The surface temperature stratification induced by solar radiation affects ocean-atmosphere fluxes, and this is illustrated vividly in the land-sea breeze cycle over coastal upwelling regions. We found in the long-term buoy observations in the upwelling regions off the California and the Fujian coasts a statistically significant negative correlation between the upwelling intensity and the amplitude of land-sea breezes. In an idealized model, land-sea breezes form a standard sinusoidal signal, but the signal becomes asymmetric in the presence of upwelling as the sea breeze is enhanced while the land breeze is suppressed. We applied the COAWST (Coupled-Ocean-Atmosphere-Wave-Sediment Transport) model to the Taiwan Strait and confirmed the negative correlation between the upwelling intensity and the amplitude of land-sea breezes. Furthermore, our model revealed that the solar radiation increases the SST in the upwelling regions and reduces the land-sea temperature contrast during the day. Consequently, the enhancement of sea breezes by upwelling is weaker than in the ideal scenario, leading to a reduced asymmetry between land and see breezes as well as an overall smaller amplitude of land-sea breezes. This research extends the study of upwelling effects on land-sea breezes, with implications for advancing the understanding of coastal cloud and rain belts, and for the evaluation of mesoscale wind energy potential in upwelling regions.

solar radiation, upwelling, ocean-atmosphere heat fluxes, surface temperature stratification, land-sea breeze