青藏高原东北部气候变化的异质性及其成因

利用1961-2016年西宁等青藏高原东北部13个气象台站气温、降水等气象资料以及国家气候中心发布的南海季风指数、西伯利亚高压指数等大气环流特征量数据,分析近56年来气候变化与高原主体的差异性及其可能的气候成因。研究表明:近56年来青藏高原东北部气候变暖趋势十分显著,年平均气温气候倾向率高达0.39℃/10 a,呈现出三次明显的阶梯性增高态势,并于1994年前后发生了由冷到暖的突变,同时具有明显的空间差异性;年降水量及四季降水量均没有明显变化趋势,虽然经历了2002年左右由少到多的变化,但并未出现明显突变,年降水量具有3年、5年的准周期,而年降水日数微弱减少,降水强度呈增加趋势;该区域气候变化的年际波动主要受到东亚季风、高原季风和南海季风的年际振荡及其相互作用的影响,而西风环流的作用并不明显,植被覆盖的恢复既是对2002年以来降水量增加的具体反应,同时也对于气候变暖趋势起到了一定的缓和作用。

The heterogeneity of climate change and its genesis in the Northeastern Qinghai-Tibet Plateau

The northeastern part of Qinghai-Tibet Plateau is situated in the transitional zone of the Qinghai-Tibet Plateau and Loess Plateau. Known as Qinghai's Hehuang areas, it is the valleys of Yellow River and Huangshui River. And it is the birthplace of civilization and cradle of economic and social development of the Qinghai-Tibet Plateau, especially Qinghai province. It is also one of the areas of earliest human activities in the Yellow River Basin. Because it is located in the intersection of China's two high plateaus, its climate and its changes have a certain heterogeneity. The northeastern part of Qinghai-Tibet Plateau has some characteristics of the East Asian monsoon climate, which is different from complete plateau continental climate. Therefore, due to complexity of its climate change and significance of its impact on economy and society, the issue of climate change in the region has received wide attention from academic community. Based on analysis of climate change in the northeastern part of Qinghai-Tibet Plateau from 1961 to 2016 and its heterogeneity in climate change over the Qinghai-Tibet Plateau, this paper discusses the causes of climate change from evolution of atmospheric circulation and changes in vegetation cover. The meteorological data such as temperature, precipitation and other meteorological data of 13 meteorological stations in the northeastern Qinghai-Tibet Plateau from 1961 to 2016, the data of atmospheric circulation characteristics such as the South China Sea summer monsoon index and Siberian High Index released by the National Climate Center were analyzed in this paper. And, the heterogeneity between climate change and plateau main body and their possible climate genesis were also analyzed in the past 56 years. The results are shown as follows: (1) Climate warming trend in the northeastern part of Qinghai-Tibet Plateau is very significant in the past 56 years. The climatic tendency rate of annual average temperature is as high as 0.39 °C/10 a, showing three obvious stepwise increases and it has mutations from cold to warm around 1994 with significant spatial variability. (2) There is no obvious change in annual and seasonal precipitation. Although it has experienced less to more changes around 2002, there is no significant mutation. The annual precipitation has a quasi-periodic variations of 3 years and 5 years, while the number of annual precipitation days is slightly reduced and precipitation intensity is increasing. (3) The interannual variability of climate change in this region is mainly affected by interannual oscillations of East Asian monsoon, plateau monsoon and South China Sea monsoon and their interactions, while effect of westerly circulation is not obvious. The restoration of vegetation cover has not only responded to precipitation increase since 2002 but also played a certain role of mitigative effect in climate warming trend.