Observations of ship-induced cloud tracks and methods for quantifying the duration of track visibility

Abstract:

Aerosols emitted by ship traffic perturb local clouds, sometimes resulting in the formation of linear cloud patterns that follow the path of the ship. These ship tracks are of interest for a number of reasons, with a primary driver being that they are observable examples of marine cloud brightening from a known emission source. Thus, the presence and persistence of these anthropogenic tracks have implications for solar climate intervention and our collective understanding of uncertainties in climate forcing. Due to complex atmospheric dynamics, it can be difficult to rigorously track aerosol perturbations and precisely characterize the duration of potential radiative impact from a single emission source. Existing modeling studies underestimate how long a track visibly persists in its linear form and thus may also be largely underestimating the effect of ship emissions on the surrounding atmosphere. In this work, we combine GOES-R satellite imagery and AIS ship tracking data to demonstrate two methods for following the trajectory of ship-induced cloud tracks that are visible in satellite radiance data. In the first method, we employ NOAA’s HYSPLIT model to compute forward trajectory analyses and compare those locations to cloud track features. The second method uses an optical flow algorithm to track visible feature movement through time, allowing us to follow a linear cloud pattern until it decays. Both approaches show that ship tracks can persist as visible linear features beyond 12 hours and sometimes longer than 24 hours. This finding has important implications for future climate modeling efforts. We will describe both methods and provide several case studies that demonstrate the temporal extent of visible, aerosol-induced cloud tracks. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525