Eluszkiewicz, Janusz and Crisp, David and Zurek, Richard and Elson, Lee and Fishbein, Evan and Froidevaux, Lucien and Waters, Joe and Grainger, R .G. and Lambert, Alyn and Harwood, Robert and Peckham, Gordon (1996) Residual Circulation in the Stratosphere and Lower Mesosphere as Diagnosed from Microwave Limb Sounder Data. Journal of the Atmospheric Sciences, 53 (2). pp. 217-240. ISSN 0022-4928 http://resolver.caltech.edu/CaltechAUTHORS:20120202-135115875
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Results for the residual circulation in the stratosphere and lower mesosphere between September 1991 and August 1994 are reported. This circulation is diagnosed by applying an accurate radiative transfer code to temperature, ozone, and water vapor measurements acquired by the Microwave Limb Sounder (MLS) onboard the Upper Atmosphere Research Satellite (UARS), augmented by climatological distributions of methane, nitrous oxide, nitrogen dioxide, surface albedo, and cloud cover. The sensitivity of the computed heating rates to the presence of Mt. Pinatubo aerosols is explored by utilizing aerosol properties derived from the measurements obtained by the Improved Stratospheric and Mesospheric Sounder instrument, also onboard UARS. The computed vertical velocities exhibit a Semiannual oscillation (SAO) around the tropical stratopause, with the region of downward velocities reaching maximum spatial extent in February and August. This behavior reflects the semiannual oscillation in temperature and ozone and mimics that seen in past studies of the October 1978–May 1979 period based on data from the Limb Infrared Monitor of the Stratosphere onboard the Nimbus 7 satellite. The SAO vertical velocities are stronger during the northern winter phase, as expected if planetary waves from the winter hemisphere are involved in driving the SAO. A possible quasi-biennial oscillation (QBO) signal extending from the middle into the upper stratosphere is also hinted at, with the equatorial vertical velocities in the region 10–1 hPa significantly smaller (or even negative) in 1993/94 than in 1992/93. Despite the short data record, the authors believe that this pattern reflects a QBO signal rather than a coincidental interannual variability, since the time–height section of vertical velocity at the equator resembles that of the zonal wind. Wintertime high-latitude descent rates are usually greater in the Northern Hemisphere, but they also exhibit significant variability there. In the three northern winters analyzed in this study, strong downward velocities are diagnosed in the lower stratosphere during stratospheric warmings and are associated with enhanced wave forcing (computed as the momentum residual) in the mid- and upper stratosphere. The implications of the computed circulation for the distribution of tracers are illustrated by the example of the “double-peaked” structure in the water vapor distribution measured by MLS.
|Additional Information:||© 1996 American Meteorological Society. Manuscript received 21 March 1994, in final form 9 June 1995. M. F. Gersten is thanked for her assiduity in assembling the cloud and albedo climatology, collaboration in debugging the radiative transfer model, and testing its sensitivities to tropospheric and surface fields. K. Rosenlof, K. K. Tung, and an anonymous reviewer provided critical reviews; comparisons using the Olaguer et al. (1992) radiative transfer code helped us to correct a coding error in our radiative model. G. Rottman and C. Pankratz of the SOLSTICE team are thanked for supplying the solar flux data, specially processed for our averaging periods. I. Fung and S. Massie provided us with information on the NASA GISS database and on the CO_2 concentrations, respectively. M. Delitsky assisted in the creation of the Fourier coefficient files from which temperature and constituent fields were constructed. M. Santee provided the streamfunction code and G. Manney the 100-hPa geopotential heights and the UKMO meteorological fields. Comments by A. Plumb are appreciated, in particular, his suggestion about the lower boundary condition for the streamfunction equation. H. Yang and R. Rood also provided helpful comments. R. Atkinson helped with the graphics at Mit. T. Luu is thanked for data management and help with the graphics at JPL. Y. Yung, E. Chang, and E. De Jong are thanked for the use of their computer facilities. This research was carried out as part of UARS Investigations at JPL/Caltech under contract with NASA and at Edinburgh and Heriot-Watt Universities sponsored by SERC. Oxford authors acknowledge funding by the Natural Environment Research Council.|
|Official Citation:||Eluszkiewicz, Janusz, and Coauthors, 1996: Residual Circulation in the Stratosphere and Lower Mesosphere as Diagnosed from Microwave Limb Sounder Data. J. Atmos. Sci., 53, 217–240. doi: http://dx.doi.org/10.11751520-0469(1996)053<0217:RCITSA>2.0.CO;2|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||27 Feb 2012 23:58|
|Last Modified:||26 Dec 2012 14:47|
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