AOPP Seminar - Essential roles of synoptic-scale transient eddies in atmosphere-ocean interactions

Midlatitude oceans play an important role in maintaining storm tracks, particularly around oceanic frontal zones with sharp sea surface temperature (SST) gradients. Air–sea heat and moisture fluxes there vary strongly with passing weather systems, yet their impact on air–sea interactions on longer time scales remains unclear. This talk examines the "rectified" effect of transient eddies on mean air-sea interactions. By quantifying the contributions of cyclones and anticylones to turbulent heat fluxes and rainfall, we show that they play different roles in the hydrological cycle, which is enhanced by sharp midlatitude SST gradients. Moisture transport from anticyclones to cyclones is also consistently strengthened. Furthermore, when synoptic-scale variability is filtered out from air–sea heat flux calculations, annual-mean heat fluxes decrease by up to 30% in frontal regions. Consistent relationships between synoptic eddy activity, heat fluxes, and SST are also found in climate models, highlighting the importance of transient eddies in shaping air–sea interactions on climatic time scales.