珠江流域多尺度极端降水时空特征及影响因子研究

基于珠江流域74个气象站点1952~2013年逐日降水和气温数据,采用POT抽样、Mann-Kendall（MK）趋势检验、泊松回归等方法,从降水量级、降水频率及发生时间等方面系统分析了珠江流域年、雨季及旱季3个时间尺度上的极端降水特征,并从降水对温度变化响应及ENSO影响等角度,探讨了极端降水变化特征的机理。研究表明：① 珠江流域极端降水年内分布不均,多发于4~9月,其中6月份发生频率最高;② 珠江流域极端降水频率在雨季及年际间分布较为均匀。但在旱季,珠三角地区极端降水在不同年份差异性较大;③ 在雨季及年际尺度上,极端降水年序列趋势性并不显著;而相对干旱季节,极端降雨量级、发生频次均随年份增加呈显著上升趋势,且发生时间提前。珠江流域农业以水稻(Oryzasativa)种植为主,旱季极端降水增加易导致冬汛及其引起的作物倒伏与农田渍涝等灾害,同时对秋冬防洪提出新的挑战,需要引起人们的关注;④ 温度升高和ENSO事件对珠江流域极端降水过程有显著影响。从ENSO影响的角度讲,在厄尔尼诺年,珠江流域西部极端降水量级和频率增加,而流域东部沿海区域极端降水量级减少,时间延后。

Spatiotemporal Characteristics of Extreme Precipitation Regimes and Related Driving Factors in the Pearl River Basin

Daily precipitation and temperature data of 74 weather stations of the Pearl River Basin in 1952-2013 were analyzed to characterize spatiotemporal characteristics of extreme precipitation in terms magnitude, frequency and occurrence time by using the peaks-over-threshold approach (POT), Mann-Kendall test(MK) and Poisson Regression Model for the whole year, wet season(April-September) and dry season(October-March). In addition, causes behind extreme precipitation changes were investigated by relating spatiotemporal patterns of extreme precipitation to ENSO and large-scale moisture circulation. The results indicate that:1) Extreme precipitation over the Pearl River Basin is in uneven. Precipitation extreme mainly occurs from April to September and highest extreme precipitation regimes can be found in June; 2) The frequency of extreme precipitation across the Pearl River Basin during wet season and whole year is even. However, occurrence rates of extreme precipitation within the Pearl River Delta during dry season tends to be uneven with significant difference in annual frequency of extreme precipitation;3) Magnification of extreme precipitation can be observed during dry season with respect to precipitation magnitude and occurrence rates. Besides, occurrence timing of extreme precipitation regimes tends to be earlier. However, no significant trend can be identified in extreme precipitation during wet season and during the entire year. Winter flood has the potential to causeagriculturalloss. Therefore, wetting tendency of dry season can pose new challenges for regional water resources management; 4) Warming climate across the Pearl River Basin and variations of warm and cold episodes of ENSO have significant effects on extreme precipitation processes. From the perspective of the ENSO’s influence, magnitude and frequency of extreme precipitation over the west of the Pearl River Basin increases in El Ni?o years with decreased magnitude of extreme precipitation in the lower Pearl River Basin.