Variation Characteristics Of Central Pacific Pattern El Ni?o Event And It’s Climate Effects

In this paper, observational data of TAO, HadISST and NCEP/NCAR assimilation data et al. have been used to study the temporal variation characteristics and forming mechanism of central Pacific pattern(CP) El Ni?o. Based on this, the impact of CP El Ni?o events on the western Pacific subtropical high, Arctic sea ice is researched by methods of Rotated empirical orthogonal function(REOF), wavelet Analysis, correlation analysis, and composite analysis. Main conclusions are listed below:1. The first and second REOF modal of SST can be a good characterization of SSTA distribution characteristics of EP and CP El Ni?o events, respectively. While the first and forth REOF modal of the tropical Pacific zonal wind could be a good characterization of zonal wind anomalies distribution characteristics in the EP and CP El Ni?o events. The correlations between the tropical Pacific zonal wind and SST are close, though the distribution characteristics are different in the EP and CP El Ni?o events.2. Based on the distribution characteristic of SSTA in the CP El Ni?o events, a CPI index is defined by using the TAO SSTA at 170°W, and latitude averaged from 2°S to 2°N to reflect the CP El Ni?o(La Ni?a) event. The CP El Ni?o(La Ni?a) is defined as the occurrence of 5 months CPI above(below) 1.0(-1.0). The new index is simpler and more practical than Nino4 Index and the second REOF time coefficient of tropical Pacific SST.3. Based on studying the temporal relation between CP El Ni?o(La Ni?a) events and the central Pacific zonal wind(ZW) field, a zonal wind convergence and divergence indices(CZWI) for the central Pacific is defined. These indices could reflect the convergence and divergence characteristics of the ZW anomalies in the CP event process. The highest correlation occurs when the CZWI are 4~5 months ahead of CPI, which could be very important for prediction of the CP El Ni?o events.4. The western Pacific subtropical high(WPSH) have observably seasonal, interannual and interdecadal variations. The Sea Surface Temperature(SST) over the central and eastern equatorial Pacific has a strong positive correlation with the area variation of WPSH, while negative correlation with the variation of the western ridge point. The highest positive correlation occurs when the CP El Ni?o Index(CPI) is 6 months ahead of the area of WPSH, while the largest negative correlation occurs when 5 months ahead of the western ridge point. Based on the close relationship between the two, a regression equation is obtained to predict the variations of the intensity and the western end of the ridge of WPSH in 2013~2015.5. The ASI converted from positive anomaly to negative anomaly in the early 1980 s. decreasing by-1.5% per decade. Although the sea ice also declined in winter(-0.7/10a), the biggest decrease appeared in summer and autumn(-2.2/10a), especially in September. So the main reason for the ASI ablation is the rapid ASI decline during summer and autumn.6. The correlation analysis shows that the rapid ASI decline closely related to the tropical Pacific SSTA. The relation between ASI and SSTA in the Midwest equatorial Pacific is closer than that between the SSTA in the East. There is a remarkable 3-year lag correlation between SSTA in Ni?o4 area and ASI. The SSTA during June to October had the larger influence to the ASI. The SSTA in Ni?o4 region influence the AO mainly through affecting the northern mid-latitude atmospheric pressure field and the meridional circulation field; ultimately affect the Arctic sea ice.