| In this paper,the index from the EN4 reanalysis data is used to distinguish two types of El Ni?o,and according to two important physical fields on the sea surface.As the entry point by the relationship between sea surface temperature anomaly?SSTA?and sea surface salinity anomaly?SSSA?.Using the time and space correlation coefficients of SSSA and SSTA to find the most important and close key areas of the two-type El Ni?o-Southern Oscillation?ENSO?,based on this,build a salinity index that can distinguish between two types of El Ni?o.One significant region of SSS field is migrated westward,another skewing southward east of the dateline as asym metric distribution during the central Pacific El Ni?o,which is different from the EP El Ni?o.In this paper,the absolute value de-gradient method is adopted,which can nearly consider the influence of each point as far as possible,and find the critical regions that can distinguish and represent both El Ni?o and La Ni?a events at the same time to the greatest extent.Finally,the article organically combines to select key areas and defines three sets of SSSA-based indicators that can effectively distinguish between two-type El Ni?o.By comparing and selecting the best one among them as an index,called CSI/ESI index,CSI=[SSSA]D-[SSSA]B-[SSSA]B?and ESI=[SSSA]A+0.5*[SSSA]A?-[SSSA]C-0.5*[SSSA]D??,on the above formula the[SSSA]A?2°-10°N,130°-153°E?,[SSSA]A'?5°-15°S,142°-160°E?,[SSSA]B?3°S-2°N,137°-155°E?,[SSSA]B'?3°-10°N,155°-170°E?,[SSSA]C?5°S-5°N,148°-168°W?,[SSSA]D?10°-20°S,105°-135°W?,[SSSA]D''?0°-10°N,80°-100°W?.In addition,research on the evolution of the SSSA in key areas of the El Ni?o period has been found.The CSI/ESI index's determination of the type of El Ni?o event is different from the previously used Oceanic Ni?o index,so the article attempts to re-classify the two types of El Ni?o by the CSI/ESI index.This paper starts from the perspective of salinity.Because of SSS and SST are subject to different physical processes.Therefore it can distinguish not only the types of El Ni?o/La Ni?a but also the intensity of events.And the test results are within an acceptable range of differences from the generally accepted event types of El Ni?o/La Ni?a... |
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