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Extra-tropical Strat-Trop Exchange
Contact: Gloria Manney


Summary

Understanding dynamical, transport and chemical processes in the extra-tropical (ET) upper troposphere and lower stratosphere (UTLS) is critical to advancing climate change and pollution transport studies. For example, water vapor and ozone are both key greenhouse gases in the UTLS, and their distributions are strongly affected by stratosphere-troposphere exchange processes. In the lowermost stratosphere (the portion of the extratropics where some part of the lower latitude region is in the troposphere), there is a complex interplay of stratospheric (e.g., chemical ozone loss) and tropospheric (e.g., pollution generation and transport, fire-related convection) processes, and intrusions of stratospheric air into the troposphere and vice versa are common.

The coupled chemistry and climate of the UTLS respond to both tropospheric climate change [e.g. Santer et al., 2004; WMO, 2007] and to O3 depletion in the lower stratosphere (link to polar processes section) [e.g., Seidel and Randel, 2006]; the complexity of causes of tropopause-level changes makes our ability to accurately detail UTLS variability especially critical. Both radiative forcing and surface temperature are most sensitive to O3 changes near the tropopause [e.g., Forster and Shine, 1999]. Radiative effects of water vapor near the ET tropopause have been shown to be instrumental in determining the thermal structure in the UTLS [e.g., Randel 2007]. Upper tropospheric winds (the jet streams whose tops extend into the lowermost stratosphere) and tropopause characteristics have been shown to be sensitive to climate change [e.g., Lorenz and DeWeaver, 2007; Archer and Caldeira, 2008]. The Antarctic O3 hole has caused significant temperature changes in the lower stratosphere; a significant part of the ozone depletion occurs in the sub-vortex (the lowest part of the polar vortex that extends into the lowermost stratosphere), where it can be more efficiently transported to midlatitudes and possibly into the troposphere. Changes in the Brewer-Dobson Circulation (the large-scale seasonally varying circulation of the stratosphere), synoptic eddies (storms) in the upper troposphere, and midlatitude convection are expected to alter the extent and consequences of ET stratosphere-troposphere exchange. Pollution products transported from the troposphere up into the lower stratosphere influence ozone chemistry there [e.g. Hegglin et al., 2006; WMO, 2007]; conversely, stratospheric O3 transported down also influences tropospheric chemistry [e.g., WMO, 2007; Hsu and Prather, 2009].

Until recent years, most satellite measurements did not extend down into the ET UTLS, and studies of the ET UTLS were primarily limited to analysis of sporadic and sparse (albeit very high spatial and temporal resolution) aircraft data. With the launch of the Aura satellite, MLS provides measurements of O3, HNO3, CO and H2O, as well as temperature, covering the lowermost stratosphere with global daily coverage; other measurements (e.g., HCl and ClO) extend into the upper part of this region. Meteorological analyses from advanced data assimilation systems (DAS) provide comprehensive information on the jet streams (the winds that control transport and mixing of trace gases), tropopause variations, and temperature structure in the UTLS, that is, the dynamical factors that control trace gas transport and influence chemical processes. Studies using MLS data, in conjunction with DAS analyses and high resolution but sparse aircraft data, can contribute to advancing our understanding of the ET UTLS and its role in climate change processes.

MLS-related publications related to extra-tropical stratosphere-troposphere exchange

2011

  1. Gettelman, A., "The Extratropical Upper Troposphere and Lower Stratosphere", num 49, 2011. Reprint Preprint
  2. Pumphrey, H.C., "Microwave Limb Sounder observations of biomass-burning products from the Australian bush fires of February 2009", vol doi:10.5194/acp-11-6285-2011, num 11, pgs. 2, 2011. Reprint Preprint
  3. Santee, M.L., "Trace gas evolution in the lowermost stratosphere from Aura Microwave Limb Sounder measurements", vol 10.1029/2011JD015590, num 116, 2011. Preprint
  4. Tian, W., "A study of upper troposphere and lower stratosphere water vapor above the Tibetan Plateau using AIRS and MLS data", vol doi:10.1002/asl.319, num 12, pgs. 2, 2011. Preprint

2010

  1. Hegglin, M.I., "Multimodel assessment of the upper troposphere and lower stratosphere: Extratropics", vol doi:10.1029/2010JD013884, num 115, 2010. Reprint Preprint

2009

  1. Manney, G.L., "Satellite Observations and Modelling of Transport in the Upper Troposphere through the Lower Mesosphere During the 2006 Major Stratospheric Sudden Warming", num 9, 2009. Reprint Preprint

2008

  1. Froidevaux, L., "Validation of Aura Microwave Limb Sounder stratospheric ozone measurements", vol doi:10.1029/2007JD008771, num 113, 2008. Reprint Preprint
  2. Hegglin, M.I., "Validation of ACE-FTS satellite date in the upper troposphere/lower stratosphere (UTLS) using non-coincident measurements", num 8, 2008. Reprint Preprint
  3. Livesey, N.J., "Validation of Aura Microwave Limb Sounder O3 and CO observations in the upper troposphere and lower stratosphere", vol doi:10.1029/2007JD008805, num 113, 2008. Reprint Preprint

2007

  1. Jiang, Y.B., "Validation of the Aura Microwave Limb Sounder Ozone by Ozonesonde and Lidar Measurements", vol doi:10.1029/2007JD008776, num 112, 2007. Reprint Preprint
  2. Lambert, A., "Validation of the Aura Microwave Limb Sounder middle atmosphere water vapor and nitrous oxide measurements", vol doi:10.1029/2007JD008724, num 112, 2007. Preprint
  3. Read, W.G., "Aura Microwave Limb Sounder upper tropospheric and lower stratospheric H2O and relative humidity with respect to ice validation", vol doi:10.1029/2007JD008752, num 112, 2007. Reprint Preprint Abstract
  4. Ricaud, P., "Impact of land convection on troposphere-stratosphere exchange in the tropics", num 7, 2007. Preprint
  5. Santee, M.L., "Validation of Aura Microwave Limb Sounder HNO3 Measurements", vol doi:10.1029/2007JD008721, num 112, 2007. Reprint Preprint

2006

  1. Folkins, I., "Testing convective parameterizations with tropical measurements of HNO3, CO, H2O, and O3: Implications fotr the water vapor budget", vol doi:10.1029/2006JD007325, num 111, 2006. Reprint Preprint

2002

  1. Kley, D., "SPARC assessment of upper tropospheric and stratospheric water vapour", num 2, pgs. WMO/ICSU/IOC, 2002.
  2. Offerman, D., "Water vapor at the tropopause during the CRISTA 2 mission", vol doi:10.1029/2001JD000700, num 107, pgs. D23, 2002. Preprint
  3. Sassi, F., "Influence of the Madden-Julian Oscillation on upper tropospheric humidity", vol doi:10.1029/2001JD001331, num 107, pgs. D23, 2002. Preprint
  4. Spichtinger, P., "The statistical distribution law of relative humidity in the global tropopause region", vol doi:10.1127/0941-2948/2002/0011-0083, num 11, 2002.

2001

  1. Gettleman, A., "El-Nino as a natural experiment for studying the Tropical Tropause Region", num 14, 2001. Preprint
  2. Pawson, S., "The Tropical Upper Troposphere and Lower Stratosphere in the GEOS-2 GCM", num 27, 2001. Preprint
  3. Read, W.G., "UARS Microwave Limb Sounder Upper Tropospheric Humidity Measurement: Method and Validation", num 106, pgs. D23, 2001. Reprint Preprint
  4. Sassi, F., "Relationship between upper tropospheric humidity and deep convection", num 106, pgs. D15, 2001. Reprint Preprint

2000

  1. Gettleman, A., "Simulations of water vapor in the lower stratosphere and upper troposphere", num 105, pgs. D7, 2000. Preprint
  2. Kley, D., "SPARC Assessment of Upper Tropospheric and Stratospheric Water Vapor", 2000.
  3. Pan, L.L., "The seasonal cycle of water vapor and saturation mixing ratio in the extratropical lowermost stratosphere", num 105, pgs. D21, 2000. Preprint
  4. Sandor, B.J., "Upper Tropospheric Humidity and Thin Cirrus", num 27, 2000. Preprint
  5. Stone, E.M., "Spatial distributions of upper tropospheric water vapor measurements from the UARS Microwave Limb Sounder", num 105, pgs. D10, 2000. Preprint
  6. Zhu, Y., "Factors controlling upper tropospheric water vapor", num 13, 2000. Preprint

1999

  1. Chen, M., "Seasonal variations of upper tropospheric water vapor and high clouds observed from satellites", num 104, pgs. D6, 1999. Preprint

1998

  1. Sandor, B.J., "Seasonal Behavior of Tropical to Mid-Latitude Upper Tropospheric Water Vapor from UARS MLS", num 103, pgs. D20, 1998. Reprint Preprint

1995

  1. Read, W.G., "Upper-tropospheric water vapor from UARS MLS", num 76, 1995. Preprint


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