The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor

Using water vapor data from HALOE and SAGE II, an anti-correlation between planetary wave driving (here expressed by the mid-latitude eddy heat flux at 50 hPa added from both hemispheres) and tropical lower stratospheric (TLS) water vapor has been obtained. This appears to be a manifestation of...

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Main Authors: S. Dhomse, M. Weber, J. Burrows
Format: Article
Language:English
Published: Copernicus Publications 2008-02-01
Series:Atmospheric Chemistry and Physics
Online Access:http://www.atmos-chem-phys.net/8/471/2008/acp-8-471-2008.pdf
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spelling doaj-3239cc8bc93146919ace8286614a66472020-11-24T22:39:12ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242008-02-0183471480The relationship between tropospheric wave forcing and tropical lower stratospheric water vaporS. DhomseM. WeberJ. BurrowsUsing water vapor data from HALOE and SAGE II, an anti-correlation between planetary wave driving (here expressed by the mid-latitude eddy heat flux at 50 hPa added from both hemispheres) and tropical lower stratospheric (TLS) water vapor has been obtained. This appears to be a manifestation of the inter-annual variability of the Brewer-Dobson (BD) circulation strength (the driving of which is generally measured in terms of the mid-latitude eddy heat flux), and hence amount of water vapor entering the stratosphere. Some years such as 1991 and 1997 show, however, a clear departure from the anti-correlation which suggests that the water vapor changes in TLS can not be attributed solely to changes in extratropical planetary wave activity (and its effect on the BD circulation). After 2000 a sudden decrease in lower stratospheric water vapor has been reported in earlier studies based upon satellite data from HALOE, SAGE II and POAM III indicating that the lower stratosphere has become drier since then. This is consistent with a sudden rise in the combined mid-latitude eddy heat flux with nearly equal contribution from both hemispheres as shown here and with the increase in tropical upwelling and decrease in cold point temperatures found by Randel et al. (2006). The low water vapor and enhanced planetary wave activity (in turn strength of the BD circulation) has persisted until the end of the satellite data records. From a multi-variate regression analysis applied to 27 years of NCEP and HadAT2 (radiosonde) temperatures (up to 2005) with contributions from solar cycle, stratospheric aerosols and QBO removed, the enhancement wave driving after 2000 is estimated to contribute up to 0.7 K cooling to the overall TLS temperature change during the period 2001–2005 when compared to the period 1996–2000. NCEP cold point temperature show an average decrease of nearly 0.4 K from changes in the wave driving, which is consistent with observed mean TLS water vapor changes of about −0.2 ppm after 2000. http://www.atmos-chem-phys.net/8/471/2008/acp-8-471-2008.pdf
collection DOAJ
language English
format Article
sources DOAJ
author S. Dhomse
M. Weber
J. Burrows
spellingShingle S. Dhomse
M. Weber
J. Burrows
The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor
Atmospheric Chemistry and Physics
author_facet S. Dhomse
M. Weber
J. Burrows
author_sort S. Dhomse
title The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor
title_short The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor
title_full The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor
title_fullStr The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor
title_full_unstemmed The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor
title_sort relationship between tropospheric wave forcing and tropical lower stratospheric water vapor
publisher Copernicus Publications
series Atmospheric Chemistry and Physics
issn 1680-7316
1680-7324
publishDate 2008-02-01
description Using water vapor data from HALOE and SAGE II, an anti-correlation between planetary wave driving (here expressed by the mid-latitude eddy heat flux at 50 hPa added from both hemispheres) and tropical lower stratospheric (TLS) water vapor has been obtained. This appears to be a manifestation of the inter-annual variability of the Brewer-Dobson (BD) circulation strength (the driving of which is generally measured in terms of the mid-latitude eddy heat flux), and hence amount of water vapor entering the stratosphere. Some years such as 1991 and 1997 show, however, a clear departure from the anti-correlation which suggests that the water vapor changes in TLS can not be attributed solely to changes in extratropical planetary wave activity (and its effect on the BD circulation). After 2000 a sudden decrease in lower stratospheric water vapor has been reported in earlier studies based upon satellite data from HALOE, SAGE II and POAM III indicating that the lower stratosphere has become drier since then. This is consistent with a sudden rise in the combined mid-latitude eddy heat flux with nearly equal contribution from both hemispheres as shown here and with the increase in tropical upwelling and decrease in cold point temperatures found by Randel et al. (2006). The low water vapor and enhanced planetary wave activity (in turn strength of the BD circulation) has persisted until the end of the satellite data records. From a multi-variate regression analysis applied to 27 years of NCEP and HadAT2 (radiosonde) temperatures (up to 2005) with contributions from solar cycle, stratospheric aerosols and QBO removed, the enhancement wave driving after 2000 is estimated to contribute up to 0.7 K cooling to the overall TLS temperature change during the period 2001–2005 when compared to the period 1996–2000. NCEP cold point temperature show an average decrease of nearly 0.4 K from changes in the wave driving, which is consistent with observed mean TLS water vapor changes of about −0.2 ppm after 2000.
url http://www.atmos-chem-phys.net/8/471/2008/acp-8-471-2008.pdf
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