Long-term simulation of large-scale urbanization effect on the East Asian monsoon

The Weather Research and Forecasting (WRF) model is used to simulate the long-term effect of urbanization on regional climate, especially the East Asian monsoon. Besides land use change from urbanization, anthropogenic heat release is an important factor for the urban climate and environment, so these two factors are included in the simulation. Two experiments were designed and executed for the 10-year period. Urbanization is not considered in one experiment, and in the other, urban land use and anthropogenic heat release are comprehensively investigated. Comparison of the two runs shows that urbanization mainly decreases low-cloud cover across most of East China, and nearly all surface energy fluxes increase except those of latent heat and upward shortwave. Based on a multiyear average, the urbanization reduced summer precipitation in urban agglomerations, but the interannual variability is very large. Local upwelling airflow is strengthened by urbanization; however, additional precipitation was not produced because of a decline of surface moisture in urban agglomeration areas. From 850 hPa circulation change and the East Asian monsoon index, the summer monsoon is strengthened slightly and the winter monsoon is always weakened by large-scale urbanization.