Study On The Characteristics Of SSTA In North Atlantic In Spring And Its Relationship With ENSO

In this study,the possible causes of the main sea surface temperature(SST)mode are explored by applying reanalysis data and the mixed-layer SST diagnostic equations,based on the extraction of the main modes of sea surface temperature anomalies(SSTA)in the North Atlantic in spring.The differences and causes of the North Atlantic SSTA,as well as the important impact of ENSO events in the next spring of 1997-1998 and 2015-2016,are analyzed.The first EOF mode in the North Atlantic Ocean spring is a tripole mode.The second mode as a whole shows a strong unipole center,and the third mode is a dipole mode.ENSO is closely related to the first and third ones.The ENSO event affects the atmospheric circulation of the North Atlantic,namely the North Atlantic Oscillation(NAO),through the eastward transfer of tropical Kelvin waves and PNA(Pacific North American Pattern)teleconnection patterns,causing changes in the Azores high and generating wind fields anomalies in the north and south,through the wind-evaporation-sea surface temperature(SST)feedback mechanism,where North Atlantic evaporation weakens(enhances)and sea surface warms(cools).Through the above mechanism,the impact of the El Ni(?)o event on the North Atlantic is greater than that of La Ni(?)a event.The tripole sea temperature is the result of the interaction between the internal ocean dynamics and the heat exchange at the sea surface.Through mixed layer diagnostic analysis,there are certain differences in the factors affecting the anomalous center of sea temperature at different latitudes.The effect of latent heat flux of the thermal factor and the zonal Ekman drift of the inside process of ocean is more significant.Changes in the thermal force are directly related to the change of the sea surface wind field.The analysis of individual cases shows that in the spring of 1998,the North Atlantic SSTA showed a clear positive-negative-positive tripole distribution,while in 2016,it showed a weak opposite negative-positive-negative pattern.The influential factors for the diagnosis of SSTA in the tropical North Atlantic show that in addition to the abnormaldecrease in latent heat from the ocean surface to the atmosphere and the increase in absorption of solar radiation in the spring of 1998,the zonal Ekman drift in the ocean also plays an important role.The thermal process is related to the negative phase of NAO that appears after the El Ni(?)o peak,which can cause the weakening of the Azores high,produces anomalous southwesterly winds,weakens the tropical North Atlantic evaporation,and warms the sea surface.The eastward shift of the sinking branch of the Walker circulation also contributes to this increase warm,but the impact of this mechanism is small.Unlike the1997-1998 El Ni(?)o event,the 2015-2016 El Ni(?)o event did not force a negative phase NAO,but a weak NAO positive phase.The tropical North Atlantic was a weak east wind anomaly,which caused a certain cooling of the sea surface and formed the significant differences in North Atlantic in the spring of 2016 and 1998.