Observed aerosol and liquid water path relationships in marine stratocumulus

Abstract

The stratocumulus-topped marine boundary layer (BL), aerosol, and cloud properties observed on research flights made off the coast of northern Chile in the Southeastern Pacific (20S, 72W) during the VAMOS Ocean-Cloud-Atmosphere-Land Study-Regional Experiment (VOCALS-REx) were used to examine the variation of liquid water path (LWP) and cloud condensation nuclei (CCN). Ten flights were made under similar meteorological conditions where the BL structure was well-mixed, clouds were solid, and the conditions at the surface and at the top of the BL were similar. A strong positive correlation between the LWP, which varied from 15 to 73 gm -2, and the BL CCN, which ranged from 190 to 565 cm -3, was observed. Analysis of the highest and the lowest CCN concentration cases confirms that the differences in the thermodynamic jumps at the top of the BL and the turbulent fluxes at the surface cannot explain the observed differences in the LWP. Cloud properties from satellite retrievals combined with a back trajectories analysis demonstrated that the LWP differences observed at the time of the aircraft flights are also prevalent during the night-time hours prior to the aircraft observations. These results provide evidence for CCN and LWP relationships that are not fully explained by current hypotheses from numerical modeling. © 2010 by the American Geophysical Union.