Abstract:

Using monthly average temperature data at 26 stations in Northeast China in 1961-2010 and the NCEP/NCAR monthly reanalysis data, the interdecadal characteristics of summer temperature anomaly over Northeast China is investigated. It is found that there are 4 different patterns of summer temperature anomaly over Northeast China by applying empirical orthogonal functions (EOFs) analysis to monthly mean summer temperature anomalies. The EOF1 presents a pattern with changes in the same direction, holding about 72% of the total variance contribution, and its time factors show multiple interdecadal variation. Three other patterns hold 10%, 4% and 3% of the total variance contribution respectively, showing north-south, east-west and mountain-plain anomaly patterns with changes in different direction, and the influence of ocean, terrain, and the difference of latitude. Multiple interdecadal variation of mode EOF1 has mutation properties further analyzed by mutation and wavelet analysis, and influenced by a period of 20 a, the time factors mainly were minus during 2007 to 2010, which should be paid more attention. Mode EOF1 is significant positive correlation with geopotential height in 500 hPa and U-wind in upper troposphere (Westerly Jet) of 30ºN-40ºN, presenting a global belt distribution. In northeast Asia, the positive correlation zone reaches 60ºN, and geopotential height in 500 hPa changes in nearly the same direction with the multiple interdecadal variation of mode EOF1. Mode EOF1 is significant positive correlation with sea surface temperature (SST) in Asian coast of Pacific, the Western Pacific Warm Pool (including the north-central areas of Indian Ocean), the south Pacific surrounding Australia, the North America coast of the Atlantic, the northern area of the North Atlantic drift, and the northern area of the equator in the Atlantic. It is also significant positive correlation with Pacific Decadal Oscilliation (PDO). Mode EOF1 is closely related with the multiple interdecadal variation of sea-air system in the Northern Hemisphere, and at the same it is influenced by global warming.

Key words: summer temperature over Northeast China, temperature anomaly pattern, sea-air system, interdecadal