Diurnally varying regional climatic simulations

• Published in: International Journal of Climatology
• Main Authors: Hunt, B. G., Gordon, H. B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1989
• Subjects: Sea ice
• Online Access: http://dx.doi.org/10.1002/joc.3370090402; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.3370090402; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.3370090402

Abstract A detailed analysis has been made of the atmospheric variability at a number of specific geographical points as simulated with a global general circulation model. The objective of this study was to assess the model's performance as regards diurnal and interdiurnal variability, but more importantly to identify critical features which should be monitored in climatic‐change experiments. Since the model contains a number of physical processes, including cloud forecasting, three independent rain‐producing mechanisms, a very responsive surface‐hydrology formulation, sea‐ice determination, etc., complex interactions among the various climatic components can occur. Results are presented for a number of longitudinal points at three selected latitudes, representative of summer, winter, and tropical conditions. One of the clearest features of the model output was the very marked longitudinal asymmetry in atmospheric forcing arising from land‐sea contrast. The vital role of the soil moisture, which depends critically on its model formulation, in determining whether this forcing is due to latent or sensible heating over the land is also demonstrated. The unique diurnal variations which were simulated at individual geographical points suggest that systematic distortions must occur in most near‐surface processes in non‐diurnal models. The extreme sensitivity of the convective mechanisms and the consequent impact on rainfall is noted, together with its implications for experiments involving climatic change. Finally, the interdiurnal variability of the model is illustrated by a number of examples, one of which highlights the potential misrepresentation of air‐sea exchanges in models employing fixed sea‐surface temperatures.