The Diagnosis And Mechanism Analysis Of Spatio-temporal Variability Of Sea Surface Height In Tropical Pacific Ocean

By using of SODA reanalysis data, OAFlux flux data, GPCP precipitation data et al during 1961-2010.On the base of empirical orthogonal function, and on the basis cross wavelet and regression analysis and other statistical methods, investigations were conducted in this paper on the low frequency (seasonal, inter-annual and inter-decadal) Spatiotemporal variability and its factors of sea surface height anomaly (SSHA) in the Tropical Pacific Ocean. The major results are summarized as shows:(1)The first Seasonal EOF mode of SSHA in the Tropical Pacific Ocean is closely related to the ENSO events in the same period, especially in autumn and winter; On inter-annual scale, the first EOF mode of SSHA is similar to the ENSO mode, the spatial distribution shows an opposite sign in the west tropical ocean and the middle east Tropical Pacific Ocean, its significant period includes 5.75 years and 3.5years; on inter-decadal scale, the first mode of SSHA in the tropical Pacific is similar to the PDO mode, the spatial distribution shows an "seasaw" pattern in the east-west direction, the high value areas lie in American coasts and the east coasts of New Guinea island, the corresponding significant period includes 10-15 years and 30 years.(2)The physical process that how each factor effects SSHA in the equator Middle East Pacific during the evolution of El Nino (La Nina) events is showed as follows:Westerly (Easterly) zonal wind stress anomaly occurs in the west tropical Pacific Ocean,and warm water converges (diverges) in the center-east tropical Pacific, the thermocline deepen (shoal),thermal expansion (cooling) effect which leads to positive (negative) SSHA in the center-east equatorial Pacific, positive (negative) heat content anomaly maintains oceanic heating (cooling) state in the same period, while negative (positive) neat heat flux anomaly slows the rapid rising (falling) of SSHA in the corresponding areas.whereas the occurrence of positive (negative) freshwater flux anomalies which could promotes positive (negative) SSHA. The comprehensive effects of these factors as above contribute to positive (negative) SSHA in the center-east equatorial Pacific. Besides, the physical process reverses in the west tropical Pacific. During the ENSO cycles, the phenomenon begins to develop in summer, then reaches to prosperous period in autumn and winter, while decays in next spring.(3)On inter-annual scale, the spatial distribution of the regression mode for each factor (wind stress, heat flux, freshwater flux) which root in the corresponding time series of the annual mode of SSHA is almost coincident with composition analysis in autumn and winter during ENSO cycle.(4) On inter-decadal scale, the salient region where SSHA is significantly associated with sea surface temperature is located in in the eastern tropical Pacific, and for heat content the areas are located in the coasts of America and east of New Guinea; while for zonal wind stress the area is located in in the tropical Pacific, while for meridional wind stress the areas mainly located in in the coastal areas. During 1961-2010, the relationship between SSHA and heat content is relatively stable, and the correlation between SSHA and zonal wind stress is fairly stable in the central tropical Pacific, while the correlation between SSHA and sea surface temperature is less stable.