川西甘孜藏族自治州1961—2015年日照时数变化特征分析

The characteristics of sunshine duration in GarzêTibetan Autonomous Prefecture of western Sichuan in China during 1961—2015

甘孜藏族自治州(简称甘孜州)位于青藏高原东南缘,是一个气候敏感区和环境脆弱区。利用多年气象数据探讨该区气候变化趋势对研究区环境保护、灾害防治和发展规划有重要意义。本文基于1961—2015年甘孜州11个气象站点的日照时数、气温、降水、相对湿度和风速数据,通过一元线性回归、5 a滑动平均、累计距平、Mann-Kendall(M-K)突变检验和样条函数插值分析方法,研究该地区年际、季度的日照时数时空变化特征以及与其他气候因子之间的关系。研究结果表明:(1)平均日照时数在年际和季度尺度上呈减少趋势,减少速率分别为25 h·(10a)^(-1)(年际)、6.4 h·(10a)^(-1)(春季)、6.8 h·(10a)^(-1)(夏季)、6.9 h·(10a)^(-1)(秋季)、6.3 h·(10a)^(-1)(冬季)。(2)空间分布上,德格的西部地区日照时数减少最快,而乡城县等极少数地区出现日照时数增加的趋势。(3)年际日照时数在1989年发生突变,在季节尺度上春季、夏季、冬季发生突变的年份分别为1989年、1991年和1994年,秋季突变不明显。(4)日照时数与气温、降水量、相对湿度均呈负相关关系,相关系数分别为-0.2、-0.6、-0.5;日照时数与风速呈显著正相关关系,相关系数为0.6。本研究可为甘孜州地区1961—2015年的气候变化提供数据支持。

Background,aim,and scope Under the trend of accelerating global warming,research on climate change on a centennial scale is particularly important.Sunshine is the most intuitive manifestation of solar radiation,an important factor influencing climate change,and an important energy source for other climate factors.GarzêTibetan Autonomous Prefecture(hereafter Garzê),located on the south-eastern margin of the Qinghai-Tibet Plateau,is the link connecting Sichuan Basin and Qinghai-Tibet Plateau.This area is vulnerable to climate and environmental changes.Therefore,based on multi-year meteorological data,studying the temporal and spatial variation characteristics in the region and their relationship is of great significance for the historical research of climate change and the prediction of climate change.This study analyzed the temporal and spatial characteristics of sunshine duration,and discussed the relations between sunshine duration and other climate factors(temperature,precipitation,relative humidity,wind speed).Materials and methods Based on the observation data of temperature,precipitation,relative humidity,wind speed and sunshine duration from 11 weather stations in Garzêfrom 1961 to 2015,we analyzed the temporal and spatial variations of sunshine duration in the region and the relationship with other climate factors on interannual and seasonal scales,through linear regression,5 a moving average,anomaly analysis,Mann-Kendall mutation test and spline interpolation.Results(1)The results manifested that the average sunshine duration showed a decreasing trend on the interannual and seasonal scales with rates of 25 h·(10a)^(-1)(interannual),6.4 h·(10a)^(-1)(spring),6.8 h·(10a)^(-1)(summer),6.9 h·(10a)^(-1)(autumn),6.3 h·(10a)^(-1)(winter),respectively.(2)From the perspective of spatial distribution,the sunshine duration in the western region of Dege County has the largest decline,while the sunshine duration in a few areas such as Xiangcheng County showed an increasing trend.(3)There was an abrupt change of sunshine duration in 1989.On a seasonal scale,abrupt changes happened in the spring of 1989,the summer of 1991 and the winter of 1994.The sunshine duration in the autumn stayed relatively stable.(4)The sunshine duration is negatively correlated with temperature,precipitation,and relative humidity,and the correlation coefficients are-0.2,-0.6,and-0.5,respectively.There is a clear positive correlation between sunshine duration and wind speed with a correlation coefficient of 0.6.Discussion The decline rate of the sunshine duration in summer and autumn is generally higher than that in spring and winter.It is mainly controlled by the change of the solar elevation angle to affect the solar radiation energy reaching the ground.It’s believed that climate factors,such as temperature and precipitation,affect the sunshine duration by changing the density of aerosol particles in the atmosphere,resulting in different amount of solar radiation reaching the ground.Conclusions Using meteorological data for many years to explore the trend of climate change in the area is of great significance to the environmental protection,hazard mitigation and development planning of the study area.Recommendations and perspectives This study provides basic data for climate change research in GarzêTibetan Autonomous Prefecture from 1961 to 2015.