Soil moisture controls on evapotranspiration, photosynthesis, and ozone dry deposition during ACT-America 2016

Abstract:

Soil moisture influences the atmosphere via evapotranspiration (ET). A major contributor to the total ET is plant transpiration, during which process water exits the plants through their stomata and trace gases such as carbon dioxide and ozone can be taken in by the stomata. The nonstomatal components of ozone dry deposition are non-negligible, and they in part depend on surface wetness, vegetation density, and weather conditions. Soil moisture data assimilation has been demonstrated to sometimes have added value to baseline model predictions of land and atmospheric conditions. Evaluation of land data assimilation works has long been strongly focusing on land and atmosphere states. The evaluation of surface fluxes is important to quantifying and understanding energy and greenhouse gas budgets but is often given less attention to. Here we present the Land Information System/WRF-Chem modeled surface states (e.g., moisture, temperatures, trace gas concentrations) and fluxes (i.e., ET, carbon uptake via photosynthesis, and ozone dry deposition) over the central/southeastern US during ACT-America 2016. We discuss how the choices of land surface models, their inputs and stomatal resistance parameterizations, as well as the assimilation of SMAP soil moisture retrievals impact the model-based results. A variety of observations and observation-derived datasets (i.e., surface and aircraft in-situ measurements, SMAP L4C, satellite vegetation, OCO-2 SIF, GPM, FLUXCOM and GOES) during this campaign are used to assess the model performance of land and atmosphere states, surface fluxes, as well as their relationships.