Numerical simulation of precipitation over the Southwestern United States during the 1994-1995 winter season

摘要

Accurate assessments of precipitation and surface snow budget during winter seasons are crucial for managing water resources in the western United States. This region receives most of its annual precipitation during winter months and relies on water stored in snowpack and reservoirs for water supply during dry summer seasons. Rainfall directly affects water inflow into reservoirs while snowmelt determines it during spring and summer. Precipitation and snow budget result from interactions among large-scale forcing, mesoscale processes, and surface energy balance. Interaction among these elements is highly nonlinear and includes various processes such as large-scale water vapor and temperature advection, precipitation physics, orographic forcing, turbulence, solar and terrestrial radiative transfer, and snow-albedo feedback. Hence, one need to take these processes into consideration in order to obtain accurate assessments of regional water resources over time scales longer than a season. A regional model that interactively couples atmospheric and land surface processes is a cost-effective tool for an assessment of precipitation and surface hydrology over large areas at a relatively fine resolution. Such models can include complex physical and dynamical processes involved in the interaction between the atmosphere and land surfaces. Another advantage of coupled atmosphere-land surface modeling is that simulations, when verified against local observations, can provide area-integrated values. Area-integrated values are useful for computing overall budgets, but they are somewhat difficult to obtain directly from local observations. Hence, a coupled atmosphere-surface model is especially useful for computing area-weighted values for areas of interest.