| Building upon the heritage of the Regional Atmospheric Modeling System (RAMS), a coupled aerosol-radiation-meteorology model, RAMS-Assimilation and Radiation Online Modeling of Aerosols (AROMA), is developed. New features in the RAMS-AROMA include an aerosol transport model with capabilities of assimilation of satellite-based aerosol optical thickness (AOT) and smoke emission as well as the incorporation of a delta four stream radiative transfer model where the aerosol radiative effects are explicitly considered. The model is used to investigate the air quality and radiative impacts of long-range transported Saharan dust during the Puerto Rico Dust Experiment (PRIDE) in July 2000, and Central American Biomass Burning (CABB) smoke over the southeastern United States (SEUS) during April 20--May 20, 2003. Model performance is evaluated by using data from PRIDE, the EPA PM2.5 (particulate matter with diameter less than 2.5 mum) observation network, the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, DOE's Atmosphere Radiation Measurements in the Southern Great Plains (ARM SGP), and AOT products from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA's Terra and Aqua satellites that are shown to have tremendous potential for air quality monitoring.; With assimilation of dust AOT data and a hourly smoke emission inventory that are both derived from the Geostationary Operational Environmental Satellite (GOES), RAMS-AROMA is able to accurately simulate the dust and smoke transport (including the diurnal variation of smoke AOT in the source region such as the Yucatan Peninsula) in hourly to daily scales. The difference between simulated and observed dust AOT is within 10%. The simulated daily-averaged smoke mass near the surface correlates well with PM2.5 mass in 36 stations in Texas and the carbon mass in 4 IMPROVE sites along the smoke pathway (with linear correlation coefficients of 0.71 and 0.76, respectively). A top-down analysis shows the total CABB smoke emission during the study time period was 1.3 Tg, among which 55% was transported to the SEUS, causing a 30%--50% increase of PM2.5 mass concentration in the downwind region (e.g., southern Texas).; The dust radiative impact can cause the simulated AOT and air temperature near the surface to differ by 10% and 0.5 °C, respectively. On 30-day average, the smoke AOT were 0.2 and 0.1 in the source and downwind regions, respectively. The smoke radiative extinction effect reduced the surface solar energy input, 2m air temperature (2mT), diurnal range of 2mT, and PBL height by about 22.5 Wm-2, 0.28°C, 0.31°C, and 41m respectively in the source region, larger than 15.8 Wm-2, 0.2°C, 0.25°C, and 17m in the downwind region. The smoke absorption of solar radiation resulted in the increase of atmospheric radiative heating rate by 0.1--0.3 K/day, thus warmed the air over the ocean surface. However, over the land surface, due to its strong coupling with the lower PBL, the warming only occurred in the upper PBL. The reduced PBL height and enhanced atmospheric stability lead to more smoke aerosol particles being trapped in the lower PBL. Using satellite-based aerosol products, this study demonstrates the possibility and necessity of including aerosol radiative impacts into meteorological and air quality models. |
