Reconstruction Of Tropical Pacific SSTA Indices And Their Relations With Regional Climate Variations In Maritime Continent

By using the monthly average sea surface temperature (SST) of the Hadley Centre and the NCEP/NCAR reanalysis data during 1963-2013,based on the different types of SST anomaly in equatorial Pacific, which are called Central Pacific type (CP) and Eastern Pacific type (EP), two new SST anomaly index namely ICP and IEp are defined to investigate the features of ENSO events and their influences.In boreal winter, compared with the previous El Nino indices, the new index shows independent SST distribution in space and time, and could represent and distinguish the two types of El Nino events better during the same period. Besides, the major air-sea coupling features in tropical Pacific related with CP type and EP type are discussed by using the new index. The results show that the abnormal warming center of the central type of El Nino events is in the central equatorial Pacific, which is different from the traditional eastern type of El Nino events during which the largest warm center located in eastern equatorial Pacific. And the ascending branch of Walker circulation moves westward and the abnormal rainfall concentrated in the central tropical Pacific while the eastern type experiences a confined anomaly in eastern equatorial Pacific. Both of the two type events, the Maritime Continent is affected. That is to say, when the CP El Nino or EP El Nino occurs, the rainfall in Maritime Continent will decrease. But the CP El Nino has the larger influence on the Maritime Continent.In boreal spring, the new indices have good correlations with the previous El Nino indices and are good enough to describe and distinguish the two types of El Nino events. The major air-sea coupling features in tropical Pacific related with CP-type and EP-type are discussed by using the new indices. When the CP type ENSO occurs, the ascending branch of Walker circulation moves westward and the abnormal rainfall concentrated in the central tropical Pacific, which is correspond to the spatial distribution of the tropical Pacific SST anomaly, presenting zonal triple pattern in velocity potential anomalies. However, when the EP type ENSO occurs, the anomalies show dipole pattern in pacific basin. Besides, the SSTA in both regions CB [178°W-152°W,5°S-5°N] and EB[105°W-79°W,5°S-5°N] can describe the intensity of different types ENSO. There, results can be good clues to monitor the different types of SST anomaly and understanding the impacts of these two types of events on the climate.In boreal summer, compared to the past El Nino indices, the new indices are not only independently in space distribution, but can better indicate and distinguish two El Nino events. Using the new group of indices, characteristics of coupled ocean-atmosphere mainly related to central and eastern type of SSTA events can be easily studied. We find that new indices can clearly indicate different ocean-atmosphere characteristics during two different types of El Nino events. The specific difference is that when the CP type El Nino event occurs, anomaly warm center will locate in the equatorial Pacific, while during the EP type El Nino event, the center is in eastern equatorial Pacific. During the CP type El Nino events, the ascending branch of vertical circulation shifts westward to 150°W, and the anomaly precipitation is in the west of date line, which stretches across the equatorial Pacific. Significant differences exist in 2m temperature between two different types El Nino events, which is consistent to the characteristic of the distribution of SSTA.