SCAM simuleringer av aerosolers effekt på skydråper : sammenligning med MODIS

Abstract

Aerosol particles , such as sulfate aerosols, can act as cloud condensation nuclei (CCN). The CCN spectrum and water vapor supply in a cloud determine the cloud droplet number concentration (CDNC) and hence shortwave optical properties of liquid clouds. The capability of aerosols to increase cloud reflectivity and thereby cool the Earths surface is referred to as the indirect effect.

The goal of this study is to compare different cases which relate aerosol mass concentration and cloud droplet number concentration. The resulting cloud droplet number is used to calculated variations in droplet effective radius, cloud cover and aerosol optical depth using NCAR single column CAM (SCAM). The results were compared with observations, Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data.

We looked at three cases, Boucher and Lohmann (1995), Menon et al. (2002) and Quaas et al. (2006). Based on model experiments, Menon et al. (2002) showed better correlation with MODIS than it was the case for Boucher and Lohmann (1995) and Quaas et al. (2006), specially for effective droplet radius.