Recent investigations by numerous authors continue to provide evidence that urban areas and their associated “heat islands” affect precipitation variability. A recent U.S. Weather Research Panel report indicated that more observational and modeling work is required to conclusively address this problem and identify primary forcing mechanisms (e.g. dynamic or aerosol microphysics). Our research addresses the aforementioned issues within the context of NASA Earth Science Enterprise’s emerging interest in understanding precipitation variability and its relationship to the Earth’s water cycle, weather, climate, and land surface hydrology. In this paper we will summarize how:

(1) NASA’s TRMM merged three-hour analysis, TRMM Precipitation Radar data, and surface radar/rain gauge data are being used in a new “downscaling approach” to identify the spatial and temporal (e.g. diurnal tendencies) variability hypothesized to be induced by cities like Houston, Atlanta and Oklahoma City. Results will illustrate “hypothesized” urban rainfall anomalies in the selected cities.

(2) Remote sensing-derived land surface parameters (e.g. albedo, skin temperature, vegetation fractions, and roughness length) are being used to improve urban land surface parameterization in models. We will show early results from sensitivity experiments for Houston, Texas (eventually Atlanta, Georgia) using improved urban land parameterizations in the recently coupled Goddard PLACE-5th Generation MM5 mesoscale model. Early model results tend to support our earlier claims and some literature work that identify dynamical processes as being of primary significance in describing links between urbanization and precipitation variability.

(3) The Studies of PRecipitation Anomalies from Widespread urban Land use (SPRAWL) field campaign is being carried out over a 2-year period to enable more focused study of hypothesized urban-induced rainfall in the Atlanta area. We will also discuss the deployment of the NASA-Clark Atlanta Urban Rain Gauge Network (NCURN).

The research and results presented will highlight ongoing and collaborative new efforts by NASA and key partners to understand the impacts of urbanization on precipitation.