Analysis of shiptrack persistence with insitu cloud measurements and satellite retrieved reflectance

Abstract

Shiptracks detected on Advanced Very High Resolution Radiometer (AVHRR) satellite images posses longer detection lives and down-track brightness than expected. A simple model of physical processes is developed to correlate the ship injected aerosols to the subsequent affects on cloud condensation nuclei, droplet distribution, effective radius, and albedo. The theoretical dispersion model is tested using measured values corresponding to the terms of the model equation. The data sets consisted of insitu aircraft droplet concentration and effective radius cross-shiptrack profiles and AVHRR satellite reflectance values collected during the Monterey Area ShipTracks (MAST) experiment. Strong reinforcement of the model's droplet concentration, effective radius, and reflectance relationships is shown. The near constant value in the observed down-track fractional change of droplet concentration disputes the decreasing fractional changes of droplets predicted by dispersion associated with track widening. The results indicate downtrack modification of cloud and droplet concentrations able to maintain track brightness and track detection life