Effects of Regional Warming due to Urbanization on Daytime Local Circulations in a Complex Basin of the Daegu Metropolitan Area, Korea

Abstract

Numerical and observational analyses were conducted using realistic and historical three-set land-use data over 40 yr from 1963 to 2002 to evaluate regional warming in the Daegu metropolitan area due to dramatic land-use alterations in the basin area and to quantitatively estimate the influence of nonuniform regional warming on complex local circulation. The results are as follows: (a) The daily mean temperature in the Daegu metropolitan area increased by 1.5 K over 40 yr, and the increase was higher than that of the mean temperature on the Korean Peninsula. (b) A simulated surface wind pattern in 2002 agreed well with the observed data. The rapid urbanization of the Daegu metropolitan area has had a large influence on the local circulation outside of the area. (c) Because of the variation in heat and momentum transfer due to land-use alteration, the prevailing wind has also changed in the central basin in the Daegu metropolitan area. The spatial distribution of the temperature change is very similar to the changes in the wind. (d) The two-dimensional mixed-height theory was applied to local circulations. By this theory, regional warming that occurs as a result of land-use alteration determines a higher critical height, which serves as an index for estimating the mixing intensity induced by a surface sensible heat flux. According to the observational data, this index can be used to quantitatively estimate regional warming in complex terrain.