Detection of Urban-Induced Rainfall Anomalies in a Major Coastal City

There is increasing evidence that large coastal cities, like Houston, Texas, can influence weather through complex urban land use–weather–climate feedbacks. Recent work in the literature establishes the existence of enhanced lightning activity over and downwind of Houston. Since lightning is a signature of convection in the atmosphere, it would seem reasonable that urbanized Houston would also impact the distribution of rainfall. This paper presents results using data from the world’s first satellite-based precipitation radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) and ground-based rain gauges to quantify rainfall anomalies that we hypothesize to be linked to extensive urbanization in the Houston area. It is one of the first rigorous efforts to quantify an urban-induced rainfall anomaly near a major U.S. coastal city and one of the first applications of space-borne radar data to the problem. Quantitative results reveal the presence of annual and warm season rainfall anomalies over and downwind of Houston. Several hypotheses have surfaced to explain how the sea breeze, coastline curvature, or urbanized Houston environment interacts with the atmospheric system to impact rainfall. This paper presents evidence that the urban heat island’s influence is of primary significance in causing the observed precipitation anomalies. Precipitation is a key link in the global water cycle and a proper understanding of its temporal and spatial character will have broad implications in ongoing climate diagnostics and prediction, Global Water and Energy Cycle (GWEC) analysis and modeling, weather forecasting, freshwater resource management, and land–atmosphere–ocean interface processes.