Summer Fog Frequency Patterns and Impact on Intertidal Organisms around Washington Coast from GOES-17 Satellite Imagery, Field Photos, and Field Sensors

Abstract

Fog can offer protection for intertidal organisms around the coast of Washington when low tides occur coincidently with warm temperatures. This protection becomes more important as extreme heatwaves are expected to increase with global warming. Using Cloud Top Height products from NASA and NOAA’s GOES-17 satellite, we created frequency maps and timeseries of fog and low clouds cover (FLCC) during the summer months of 2022 over Washington’s coastal areas. Our results showed that FLCC increased significantly in both coastal and ocean locations from May to August. On San Juan Island, FLCC was least frequent in the Northeast area, which contained the town of Friday Harbor. Intertidal organisms around False Bay and Cattle Point had protection from FLCC against heat stress during around 50% of the cumulative midday low tide hours in summer 2022, while it was only around 14% for the ones around the UW Friday Harbor Lab. We also used photos from our field cameras to acquire more accurate fog presence at local sites on the island. We trained an SVC Machine Learning model to do binary classification on all the photos, and the results were compared with the FLCC presence results that we inferred from satellite data. Comparisons suggested that we have yet to be able to use the satellite’s Cloud Top Height products to make conclusions about FLCC presence in a small-scale area at a specific timestamp, but we can use them to make good estimation of FLCC patterns over time at large spatial scales from the products.