青藏高原冬季平均温度、湿度气候特征的REOF分析

通过对青藏高原123个测站, 1961~1998年冬季 (12月至翌年2月) 平均温度、相对湿度资料做气候特征分析, 得到32°~33°N附近地区可能是高原南北温湿变化的分水岭, 以北主要受干冷空气影响, 以南主要受暖湿空气影响。用方差极大正交旋转EOF (即REOF) 方法对以上资料进行分析, 可以将青藏高原温度、相对湿度进行分型、分区, 并对各区的温度、相对湿度特征进行分析。结果表明, 近40年来, 各区的温度总趋势是在波动中逐步升高的。增温时段主要出现在1978~1981年及1983年至今。1983年开始的增温, 是近40年来最强的一次, 增温幅度大且持续时间长, 但从90年代开始增温幅度及范围出现波动。从温度线性倾向来看, 东部高原增温幅度从南到北存在“大—小—大”的现象。高原大部分地区湿度变化总趋势是在波动中逐步增湿的, 但高原北界以变干为主。从80年代后期至今高原进入显著增湿阶段, 但从90年代中后期开始增湿幅度及范围出现波动。从湿度线性倾向来看东部高原增湿幅度从南到北存在逐步减小现象, 甚至祁连山地区出现变干现象。

REOF Analysis of Climatic Characteristics of Winter Temperature and Humidity on Xizang-Qinghai Plateau

The Analysis of climatic characteristics of temperature and humidity on the Xizang-Qinghai Plateau is made based on the data set from 123 stations on the Xizang-Qinghai Plateau and its vicinity. The results indicate that the region near 32°-33°N may be the divide of the climatic difference from south to north on the plateau. The northern plateau is influenced by dry and cold air and the southern by humid and warm air. Using the REOF method, we can separate the temperature and humidity on the plateau into different patterns and then analyze the characteristic of each pattern. The results indicate that in recent 40 years temperature has been increasing gradually, fluctuating with time. The temperature increase occurred mainly in the periods of 1978 to 1981 and 1983 to now, and the increase in the last period is the greatest. The amplitude of the temperature increase takes on a pattern of "big-small-big" from south to north on the plateau. The humidity in recent 40 years is also on the increase trend fluctuating with time in most part of the plateau, but the northern boundary of the plateau become drier. The main period of humidity increase is the late 1980s. The amplitude of humidity increase takes on a pattern "big-small" from south to north on the plateau; especially, the region around Qilian Mountain become drier.