We use NASA s satellite data and models to document past, present and future land surface conditions and produce an extensive assessment of the impacts of urbanization as a form of land use on the US continental surface climate. We propose to develop two observation-based and two scenario-based maps characterizing distant-past (pre-urban), recent-past (2001), present (2010) and near-future (2020) land cover and land use including urbanized areas, and simulate their impacts on the US surface climate using a NASA modeling testbed that includes a suite of land surface models and a weather forecast model. We will also link the model output to assess the socioeconomic impacts of environmental change on urban systems. The observation-based maps for 2001 and 2010 will be based on Landsat data at 30m resolution and MODIS at 1km and generated at 5x5 km nominal spatial resolution while retaining the sub-grid heterogeneities at 30m and 1km in the form of fractional coverage. Based on the 2001 and 2010 cover maps, two scenarios representing the pre-urban and near-future conditions will be developed. While the observation-based 2001 and 2010 maps provide an excellent baseline for a decadal assessment of the observed land use dynamic trajectory, the pre-urban map provides the first ever integrated impact of urbanization on land use and surface climate in the US and the 2020 map will provide a plausible and realistic projection of land use and climate conditions. For each of the four land cover maps, detailed sets of biophysical parameters describing vegetation phenological behavior and urban characteristics will be derived from MODIS and Landsat. Each of the four land cover maps along with its associated biophysical parameters will then be used in a suite of land surface models, of different complexity, driven by the appropriate meteorological observations to assess the impacts of urbanization on surface climate. An interesting aspect of this research will be the determination of an optimal fraction of vegetation and water bodies surrounding an urban area in order to best mitigate the loss of carbon sequestration, fresh surface water to runoff and the excess heating caused by impervious surfaces. Given a certain population to support and a regional climate regime, we postulate that it should be possible to formulate the ideal organization of land-cover elements to produce a desired microclimate. This type of analysis could become an important urban planning consideration in future decades as climate changes and population pressures continue to demand rapid expansion of cities. We will also use an advanced Weather Research and Forecasting (WRF) model to assess the impacts of urbanization on the atmospheric regional circulation in the Northeastern US including precipitation and temperature, as well as the potential impacts and feedbacks of those changes in those areas and the surrounding environment. A key novelty of this regional analysis will be to explore and estimate the aggregate effects of the Northeastern US urban archipelago (urban chain) on regional climate. Allied with the physical climate a socio-economic analysis will be performed to assess the impact of urban modification of surface climate on human population s behavior. This analysis is an important first step in integrating Earth sciences with urban economic analyses and will likely assist urban planners in identifying areas and populations most vulnerable to adverse effects of these changes. This has even larger implications for mitigation (e.g. geo-engineering) approaches such as implementing green canopies on rooftops or using more reflective material in urban buildings and surfaces to alleviate the urban heating effect.