不同时间尺度下华北平原干湿气候时空变化及成因分析

利用华北平原62个气象站点1961-2014年逐日地面观测资料以及同期降水量资料,基于Penman-Monteith方法计算的参考作物蒸散量(ET_0)研究近54a研究区干湿气候时空变化特征,并利用敏感性和贡献率法分析气候变化背景下主要气象因子对ET_0的影响,对干湿气候变化的成因进行探讨。结果表明:华北平原在3个时间段(时段1:1961-1980;时段2:1981-2000;时段3:2001-2014)半干旱区和半湿润区的分界线呈东扩和南移,半干旱区面积不断扩大,湿润区面积变化不明显;研究区1961-2014年ET_0呈显著下降趋势,空间差异大,河南和山东部分地区由于ET_0下降趋势大于降水量减少趋势,气候变湿润;鲁东、天津、河北东部地区降水量减少且ET_0增加,干旱化趋势明显。就月尺度而言,降水量在7月和8月减少幅度最大,夏季ET_0减少幅度较大,5月和6月气候呈变湿趋势。ET_0对相对湿度的变化最敏感,各月导致ET_0变化的主要贡献因子不一,11月-翌年1月风速起主导作用,2月温度为主导因子,6-9月日照时数为主导因子,其它月份为相对湿度、风速等综合作用的结果。

Spatiotemporal Variation and Causes Analysis of Dry-wet Climate at Different Time Scales in North China Plain

Global warming has caused non-uniform changes in precipitation intensity and distribution, which will inevitable impact on the wet and dry climate. In order to make clear the distribution of dry-wet climate zone and changes have occurred in recent 54 years, authors analyzed the temporal and spatial variation characteristics of dry and wet climate in North China Plain over the period 1961 to 2014 in this paper. The influence of main meteorological factors on ET0 was also been studied by using the sensitivity and contribution rate method, as well as the causes for dry-wet climate variation. In this study, 62 meteorological stations each with 54-year data record (from 1961 to 2012) were selected in China (including Beijing, Tianjin, Shandong, Henan and Hebei), ET0 was then calculated by using Penman-Monteith method. The results showed that the area of semi-arid area was expanding continuously since the dividing line for semi-arid area and semi-humid area extended eastward and southward in three periods (period 1:1961-1980; period 2:1981-2000; period 3:2001-2014). However, the humid area did not show significant changing trend. Precipitation showed non-significant trend over the period 1961 to 2014, while ET0 showed a significant decreasing trend with large spatial differences. In most parts of Henan and Shandong, the climate became wet because that the negative trend for ET0 is larger than the decreasing trend for precipitation. On the contrast, most of Tianjin and Hebei regions showed significant dry trend rates with the decreasing precipitation and increasing ET0. As for the main contribution factor to ET0 changes in each month, wind speed was the dominant factor in November to the following January, temperature in February, and sunshine hours in June to September. The main contribution factors to ET0 in other months were result from the combined effects of relative humidity and wind speed.