Alex K. Arnold

Tides in shelf seas greatly impact ocean mixing and temperature structure. Using a regional‐coupled ocean–atmosphere prediction system, at ocean coastal process and atmosphere convection permitting scales, we assess the influence of tides on British weather by comparing simulations with and without tides. In summer, when seasonal stratification is particularly sensitive to tides, the sea‐surface temperature is up to 6 K cooler in simulations with tidal mixing. Tides cool the air temperature over the sea by up to 3 K, and nearby land by up to 1.4 K. The mean air temperature across Great Britain land areas cools by 0.3 K with tides. Changes in near‐surface stability result in decreases in summer mean wind speeds over the ocean. A 6% reduction in summer precipitation is found with tides, consistent with cooler temperatures. This study has implications for climate projections since global‐coupled models typically do not include tides.

This study presents a numerical simulation assessing the effect of dynamical ocean–atmosphere coupling on the structure of the marine atmospheric boundary layer over the southern North Sea. Using a high‐resolution regional coupled ocean‐atmosphere prediction system, with a coupling frequency of 1 h, a diurnal variation of sea surface temperature simulated by the ocean model is applied to the atmosphere component. This results in a surface warming in the coupled compared to an atmosphere‐only run. Shallow convection initiated by heating of the lower atmosphere by a relatively warmer ocean surface leads local formation of low level clouds between 1300 h and 1700 h in the coupled run. The impact of these clouds in reflecting incoming solar radiation is demonstrated through a relative cooling of the sea surface temperature in the coupled simulation compared to an ocean‐only run forced by an atmosphere‐only run without representation of ocean‐atmosphere interactions.