Regional climate modeling of the monsoon season over the Rio Grande Basin

Regional climate modeling is being undertaken to simulate the hydrologic cycle of the Upper Rio Grande basin. A coupled modeling system developed at Los Alamos is being used for this modeling effort. This coupled modeling system includes a mesoscale atmospheric model, surface hydrology, groundwater, and river models. We will present results of summer convection of the monsoon (between July and September) and discuss several important issues in parameterizing convection in regional climate modeling. One of the pertinent issues to be discussed is the quantitative precipitation forecasting (QPF). QPF is one of the critical atmospheric components in simulating the hydrologic cycle. QPF is known to be even more difficult in complex terrain of the southwest as no known cumulus parameterization scheme is robust. At the same time, explict microphysical modeling, while computationally expensive, may not produce desirable QPFs for an entire monsoon season. Grid nesting, resolution in each grid, the convection parameterizations used are a few critical modeling issues that are at the focal point of the research.

A coarse grid (grid 1) covering most of the continental U.S., parts of Canada, and parts of the Pacific ocean is required for these simulations. Finer-scale domains are spawned within the above coarse grid to achieve resolution of 5 km within the inner most grid (grid 3) that encompasses the Rio Grand basin. The Regional Atmospheric Modeling System (RAMS) is used for these simulations. The National Center for Environmental Prediction (NCEP) data are used to initialize RAMS. Surface observations are used to compare and validate the model results when applicable.