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Southern Hemisphere extra-tropical forcing: a new paradigm for ENSO. Pascal Terray , 2010. R98229029 陳漢卿. Numerous studies have documented the significant influence of ENSO on climate variability in the Southern hemisphere. - PowerPoint PPT Presentation
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Southern Hemisphere extra-tropical forcing: a new paradigm for ENSO
Pascal Terray, 2010
R98229029 陳漢卿
• Numerous studies have documented the significant influence of ENSO on climate variability in the Southern hemisphere. (Karoly 1989; Kidson and Renwick 2002; Trenberth et al. 2002; Carleton 2003)
• Some indicate that ENSO are influenced by Antarctic Circumpolar Wave(ACW) or the Southern Annular Mode (SAM). (Van Loon and Shea 1987; Peterson and White 1998; White et al. 2002; White and Annis 2004)
The associated EOF modes can be regarded as the regional expression of a global-scale Southern Hemisphere mode of variability.
Southern Hemisphere Subtropical air-sea feedbacks
SSTa propagate to tropics
Weakening of ITCZ forces Cold Kelvin wave response in upper troposphere
Western wind & convective anomalies over the western Pacific
ENSO onset
Indian Ocean Atlantic Ocean
Surface latent heat, Cloudiness, wind-induced mixing
Southern Hemisphere Subtropical air-sea feedbacks
SSTa propagate to tropics
Weakening of ITCZ forces Cold Kelvin wave response in upper troposphere
Western wind & convective anomalies over the western Pacific
ENSO onset
Kelvin wave
Southern Hemisphere Subtropical air-sea feedbacks
SSTa propagate to tropics
Weakening of ITCZ forces Cold Kelvin wave response in upper troposphere
Western wind & convective anomalies over the western Pacific
ENSO onset
Sets the stage for deep convection by destabilizing the vertical structure of the atmosphere (e.g. due to the increased vertical temperature gradient) Decreasing the value of surface boundary layer moisture required for the convection to occur over the western equatorial Pacific
Westerly wind
Downwelling Kelvin waves
along the thermocline
Warming in eastern &
central Pacific
Bjerkness feedback
Southern Hemisphere Subtropical air-sea feedbacks
SSTa propagate to tropics
Weakening of ITCZ forces Cold Kelvin wave response in upper troposphere
Western wind & convective anomalies over the western Pacific
ENSO onset