An Introduction

RAMS, the Regional Atmospheric Modeling System, is a highly versatile numerical code developed by scientists at Colorado State University for simulating and forecasting meteorological phenomena, and for depicting the results. Its major components are:

  1. An atmospheric model which performs the actual simulations
  2. A data analysis package which prepares initial data for the atmospheric model from observed meteorological data
  3. A post-processing model visualization and analysis package which interfaces atmospheric model output with a variety of visualization software utilities.

The atmospheric model is constructed around the full set of primitive dynamical equations which govern atmospheric motions, and supplements these equations with optional parameterizations for turbulent diffusion, solar and terrestrial radiation, moist processes including the formation and interaction of clouds and precipitating liquid and ice hydrometeors, sensible and latent heat exchange between the atmosphere, multiple soil layers, a vegetation canopy, surface water, the kinematic effects of terrain, and cumulus convection. RAMS is fundamentally a limited-area model, but may be configured to cover an area as large as a planetary hemisphere for simulating mesoscale and large scale atmospheric systems. There is no lower limit to the domain size or to the mesh cell size of the model's finite difference grid: microscale phenomena such as tornadoes and boundary layer eddies, as well as sub-microscale turbulent flow over buildings and in a wind tunnel, have been simulated with this code. Two-way interactive grid nesting in RAMS allows local fine mesh grids to resolve compact atmospheric systems such as thunderstorms, while simultaneously modeling the large scale environment of the systems on a coarser grid. RAMS is most strongly supported for execution under the UNIX operating system, but is also supported to some degree on computers for employing COS, VMS, or CTSS. The code is written almost exclusively in FORTRAN 77 with some common extensions, although some C code is used to facilitate I/O procedures and dynamic memory allocation. In order to utilize the standard graphics capability of RAMS, the computer installation should have the GKS Version 3.0 of NCAR Graphics.

RAMS is an outgrowth of two earlier atmospheric modeling programs conducted independently during the 1970's. A cloud model developed under the direction of Dr. William R. Cotton contributed state-of-the-art methods for modeling microscale dynamic systems and cloud processes. A mesoscale model developed under the direction of Dr. Roger A. Pielke contributed expertise in the modeling of mesoscale systems and the influence of land-surface characteristics of the atmosphere. In 1986, the process was begun of merging the capabilities of the two models into a unified multi-purpose modeling system, and thus was born the new RAMS code. In order to introduce a high degree of flexibility and versatility in RAMS, particularly regarding its new grid nesting capability, and to take advantage of the ever-increasing capabilities in computer hardware and software, RAMS was built on an entirely new framework, with the numerical schemes and parameterizations from the earlier models adapted to the new model structure. After two years of concerted effort, the first Version of the new RAMS code was in use as a research tool. A major program of development has continued to the present day, resulting in many improvements and new capabilities. The planning, design, and construction of the RAMS code has been conducted primarily by Drs. Robert L. Walko and Craig J. Tremback under the supervision of Drs. William Cotton and Roger Pielke. This effort has been carried out with a major emphasis given to uniformity of design of the code, and nearly all developments have involved cross-discussion and/or debate which we hope has resulted in the best of our ideas being incorporated. Many valuable ideas and experiences with RAMS have been shared by the students of Drs. Pielke and Cotton and by other users over the years, which has led to significant improvements in RAMS.

A more detailed description of R.A.M.S.

The RAMS Homepage at CSU