基于ERA-Interim的青藏高原近40年云量的时空分布特征

Spat-Temporal Distribution of the Cloud Amount in the Qinghai-Tibet Plateau of China for the Past 40 Years Based on ERA-Interim

青藏高原云量变化直接影响对流层中上部地气系统能量交换和大气水分循环,影响区域和全球气候。已有研究主要集中在总云量,鲜见对云量进行全要素分析,无法形成对青藏高原云量变化特征的全面认识。本文利用欧洲中期数值预报中心(ECMWF) 1979—2018年高水平分辨率ERA-Interim再分析资料,采用区域平均法、线性趋势分析和经验正交函数(EOF)等方法,分析青藏高原云量全要素的时空分布及气候特征。结果表明:(1)受高原大地形和山脉走向的影响,青藏高原云量具有明显的空间分布特征,且低云量对总云量的空间分布型贡献最大。(2)近40年,总云量增多趋势显著的区域主要分布在青藏高原北部和东部边缘等地,减少趋势较明显的区域主要分布在西藏东部和西南部;高云量在高原南部有显著增加趋势,其他区域增减不明显;中云量在高原中部呈减少趋势,北部和南部边缘呈显著增多趋势;低云量在高原东南部和西南部呈显著减少趋势,其他大部分区域呈增多趋势。(3)总云量和高云量第一空间模态均表现为青藏高原大部区域一致性变化,中云量和低云量在青藏高原均没有显著一致变化的空间模态。研究结果可以为应对青藏高原气候变化和生态修复型人工影响天气业务规划提供科学依据。

Changes in cloud cover of the Qinghai-Tibet Plateau directly affects the energy exchange and atmospheric moisture circulation of the upper-mid tropospheric geo-gas system, and consequently affects both regional and global climate. Past studies mainly concerned about total cloud cover, scarcely relative to the total factor analysis of cloud cover, resulting in an incomplete knowledge of the pattern of cloud cover changes in the Qinghai-Tibet Plateau. In this paper, the spat-temporal distribution and climate characteristics of the total factor of cloud cover in the Qinghai-Tibet Plateau were analyzed by using the high-level resolution ERA-Interim reanalysis data of 1979-2018 obtained from the European Center for Medium-Term Numerical Forecast(ECMWF), using the methods of regional average, linear trend analysis and empirical orthogonal function(EOF).Results show that:(1) Due to the influence of the plateau topography and the mountain tendency, the cloud cover over the Qinghai-Tibet Plateau showed obvious spatial distribution characteristics, and the low cloud cover contributed the most to the spatial distribution pattern of the total cloud cover.(2) In the past 40 years, the regions with a significant increase tendency in total cloud cover were mainly distributed in northern and eastern margins of the Qinghai-Tibet Plateau, whereas the regions with a significant decrease tendency were mainly distributed in eastern and southwestern parts of Tibet;high cloud cover had a significant increase tendency in southern part of the plateau, whereas the increase and decrease in other regions were not obvious;the medium cloud cover decreased in the central part of the plateau, and increased significantly in northern and southern regions;low cloud cover decreased significantly in the southeast and southwest of the plateau, and increased in most other regions.(3) The first spatial mode of total cloud cover and high cloud cover showed consistent variation in most regions of the Qinghai-Tibet Plateau, whereas the spatial mode of medium cloud cover and low cloud cover had no significant consistent change in the Qinghai-Tibet Plateau. The research results can provide scientific basis for the climate change of the Qinghai-Tibet Plateau and the operational planning of weather modification for ecological restoration.