Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA A climate version of the regional atmospheric modeling system  G. E. Liston and R. A. Pielke With 12 Figures Received September 27, 1999 Revised December 11, 1999 Summary The Regional Atmospheric Modeling System (RAMS) has been widely used to simulate relatively short-term atmo- spheric processes. To perform full-year to multi-year model integrations, a climate version of RAMS (ClimRAMS) has been developed, and is used to simulate diurnal, seasonal, and annual cycles of atmospheric and hydrologic variables and interactions within the central United States during 1989. The model simulation uses a 200-km grid covering the conterminous United States, and a nested, 50-km grid covering the Great Plains and Rocky Mountain states of Kansas, Nebraska, South Dakota, Wyoming, and Colorado. The model's lateral boundary conditions are forced by six- hourly NCEP reanalysis products. ClimRAMS includes simpli®ed precipitation and radiation sub-models, and representations that describe the seasonal evolution of vegetation-related parameters. In addition, ClimRAMS can use all of the general RAMS capabilities, like its more complex radiation sub-models, and explicit cloud and precipitation microphysics schemes. Thus, together with its nonhydrostatic and fully-interactive telescoping-grid cap- abilities, ClimRAMS can be applied to a wide variety of problems. Because of non-linear interactions between the land surface and atmosphere, simulating the observed climate requires simulating the observed diurnal, synoptic, and seasonal cycles. While previous regional climate modeling studies have demonstrated their ability to simulate the seasonal cycles through comparison with observed monthly-mean temperature and precipitation data sets, this study demonstrates that a regional climate model can also capture observed diurnal and synoptic variability. Observed values of daily precipitation and maximum and minimum screen-height air temperature are used to demonstrate this ability. 1. Introduction Current global-scale, general circulation models (GCMs) used to simulate weather and climate do not operate at ®ne enough grid resolutions to resolve many observed regional weather and climate features. To simulate these meteorological features, regional or limited-area atmospheric models have been used. These models are run at higher resolution than the GCMs and are thus able to better represent mesoscale dynamics and thermodynamics, including processes resulting from ®ner-scale topographic and land-surface features. Typically the regional atmospheric model is run while receiving lateral boundary- condition inputs from a relatively-coarse resolu- tion atmospheric analysis model or from the output of a GCM. The model simulations performed as part of the Project to Intercompare Regional Climate Simulations (PIRCS) (Takle et al., 1999) are an example of these kinds of simulations. Additional discussions of regional climate modeling efforts can be found in Giorgi (1995), Christensen et al. (1997), McGregor (1997) and Beniston (1998). Typically, full-year regional climate model integrations have been validated against monthly mean temperature and precipitation observations Theor. Appl. Climatol. 68, 155±173 (2001)  This article has been published for the ®rst time in Theoretical and Applied Climatology 66: 29±47 (2000). Due to the extremely poor quality of the ®gures caused by the printer we decided to reprint the article again in this issue to guarantee a proper pre- sentation of the paper. The Publisher