Extreme Rainfall Variations in Response to Urban Land Use/Cover: A High Spatial-Temporal Resolution Radar Data-Based Evidence

Extreme rainfall (ER)-induced flooding results in large-scale damages with other noticeable social and environmental impacts. Various factors such as physiology, meteorology, and land cover could influence ER. In this context, the critical role of urbanization, which causes substantial land cover change, necessitates more understanding. As urbanization occurs, local climatology and rainfall may significantly change. Exploring ER variations in the face of urbanization requires rainfall information at a high spatial resolution to capture the role of diverse land covers. Many observation-based urban rainfall studies struggle to capture the fractional variations in rainfall due to several limitations, such as the coarse resolution offered by various remote sensing products. In connection with this, we used the Multi Radar Multi-Sensor data (high resolution of 1 x 1 km) in the Dallas-Fort Worth (DFW) metropolitan area to investigate urbanization’s influence on ER during 2000-2016. Days exceeding the 95^th percentile with minimum synoptic activity were selected for extreme rainfall variability. DFW was divided into 256 equal-sized grids and urbanization levels were calculated based on the percentages of developed land classes (high, medium, low intensity, and open space) in the National Land Cover Database. The relationship between each developed land class and ER was also analyzed. Overall, urbanization and ER showed a high spatial association (R² = 0.92) as evident from Geographically Weighted Regression. The grids with the highest percentages of medium-intensity developed land received the maximum rainfall in DFW. Instead of the climatological downwind area, the urban core in DFW received the maximum rainfall. Higher rainfall in the downwind as compared to the upwind area was dependent on the prevailing wind direction. Moreover, lower wind speeds caused higher rainfall in the upwind area in comparison to downwind area. The study provides useful insights regarding the role of urbanization on ER in a complex metropolitan area, which may offer innovative adaptation related recommendations to mitigate ER-induced impacts in the face of climate change and urbanization.