Individual and combined roles of ENSO and NAO in the development of the North Atlantic tripole SST anomalies during boreal spring.

Sea surface temperature (SST) anomalies often display a tripole pattern in the North Atlantic Ocean. This study investigates the formation of large amplitude North Atlantic tripole SST anomaly pattern during boreal spring when the El Niño-Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) act individually and synthetically. It is found that the tripole SST anomalies have a larger amplitude when ENSO and NAO act together than when ENSO or NAO acts alone. The effects of ENSO are mainly in the tropics. The effects of NAO are larger in the high latitude. The large amplitude tripole SST anomaly pattern is associated with a similar tripole pattern in surface latent heat flux anomalies. Surface sensible heat flux and ocean horizontal advection also contribute to the high-latitude SST anomalies and have a supplementary effect on the mid-latitude SST anomalies. Latent heat lux anomalies are attributed to the effect of wind speed in the tropics and middle latitude and sea-air humidity difference in the high latitude. Sensible heat flux anomalies are mainly attributed to the effect of sea-air temperature difference. [ABSTRACT FROM AUTHOR]