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LIU Ge, JI Liren, SUN Shuqing, XIN Yufei. 2013: A Discussion on the East Asian Winter Monsoon Index—Differences between the East Asian Winter Monsoon at Mid-high and Low Latitudes. Chinese Journal of Atmospheric Sciences, 37(3): 755-764. DOI: 10.3878/j.issn.1006-9895.2012.12054
Citation: LIU Ge, JI Liren, SUN Shuqing, XIN Yufei. 2013: A Discussion on the East Asian Winter Monsoon Index—Differences between the East Asian Winter Monsoon at Mid-high and Low Latitudes. Chinese Journal of Atmospheric Sciences, 37(3): 755-764. DOI: 10.3878/j.issn.1006-9895.2012.12054

A Discussion on the East Asian Winter Monsoon Index—Differences between the East Asian Winter Monsoon at Mid-high and Low Latitudes

  • The National Centers for Environmental Prediction (NCEP) reanalysis data and the National Oceanic and Atmospheric Administration (NOAA) Extended Reconstructed Sea Surface Temperatures (SSTs) are used in this study to investigate characteristics of the East Asian winter monsoon (EAWM) at various latitude zones. On the basis of two indices describing the strengths of the low-latitudinal EAWM (EAWM-L) and mid latitudinal EAWM (EAWM-M), their variation characteristics, associated atmospheric circulation, and related SST patterns are examined. The results indicate that although both the EAWM-M and EWAM-L indices can reflect the intensity of the EAWM, the atmospheric circulation associated with the two indices is clearly distinct. In the lower troposphere, the EAWM-L is closely related to anomalous circulation around the South China Sea and the Philippines, while the EAWM-M presents a closer relationship with the circulation adjacent to Lake Baikal, known as the Baikal blocking high. In the middle troposphere, the close relationship of EAWM-M and the Baikal blocking high remains persistent, while the EAWM-L has a relatively closer linkage with a major Asian trough. In the upper troposphere, variation in the intensity of a subtropical westerly jet may modulate secondary circulation and is eventually linked with the EAWM-L index, while the variation of EAWM-M is mainly related to a shift of the north boundary of the westerly jet. In addition, the EAWM-L is significantly correlated with SSTs in the central and eastern equatorial Pacific and that in the tropical Indian Ocean, while the EAWM-M has a closer relationship with the latter than with the former. The close relationships of the EAWM-L with the central and eastern equatorial Pacific and with the tropical Indian Ocean are clearly revealed on interannual and interdecadal scales; however, the significant linkage of the EAWM-M with the tropical Indian Ocean exists mainly on the interdecadal scale.
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