Comparison of rainfall profiles in the West African monsoon as depicted by TRMM PR and LMDZ climate model
Résumé
Vertical rainfall profiles obtained with TRMM-PR 2A25 standard products are compared with rain profiles deduced from LMDZ model with two parametrization schemes: Emanuel (1991) and Tiedkte (1989). We focus on the low layers of the atmosphere over West Africa during the monsoon season (JJAS). The precipitation decrease above 4km is systematically not represented in rainfall profiles generated by Emanuel's parametrization scheme. However, Emanuel's shows a decrease similar to the observation from 4km down to the surface, especially in the Sahel (proper depth of the layer dominated by re-evaporation). As to Tiedkte's scheme, it describes best the downward increase in the upper levels of the atmosphere, whereas the downward decrease in the lower levels begins too low when compared to the observation. Tiedkte's parametrization shows an overestimation of liquid water production over Ocean and over the Guinean region and a slightly too strong re-evaporation in Sahara and Sahel. The zonal distribution of vertical rain profiles is then biased with this model scheme compared to the 2A25-PR product. On the other hand, although Emanuel's scheme detects too much re-evaporation over Sahara and underestimates liquid water production over Ocean compared to PR observation. It shows a good meridional distribution of these parameters. This is especially true in Sahel where Emanuel's scheme gives the best representation of re-evaporation.
Domaines
Météorologie
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