近55年来澜沧江流域降水时空变化特征分析

本文利用澜沧江流域及周边共30个气象站点1960-2014年的逐月降水数据,采用气候倾向率、Mann-Kendall趋势检验、Morlet小波分析、Co-Kriging插值以及重心模型等方法,分析了澜沧江流域降水的时空变化特征。结果表明：① 分析时段内全区、北部和中部年降水量呈现增加趋势,南部年降水量出现减少趋势。春季全区、北部、中部和南部降水均呈增加趋势;夏季均呈减少趋势;秋季全区和南部降水呈现减少趋势,北部和中部呈增加趋势;冬季全区、中部和南部呈下降趋势,只有北部呈增加趋势。② 近55年来,全区包括北部、中部和南部年降水都存在近29年、近22年和5-10年左右的周期,这3个周期在分析时段内表现很稳定,具有全域性。全区、北部和南部还存在明显的13年左右的周期,中部1975年前和1995年后也存在13年左右的周期,北部1975年前存在明显的7-10年的周期,1995年后,7-10年的周期表现也比较稳定。降水量变化的第一主周期是近29年,第二主周期是近22年。③ 澜沧江流域多年平均降水量由南部向北部减少,流域南部降水最多,多年平均降水量在1200 mm以上,中部多年平均降水量处于800~1100 mm,北部多年平均降水量多小于800 mm,大部分在400~800 mm;澜沧江流域年降水重心和月降水重心都集中在中部,其中11月的降水重心迁移距离最大,向东南方向迁移了131.82 km。从季节来看,春季、夏季和秋季降水重心向东南迁移,冬季的向西北方向迁移,雨季降水重心相对比较集中,旱季降水重心相对 比较分散。

Analysis of the Temporal and Spatial Variation Characteristics of Precipitation in the Lancang River Basin over the Past 55 Years

Based on the monthly precipitation data from 30 meteorological stations in and surrounding the Lancang River basin, we analyzed the temporal and spatial characteristics of precipitation from 1960 to 2014 using the climate tendency rate, Mann Kendall trend test, Morlet wavelet analysis, interpolation co-Kriging, and gravity center model methods. The results showed that: (1) in the analysis period, the overall precipitation and regional precipitation in the northern and central regions showed a rising trend, but a decreasing trend on precipitation for the southern region occurred. The overall, northern, central and southern precipitations showed an increasing trend in spring, while in summer they showed a decreasing trend. In autumn, there was a decreasing trend of precipitation in the whole region and in the south. The northern and central parts of the region were having an increasing trend. The precipitation in the whole region, the middle and the southern parts showed a downward trend in winter with the exception of the northern part. (2) There were cycles in precipitation of 29 years, 22 years and 5 to 10 years within the region, including the northern, central and southern parts in the past 55 years. The performance of the three cycles in the analyzed period was very stable, indicating a domain-wide characteristic. There was also a significant cycle of around 13 years in precipitation for the whole, northern and southern regions. Before mid 1975 and after 1995, there was also a cycle of about 13 years in precipitation for the central area. In the northern area before 1975 and after 1995, there was a cycle of 7-10 years in precipitation. The first grade main cycle in precipitation was 29 years, and the second grade main cycle was 22 years. (3) The average annual precipitation decreased in the Lancang River Basin from the south to the north. The precipitation in the southern basin was the heaviest, with an average precipitation of more than 1200 mm. The average annual precipitation in the middle area was 800-1100 mm, while the average annual precipitation in the northern part was usually less than 800 mm, mostly in the range of 400-800 mm; the annual and monthly precipitation gravity centers of the Lancang River Basin were located in the central region. The precipitation gravity center of November had the largest migration distance, which migrated southeast by a distance of 131.82 km. From the seasonal point of view, the precipitation gravity centers in spring, summer and autumn had migrated toward the southeast, while in winter, it migrated toward the northwest. The precipitation gravity centers in the rainy seasons were relatively aggregated, while in the dry seasons they were relatively dispersed.