Global evidence of hydroclimate changes due to urbanization

NASA's Precipitation Measurement Missions (PMM) program continues to play an important role in understanding precipitation variability at weather and climate scales. The 2007 Intergovernmental Panel on Climate Change Assessment Report 4 highlighted the role that both urban land cover and pollution play in precipitation processes. Renewed interest in urban effects on precipitation has been sparked by several recent satellite-based studies that emerged from our previous TRMM work (Souch and Grimmond 2006). Additionally, several major meetings (e.g., the 89th Annual American Meteorological Society, Jan10-15th 2009, IAUC International Urban Climate Meeting, Yokohama Japan) had urban weather and climate as the theme or a significant focus.

With this legacy, we have aligned our research paradigm to build on our previous knowledge while advancing scientific understanding and applicability in the Global Precipitation Measurement (GPM) era. The paradigm is to use our overarching research topic, “human influences on precipitation and hydroclimate variability,” as an organizing principle to demonstrate (1) Utilization of satellite/GV products for process studies and model development and (2) Methodology development for improved applications of satellite products. PMM-based measurements from the Tropical Rainfall Measuring Mission (TRMM), AMSR-E, SSM/I, TRMM ground validation assets (radar, gauges, and disdrometers) and hopefully even GPM will be the core observational resources; however, our unique interdisciplinary approach will require cross-integration of other NASA datasets such as MODIS, CALIPSO, CloudSat, GLORY, and other emerging resources.

We will present recent and preliminary results identifying geographical tendencies in hydroclimate variability that may be driven or modulated by a combination of urban land cover and aerosols. We employ methods developed by Hand and Shepherd (2009) among others as a unifying methodology to examine individual and synergistic contributions to the “urban hydroclimate signal." Our results will identify statistically significant warm season rainfall anomalies in multiple global urban areas in North America, South America, Europe, and Asia. Further, we present some of the first results of multiple global “urban rainfall effects” using the same research framework rather than the typical isolated city or few cities approach.