Use of Limited Area Models to Develop Regional Climate Scenarios

We describe the first simulation experiment and output archives of the Project to Intercompare Regional Climate Simulations (PIRCS). Initial results from simulations of the summer 1988 drought over the central U.S. indicate that limited-area models forced by large-scale information at the lateral boundaries are able to reproduce bulk temporal and spatial characteristics of meteorological fields. In particular, the 500 hPa height field's time average and temporal variability are generally well simulated by all participating models. Model simulations of precipitation episodes vary depending on the scale of the relevant dynamical forcing. Organized synoptic-scale precipitation systems are simulated deterministically in that precipitation occurs at close to the same time and location as observed (though the amounts may vary from the observations). Episodes of mesoscale and convective precipitation are represented in a more stochastic sense, with less precise agreement in temporal and spatial patterns. Differences in daily maximum temperatures are linked to the Bowen ratio differences, indicating strong local, surface influence on this field. Although some of the models have bias with respect to the FIFE observations, they all tend to reproduce the synoptic variability of observed daily maximum and minimum temperatures.