Enlarging disparity of VPD between dry and wet lands due to divergent warming-induced atmospheric moistening

With warming of the atmosphere, the saturation limit for water vapor pressure is enhanced, thus more water vapor can stay in the atmosphere. However, the increase of water vapor pressure will not exactly equate to the increase of saturated water vapor pressure, thereby it will result in a change in vapor pressure deficit (VPD) of the atmosphere. Thus, how large is the increment of atmospheric water vapor and how the VPD changes could be interesting questions to be explored. Given that the VPD has significant influences on terrestrial ecosystems, here we choose to study the water vapor and VPD changes in the near-surface atmosphere over the non-desert lands. By generalizing the empirical Magnus expression of the Clausius-Clapeyron equation, we partitioned the VPD anomaly into contributions from warming and water vapor changes in the recent 42 years (1981-2022). Results showed the VPD gap between wet and dry regions is widened, and this widening gap is dominated by the uneven warming-induced atmospheric hydrating.