Transport in the middle atmosphere

Journal of the Meteorological Society of Japan

Volumn 85 B, Issue , 2007, Pages 165-191

  Shepherd, Theodore G ^a  

^a UNIVERSITY OF TORONTO   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

AIRBORNE SURVEY; ATMOSPHERIC CIRCULATION; ATMOSPHERIC TRANSPORT; MIDDLE ATMOSPHERE; OZONE DEPLETION; SATELLITE IMAGERY; STRATOSPHERE;

EID: 34547836209     PISSN: 00261165     EISSN: None     Source Type: Journal    
DOI: 10.2151/jmsj.85B.165     Document Type: Review

References (121)

1. 2: Quantitative evidence for a subtropical "barrier" to horizontal transport. J. Geophys. Res., 106, 10257-10274.
2. Andrews, D.G. and M.E. McIntyre, 1976: Planetary waves in horizontal and vertical shear: the generalized Eliassen-Palm relation and the mean zonal acceleration. J. Atmos. Sci., 33, 2031-2048.
3. Andrews, D.G., J.R. Holton, and C.B. Leovy, 1987: Middle Atmosphere Dynamics. Academic Press, 489 pp.
4. Appenzeller, C., H.C. Davies, and W.A. Norton, 1996: Fragmentation of stratospheric intrusions. J. Geophys. Res., 101, 1435-1456.
5. Austin, J., D. Shindell, S.R. Beagley, C. Brühl, M. Dameris, E. Manzini, T. Nagashima, P. Newman, S. Pawson, G. Pitari, E. Rozanov, C. Schnadt, and T.G. Shepherd, 2003: Uncertainties and assessments of chemistry-climate models of the stratosphere. Atmos. Chem. Phys., 3, 1-27.
6. Bacmeister, J.T., S.D. Eckermann, P.A. Newman, L. Lait, K.R. Chan, M. Loewenstein, M.H. Proffitt, and B.L. Gary, 1996: Stratospheric horizontal wavenumber spectra of winds, potential temperature, and atmospheric tracers observed by high-altitude aircraft. J. Geophys. Res., 101, 9441-9470.
7. Balluch, M.G. and P.H. Haynes, 1997: Quantification of lower stratospheric mixing processes using aircraft data. J. Geophys. Res., 102, 23487-23504.
8. Barry, L., G.C. Craig, and J. Thuburn, 2002: Poleward transport by the atmospheric heat engine. Nature, 416, 774-777.
9. Beagley, S.R., J. de Grandpré, J.N. Koshyk, N.A. McFarlane, and T.G. Shepherd, 1997: Radiative-dynamical climatology of the first-generation Canadian middle atmosphere model. Atmos.-Ocean, 35, 293-331.
10. Bernath, P.F., et al., 2005: Atmospheric Chemistry Experiment (ACE): Mission overview. Geophys. Res. Lett., 32, doi: 10.1029/ 2005GL022386.
11. Bethan, S., G. Vaughan, and S.J. Reid, 1996: A comparison of ozone and thermal tropopause heights and the impact of tropopause definition on quantifying the ozone content of the troposphere. Quart. J. Roy. Meteor. Soc., 122, 929-944.
12. Birner, T., 2006: Fine-scale structure of the extra-tropical tropopause region. J. Geophys. Res., 111, D04104, doi: 10.1029/ 2005JD006301.
13. Birner, T., D. Sankey, and T.G. Shepherd, 2006: The tropopause inversion layer in models and analyses. Geophys. Res. Lett., 33, doi: 10.1029/2006GL026549.
14. 2O correlations during SPADE. Geophys. Res. Lett., 21, 2567-2570.
15. Boone, C.D., R. Nassar, K.A. Walker, Y. Rochon, S.D. McLeod, C.P. Rinsland, and P.F. Bernath, 2005: Retrievals for the Atmospheric Chemistry Experiment Fourier Transform Spectrometer. Appl. Opt., 44, 7218-7231.
16. Bowman, K.P., 1989: Global patterns of the Quasi-Biennial Oscillation in total ozone. J. Atmos. Sci., 46, 3328-3343.
17. Brewer, A.W., 1949: Evidence for a world circulation provided by the measurements of helium and water vapor distribution in the stratosphere. Quart. J. Roy. Meteor. Soc., 75, 351-363.
18. Butchart, N. and E.E. Remsberg, 1986: The area of the stratospheric polar vortex as a diagnostic for tracer transport on an isentropic surface. J. Atmos. Sci., 43, 1319-1339.
19. Charney, J. and P.G. Drazin, 1961: Propagation of planetary-scale disturbances from the lower into the upper atmosphere. J. Geophys. Res., 66, 83-109.
20. Chipperfield, M.P., 2003: A three-dimensional model study of long-term mid-high latitude lower stratosphere ozone changes. Atmos. Chem. Phys., 3, 1253-1265.
21. Chipperfield, M.P., 2006: New version of the TOM-CAT/SLIMCAT off-line Chemical Transport Model: Intercomparison of stratospheric tracer experiments. Quart. J. Roy. Meteor. Soc., 132, 1179-1203.
22. Danielsen, E.F., 1968: Stratospheric-tropospheric exchange based on radioactivity, ozone and potential vorticity. J. Atmos. Sci., 25, 502-518.
23. Dobson, G.M.B., 1956: Origin and distribution of the polyatomic molecules in the atmosphere. Proc. Roy. Soc. Lond. A, 236, 187-193.
24. Dunkerton, T.J., 1978: On the mean meridional mass motions of the stratosphere and mesosphere. J. Atmos. Sci., 35, 2325-2333.
25. Dunkerton, T.J., 1989: Nonlinear Hadley circulation driven by asymmetric differential heating. J. Atmos. Sci., 46, 956-974.
26. Ehhalt, D.G., E.P. Roth, and U. Schmidt, 1983: On the temporal variance of stratospheric gas concentrations. J. Atmos. Chem., 1, 27-51.
27. Eluszkiewicz, J., R.S. Hemler, J.D. Mahlman, L. Bruhwiler, and L.L. Takacs, 2000: Sensitivity of age-of-air calculations to the choice of advection scheme. J. Atmos. Sci., 57, 3185-3201.
28. Eyring, V., et al., 2006: Assessment of coupled chemistry-climate models: Evaluation of dynamics, transport characteristics and ozone. J. Geophys. Res., 111, doi: 10.1029/2006JD007327.
29. Fioletov, V.E. and T.G. Shepherd, 2003: Seasonal persistence of midlatitude total ozone anomalies. Geophys. Res. Lett., 30, doi: 10.1029/2002GL016739.
30. Fioletov, V.E. and T.G. Shepherd, 2005: Summertime total ozone variations over middle and polar latitudes. Geophys. Res. Lett., 32, doi:10.1029/2004GL022080.
31. Fischer, H., F.G. Weinhold, P. Hoor, O. Bujok, C. Schiller, P. Siegmund, M. Ambaum, H.A. Scheeren, and J. Lelieveld, 2000: Tracer correlations in the northern high latitude lowermost stratosphere: Influence of cross-tropopause mass exchange. Geophys. Res. Lett., 27, 97-100.
32. Folkins, I., M. Loewenstein, J. Podolske, S.J. Oltmans, and M. Proffitt, 1999: A barrier to vertical mixing at 14 km in the tropics: Evidence from ozonesondes and aircraft measurements. J. Geophys. Res., 104, 22095-22102, doi: 10.1029/1999JD900404.
33. Fortuin, J.P.F. and H. Kelder, 1998: An ozone climatology based on ozonesonde and satellite measurements. J. Geophys. Res., 103, 31709-31734.
34. Fueglistaler, S., H. Wernli, and T. Peter, 2004: Tropical troposphere-to-stratosphere transport inferred from trajectory calculations. J. Geophys. Res., 109, D03108, doi: 10.1029/ 2003JD004069.
35. Fueglistaler, S., M. Bonazzola, P.H. Haynes, and T. Peter, 2005: Stratospheric water vapor predicted from the Lagrangian temperature history of air entering the stratosphere in the tropics. J. Geophys. Res., 110, D08107.
36. Fusco, A.C. and M.L. Salby, 1999: Interannual variations of total ozone and their relationship to variations of planetary wave activity. J. Climate, 12, 1619-1629.
37. Garcia, R.R. and B.A. Boville, 1994: "Downward control" of the mean meridional circulation and temperature distribution of the polar winter stratosphere. J. Atmos. Sci., 51, 2238-2245.
38. Grant, W.B., et al., 1994: Aerosol-associated changes in tropical stratospheric ozone following the eruption of Mount Pinatubo. J. Geophys. Res., 99, 8197-8211.
39. Hall, T.M. and R.A. Plumb, 1994: Age as a diagnostic of stratospheric transport. J. Geophys. Res., 99, 1059-1070.
40. Hall, T.M. and D. Waugh, 1997: Tracer transport in the tropical stratosphere due to vertical diffusion and horizontal mixing. Geophys. Res. Lett., 24, 1383-1386.
41. Hall, T.M., D.W. Waugh, K.A. Boering, and R.A. Plumb, 1999: Evaluation of transport in stratospheric models. J. Geophys. Res., 104, 18815-18839.
42. Hasebe, F., 1994: Quasi-biennial oscillations of ozone and diabatic circulation in the equatorial stratosphere. J. Atmos. Sci., 51, 729-745.
43. Haynes, P.H., 2003: Critical layers. In Encyclopedia of Atmospheric Sciences (ed. J.R. Holton, J.A. Pyle and J.A. Curry), Academic Press.
44. Haynes, P. and J. Anglade, 1997: The vertical-scale cascade in atmospheric tracers due to large-scale differential advection. J. Atmos. Sci., 54, 1121-1136.
45. Haynes, P.H., C.J. Marks, M.E. McIntyre, T.G. Shepherd, and K.P. Shine, 1991: On the "downward control" of extratropical diabatic circulations by eddy-induced mean zonal forces. J. Atmos. Sci., 48, 651-678.
46. Haynes, P., J. Scinocca, and M. Greenslade, 2001: Formation and maintenance of the extratropical tropopause by baroclinic eddies. Geophys. Res. Lett., 28, 4179-4182.
47. Haynes, P.H. and T.G. Shepherd, 2001: Report on the SPARC Tropopause Workshop. SPARC Newsletter, 17, 3-10.
48. Haynes, P. and E. Shuckburgh, 2000: Effective diffusivity as a diagnostic of atmospheric transport. 1. Stratosphere. J. Geophys. Res., 105, 22777-22794.
49. Haynes, P.H. and J. Vanneste, 2004: Stratospheric tracer spectra. J. Atmos. Sci., 61, 161-178.
50. Haynes, P.H. and W.E. Ward, 1993: The effect of realistic radiative transfer on potential-vorticity structures, including the influence of background shear and strain. J. Atmos. Sci., 50, 3431-3453.
51. Hegglin, M.I., et al., 2004: Tracing troposphere-to-stratosphere transport above a mid-latitude deep convective system. Atmos. Chem. Phys., 4, 741-756.
52. Hegglin, M.I., D. Brunner, T. Peter, J. Staehelin, V. Wirth, P. Hoor, and H. Fischer, 2005: Determination of eddy-diffusivity in the lowermost stratosphere. Geophys. Res. Lett., 32, L13812, doi: 10.1029/2005GL022495.
53. 3 during SPURT: Implications for transport and chemistry in the lowermost stratosphere. Atmos. Chem. Phys., 6, 1331-1350.
54. Held, I.M. and B.J. Hoskins, 1985: Large-scale eddies and the general circulation of the troposphere. Advances in Geophys., 28A, 3-31.
55. Highwood, E.J. and B.J. Hooskins, 1998: The tropical tropopause. Quart. J. Roy. Meteor. Soc., 124, 1579-1604.
56. Holton, J.R., P.H. Haynes, M.E. McIntyre, A.R. Douglass, R.B. Rood, and L. Pfister, 1995: Stratosphere-troposphere exchange. Rev. Geophys., 33, 403-439.
57. Holton, J.R. and H.-C. Tan, 1980: The influence of the equatorial quasi-biennial oscillation on the global circulation at 50 mb. J. Atmos. Sci., 37, 2200-2208.
58. Hoor, P., C. Gurk, D. Brunner, M.I. Hegglin, H. Wernli, and H. Fischer, 2004: Seasonality and extent of extratropical TST derived from in-situ CO measurements during SPURT. Atmos. Chem. Phys., 4, 1427-1442.
59. Hoskins, B.J., M.E. McIntyre, and A.W. Robertson, 1985: On the use and significance of isentropic potential-vorticity maps. Quart. J. Roy. Meteor. Soc., 111, 877-946.
60. IPCC/TEAP, 2005: Safeguarding the Ozone Layer and the Global Climate System: Issues Related to Hydrofluorocarbons and Perfluorocarbons. IPCC/TEAP Special Report (ed. B. Metz et al.), Cambridge University Press, 478 pp.
61. Jockel, P., R. von Kuhlmann, M.G. Lawrence, B. Steil, C.A.M. Brenninkmeijer, P.J. Crutzen, P.J. Rasch, and B. Eaton, 2001: On a fundamental problem in implementing flux-form advection schemes for tracer transport in 3-dimensional general circulation and chemistry transport models. Quart. J. Roy. Meteor. Soc., 127, 1035-1052.
62. Juckes, M.N. and M.E. McIntyre, 1987: A high resolution, one-layer model of breaking planetary waves in the stratosphere. Nature, 328, 590-596.
63. Kida, H., 1983: General circulation of air parcels and transport characteristics derived from a hemispheric GCM. 2. Very long-term motions of air parcels in the troposphere and stratosphere. J. Meteor. Soc. Japan, 61, 510-523.
64. Koshyk, J.N., B.A. Boville, K. Hamilton, E. Manzini, and K. Shibata, 1999: The kinetic energy spectrum of horizontal motions in middle-atmosphere models. J. Geophys. Res., 104, 27177-27190.
65. Legras, B., I. Pisso, G. Berthet, and F. Lefevre, 2005: Variability of the Lagrangian turbulent diffusion in the lower stratosphere. Atmos. Chem. Phys., 5, 1605-1622.
66. Lin, S.-J. and R.B. Rood, 1996: Multidimensional flux-form semi-Lagrangian transport schemes. Mon. Wea. Rev., 124, 2046-2070.
67. Lukovich, J.V. and T.G. Shepherd, 2005: Stirring and mixing in two-dimensional divergent flow. J. Atmos. Sci., 62, 3933-3954.
68. McIntyre, M.E., 2000: On global-scale atmospheric and oceanic circulations. In Perspectives in Fluid Dynamics (ed. G.K. Batchelor, H.K. Moffatt and M.G. Worster), Cambridge University Press.
69. McIntyre, M.E. and T.N. Palmer, 1983: Breaking planetary waves in the stratosphere. Nature, 305, 593-600.
70. Meijer, E.W., B. Bregman, A. Segers, and P.F.J. van Velthoven, 2004: The influence of data assimilation on the age of air calculated with a global chemistry-transport model using ECMWF wind fields. Geophys. Res. Lett., 31, L23114.
71. 4 derived from ATMOS measurements. J. Geophys. Res., 103, 28347-28359.
72. Monge-Sanz, B.M., M.P. Chipperfield, A.J. Simmons, and S.M. Uppala, 2007: Mean age of air and transport in a CTM: Comparison of different ECMWF analyses. Geophys. Res. Lett., 34, doi: 10.1029/ 2006GL028515.
73. Mote, P.W., et al., 1996: An atmospheric tape recorder: The imprint of tropical tropopause temperatures on stratospheric water vapor. J. Geophys. Res., 101, 3989-4006.
74. Murphy, D.M., D.W. Fahey, M.H. Proffitt, C.S. Liu, K.R. Chan, C.S. Eubank, S.R. Kawa, and K.K. Kelly, 1993: Reactive nitrogen and its correlation with ozone in the lower stratosphere and upper troposphere. J. Geophys. Res., 98, 8751-8773.
75. Neu, J.L. and R.A. Plumb, 1999: Age of air in a "leaky pipe" model of stratospheric transport. J. Geophys. Res., 104, 19243-19255.
76. Neu, J.L., L.C. Sparling, and R.A. Plumb, 2003: Variability of the subtropical "edges" in the stratosphere. J. Geophys. Res., 108, 4482.
77. Newman, P.A., J.F. Gleason, R.D. McPeters, and R.S. Stolarski, 1997: Anomalously low ozone over the Arctic. Geophys. Res. Lett., 24, 2689-2692.
78. Ngan, K. and T.G. Shepherd, 1997a: Chaotic mixing and transport in Rossby-wave critical layers. J. Fluid Mech., 334, 315-351.
79. 3 tracer spectra in the stratospheric surf zone. J. Geophys. Res., 102, 24001-24004.
80. Ngan, K. and T.G. Shepherd, 1999: A closer look at chaotic advection in the stratosphere. Part I: Geometric structure. J. Atmos. Sci., 56, 4134-4152.
81. Orsolini, Y.J., P. Simon, and D. Cariolle, 1995: Filamentation and layering of an idealized tracer by observed winds in the lower stratosphere. Geophys. Res. Lett., 22, 839-842.
82. Palmén, E. and C. Newton, 1969: Atmospheric Circulation Systems. Academic Press, 603 pp.
83. Pendlebury D. and T.G. Shepherd, 2003: Planetary-wave-induced transport in the stratosphere. J. Atmos. Sci., 60, 1456-1470.
84. Pierrehumbert, R.T., 1991: Large-scale horizontal mixing in planetary atmospheres. Phys. Fluids A, 3, 1250-1260.
85. Plumb, R.A., 1996: A "tropical pipe" model of stratospheric transport. J. Geophys. Res., 101, 3957-3972.
86. Plumb, R.A., 2002: Stratospheric transport. J. Meteor. Soc. Japan, 80, 793-809.
87. Plumb, R.A. and M.K.W. Ko, 1992: Interrelationships between mixing ratios of long-lived stratospheric constituents. J. Geophys. Res., 97, 10145-10156.
88. Plumb, R.A., D.W. Waugh, and M.P. Chipperfield, 2000: The effects of mixing on tracer relationships in the polar vortices. J. Geophys. Res., 105, 10047-10062.
89. Polavarapu, S. and T.G. Shepherd, 2006: Report on the Joint SPARC Workshop on Data Assimilation and Stratospheric Winds. SPARC Newsletter, 26, 20-27.
90. Polvani, L.M. and R.A. Plumb, 1992: Rossby-wave breaking, microbreaking, filamentation, and secondary vortex formation - The dynamics of a perturbed vortex. J. Atmos. Sci., 49, 462-476.
91. Polvani, L.M., D.W. Waugh, and R.A. Plumb, 1995: On the subtropical edge of the stratospheric surf zone. J. Atmos. Sci., 52, 1288-1309.
92. Postel, G.A. and M.H. Hitchman, 1999: A climatology of Rossby wave breaking along the subtropical tropopause. J. Atmos. Sci., 56, 359-373.
93. Poulida, O., R.R. Dickerson, and A. Heymsfield, 1996: Stratosphere-troposphere exchange in a midlatitude mesoscale convective complex. J. Geophys. Res., 101, 6823-6836.
94. x enhancements in the southern hemisphere vortex in winter/spring of 2000. Geophys. Res. Lett., 28, 2385-2388.
95. Randel, W.J. and I.M. Held, 1991: Phase speed spectra of transient eddy fluxes and critical layer absorption. J. Atmos. Sci., 48, 688-697.
96. 2O observed in UARS HALOE data. J. Atmos. Sci., 55, 163-185.
97. Randel, W.J., F. Wu, and R. Stolarski, 2002: Changes in column ozone correlated with the stratospheric EP flux. J. Meteor. Soc. Japan, 80, 849-862.
98. Randel, W.J., F. Wu, S.J. Oltmans, K. Rosenlof, and G.E. Nedoluha, 2004: Interannual changes of stratospheric water vapor and correlations with tropical tropopause temperatures. J. Atmos. Sci., 61, 2133-2148.
99. Ray, E.A., F.L. Moore, J.W. Elkins, G.S. Dutton, D.W. Fahey, H. Vomel, S.J. Oltmans, and K.H. Rosenlof, 1999: Transport into the Northern Hemisphere lowermost stratosphere revealed by in situ tracer measurements. J. Geophys. Res., 104, 26565-26580.
100. Rex, M., R.J. Salawitch, P. von der Gathen, N. Harris, M.P. Chipperfield, and B. Naujokat, 2004: Arctic ozone loss and climate change. Geophys. Res. Lett., 31, doi: 10.1029/2003GL018844.
101. Rosenlof, K.H., A.F. Tuck, K.K. Kelly, J.M. Russell III, and M.P. McCormick, 1997. Hemispheric asymmetries in water vapor and inferences about transport in the lower stratosphere. J. Geophys. Res., 102, 13213-13234.
102. Sankey, D. and T.G. Shepherd, 2003: Correlations of long-lived chemical species in a middle atmosphere general circulation model. J. Geophys. Res., 108, doi: 10.1029/2002JD002799.
103. Schoeberl, M.R., A.R. Douglass, Z. Zhu, and S. Pawson, 2003: A comparison of the lower stratospheric age spectra derived from a general circulation model and two data assimilation systems. J. Geophys. Res. 108, doi: 10.1029/2002JD002652.
104. Semeniuk, K. and T.G. Shepherd, 2001a: The middle-atmosphere Hadley circulation and equatorial inertial adjustment. J. Atmos. Sci., 58, 3077-3096.
105. Semeniuk, K. and T.G. Shepherd, 2001b: Mechanisms for tropical upwelling in the stratosphere. J. Atmos. Sci., 58, 3097-3115.
106. Shepherd, T.G., 2000: The middle atmosphere. J. Atmos. Solar-Terres. Phys., 62, 1587-1601.
107. Shepherd, T.G., 2003: Large-scale atmospheric dynamics for atmospheric chemists. Chem. Reviews, 103, 4509-4531.
108. Shepherd, T.G., J.N. Koshyk, and K. Ngan, 2000: On the nature of large-scale mixing in the stratosphere and mesosphere. J. Geophys. Res., 105, 12433-12446.
109. SPARC, 2002: SPARC Intercomparison of Middle Atmosphere Climatologies. SPARC Report No. 3 (ed. W. Randel, M.-L. Chanin and C. Michaut), WCRP-116, WMO/TD No. 1142.
110. Sparling, L.C., 2000: Statistical perspectives on stratospheric transport. Rev. Geophys., 38, 417-436.
111. Sparling, L.C., J.A. Kettleborough, P.H. Haynes, M.E. McIntyre, J.E. Rosenfield, M.R. Schoeberl, and P.A. Newman, 1997. Diabatic cross-isentropic dispersion in the lower stratosphere. J. Geophys. Res., 102, 25817-25829.
112. 2O measurements. 2. Tracer variability and diabatic meridional circulation. J. Geophys. Res., 99, 10319-10332.
113. Tegtmeier, S. and T.G. Shepherd, 2007: Persistence and photochemical decay of springtime total ozone anomalies in the Canadian Middle Atmosphere Model. Atmos. Chem. Phys., 7, 485-493.
114. Thuburn, J. and G.C. Craig, 2002: On the temperature structure of the tropical substratosphere. J. Geophys. Res., 107, 4017, doi: 10.1029/2001JD000448.
115. Trepte, C.R. and M.H. Hitchman, 1992: Tropical stratospheric circulation deduced from satellite aerosol data. Nature, 355, 626-628.
116. Volk, C.M., J.W. Elkins, D.W. Fahey, R.J. Salawitch, G.S. Dutton, J.M. Gilligan, M.H. Proffitt, M. Loewenstein, J.R. Podolske, K. Minschwaner, JJ. Margitan, and K.R. Chan, 1996: Quantifying transport between the tropical and midlatitude lower stratosphere. Science, 272, 1763-1768.
117. Walker, K.A., C.E. Randall, C.R. Trepte, C.D. Boone, and P.F. Bernath, 2005: Initial validation comparisons for the Atmospheric Chemistry Experiment (ACE-FTS). Geophys. Res. Lett., 32, doi: 10.1029/2005GL022388.
118. Waugh, D.W., R.A. Plumb, R.J. Atkinson, M.R. Schoeberl, L.R. Lait, P.A. Newman, M. Loewenstein, D.W. Toohey, L.M. Avallone, C.R. Webster, and R.D. May, 1994: Transport out of the lower stratospheric Arctic vortex by Rossbywave breaking. J. Geophys. Res., 99, 1071-1088.
119. Waugh, D.W. and T.M. Hall, 2002: Age of stratospheric air: Theory, observations, and models. Rev. Geophys., 40, 1010.
120. Williamson, D.L. and P.J. Rasch, 1989: Two-dimensional semi-Lagrangian transport with shape-preserving interpolation. Mon. Wea. Rev., 117, 102-129.
121. Yulaeva, E., J.R. Holton, and J.M. Wallace, 1994: On the cause of the annual cycle in tropical lower stratospheric temperatures. J. Atmos. Sci., 51, 169-174.