1981—2023年雅鲁藏布江流域大气饱和水汽压差变化及影响因素

Spatio-temporal variation of vapor pressure deficit and impact factors in the Yalung Zangbo River basin from 1981 to 2023

饱和水汽压差(vapor pressure deficit,VPD)可反映大气对水分的需求,厘清VPD时空变化特征有助于了解区域大气干湿程度对气候变化的响应。基于近43年(1981—2023年)雅鲁藏布江流域(简称雅江流域)34个气象站点逐月日照时数、平均气温、平均最高气温、平均最低气温、降水量(P_(r))、相对湿度、水汽压和平均风速等资料,采用线性倾向估计、R/S分析、Mann-Kendall法、Morlet小波分析和逐步回归等方法,分析近43年雅江流域VPD时空变化特征及影响因子。结果表明:(1)雅江流域年、季VPD总体上呈东西部低、中部高分布特征;月际变化呈双峰型,第1、2峰值分别在6、10月,1月最小;VPD夏季最大,春季次之,冬季最小。(2)年VPD以0.030 kPa/(10 a)的速率显著增加,主要表现在夏秋季,尤其近23年(2001—2023年)增速明显。年、季VPD在21世纪前10年中后期发生了突变,且未来持续增大的可能性很高。20世纪80和90年代年、季VPD均偏低,以90年代最明显;21世纪前10年因夏、冬两季VPD偏高,年VPD偏高;21世纪10年代年、季VPD均偏高,主要表现在夏、秋两季。VPD在春、夏、秋3季都存在3~4 a显著周期,冬季有2~3 a周期,年VPD无显著周期。(3)四季和年VPD与地理因子的线性关系不显著,但存在极显著的二次曲线关系。(4)年、季平均气温升高是致使VPD增加的主导因子;2004年以后,年平均气温、水汽压对VPD贡献率有所降低,P_(r)的作用明显增大。

Vapor pressure deficit(VPD) reflects the atmospheric water demand,and clarifying the spatial and temporal characteristics of VPD is helpful to understand the response of regional atmospheric dryness and wetness to climate change.Based on the data of monthly sunshine duration,average temperature(Tm),average maximum temperature,average minimum temperature,precipitation(Pr),relative humidity,vapour pressure(e) and wind speed of 34 meteorological stations in the Yalung Zangbo River basin(YZRB) from 1981 to 2023,the spatiotemporal characteristics and influencing factors of VPD in YZRB during recent 43 years were analyzed by linear trend estimate,R/S analysis,Mann-Kendall method,Morlet wavelet analysis and stepwise regression method.The results show that:(1) The annual and seasonal VPD in YZRB were generally lower in the east and west,and higher in the middle.The monthly variation showed a bimodal pattern,with the 1st and 2nd peaks in June and October,respectively,and the minimum in January.VPD was the largest in summer,followed by spring,and the smallest in winter.(2) The annual VPD increased significantly with a rate of 0.030 kPa/(10 a),mainly in summer and autumn,especially in the last 23 years(2001-2023).The annual and seasonal VPD mutation occurred in the mid-to-late 2000s,and the possibility of continuous increase in the future is very high.The annual and seasonal VPD were lower in the 1980s and 1990s,especially in the 1990s.In the 2000s,due to the higher VPD in summer and winter,the annual VPD was higher.Annual and seasonal VPD were higher in the 2010s,mainly in summer and autumn.VPD had a significant 3-4 a cycle in spring,summer and autumn,2-3 a cycle in winter,and annual VPD had no significant cycle.(3) Seasonal/annual VPD had no significant linear relationship with geographical factors,but there was a very significant quadratic curve relationship between them.(4) The increase of annual and seasonal Tm was the dominant factor causing the increase of VPD.After 2004,the contribution of annual Tm and e to VPD decreased,and the role of Pr increased significantly.