Applications of satellite remote sensing data for estimating dry deposition in eastern Texas

The sensitivity of dry deposition velocities and air quality model predictions to land use/land cover (LULC) is examined. Four LULC data sets are employed; three of the data sets are derived from recent satellite imagery and the fourth data set is the LULC database currently used in air quality models by the State of Texas. Effects of the land cover data on estimates of dry deposition velocities and modeled ozone concentrations are examined using the Comprehensive Air Quality Model with extensions (CAMx) during an 22 August 2000–6 September 2000 episode developed for the Houston/Galveston area. All land cover data sets showed good general agreement with a few significant differences in classification and spatial extent of certain land cover categories. Dry deposition decreased in urban areas with the new land cover data during peak hours on some days, leading to ozone concentrations that were approximately 2 ppb higher in the Houston area. Ozone concentrations were lower west of Houston due to increased stomatal uptake by increased agricultural land coverage in the new data sets. These results indicate that the satellite-based LULC data, specifically the data derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, can be used to provide periodic updates to land cover information used in CAMx and similar photochemical models.