Characterizing and predicting along-coast and diurnal marine stratus variability on the U.S. West Coast

Marine stratus and fog characterizes much of the U.S. West Coast during summer months, which impacts on a variety of coastal activities, such as aviation and firefighting, as well as on coastal climates. Predicting diurnal clearing and smaller scale spatial variability remain challenging. This study utilizes a trajectory-based approach to examine the diurnal and spatial evolution of marine layer properties that result in along coast variations in the formation and dissipation of marine stratus. The 13 km RAP and 32 km NAM analyses are used to examine 2 and 3 dimensional air parcel trajectories during a period of large time and spatial variability in the marine stratus near the Monterey and San Francisco Bay areas as illustrated in Fig. 1. The overall goal is to relate key changes in marine layer properties that lead to clearing versus clouds so that these signals can be used in more robust forecast techniques. The evolution of marine layer temperature, dewpoint, depth, and surface interaction are examined to highlight the most important processes responsible for these diurnal and small spatial scale variations in marine stratus.