Ship tracks have been considered the Rosetta Stone demonstrating the effects of anthropogenic aerosols on cloud radiative properties through alteration of cloud microphysical properties. Previous ship-track studies have focused on identifying the signatures of indirect aerosol effects (e.g. enhanced droplet concentration) caused by ship emissions, and have been mainly concerned with comparing cloud properties within ship tracks to those of surrounding clouds on an individual track-by-track basis. Here we show that, examined together, ship-track studies can also provide crucial insights into cloud parameterizations in climate models, as well as understanding the conditions conducive to ship-track formation. It is found that unlike the measurements from general stratiform clouds where the effective radius is larger than the mean volume radius, the effective radius is smaller than the mean volume radius for some clouds in which ship tracks form. The radius ratio (the ratio of the effective radius to the mean volume radius) varies significantly and cannot be ignored in cloud parameterizations. The relation between the radius ratio and the spectral shape descriptors (relative dispersion and skewness) of the cloud droplet size distribution is further examined, revealing that the clouds with the effective radius smaller than the mean volume radius are likely to have negatively skewed cloud droplet size distributions with a higher concentration of relatively big droplets.
|Number of pages
|Asia-Pacific Journal of Atmospheric Sciences
|Published - 2008
All Science Journal Classification (ASJC) codes
- Atmospheric Science