Comparing Mechanistic Patterns of Terrestrial Hydroclimatic Change in Global Models and Reanalysis Data

Here we apply and extend the new Soil Moisture-Aridity Index framework (Duan et al., 2023) which uses local climatological aridity and the probability distribution function of daily soil moisture to understand how soil moisture constraints and boundary layer-mediated processes impact the behavior of daily latent and sensible heat fluxes, and how those fluxes, in turn, impact near-surface temperature in a changing climate. This process-oriented diagnostic framework demonstrates how the non-linear relationship between soil moisture and latent heat flux plays out differently in wet-tropical, temperate, semi-arid, and arid regions, providing an overarching methodology for exploring land-atmosphere interactions in different climate regimes.

This framework is a guide to understanding vulnerabilities to heat waves and drought, opening the door to improved predictions of these extremes. The framework reveals model-specific behaviors and biases that can be helpful for model evaluation and model development purposes. We analyze the behavior of multiple CMIP models and the ERA5 reanalysis data set, gaining insight into the biases, tendencies, and limitations of each. We extend this framework to understand how terrestrial moisture availability (precipitation-minus-evaporation) changes in a warming climate, and how land-atmosphere coupling impacts regional-scale wet and dry seasons in a changing climate.