Climate variations of extreme continuous rainstorms in Hunan during 1960-2009
湖南近50年极端连续降水的气候变化趋势

Using daily precipitation data of 88stations from 1960 to 2009,the spatio-temporal distribution of extreme continuous rainstorms in Hunan is examined by linear regression,wavelet analysis and abrupt change analysis.In addition,the factors affecting rainstorms in Hunan are analysed using NCEP reanalysis data.The results showed that there are high value areas with extreme continuous rainstorms in northwestern,southeastern and northeastern Hunan,and low value areas in the remaining part of the province.And the intensity of extreme continuous rainstorms may weaken in northern and northwestern Hunan.Extreme continuous precipitation may become less in central,southwestern and northwestern Hunan,but occurs more frequently in other parts.The frequency of extreme continuous rainstorm events is increasing,and the intensity is aggravated.Generally,the extreme continuous rainstorms presented variations in three quasi-periods of 2-3a,5-7a and 12-16a.The increase of extreme continuous rainstorms is characterized by abrupt changes from the 1990s to early 2000s.Interaction between topography and air flow is one of the main reasons for spatial difference of extreme continuous rainstorms in Hunan.Atmospheric moisture content and net gain of moisture in west and south mountainous areas is more than those in the central and northern plains.There is a good correspondence between the net moisture gain or net moisture loss and extreme continuous rainstorms distribution in Hunan.