A possible correlation between satellite-derived cloud and aerosol microphysical parameters

The column aerosol particle number and low cloud microphysical parameters d erived from AVHRR remote sensing are compared over ocean for four months in 1990. There is a positive correlation between cloud optical thickness and aerosol number concentration, whereas the effective particle radius has a n egative correlation with aerosol number. The cloud liquid water path (LWP), on the other hand, tends to be constant with no large dependence on aeroso l number. This result contrasts with results from recent model simulations which imply that there is a strong positive feedback between LWP and aeroso l number concentration. Estimates for indirect forcing over oceans derived from the satellite data/model comparison range from -0.7 to -1.7 Wm(-2).