The Influence And The Interdecadal Change Of The Tropical Indian-Pacific Sea Surface Temperature On The Climate Over China

In this study, the coupling between the tropical Pacific-Indian Ocean sea surface temperature (SST) and the atmospheric circulation in Northern Hemisphere (NH) is investigated using a series of dataset, including HadISST Monthly mean SST data, NCEP/NCAR monthly average global atmospheric reanalysis data and surface air temperature data(SAT) of160meteorological stations in China during the period from1951to2010and the output of coupled ocean-atmosphere numerical models during the period from1960to2006. The influence of the large scale atmospheric modes to the climate variability in China is examined as well as its interdecadal change.The main results are summarized as follows.1)During the period from1951to2010, the atmospheric component of the SVD1is characterized by dominate positive anomalies in NH. The SST component of the SVD1shows a narrow band of negative SST anomalies along the eastern equatorial Pacific. The spatial distribution of the atmospheric component of the SVD2bears many similarities to the Pacific North American mode (PNA) while its SST component reflects an El Nino signal in the ocean. The relationship between the SVD1and the SAT in China in summer are mainly positive temperature anomalies whereas relationship between the SVD2and the SAT are mainly negative temperature anomalies. When the SVD1is in its positive phase, the low pressure system over Eurasia is weaker-than-normal and the SAT over China is mainly influenced by the northern thermal advection along the east coast of China. In the mid-troposphere, the Baikal Trough becomes weaker than normal and associated with positive temperature anomalies in a large area of China. Corresponding to a positive SVD2both the Eurasia low pressure and the Subtropical high pressure systems become weaker-than-normal. The pressure gradient between the two systems becomes weak and the associated southerly from the Indian Ocean, the South China Sea and the Pacific becomes weaker-than-normal while the trough around the Baikal in the mid-troposphere is deeper-than-normal together with a stronger-than-normal upper-level jet which make the SAT in China abnormally cold. 2) The characteristic of the atmospheric component of the SVD1is a PNA-like pattern during the two subperiods of1951-1980and1981-2010. However, the wave train signal over the North Pacific-North America sector becomes weaker after1980. The spatial distribution of the SST component reflects an El Nino signal in the two subperiods. However the SST anomalies in the eastern equatorial Pacific SST are weakened after1980. There is obvious interdecadal change of the relationship between the SVD1and the SAT in China. After1980the relationship between the SVD1and the SAT turn from a mainly positive temperature anomalies to a mainly negative temperature anomalies. When SVD1is in its positive phase, the subtropical western Pacific high becomes much weaker after1980comparing to its counterpart in the period before1980. The low pressure system over Eurasia and the subtropical Pacific high become weaker at the same time causing the pressure gradient between them become weaker-than-normal. The Eastern coastal areas of is influenced by the anomalies northerly. The deepened trough near Baikal lake in the atmospheric component favors the southward penetration of the cold air from high-latitude. The temperature of most part of China is colder than normal. Compared to the period from1951to1980, the potential predicted period for the SVD2become shorter by around one month after1980.3) The spatial distributions of the SVD2before and after1980are different. During the period from1951to1980, the atmospheric component of the SVD2looks more like a AO distribution than its counterpart after1980. The negative SST anomalies over the tropical Pacific are expended and enhanced after1980. The correlation between the SVD2and the SAT in China turns from positive to negative.4) The winter SAT over China is significantly correlated to the Pacific SST related SVD2, which is to a large extent the display of the long-term climate trends in the atmosphere and in the SST fields for both the observations and MME forecasts. Corresponding to a positive SVD2, the SAT in China in winter time is warmer than normal.