Progress in Understanding How Human Activity in Cities Affects Precipitation

Although currently a relatively small percentage of the land is considered urban, the spatial coverage and density of cities are expected to rapidly increase in the near future. The United Nations estimates that by the year 2025, 60% of the world's population will live in cities. Human activity in urban environments alters atmospheric composition; impacts components of the water cycle; and modifies the carbon cycle and ecosystems. However, our understanding of urbanization on the total Earth-climate system is incomplete. The U.S. Climate Change Science Program (CCSP) strategic plan states “…a world that is more populated, urban, and interconnected than ever…A more integrated understanding of the complex interactions of human societies and the Earth System is needed.” Additionally, a recent U.S. Weather Research Program report stated that there is a substantial need for more observational and modeling work to improve basic understanding of weather and climate impacts in the urban zone. To understand the urban-climate system linkage, an interdisciplinary effort combining in-situ and remote sensing, modeling, and human dimension assessments is ultimately required. We will provide a synopsis of our recent satellite remote sensing and modeling research on how current and future urban environments affect the precipitation (and related) components of the water cycle.