Comparisons of the Multiple East Asian Winter Monsoon Indices and Their Relations to Climate over Eastern China

Abstract

The East Asian winter monsoon(EAWM) is one of the most active systems in northern hemisphere during boreal winter. The EAWMexerts an essential influence on controlling winter climate over most of China, and its interannual and interdecadal variabilities are of significantimportance in predicting and inspecting winter climate over China. Based on the NCEP/NCAR reanalysis date and the 160-station observationaldata, a comparison for 12 EAWM indices and their relations to winter temperature and precipitation over eastern China have been performedin this paper. Furthermore, the stability of the relations between EAWM indices and temperature and precipitation in Ei Nino status or La Ninastatus has also been detected. The results indicate that most of the EAWM indices share the same variations year-to year, but there are somedifferences between them at the same time, which suggest that the focuses of each index in capturing the integrity or partial features are different.It was found that the intensity of the EAWM system reduced obviously during the last 60 years, especially in the latest 30 years with a trend of-0.25σ/10a averaging from the 10 EAWM indices. All of the 12 EAWM indices showed intense interannual variabilities and interdecadal variationsduring the last six decades. Although the exact periods of each index are not unified, the dominant interannual periods of ~2 to ~4a and ~8 to~9a, and the dominant interdecadal periods of ~13.3a and ~20a of the EAWM indices can be identified from a power spectrum analysis. Thereare ten(eight) EAWM indices correlated significantly (0.1%) with the first mode time series(PC1) of winter temperature(precipitation) over easternChina. Among them, the Siberian High index can explain 53.3% variance in winter temperature PC1, and the East Asian meridional windindex derived from the middle-high troposphere can explain 50.4% variance in winter precipitation PC1. The relationships between each EAWMindex and winter temperature and precipitation over eastern China during Ei Nino status and La Nina status are not consistent completely. So,the different reference significances of each EAWM index in Ei Nino status or La Nina status should be considered carefully when used in winterclimate monitoring.