Temporal effects of shiptracks on clouds

Abstract

The physical and optical characteristics of 27 shiptracks are analyzed using AVHRR satellite data. Channel 1 (.63um), and channel 3 (3.7um), are utilized to determine the temporal variations in shiptrack albedo and track width. In most cases, shiptracks mirror the trend of albedo changes exhibited by the ambient clouds in which they are formed. Under special circumstances, shiptrack albedo increases when ambient cloud albedo decreases due to cloud thinning. Shiptrack widths show uniformity of growth, with rapid growth rates of 4-6 km/hr in the near-source region, decreasing to 1-2 km/hr in the far field. Maximum width ranges from 10 to 12 kilometers. Predicted growth rates based on a parameterization of the standard deviation of plume concentration correlate well with observed track width values.