The Research Of The Relationship Between Victoria Mode In The North Pacific And SST In The Tropical Pacific

The interannual?interdecadal?variables in the North Pacific have significant effects on the sea surface temperature?SST?and climate in the tropical Pacific,in which the interdecadal variation of SST in the North Pacific are closely related to the ENSO events.Based on the sea surface temperature data of NOAA in the United States and the monthly mean ocean assimilation data set,SODA3.3.1 provided by the University of Maryland in the United States,the interannual relationship between ENSO and the Victoria modes?VM,the EOF2 of North Pacific SST anomalies in winter?DJF??and the possible physical mechanism of VM affecting ENSO are analyzed emphaticall.The main conclusions of the study are as follows:?1?VM and NPGO are different manifestations of the same physical process in different elements,both of which are characterized by a north-south reverse meridional dipole structure.The temporal and spatial characteristics and periods of the two modes are very similar,but the interannual variation of VM index is more significant.From the analysis of different time scale,the results show the correlation between VM and ENSO is weak on the interdecadal scale,but strong on the interannual scale.VM has significant negative correlation with ENSO in the same year,and has strong positive correlation with ENSO in the following year.?2?On the interannual scale,VM and ENSO are causal relationship with each other.VM has no?significant?effect on ENSO in the same winter?the following winter?,and the effect of VM on the ENSO of the following year is more significant than that of ENSO on the VM of the same year.?3?There is a certain asymmetry between the positive and negative VM events and ENSO warm and cold phases in interannual scale.The relationship between the positive VM events and the SST anomalies in the tropical central and eastern Pacific in the same winter is weak,but El Ni?o events often occur in the following year.In contrast,negative VM events are usually accompanied by El Ni?o events in the same year,but there is no significant relationship between the negative VM events and the SST of the tropical central and eastern Pacific in the following winter,and there are very few ENSO events occurring.Therefore,the influence of VM on the ENSO of the following year is not symmetrical,the positive VM events can promote the occurrence and development of El Ni?o in the following year,while the negative VM events have no obvious influence on the ENSO events of the following year.?4?The advection terms of VM affecting the SST of the tropical Pacific in the following year are mainly-u?^? indicating the zonal anomaly advection of seawater temperature,-???^? indicating the meridional advection of seawater temperature anomaly and-???^? indicating the vertical advection seawater temperature anomaly.According to the changes of physical factors reflected by the three advection terms,the possible physical process of VM affecting ENSO is determined.When the positive VM events occur in the North Pacific in winter,the westerly anomalies in the western subtropical region of the North Pacific cause the equatorial Kelvin wave to propagate eastward,and the easterly anomalies in the tropical central and eastern Pacific transmit cold current westward.By the spring of the following year,the tropical central and eastern Pacific SST began to warm up with an upwelling warm current.In the summer of the following year,the continuous warming in the tropical central and eastern Pacific makes all the easterly anomalies in the 850 hPa wind field turn into westerly anomalies and develop continuously.Finally,in the autumn and winter of the following year,it develops into the significant El Ni?o-like SST structure.