Imperial College London

Professor Joanna D. Haigh

Faculty of Natural SciencesThe Grantham Institute for Climate Change

Co-Director,Grantham Institute forClimate Change&Environment
 
 
 
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Contact

 

+44 (0)20 7594 5798j.haigh Website

 
 
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Location

 

Electrical EngineeringSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Haigh:2006,
author = {Haigh, JD and Blackburn, M},
journal = {SPACE SCI REV},
pages = {331--344},
title = {Solar influences on dynamical coupling between the stratosphere and troposphere},
volume = {125},
year = {2006}
}

RIS format (EndNote, RefMan)

TY  - JOUR
AB - We use a simplified atmospheric general circulation model (AGCM) to investigate the response of the lower atmosphere to thermal perturbations in the lower stratosphere. The results show that generic heating of the lower stratosphere tends to weaken the sub-tropical jets and the tropospheric mean meridional circulations. The positions of the jets, and the extent of the Hadley cells, respond to the distribution of the stratospheric heating, with low latitude heating displacing them poleward, and uniform heating displacing them equatorward. The patterns of response to the low latitude heating are similar to those found to be associated with solar variability in previous observational data analysis, and to the effects of varying solar UV radiation in sophisticated AGCMs. In order to investigate the chain of causality involved in converting the stratospheric thermal forcing to a tropospheric climate signal we conduct an experiment which uses an ensemble of model spin-ups to analyse the time development of the response to an applied stratospheric perturbation. We find that the initial effect of the change in static stability at the tropopause is to reduce the eddy momentum flux convergence in this region. This is followed by a vertical transfer of the momentum forcing anomaly by an anomalous mean circulation to the surface, where it is partly balanced by surface stress anomalies. The unbalanced part drives the evolution of the vertically integrated zonal flow. We conclude that solar heating of the stratosphere may produce changes in the circulation of the troposphere even without any direct forcing below the tropopause. We suggest that the impact of the stratospheric changes on wave propagation is key to the mechanisms involved.
AU - Haigh,JD
AU - Blackburn,M
EP - 344
PY - 2006///
SP - 331
TI - Solar influences on dynamical coupling between the stratosphere and troposphere
T2 - SPACE SCI REV
VL - 125
ER -