An optical flow approach to tracking ship track behavior using GOES-R satellite imagery

TL;DR

This paper introduces an optical flow method to track ship-emitted aerosols in satellite imagery, revealing their persistence and aiding understanding of marine cloud brightening effects on climate.

Contribution

It presents a novel optical flow technique specifically designed to isolate and track ship tracks in satellite images, improving over existing large-scale atmospheric motion estimates.

Findings

Ship tracks can be tracked for over 9 hours using the method.

The approach effectively distinguishes ship tracks from other cloud movements.

Ship tracks sometimes persist longer than 24 hours.

Abstract

Ship emissions can form linear cloud structures, or ship tracks, when atmospheric water vapor condenses on aerosols in the ship exhaust. These structures are of interest because they are observable and traceable examples of marine cloud brightening, a mechanism that has been studied as a potential approach for solar climate intervention. Ship tracks can be observed throughout the diurnal cycle via space-borne assets like the Advanced Baseline Imagers on the National Oceanic and Atmospheric Administration Geostationary Operational Environmental Satellites, the GOES-R series. Due to complex atmospheric dynamics, it can be difficult to track these aerosol perturbations over space and time to precisely characterize how long a single emission source can significantly contribute to indirect radiative forcing. We propose an optical flow approach to estimate the trajectories of ship-emitted aerosols after they begin mixing with low boundary layer clouds using GOES-17 satellite imagery. Most optical flow estimation methods have only been used to estimate large scale atmospheric motion. We demonstrate the ability of our approach to precisely isolate the movement of ship tracks in low-lying clouds from the movement of large swaths of high clouds that often dominate the scene. This efficient approach shows that ship tracks persist as visible, linear features beyond 9 hours and sometimes longer than 24 hours.