Black Carbon and West African Monsoon precipitation: observations and simulations

J Huang,A Adams,C Zhang,C Wang

doi:10.5194/angeo-27-4171-2009

Abstract

Abstract. We have recently investigated large-scale co-variability between aerosol and precipitation and other meteorological variables in the West African Monsoon (WAM) region using long term satellite observations and reanalysis data. In this study we compared the observational results to a global model simulation including only direct radiative forcing of black carbon (BC). From both observations and model simulations we found that in boreal cold seasons anomalously high African aerosols are associated with significant reductions in cloud amount, cloud top height, and surface precipitation. These results suggest that the observed precipitation reduction in the WAM region is caused by radiative effect of BC. The result also suggests that the BC effect on precipitation is nonlinear.

Highlights

By absorbing and scattering solar radiation, aerosols can affect precipitation through its radiative effect on surface and atmospheric heat budgets, which modulate the large scale circulation (e.g. Chung and Seinfeld, 2005; Haywood and Boucher, 2000)
A possible reason for the resolvable large-scale precipitation not affected by the local black carbon (BC) radiative effect is that large-scale precipitation is more controlled by the large-scale circulation and less sensitive to local changes in radiative heating/cooling
Using long-term satellite data and GCM simulations, we have demonstrated that aerosols from Africa significantly re

Summary

Introduction

By absorbing and scattering solar radiation, aerosols can affect precipitation through its radiative effect on surface and atmospheric heat budgets, which modulate the large scale circulation (e.g. Chung and Seinfeld, 2005; Haywood and Boucher, 2000). By absorbing and scattering solar radiation, aerosols can affect precipitation through its radiative effect on surface and atmospheric heat budgets, which modulate the large scale circulation Due to the natural variability and complexity of many processes involved (Menon, 2004), observational and modeling studies on aerosol-cloud-precipitation interaction do not always produce consistent results Few attempts have been made to compare large-scale observed and simulated aerosol-precipitation relationships. Such comparisons are needed for evaluating the performance of the models and to build our confidence in using these tools to specify and quantify certain physical mechanisms that would be otherwise difficult to reveal with observations alone

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Results

Conclusion