May 29, 2017

Large anomalies in lower stratospheric water vapour and ice during the 2015-2016 El Niño

by
Melody A. Avery, Sean M. Davis, Karen H. Rosenlof, Hao Ye, Andrew E. Dessler
,
Nature Geoscience
  • States that the coldest tropical tropopause temperature regulates the amount of water vapour entering the stratosphere by controlling the amount of dehydration in the rising air
  • Shows that tropical convective cloud ice and associated cirrus sublimating at unusually high altitudes might also have a role in stratospheric hydration
  • Notes that the 2015–2016 El Niño produced decadal record water vapour amounts in the tropical Western Pacific, coincident with warm tropopause temperature anomalies
  • States that in the Central Pacific, convective cloud ice was observed 2 km above the anomalously cold tropopause
  • Finds that trajectory-based dehydration model based on two reanalysis temperature and wind fields can account for only about 0.5–0.6 ppmv of the ~0.9 ppmv tropical lower stratospheric moistening observed during this event
  • Finding suggests that unresolved convective dynamics and/or associated sublimation of lofted ice particles also contributed to lower stratospheric moistening
  • Observations suggest that convective moistening could contribute to future climate change-induced stratospheric water vapour increases