Impact of High Resolution Sea Surface Temperature on Simulated Sea Breezes

Sea breezes are mesoscale atmospheric coastal circulations that develop in response to diurnal variations in the land-sea thermal gradient. Previous research illustrated the importance of properly representing the coastline in numerical simulations of sea breezes around Long Island Sound. Errors in the land-sea temperature gradients and sea breeze circulations resulted from a poor representation of the southern New England coastline in the initial conditions. Recent work explores the influence of sea surface temperature resolution on numerically simulated sea breezes in the same region.

In this study, a series of sensitivity experiments are performed to highlight the impact of the horizontal resolution of SST on simulated sea breeze dynamics. The 8 July and 21 August 2013 coastal Connecticut sea breeze events are simulated using the Weather and Research Forecasting (WRF) model, initialized with the 32 km North American Regional Reanalysis (NARR) for atmospheric conditions. Sea surface temperature sensitivity experiments compare a spatially uniform SST (22˚C), NARR (32 km) spatially varying SST, and the GHRSST Global 1-km SST (G1SST; 1km) spatially varying SST. The uniform SST experiment value is the average of the G1SST within Long Island Sound for the day of the sea breeze event. In all simulations, the SST is temporally constant. 

For sea breezes associated with the Long Island Sound estuary, circulations are weakly sensitive to the resolution of the SST, with minimal differences in structure and inland propagation distance between sensitivity experiments. Surface sensible and latent heat fluxes respond to the varying SST products, though the impact on the overlying air temperature is confined to the lowest 100 m of the marine atmospheric boundary layer (MABL) due to the relatively high stability limiting vertical mixing. However, differences in daily accumulated sensible and latent surface heat fluxes between SST products can be as large as 200%, which may impact coastal atmospheric and oceanic phenomena on longer time scales.