Convective transport of water vapor and air pollutants in the southeastern US: a multiscale modeling study including soil moisture and multispecies chemical data assimilation

Convective transport of water vapor and air pollutants in the southeastern US is investigated primarily using the regional-scale NASA-Unified Weather Research and Forecasting (NUWRF) model with online chemistry. Selected events in Fall 2013 and Fall 2016 are studied, when NASA's SEAC⁴RS/DISCOVER-AQ-TX and ACT-America airborne campaigns were conducted in the southeastern US providing intensive in-situ observations for model evaluation and analysis. Using the NUWRF, we quantify the impacts of: 1) model horizontal and vertical resolutions; 2) cumulus schemes; and 3) land initialization (including assessing the usefulness of assimilating satellite soil moisture using the EnKF method) on simulating distributions and evolutions of pollutants as well as their feedbacks to the weather fields. The NUWRF modeled three-dimensional weather and chemical fields are evaluated with various in-situ and remote sensing observations during these campaigns. The NUWRF simulated chemical and weather-dependent emission fields (e.g., lightning emissions of nitric oxide) are also discussed together with those based on several global-scale modeling systems that assimilate multiple chemical species using different methods (i.e., ECMWF C-IFS/4D-Var, GEOS-Chem/EnKF, and Japanese CHASER/EnKF), some of which serve as NUWRF's chemical inputs. The different hydrological anomalies in Fall 2013/2016 (as indicated by drought indexes and soil moisture anomalies), as well as the temporal changes of US anthropogenic emissions and chemical regimes during 2013-2016, are accounted for when comparing the results for these two periods. Finally, recent modeling efforts and analysis of special satellite (e.g., CrIS and TROPOMI) retrieval products in support of the NOAA-NASA FIREX-AQ campaign will be briefly introduced.