Decadal Variation Of The Relationship Between Autumn SST And The East Asian Winter Monsoon And The Simulation Of Teleconnection In CMIP5

Using observed datasets to document the decadal variation of the relationship between the sea surface temperature anomaly (SSTA) in different sea area and East Asian Winter Monsoon (EAWM) as well as the forces of their decadal abrupt change. Moreover, we alse applied the Phase 5 of the Coupled Model Intercomparison Project (CMIP5) simulation data to evaluate and estimate the modeling capability of teleconnection patterns which have a significant effect on East Asian winter climate. The main conclusions were as following:1. The relationship between early autumn Indian Ocean (IO) SSTA and EAWM show instable interdecadal variation, which can be divided into three preiods: significant out-phase relationship during 1948-1960 and 1999-2012, but insignificant out-of-phase relationship during 1962-1988. During 1948-1960 and 1999-2012, the 500hPa height anomaly is a north-south dipole distribution in the Asian region and East Asian trough area is significantly positive anomaly. Winter geopotential height at 200 hPa shows a "+,-,+,-" wave-like distribution from IO to the north of Asia. Significant southerly wind anomalies prevail over coastal East Asian, resulting in a weakening of the East Asian Winter Monsoon. However, for the 1962-1988, there is no significant relationship between IO SSTA and the atmospheric circulation in East Asia in late winter, leading to a weakening relationship between SSTA and EAWM. Also, the relationship between surface temperature in East Asia and IO SSTA showed significant interdecadal variation. One possible mechanism for the interdecadal change is that the response of winter precipitation in Indo-Pacific region to early autumn IO SSTA is a diople pattern which can motivate a meridional Rossby wave through heat source anomaly during 1948-1960 and 1999-2012, but there is no robust connection between IO SSTA and Indo-Pacific dipole-like precipitation pattern during 1962-1988, especially for west Pacific rainfall.2. The connection between autumn Gulf Stream (GS) SSTA and EAWM is significant in-phase during 1948-1976 (PI), whereas out-of-phase during 1980-2012 (P2). Meanwhile, the circulation anomalies related to GS SSTA show obvious differences. During PI, when the SSTA is significant positive in autumn, the anomalies of winter geopotential height at 500 hPa is significant positive over east of Urals and negative over East Asian, which lead to East Asian trough deepened. Thus, significant northerly wind anomalies occur over coastal East Asian. But for the P2, the anomalies of 500 hPa geopotential height over East Asian trough region are insignificant positive. Therefore, East Asian prevail insignificant southerly wind anomalies. Further study suggests that during PI, the positive of the GS SSTA in autumn easily triggered ’+,-,+,-’ anomalous wave-train structure from Northeast Atlantic to East Asian and the in-phase superimposition of the anomalous wave-train and Eurasian (EU) teleconnection pattern, resulting in a strong EAWM. However, during P2, insignificant negative EU-like pattern arise when the SSTA is positive high in autumn while the centres of action related GS SSTA have some location deviations comparing with traditional EU pattern. Therefore, opposite to P1, the connection between the GS SSTA and EAWM is insignificant and no robust during P2.3. Most of models in CMIP5 have good ability in simulating the spatial pattern of EU and Western Pacific (WP), but there still exist position deviations. All of the models’simulation capability is very poor in terms of time variability. Some of these models could reproduce the negative correlativity between EU and East Asian and North Pacific surface air temperature, but a poor skill in simulating the relationship between EU and precipitation in North China and Huang Huai Valley. Meanwhile, all of models underestimated the relationship between EU and temperature and precipitation in East Asia. Each mode has a high profile modeling capabilities in relationship between WP and temperature in East Asia-Western Pacific region. The positive correlation between WP and precipitation in the Northeast Asia and Okhotsk Sea can be well reproduced, but for China’s mainland to the western Pacific, the negative correlation simulation capability is weak. It is found that all models for the relationship between WP and temperature are better than WP and precipitation. In terms of simulation ability score, GISS-E2-R on the EU is strongest and NorESMl-M on WP is best. However, HadCM3 has worst model skill scores. Under the RCP4.5 scenario, EU and WP in the future tend to be slightly negative phase of development. The area of exceeding confidence level in the correlation between EU and temperature and precipitation northward in GISS-E2-R, while the one between WP and temperature westward and precipitation became stronger in NorESM1-M, respectively.