华南地区5月降水的水汽特征分析

利用国家气候中心的降水资料及NCEP/NCAR再分析资料、NOAA海温资料分析了华南地区5月降水的主要水汽通道及变异机制。发现异常多雨年的水汽主要来自南海、孟加拉湾和青藏高原南侧;异常少雨年则因西太平洋副热带高压(简称副高)偏东,来自南海的水汽缺失,只有来自孟加拉湾和高原南侧的两股水汽,因而南海的水汽是影响华南地区5月降水的重要因素。分析发现当北太平洋的准东西向海温异常是"负正负"分布时,南海地区为异常的反气旋性环流,有利于副高西伸加强;北太平洋海温距平为"正负正"异常分布时,南海地区为异常的气旋性环流,副高东退减弱。此外,北方南下冷空气的阻挡使得季风北界位置偏南,冷空气和季风在华南地区交汇导致5月降水异常增多。

Vapor Source Characteristics of Precipitation in South China during May

Based on monthly precipitation datasets of 89 meteorological stations and 38 hydrological rain gauges from 1961 to 2005 in Xinjiang, China, differences in temporal-spatial variations of Xinjiang precipitation detected by these two precipitation observations have been compared and causations for these differences have been analyzed. Meanwhile, the relationships between precipitations with topography features (altitude, slope, and aspect) under increasing warming background have been discussed. The results indicate that: 1) Multiyear mean annual precipitation in Xinjiang observed by hydrological rain gauges is 221.4 mm, which is 69.3 mm more than that observed by meteorological stations (152.1 mm). However, meteorological and hydrological observations show the same spatial-temporal change characteristics; 2) Differences between meteorological and hydrological observations are mainly affected by altitude. Besides, slope and aspect are also crucial factors. Precipitation shows huge spatial-temporal variations in Xinjiang because of complicated landform. As a result of uneven distribution of rainfall gauges, there exists great bias in precipitation estimation. In the future, it would be an effective method to objectively assess precipitation in Xinjiang that multi-source precipitation datasets combine together.