Spatio-temporal variations of vapor pressure deficit in China from 1961 to 2015
Vapor pressure deficit(VPD)is a critical meteorological variable with significant implications for hy-drology,ecology,and climate change.Numerous studies have demonstrated that VPD,a key indicator of atmos-pheric dryness,has undergone substantial changes in response to global climate warming.Investigating the spatio-temporal variations of VPD across different regions of China is essential for advancing climate change research and supporting agricultural and pastoral practices.While regional-scale VPD studies have been conducted by do-mestic scholars,comparative analysis of VPD changes at the national scale remain limited.This study uses daily mean air temperature and relative humidity data from 772 meteorological stations across China,applying Tetens'empirical formula to calculate VPD.Through co-Kriging interpolation,Mann-Kendall trend tests,and correlation and partial correlation analyses,the spatiotemporal variability and trends of VPD across different time scales and geographical regions from 1961 to 2015 were examined.Additionally,the study explores the relationships between VPD,temperature,and relative humidity,identifying the dominant factors influencing VPD changes over different periods.The results indicate significant spatiotemporal variation in VPD across China from 1961 to 2015,with higher values in summer and lower values in winter.Spatially,high annual average VPD values were concentrated in the arid and semi-arid regions of Northwest China,while lower values were found in Northeast China,the Qinghai-Xizang Plateau,and parts of the southern region.The annual average VPD across China ranged from 0.127 kPa to 1.547 kPa,with an overall average of 0.526 kPa.Most regions showed an increasing VPD trend o-ver time.Between 1961 and 1999,57％stations exhibited increasing VPD trends,and this proportion rose to 67％between 2000 and 2015,with the year 2000 identified as a mutation point.The average VPD increase accelerated from 1.519 6 hPa/(10 a)to 7.074 3 hPa/(10 a)after 2000.Correlation and partial correlation analyses revealed that VPD was significantly positively correlated with temperature and negatively correlated with relative humidity in all regions.Maximum temperature was the dominant factor driving VPD changes in southern and northern Chi-na,while average temperature and relative humidity played a greater role in the Northwest and Qinghai-Xizang re-gions.These dominant factors remained consistent before and after the mutation point.While the primary factors influencing VPD changes were explored,further investigation is needed to assess the impact of other potential fac-tors such as topography,vegetation cover,and broader climatic conditions.This study provides insights into the characteristics and drivers of VPD changes across seasons and regions,offering a scientific foundation for climate-ecological and vegetation modeling studies and valuable guidance for policy-makers and relevant stakeholders.
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