Comparing Study For Main Mode Of Local Ocean-atmosphere Interaction In North Pacific

Ocean-atmosphere interaction in North Pacific plays an important role in global climate change and is an important factor to influence. climate in China. In order to reveal the physical essence of local SST anomaly in winter and spring affecting atmospheric circulation in this area, based on output of mixed layer model CCM_ML and that of Picntrl scenarios of IPCC model (BCM2.0, CSIRO_MK3.5), by using different types of statistical methods (e.g., SVD, MCA, regression, correlation, composite analysis, etc), both model data and observation data are analyzed to confirm some previous results of ocean-atmosphere interaction in North Pacific, and obtain the innovative achievements by the following:1. By analyzing and comparing outputs of Picntrl scenarios of coupled model BCM2.0 and CSIRO_MK3.5 and mixed layer model CCM_ML, it is found that the main modes of local ocean-atmosphere interaction in North Pacific in these models are analogous, no matter whether ocean dynamics processes is included. The process of atmosphere impacting ocean corresponding this mode shows a "horse shoe" pattern of sea surface temperature (SST) anomaly that forced by anti-cyclonic wind anomaly, which leads ocean by one month in winter. Oceanic feedbacks on atmosphere show as "horse shoe" SSTA of warm centre can not only lead to intensification of anti-cyclonic circulation, but also last 4-7 months and affect the atmospheric circulation in summer or autumn. The possible response of atmospheric circulation in summer to "horse shoe" SSTA of warm centre in winter is cyclonic circulation, and the maximum wind speed appears above (BCM2.0, CSIRO_MK3.5) or south of (CCM_ML) the warm centre. The main features of the main mode obtained in all the above models are roughly same as that of observations.2. There are some differences among the three models:the difference of the locations of "horse shoe" SSTA, "horse shoe" SSTA of warn centre is located in the central and western North Pacific in BCM2.0 and CCM ML mode, while in the east in CSIRO_MK3.5; the difference of the time of SSTA affecting the later atmosphere, SSTA in late spring affects atmosphere in early autumn most significantly in BCM2.0; SSTA in late.winter affects atmosphere in autumn most, significantly in CSIRO_MK3.5; while SSTA in spring affects atmosphere in early summer most significantly in CCM_ML. The simulation of CCM_ML is closest to that of observations among the three models.3. According to the analysis of outputs from the coupled model CCM_ML which doesn't include the ocean advection anomaly, wind-evaporation-SST (WES) mechanism plays an important role in the formation and persistence of "horse shoe" SSTA in North Pacific in wintertime:Aleutian low weakening would cause the decrease of sea surface wind (Easterly Anomaly) the central and western North Pacific in winter, the surface heat loss would decrease and SST anomaly is positive; at the same time, westerly on the north of Westerly increases, and the northeast trade wind above the eastern and southern parts of North Pacific increases, leading to the surface heat loss increasing and negative SST anomaly; the "horse shoe" SST anomaly and Aleutian low anomaly have positive feedback through WES mechanism, which is favorable for "horse shoe" SST anomaly; from spring to summer, the warm center of "horse shoe" SST anomaly corresponds to cyclonic circulation anomaly in middle latitude of North Pacific. WES mechanism makes contribution to the persistence of "horse shoe" SST anomaly at the southwestern part of SST positive anomaly area and most negative SST anomaly area, which is less than the contribution of WES mechanism in wintertime. Similar analysis based on observations also confirms the importance of WES mechanism in the persistence of "horse shoe" SST anomaly.The study in this paper confirms the existence of main mode of ocean-atmosphere interaction in North Pacific that is revealed in previous study, estimates the WES mechanism in the formation of the main mode and SST anomalies that persistent from winter and spring to summer and autumn, and provides important theoretical basis for forecasting atmospheric circulation in summer and autumn by using of winter and spring SST anomaly.