Impact of irrigation over the California Central Valley on regional climate

AbstractIrrigation, while being an important anthropogenic factor affecting the local to regional water cycle, is not typically represented in regional climate models. An irrigation scheme is incorporated into the Noah land surface scheme of the Weather Research and Forecasting (WRF) Model that has a calibrated convective parameterization and a tracer package is used to tag and track water vapor. To assess the impact of irrigation over the California Central Valley (CCV) on the regional climate of the U.S. Southwest, simulations are run (for three dry and three wet years) both with and without the irrigation scheme. Incorporation of the irrigation scheme resulted in simulated surface air temperature and humidity that were closer to observations, decreased depth of the planetary boundary layer over the CCV, and increased convective available potential energy. The result was an overall increase in precipitation over the Sierra Nevada range and the Colorado River basin during the summer. Water vapor rising f...