Regional atmospheric environment owing to the effect of the artificial environment due to the industrialization and urbanization is rapidly changing. Such overpopulation to the urban areas brings densely built-up areas, and it causes increase of paving rate of the urban surfaces and a change in the distribution of vegetation, and affects considerably to the urban meteorological fields.
In recent years, the urban thermal environment has become worse, such as days on which the temperature goes above 30℃, sultry nights and heat stroke increase, due to the changes in terrestrial cover such as concrete and asphalt and increased anthropogenic heat emission accompanied by artificial structure. The land use type is an important determinant to near-surface air temperature.
Due to these reasons we need to understand and improve the urban thermal environment.
In this study, the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model(MM5) was applied to the metropolitan of Daegu area in order to investigate the influence of land cover changes and urban modifications increase of Albedo to the surface energy budget on the simulated near-surface air temperature and wind speed. The single urban category in existing 24-category U.S. Geological survey land cover classification used in MM5 was divided into 6 classes to account for heterogeneity of urban land cover.
The new land cover classification(MLU) improved the capability of MM5 to simulate the daytime part of the diurnal temperature cycle in the urban area. The 'MLU' simulation produced the observed temperature field reasonably well, including spatial characteristics. The warm cores in western Daegu is characterized by an industrial area. The 'LLU' simulation wind field were quit similar to those of the 'MLU' experiment. However , there were considerable differences between the two experiments for the daytime wind field.
As a result of the numerical simulation intended for the metropolitan of Daegu assumed the increase of Albedo of roofs, buildings, or roads, the increase of Albedo (Cool scenario)can make decrease radiation effect of surface, so that it caused drops in ambient air temperature from 0.2 to 0.3 on the average during the daylight hours and smaller (or near-zero) decrease during the night. The Sensible heat flux and Wind velocity is decreased.
Modeling studies suggest that increased surface albedo in urban area can reduce surface and air temperatures near the ground and affect related meteorological parameters such as winds and the depth of the mixed boundary layer.