Analysis of Dry-Wet Climate Change Characteristics and Main Influencing Factors in Main Grain Producing Area of Tibet from 1980 to 2021

Based on the daily meteorological observation data of seven meteorological stations in southern Tibet from 1980 to 2021 (April-October), the temporal and spatial variation characteristics and influencing factors of aridity index ( AI ) in the growing season of major grain producing areas in Tibet were studied by using climate tendency rate, Mann-Kendal test, Morlet wavelet analysis, GIS hybrid interpolation method, Pearson correlation coefficient, contribution rate analysis and other methods. The results showed that the average AI in the main grain producing areas of Tibet was 1.7, which belonged to the semi-arid area, and the overall trend was decreasing (humidifying) (-0.036/10 a). The linear decreasing trend was different in different regions, and the area around Lhatse County was the most significant (-0.26/10 a). AI had no obvious abrupt change, and had long- and medium-term fluctuation characteristics of 24 years, 6 years. The spatial distribution was uneven, and had the characteristics of ‘shrinking arid area and expanding humid area . The contribution rates of the main climate influencing factors of AI varied in different regions. In general, the contribution rates after quantification was as follows: precipitation (34.9%)>relative humidity (28.4%)>sunshine (19.9%)>maximum temperature (12.4%).

基于ERA-Interim的青藏高原近40年云量的时空分布特征

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。