EXploring Land-Atmosphere Interaction over Dryland during Morning and Evening Transitions (XLAID-MET)

The recent “widespread, rapid, and intensifying” climate change and associated global warming have challenged the distinction between short-term weather phenomenon and long-term climatological patterns to merge into a continuum of atmospheric processes rather than two distinct phenomena. In arid and semi-arid regions (i.e., drylands), climate change is causing more severe droughts and prolonged fire seasons, yielding more catastrophic natural hazard conditions, and increasing the risks to health and safety of human, animals, plants, and their shared environment. Drylands are home to 2.5 billion people and occupy approximately 41% of terrestrial land surfaces globally. More than 20% of land surface is projected to cross an aridity threshold by 2100, which could lead to widespread desertification, including the region comprising the Southwestern United States. Within a recent NASEM (National Academies of Sciences, Engineering, and Medicine) workshop on the “Future of Atmospheric Boundary Layer (ABL)”, the state-of-the-art in observations and simulations was reported which included a better understanding of ABL thermodynamics over urbanized areas, coastal regions, marine environments, complex terrain, polar regions and across interfaces. However, ABL features over drylands on different timescales (semi-diurnal, diurnal, synoptic, annual, and inter-annual) and across different spatial scales (local through regional to continental) have received little attention. A holistic approach to evaluate numerical weather prediction models for drylands remains sparse due to a lack of measurements with high temporal and spatial resolutions in arid regions. In particular, the modulation of land-atmosphere interaction (LAI) via variable soil moisture through the exchanges of latent and sensible heat fluxes during both early morning transition (EMT) and early evening transition (EET) across diverse weather conditions (e.g., frontal passages, drylines) over drylands remained underexplored. The overarching goals of this project entitled “EXploring Land-Atmosphere Interaction over Dryland during Morning and Evening Transitions (XLAID-MET) is to utilize high resolution observations of near-surface meteorological parameters to explore the impact of soil moisture on both EMT and EET. Based on the concept of the encroachment model, we will show selected empirical findings on the relationship between soil moisture, near-surface meteorological conditions, and associated land-atmosphere interaction over the drylands of the southwest US using the measurements of near-surface atmospheric conditions collected by the West Texas Mesonet.