The portrayal of the Australian monsoon equatorial monsoon shear line by GCMs: enhanced greenhouse scenario implications

A critical test of a general circulation model is its performance on the regional scale. In this paper we examine the summer climatology of the CSIRO4 (4-layer) climate model over the Australian tropical region. The benchmark for the study is the positioning of the monsoon equatorial trough. We compare the CSIRO4 model climatology with the climatologies from the GFDL and GISS models and we report on the sensitivity of the position of the monsoon shear line and the strength of the monsoon westerly winds to the doubling of carbon dioxide in the atmosphere. The model results show that under the greenhouse scenario the monsoon is strengthened, but the average location of the monsoon shear line is not sensitive to the doubling of CO₂. Offprint requests to: BF Ryan