Impact of climate change on the local and regional energy balance

Increasing population and possibly a changing climate have put increasing demands on water use and economy, and our current hydrology models are not keeping pace. To better manage water now and in the future, we can use models and measurements to enhance our understanding of the physical processes related to land-atmosphere interaction. Intensification of the hydrologic cycle due to climate change, and land use changes and their relation to extreme weather events and water demand need a thorough study. Based on past generation global climate model results, the Pacific Northwest (PNW) is expected to have increases in annual temperature of about 1.1°C by the 2020s, 1.8°C by the 2040s, and 3.0°C by the 2080s, when compared to 1970 -1999 climate model averages. There are other sources of climate information beyond that provided by global climate models, such as the observationally-based North American Regional Reanalysis (NARR), available from 1979 to the present on a 32.5-km grid for high resolution verification (e.g., of land surface models), and North American Regional Climate Change Assessment Program (NARCCAP) regional climate model simulation data, which is generated at a 50 km resolution, making it quite useful for impact assessment studies. In this study, we will analyze the impacts of climate change on evapotranspiration over various watersheds in the PNW. The offline Noah Land Surface Model (LSM), which will account for irrigated areas in the region, will be used with an uncoupled and one-way coupled configuration to evaluate the impacts at a relatively high resolution (2 km) over the PNW, and to evaluate how climate forcings impact the regional energy balance and some boundary layer attributes. In the one-way coupled experiment, we first further dynamically downscale both NARR and NARCCAP simulations to 2-km using the Weather Research and Forecasting (WRF) model, and then use those 2-km simulations to force the Noah LSM. In our uncoupled experiments, HRLDAS (the High Resolution Land Data Assimilation System) is used to directly force Noah with the NARR and NARCCAP simulation data. These experiments will serve as a guiding factor to provide insights into future water availability for agriculture in the region.