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Seasonal and regional signatures of ENSO in upper tropospheric jet characteristics from reanalyses
  • Gloria L Manney,
  • Michaela I Hegglin,
  • Zachary D Lawrence
Gloria L Manney
NorthWest Research Associates

Corresponding Author:[email protected]

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Michaela I Hegglin
University of Reading, UK
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Zachary D Lawrence
Cooperative Institute for Research in Environmental Sciences (CIRES)
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Regionally and seasonally resolved relationships of upper tropospheric jet variability to El Niño / Southern Oscillation (ENSO) in multiple reanalyses are presented, with subtropical and polar jets analyzed separately. Previously reported results confirmed herein include strengthening of tropical jets associated with monsoons and Walker circulation during La Niña and a statistically significant subtropical jet latitude decrease (increase) during El Niño (La Niña) in the zonal mean view in both hemispheres. However, subtropical jet latitudes increase significantly during El Niño over the NH eastern Pacific in DJF, and in different limited SH regions in MAM and SON. Subtropical jet altitudes increase significantly during El Niño in the zonal mean in all seasons (DJF / MAM) in the NH (SH). Subtropical jet windspeed correlations with ENSO vary, showing increasing windspeed during El Niño in both hemispheres in DJF and MAM. Polar jet correlations with ENSO are typically not significant in the zonal mean, but there are a few regions/seasons with significant correlations with ENSO, particularly in the SH, where polar jet latitudes decrease over Asia and the western Pacific in DJF, and increase over the eastern Pacific in JJA and SON, during El Niño. Typically, significantly weaker (stronger) polar jet windspeeds are associated with El Niño (La Niña) in the western than in the eastern hemisphere in both NH and SH. All reanalyses analyzed agree well. This work highlights the importance of regional and seasonal variations in the upper tropospheric jet response to ENSO and provides new information for model evaluation.