An Annual Zonally Averaged Global Climatic Model with Diffuse Cloudiness Feedback

Abstract

An annual, zonally averaged, steady-state global climate model is developed which represents an extension of the hemispherical model reported by Temkin and Snell (1976). The model employs twelve 15° zones and incorporates the diffuse thin cloud tropospheric structure of Weare and Snell (1974) as a feedback mechanism calculated separately over land and ocean employing the appropriate mean land height temperatures and ocean level temperatures. Radiative calculations are also carried separately over land and ocean. Meridional energy transport is parameterized very similar to that of Temkin and Snell but also includes transport across the equator linearly related to the temperature difference. The response of the model to variations in various climatic determinants is studied, including global variations in carbon dioxide, aerosol and solar constant as well as additions of chlorofluorocarbons to the atmosphere. The model reveals that the Southern Hemisphere is more stable than the Northern Hemisphere by a factor of about 1.4 due to the dominance of ocean between 30° and 65°S with very little land-snow positive feedback. The Northern Hemisphere response is very similar to that reported by Temkin and Snell; therefore on a global basis the model shows somewhat greater stability. The response to additions of chlorofluorocarbons is about one-half of that reported by Ramanathan, giving an increase of 0.2 K in global average temperature at 1 ppbv for both CF₂Cl₂ and CFCI₃.