The Kuroshio-Oyashio Extension and Gulf Stream oceanic frontal zones
with sharp sea-surface temperature gradients are characterized by
enhanced activity of synoptic-scale cyclones and anticyclones and
vigorous air-sea exchange of heat and moisture in the cold season.
However, the air-sea exchanges attributed separately to cyclones and
anticyclones have not been assessed. Here we quantify cyclonic and
anticyclonic contributions around the oceanic frontal zones to surface
turbulent heat fluxes, precipitation, and the associated hydrological
cycle. The evaluation reveals that precipitation exceeds evaporation
climatologically within cyclonic domains while evaporation dominates
within anticyclonic domains. These features as well as the net moisture
transport from anticyclonic to cyclonic domains are all enhanced in the
presence of the frontal zones. Oceanic frontal zones thus
climatologically act to strengthen the hydrological cycle through
increasing low-level storm-track activity and specific humidity. These
findings aid our understanding of the relationship between midlatitude
air-sea interactions on synoptic- and longer-time scales.