黑龙江初夏降水的主模态特征及其前兆海洋信号分析

基于NCEP/NCAR再分析资料, 采用EOF分解、滑动t检验、相关系数等方法对黑龙江省初夏降水及其前兆信号进行了诊断分析。结果表明, 黑龙江全省初夏降水距平的空间分布以总体一致型为主, 此外, 还呈现东西反向型。总体一致型模态时间系数在1993年前后有明显的突变点。分析突变点前后降水主成分与500hPa位势高度、200 hPa纬向风、850 hPa矢量风以及前期海温的关系, 发现在突变前后影响初夏降水的同期主要系统均为东北冷涡和高空西风急流轴, 但冬季(北半球, 下同)澳大利亚周边海温对初夏降水的影响在突变前后存在明显变化。突变前在澳洲西北部, 暖海温造成东亚南高北低环流, 东北冷涡强, 高空急流偏北; 突变后在澳洲东北部, 冷海温导致东亚“+, -, +”波列, 东北冷涡弱, 高空急流偏南。 

ANALYSIS OF PRINCIPAL MODE CHARACTERISTICS AND ITS PRECURSOR OCEAN SIGNAL FOR EARLY SUMMER PRECIPITATION IN HEILONGJIANG PROVINCE

Based on the NCEP reanalysis data and methods like the EOF, running t-test and correlation efficient analysis, the present study analyzes the early summer precipitation in Heilongjiang Province and its precursor signals. The results show that mutation is obvious around 1993. By analyzing the correlation coefficient between the principal component and 500 hPa geopotential height, 200 hPa zonal wind, 850 hPa vector wind before and after mutation, we find that the main systems affecting the early summer precipitation are the cold vortex over the Northeast and westerly jet axis. However, the influence of SST around Australian coast in winter (Northern Hemisphere) on precipitation in early summer has changed obviously. Before the mutation, the warmer SST in northwest Australia renders the circulation higher in the south and lower in the north along the East Asian coast, and results in the northward westerly jet axis. After mutation, the colder SST in northeast Australia results in the PJ teleconnection pattern along the East Asian coast, and the southward westerly jet axis.