Abstract:

 Based on the monthly mean temperature data from 53 observational stations in Liaoning province during 1961 to 2012 and the NCEP/NCAR reanalysis data such as the monthly mean height field, wind field and sea surface pressure, the spatial and temporal features of the winter air temperature were analyzed. The previous definitions of six East Asian winter monsoon indexes were reviewed and calculated, and the relationships of winter air temperature in Liaoning province with the six indexes were compared. The results show that the mean variance of winter air temperature is greater in the eastern region than in the western region during 1961 to 2011, and it is in a significant positive trend in most regions of Liaoning province. The first pattern of EOF shows that winter air temperature in Liaoning province is abnormal high or low. The time coefficient is in a significant increasing trend and the abrupt change occurs in 1977. There are cycles of 4.5 years, 2.0 years and 3.0 years cycles for winter air temperature in Liaoning province. The East monsoon index  defined by Zhu has the best relationship with winter air temperature in Liaoning province regardless of the abrupt change time, periodic characteristics, correlation coefficients and inverting corresponding relations. The relationship can be clearly explained in 850 hPa meridional wind field and sea surface pressure field.

Key words: East Asian winter monsoon index, EOF (empirical orthogonal function), Maximum entropy spectrum analysis