This project will examine anticipated changes in the statistics of weather and hydroclimate over western North America in coming decades from the point of view of needs in the management of water and ecosystems. This work is overdue in that western North America is already experiencing significant climate and hydroclimate change. Models project that over the next few decades warming will continue, southwestern North America and the southern Plains will become more arid and the northern Rockies and Plains will become modestly more humid. Additionally precipitation is projected to become more intense, variability on all timescales stronger and significant shifts to occur in the seasonal cycles of precipitation, soil moisture and streamflow. While these projected changes will have serious implications for water resources, agriculture, rangelands, wildlife management and natural ecosystems including forests, fire, etc. it must be noted that the model simulations of radiatively-driven hydroclimate change to data are not in close accord with actual change. This could be because the models are wrong or radiatively-driven change is being obscured by potent natural variability.
The proposed work will involve three interwoven efforts:
Evolution of near term climate due to both natural variability and forced change will be considered, including changes in frequencies and locations of storms, lengths of dry spells, extreme wet or dry years, seasonality etc. Observational records and Reanalyses, including the 20th Century Reanalysis, will be analyzed as well as the models participating in Coupled Model Intercomparison Project 5. Long control runs and last millennium simulations will allow an unprecedented assessment of the range of natural variability of hydroclimate and archiving of daily data will allow a pioneering assessment of how climate change impacts weather in the near term future. The geographic area of focus extends from the Pacific coast to the Great Plains and from Canada into Mexico. We will consider large-scale climate features and short term weather and how these features may shift in time and space, influencing the landscapes and ecoregions of the future.