甘肃中北部第一场透雨的气候特征及其相关因子分析

Analysis of the Climatic Characteristics and Its Influence Factors of the First Soaking Rain in North-Central Gansu Province

摘要: 利用1957~2014年甘肃中北部4个台站逐日降水资料，分析了第一场透雨发生的气候特征及其影响因子。结果表明：第一场透雨出现日期在空间上从南向北推迟，区域性平均第一场透雨日期集中出现在5月，平均日期在5月中旬，也是出现频率最高的旬；区域性平均第一场透雨无显著的气候特征趋势，但有明显的年代际变化：1950年代末至1960年代初、1970年代中后期、1990年代初期至2000年代后期迟于6月以后；1960年代中期至1970前期、1980年代、2010年以后普遍偏早于4月下旬，有提前的趋势；透雨与春季降水有显著的负相关，透雨偏早，则春季降水偏多，特别是4月、5月降水偏多；前期1月亚洲中高纬500 hPa高度距平场呈“− + −”、甘肃中北部经向风距平场出现偏南风，则透雨偏早，反之偏迟；上年5~7月大西洋中北部、欧洲中西部、西西伯利亚OLR增强(减弱)，对应的甘肃中北部透雨偏迟(早)；透雨的年际变化从南向北增大，均方差会宁26 d，靖远31 d，景泰35 d，白银41 d，这就决定了其预测难度大，稳定性差。

Abstract: In this paper, the first soaking rain climate characteristics as well as its influence factors are ana-lyzed statistically based on daily precipitation data of four stations in north-central region of Gansu from 1957 to 2014. The results show that: the first soaking rain has delayed from south to north and regional soaking rain which concentrated in May, frequently in mid-may, is insignificant in climate change trend but obvious in terdecadal changes: for example, from late 1950s to early 1960s, in the mid to late 1970s and from early 1990s to the late 2000, regional soakers are later than June, while from mid 1960s to early 1970s, in 1980s, and after 2010 they are generally before late April, with tendency of advance. It also shows that the soaker has significant negative correla-tion with the spring precipitation, that is, if the soaking rain is earlier, the spring precipitation es-pecially in April and May is more. If the anomaly field presented negative, positive and negative at 500 hPa of middle and high latitude areas in Asia of previous period in January, and the Radial wind anomaly field appeared southerly wind in north-central Gansu province, the soaking rain occurred early, or vice versa. OLR was enhanced in north central in the Atlantic, the west central Europe and west Siberia from May to July in the year before corresponded to soaking rain later in north-central Gansu province, or vice versa. And interannual variability of soaker increases from south to north, for example, mean square deviation of Huining is 26 d, Jingyuan 31 d, Jingtai 35 d, Baiyin 41 d, which means the soaker is difficult to predict and its result is unstable.