The Analysis Of The Influence Of Dynamic And Thermal Effects On The Sea Temperature In The Tropical Pacific Ocean During The Spring

The spring predictability barrier?SPB?of El Ni?o-Southern Oscillation?ENSO?is a difficult problem in the ENSO prediction.To understand how the dynamic and thermal factors affect the variability of sea surface temperature over the tropical Pacific Ocean during the spring is very important to understand the changes of SST in key area and resolve the SPB problem.Based on the second generation Beijing Climate Center Climate System Model?BCC-CSM2-MR?,the temperature field and wind field from the ECMWF-Interim reanalysis data and the BCC_GODAS sea surface data are used to force the climate model and produce a set of data which are coordinated with each other during the period of 1986 to 2017 including monthly wind stress,all kinds of energy flux and ocean current as the substitute of observation data.Based upon these data,we analyzed and diagnosed the dynamic and thermal influences and their contributions to the seasonal variability of the sea surface temperature and the sea surface temperature anomaly.At the end of this dissertation,we analyzed and diagnosed the data from the BCC-CSM2-MR model forecast experiment which started from March 1^st and maintained for 6 months during the period of 1986 to 2014.The main results show as follows:?1?The sea surface temperature?hereafter,?in spring,compared with in other seasons,presents a unique asymmetric seasonal shift that is from warming to cooling in the Ni?o3.4area.It is due to a similar shift in the wind stress,net energy fluxes,and ocean current which have a robust relationship with.Further analyses demonstrate that the thermal effect plays an important role in the variability of local.Differently,the meridional advection always shows a negative contribution to the seasonal variability of.Meanwhile,the zonal advection terms turn into a cooling effect from a warming effect toduring the spring and the superficial zone vertical advection effect is quite weak.According to the forecast result,the shift characteristic of zonal ocean current in spring is weaker than the observation result that may be caused by the weak model simulation of wind stress.In addition,the correlation between the zonal advection term and the tendency ofin the middle tropical area during April to June is negative in observation while it turns to positive in forecast result.?2?The interannual correlation between the tendency ofand its anomaly?TSA?during the period of 1986 to 2017 and the dynamic/thermal effect shows that the thermal heating is positively associated with the Ni?o3.4 TSA in the spring,as well as the zonal advection.However,the correlation between the meridional advection and the TSA changes from negative to positive during the spring.During the forecast process,the interannual correlation between the tendency of sea surface temperature and its anomaly and the dynamic/thermal effect can be shown by the model.But there are some biases in the forecast results of meridional and superficial zone vertical advection,and the correlation between the tendency ofand its anomaly and the thermal effect is stronger.?3?The quantitative analysis of the dynamic and thermal variance contributions in the Ni?o3.4 region also suggests that,the contribution rate of thermal effect is more than 50%,and the corresponding correlation coefficient is over 0.7.The contribution of zonal and meridional advection is about 10-20%,respectively,but they are opposite to each other.And the other items provide less contribution.Compared with the diagnosis results of forecast results,the contribution of thermal effect is overestimated by 5%-10%,while the contribution of horizontal advections is underestimated by 5%-10%.?4?According to the analysis of 3 typical El Ni?o and 3 typical La Ni?a events,the essentialities of thermal and dynamic effects are same whether in observation or prediction.And the positive contribution of those two effects will lead to the increase of TSA.But after the TSA growing to a certain degree,the contributions of the thermal effect turns to positive and restrains the development of the anomaly,even lead to the decline and perish.It has been proved by comparing with SODA data that the conclusion above is not dependent on the model.