All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 164 24 3
PDF Downloads 24 15 0

GCM Estimate of the Indirect Aerosol Forcing Using Satellite-Retrieved Cloud Droplet Effective Radii

View More View Less
  • 1 Laboratoire de Météorologie Dynamique du CNRS, Ecole Normale Supérieure, Paris, France
Restricted access

Abstract

In a recent paper, Han et al. analyzed satellite data radiances to retrieve cloud droplet effective radii and reported significant interhemispheric differences for both maritime and continental clouds. The mean cloud droplet radius in the Northern Hemisphere is smaller than in the Southern Hemisphere by about 0.7 μm. This hemispheric contrast suggests the presence of an aerosol effect on cloud droplet size and is consistent with higher cloud condensation nuclei number concentration in the Northern Hemisphere due to anthropogenic production of aerosol precursors. In the present study, we constrain a climate model with the satellite retrievals of Han et al. and discuss the climate forcing that can be inferred from the observed distribution of cloud droplet radius. Based on two sets of experiments, this sensitivity study suggests that the indirect radiative forcing by anthropogenic aerosols could he about −0.6 or −1 W m−2 averaged in the 0°–50°N latitude band. The uncertainty of these estimates is difficult to a assess but is at least 50%.

Abstract

In a recent paper, Han et al. analyzed satellite data radiances to retrieve cloud droplet effective radii and reported significant interhemispheric differences for both maritime and continental clouds. The mean cloud droplet radius in the Northern Hemisphere is smaller than in the Southern Hemisphere by about 0.7 μm. This hemispheric contrast suggests the presence of an aerosol effect on cloud droplet size and is consistent with higher cloud condensation nuclei number concentration in the Northern Hemisphere due to anthropogenic production of aerosol precursors. In the present study, we constrain a climate model with the satellite retrievals of Han et al. and discuss the climate forcing that can be inferred from the observed distribution of cloud droplet radius. Based on two sets of experiments, this sensitivity study suggests that the indirect radiative forcing by anthropogenic aerosols could he about −0.6 or −1 W m−2 averaged in the 0°–50°N latitude band. The uncertainty of these estimates is difficult to a assess but is at least 50%.

Save