Interannual Salinity Variability in the Tropical Pacific in CMIP5 Simulations  

作　　者：Hai ZHI Rong-Hua ZHANG Pengfei LIN Peng YU Rong-Hua ZHANG 

机构地区：[1]College of Atmospheric Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China [2]Key Laboratory of Ocean Circulation and Waves,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China [3]Laboratory for Ocean and Climate Dynamics,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266237,China [4]University of Chinese Academy of Sciences,Beijing 100029,China [5]State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG),Institute of Atmospheric Physics (IAP),Chinese Academy of Sciences,Beijing 100029,China [6]The Cooperative Institute for Climate and Satellites(CICS),University of Maryland,College Park,MD 20740,USA

出　　处：《Advances in Atmospheric Sciences》2019年第4期378-396,共19页大气科学进展（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 41690122, 41690120 and 41475101);the NSFC–Shandong Joint Fund for Marine Science Research Centers (Grant No. U1406401);the NSFC Innovative Group Grant (Project No. 41421005);Taishan Scholarship

摘　　要：Salinity variability and its causes in the tropical Pacific are analyzed using observations, reanalysis products and model simulations. The mixed-layer salinity(MLS) budget analyses from observations and reanalysis products indicate that its interannual evolution is closely related to ENSO and is predominantly governed by surface forcing and surface advection in the western-central equatorial Pacific. It is found that the observed MLS tendency leads Nin?o3.4 by about 12 months due to the effect of negative freshwater flux(evaporation minus precipitation). These observation-based analyses are used to evaluate the corresponding simulation using GFDL-ESM2 M. It is evident that the model can simulate the spatiotemporal variations of MLS with some discrepancies compared to observations. In the warm pool of the equatorial Pacific the MLS tendency in the model is sensitive to ocean dynamics, however model biases cause the tendency to be underestimated. In particular, the freshwater flux is overestimated while the ocean surface zonal current and vertical velocity at the base of the mixed layer are underestimated. Due to model biases in representing the related physics, the effects of surface forcing on the simulated MLS budget are overestimated and those of subsurface and surface advection are relatively weak. Due to weaker surface advection and subsurface forcing than observed, the simulated compensations for surface forcing are suppressed, and the simulated MLS tendency that leads Nin?o3.4 by 8–10 months, which is shorter than the observed lead time. These results are useful for the interpretation of observational analyses and other model simulations in the tropical Pacific.Salinity variability and its causes in the tropical Pacific are analyzed using observations, reanalysis products and model simulations. The mixed-layer salinity(MLS) budget analyses from observations and reanalysis products indicate that its interannual evolution is closely related to ENSO and is predominantly governed by surface forcing and surface advection in the western-central equatorial Pacific. It is found that the observed MLS tendency leads Nin?o3.4 by about 12 months due to the effect of negative freshwater flux(evaporation minus precipitation). These observation-based analyses are used to evaluate the corresponding simulation using GFDL-ESM2 M. It is evident that the model can simulate the spatiotemporal variations of MLS with some discrepancies compared to observations. In the warm pool of the equatorial Pacific the MLS tendency in the model is sensitive to ocean dynamics, however model biases cause the tendency to be underestimated. In particular, the freshwater flux is overestimated while the ocean surface zonal current and vertical velocity at the base of the mixed layer are underestimated. Due to model biases in representing the related physics, the effects of surface forcing on the simulated MLS budget are overestimated and those of subsurface and surface advection are relatively weak. Due to weaker surface advection and subsurface forcing than observed, the simulated compensations for surface forcing are suppressed, and the simulated MLS tendency that leads Nin?o3.4 by 8–10 months, which is shorter than the observed lead time. These results are useful for the interpretation of observational analyses and other model simulations in the tropical Pacific.

关 键 词：MIXED-LAYER SALINITY salt BUDGET INTERANNUAL VARIABILITY tropical Pacific model simulation 

分 类 号：P714.1[天文地球—海洋科学] P731.12