A numerical study to understand impact of meteorological changes due to land use and land cover differences on Houston's high ozone problem.

摘要

The Houston-Galveston-Brazoria area (HGB) is known as the most severe ozone non-attainment region in the United States. Houston's high ozone concentration is primarily the product of the precursor volatile organic compound (VOC) emissions from petrochemical and industrial emission sources (e.g. the Ship Channel), and nitrogen oxides (NOx) emissions from mobile sources. Furthermore, specific meteorological conditions typical of the HGB, such as the land/sea breeze; have the ability to greatly enhance O3.; To predict atmospheric conditions in an urban environment well, the land surface processes must be accurately described through the use of land use (LU) and land cover (LC) data. Meteorological simulation for the HGB area using the Fifth-generation Mesoscale Model (MM5) with the Noah land surface model (LSM) and the default U.S. Geological Survey (USGS) 25-category data resulted in the over-prediction of daytime temperature in the downtown area because the extensive area was treated as a completely urban (impervious) surface. The Texas Forest Service (TFS) LULC dataset established with the LANDSAT satellite imagery represents the area as the mixtures of urban, residential, grass, and forest LULC types, and correctly identifies the urban surface type for the central business district (CBD) and industrial complexes in the Ship Channel, and the inclusion of the residential type extends the developments to the large surrounding areas.; The primary goal is to show the benefits of using the high-resolution LULC dataset for meteorological modeling. The secondary goal is to determine the effects of modified meteorological inputs on Houston's high O3 predictions.; The simulation results demonstrated different LULC modified the surface heat flux conditions; resulting in changes in the local wind pattern particularly under weak synoptic atmospheric conditions. In the Ship Channel high emission area, the mixing characteristics and wind transport are better simulated in the MM5-TFS simulation, which in turn improves the air quality simulation particularly the O3 precursor species such as VOC and NOx. The observed maximum O3 concentration on August 30, around 200 ppb, cannot be solely attributed to the meteorological factors, improvements in the emissions data and representation of chemical reactivity are also necessary.