中国西南地区饱和水汽压差的年际变化及其影响因素

Temporal variation of vapor pressure deficit and its influencing factors in southwest China

厘清饱和水汽压差(VPD)的年际动态特征有助于深入理解大气干湿程度对气候变化的响应。本研究基于我国西南地区105个台站1982—2015年的气象观测资料,利用Mann-Kendall突变检验分析VPD的突变特征,基于统计分析探讨突变点前后的VPD变化趋势及影响因素。研究结果表明,西南地区1982—2015年VPD变化以2000年为突变年,增速由0.001 kPa/a变为0.005 kPa/a,并且VPD呈增加趋势的站点在2000年后增多。VPD在时间动态上出现变化的主要原因是在2000—2015年间相对湿度下降幅度增加,导致西南地区出现更干燥的气候特征。作为大气主要水汽来源的外来水汽通量和局地实际蒸散发在2000年后表现为增长趋势,但由于2000年后更高的空气温度引起饱和水汽压比实际水汽压增幅更大,即大气中实际水汽增加远低于饱和水汽容量增加,进而导致VPD增幅更大。本研究表明在突变点后西南地区VPD显著变化的原因主要是温度上升对相对湿度的影响,研究结果有助于深入理解中国西南地区的气候变化,明晰VPD变化背后的相关机制,为该地区的生态系统构建和未来气候变化应对提供参考。

Clarifying the spatial and temporal variation of vapor pressure deficit (VPD) can help to investigate the response of air dryness to climate change.Based on the meteorological observation data of 105 stations in southwest China and empirical formula of VPD,this study used Mann-Kendall test to analyze the abrupt shift of VPD during 1982-2015.According to the partial correlation analysis,we discussed the temporal variation in VPD before and after the breakpoint year,and further to identify the climate factors which affect the trend of VPD.The results showed that the year 2000 was the breakpoint for the temporal variation in VPD for the period of 1982-2015.VPD change trends abruptly increased from 0.001 kPa/a to 0.005 kPa/a,and more and more stations showed increasing trend of VPD after 2000.This phenomenon indicated that area of southwest China has shown a drier air stress after 2000 since the relative humidity decreased more than that before 2000.Further study on the abrupt change in progress of VPD showed that,although the increasing external water vapor flux and actual evapotranspiration after 2000 may bring more water into air (namely,increasing actual vapor pressure),the rapidly rising temperature induced more water holding capacity in air,and thereby resulting in enhancing VPD increasing trends.This study suggests that higher temperature after 2000 indirectly affecting VPD via disproportionally increasing saturated vapor pressure played a more dominant role.This study is helpful in deep understanding of the climate change and revealing the relevant mechanisms behind the change of VPD.The results of this study would provide scientific support for ecosystem construction and climate change adaptation for southwest China.