather systems are comprehensively analyzed. The results exhibited the change of mainly weather systems influencing tropical region of China --Hainan Island and the impacting of those changes on Hainan Island's rainfall, flood, and drought. They are:(1) Hainan Island's rainfall in different rank has different contribution to total rainfall. Their spatial distribution is associated with influencing weather systems and topography of the island.(2) TC is important to Hainan Island's rainfall. TC rainfall contributes to different rank precipitation increases with rank's upraising.(3) Non-TC rainfall's influenced weather systems mainly include Cold Weather Process, Southwest Monsoon Trough, ITCZ, and Sub-tropical High, among which Cold Weather Process does greatest contribution to annual precipitation and Sub-tropical High contribute least.(4) Hainan Island's annual rainfall days decreased notably during the last 40 years, most obviously in autumn. Cold Weather Process attributes most to the decline trend.(5) Hainan Island's annual precipitation increased weakly during the last 40 years, and ITCZ's rainfall contribute most to the trend.(6) Hainan Island's rainfall intensity strengthened obviously. Only Cold Weather Process has no attribution to the change.(7) Hainan Island's rainfall extremes mainly caused by TC and Cold Weather Process, both of them contribute one third. Extreme rainfall also caused by them. The former contribute forty percent, and the latter contribute thirty percent. Extreme rainfall was connected with total precipitation closely, and influenced Hainan Island's flood-drought greatly.(8) The tropical cyclones influencing Hainan generating in Nothern West Pocipical Ocean have decreased significantly during past 40 years while the intensity of the tropical cyclones influencing Hainan generating in The South China have increased significantly.