Does the Summer Heavy Rainfall Climatology over east United States show Urbanization Impacts?

We evaluate the relationship between rainfall characteristic and urbanization over eastern US region in last few decades. Rainfall records from 8000 surface stations in US over last 50 years, high-resolution reanalysis rainfall data, winds and gridded human population data are analyzed. Results indicate that both the amount and heavy rainfall event frequency shows possible bias to regions of urbanization. Especially the rainfall amount may be increasing downtown of urban-rural boundaries. Analysis of very heavy and extreme rainfall events indicates increased trends over both urban and rural area, but the trend over urban area is significantly more than rural area. Spatially, the urbanization impact is more in northwestern and Midwestern US where an increase is noted while Southeastern US experienced slight decrease of rainfall amount and heavy rainfall event frequency. Results suggest that urbanization as another anthropogenic influence affecting regional precipitation.