A Two–Dimensional Global Climatic Model

Abstract

A two?dimensional global climatic model has been developed, using a 10° longitude by 10° latitude box grid and a one-month time step. The lapse rates of temperature and the meridional component of the flow in the oceans and atmosphere and of specific humidity in the atmosphere are parameterized in terms of their respective sea-level values. The model then utilizes the vertically-averaged thermodynamic energy equation, the equation of motion for the boundary layer, the thermal wind equation, the hydrostatic equation, the surface water balance equation, and empirical relations between the sea-level temperature and pressure gradient fields and between cloud cover and precipitation to determine the global distribution by months of sea-level pressure, temperature, wind speed and direction, and relative humidity, precipitation, evaporation, runoff, soil mositure content, ice and snow cover and thickness, cloud cover, and poleward energy transport. A simple ocean model is included. Two 100 model-year runs were made on the NCAR CDC 7600 computer. Each required about 27 min of computer time. They differed only in the value of the solar constant used. Both runs indicate that the model is extremely stable. In almost all grid boxes only minor changes in any variable in any month occurred after the first 40 to 50 years. There are strong similarities between computed and observed fields of many of the variables. However, there are also several cases where the model predictions are completely unrealistic.