1961~2017年雅鲁藏布江河谷地区夏季气候暖干化趋势

Warming and Drying Trend of Summer Climate along the Yarlung Zangbo River Valley Area from 1961 to 2017

基于1961~2017年青藏高原腹地雅鲁藏布江河谷地区4个站(拉萨、日喀则、泽当和江孜)夏季(6~8月)月平均气温、降水和相对湿度等观测资料,分析了该地区夏季气候年际和年代际演变特征,并探讨了气温、降水和相对湿度在年际和年代际时间尺度上的相互关系以及与总云量和地面水汽压的联系。结果表明:(1)1961~2017年该地区夏季气候出现了暖干化趋势。气温(相对湿度)显著升高(下降),降水趋势变化不明显;本世纪初气温(相对湿度)均发生了显著的突变。(2)该地区夏季气候因子间在年际和年代际时间尺度上存在密切关系:气温与相对湿度和降水均存在明显的负相关,降水与相对湿度为正相关。(3)该地区夏季气候因子间的年际和年代际变化与同期总云量和地面水汽变化有关。1961~2017年总云量持续减少是气温显著升高的主要原因之一,气温的显著升高和降水变化不明显又造成了相对湿度的显著下降。

Based on observations of monthly mean temperature,precipitation,and relative humidity at Lhasa,Shigatse,Zedang,and Jiangzi stations over the Yarlung Zangbo River valley in the hinterland of the Tibetan Plateau in the past 57 years(1961-2017),the evolution characteristics of interannual and interdecadal variations of the climate series in the region are analyzed.The relationships between the climate series and their connections to the total cloud cover and surface water vapor pressure during the same period on interannual and interdecadal scales are also discussed.The results show the following:(1)In the past 57 years,the summer climate in the region has exhibited a trend of warming and drying.The temperature(relative humidity)increased(decreased)significantly,and the precipitation trend is not obvious.(2)A close relationship exists between the summer climate factors in the region and the interannual and interdecadal variations:A significant negative correlation exists between temperature and relative humidity(precipitation),while a significant positive correlation exists between precipitation and relative humidity;(3)The interannual and interdecadal variations of summer climatic factors in the region are related to the total cloud cover and surface water vapor changes over the same period.The continuous reduction of the total cloud cover in the past 57 years is one of the main causes of the significant increase in temperature;however,the significant increase in temperature and the change in precipitation do not cause a significant decrease in relative humidity.