Atmospheric Drought under Climate Change: Vapour Pressure Deficit Trends and Impacts in Czechia

Vapour pressure deficit (VPD) is a key indicator of atmospheric dryness, plant water stress, stomatal conductance, and crop productivity. Under climate change, rising air temperatures increase the capacity of the atmosphere to hold water vapor, leading to higher VPD even in regions where precipitation has not declined.  Atmospheric drought is therefore an important but still underrepresented component of drought risk assessments, which have traditionally focused on precipitation and soil moisture alone. In Central Europe, recent heatwaves and drought events have caused substantial agricultural and ecological impacts, but the long-term behaviour of VPD and its interaction with soil moisture remain not fully clarified.

The objective of this study is to assess long-term changes in atmospheric drought, evaluating the reliability of reanalysis-based VPD, and quantifying the coupling between atmospheric conditions, soil moisture, and agricultural productivity in Czechia. The results will support improved drought monitoring and impact assessment in the context of ongoing climate change.

This study analyses VPD from station observations and reanalysis data in Czechia for 50 years (1975-2024), together with soil moisture data from reanalysis and annual crop yield data. The performance of reanalysis-based VPD is evaluated against station observations using bias, root-mean-square error, correlation, and their ability to reproduce observed extreme VPD events. This comparison assesses whether reanalysis data are suitable for studying atmospheric drought and extremes at regional scale. Long-term changes in VPD and soil moisture are evaluated using non-parametric trend methods. Analyses are performed for annual and growing-season means as well as for drought-relevant metrics, including maximum VPD and the annual number of extreme VPD days. The relationship between atmospheric and soil drought is investigated across daily to monthly time scales. Impacts on agriculture are assessed by relating annual crop yields to growing-season VPD and soil moisture.