SGER: Diagnosis of North American Hydroclimate Variability in Coupled Model Simulations

University Of Maryland, College Park, College Park MD

Investigators

Abstract

This is a grant under a Climate Variability and Predictability (CLIVAR) Program pilot project called CMEP, for Climate Model Evaluation Project, with a special emphasis on water cycle, precipitation and land surface interaction. The PIs will analyze the interannual variability of North American hydroclimate during summer and winter months in two coupled simulations of the 20th century climate. Current state-of-the-art atmospheric general circulation models have rather limited potential in simulating hydroclimate variability over North America, especially during summer when the climatological evaporation is large. The models exhibit intense local recycling of precipitation and weak convergent moisture fluxes, in contrast with warm-season observations. The PIs will first evaluate precipitation variability and the associated structure of the atmospheric water cycle during summer and winter in the Community Climate System Model (CCSM), Geophysical Fluid Dynamics Laboratory (GFDL) and Goddard Institute for Space Studies (GISS) coupled simulations. The analysis will be carried out using monthly fields. However the issue of local recycling of precipitation (via surface-atmosphere feedback) versus remote water sources of precipitation (via convergent moisture fluxes) in the North American region will be given special consideration. The PIs will use both monthly and pentad anomalies to investigate the precipitation recycling issue in models and observations. Lead/lag analysis is expected to be particularly insightful here. They will also examine the linkages of the two adjoining ocean basins on North American summer hydroclimate. They will undertake principal component analysis of 700 hPa geopotential height and SST to identify the basin connections in the simulations; the corresponding observational analysis has been completed. The PIs have a number of target data sets like the newly available European Center for Medium Range Weather Forecasting (ECMWF) reanalysis as well as other gridded observations for precipitation, evaporation, sea surface temperature, and satellite-based precipitation estimates that will be used to assess the simulations. Broader Impacts: If successful, this research will result in the improvement of climate model projections of climate variability in a changing climate. This had great potential benefit to people and their environments.