Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 20 2008 10.5194/acp-8-6051-2008 http://www.atmos-chem-phys.net/8/6051/2008/ http://www.atmos-chem-phys.net/8/6051/2008/acp-8-6051-2008.html http://www.atmos-chem-phys.net/8/6051/2008/acp-8-6051-2008.pdf 6051 6067 2008-10-21 The roles of convection, extratropical mixing, and in-situ freeze-drying in the Tropical Tropopause Layer W. G. Read bill@mls.jpl.nasa.gov M. J. Schwartz A. Lambert H. Su N. J. Livesey W. H. Daffer C. D. Boone Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA Department of Chemistry, University of Waterloo, Ontario, Canada Mechanisms for transporting and dehydrating air across the tropical tropopause layer (TTL) are investigated with a conceptual two dimensional (2-D) model. The 2-D TTL model combines the Holton and Gettelman cold trap dehydration mechanism (Holton and Gettelman, 2001) with the two column convection model of Folkins and Martin (2005). We investigate 3 possible transport scenarios through the TTL: 1) slow uniform ascent across the level of zero radiative heating without direct convective mixing, 2) convective mixing of H₂O vapor at 100% relative humidity with respect to ice (RHi) with no ice retention, and 3) convective mixing of extremely subsaturated air (100% RHi following the moist adiabatic temperature above the level of neutral buoyancy) with sufficient ice retention such that total H₂O is 100%RHi. The three mechanisms produce similar seasonal cycles for H₂O that are in good quantitative agreement with the Aura Microwave Limb Sounder (MLS) measurements. We use Aura MLS measurement of CO and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer measurement of HDO to distinguish among the transport mechanisms. Model comparisons with the observations support the view that H₂O is predominantly controlled by regions having the lowest cold point tropopause temperature but the trace species CO and HDO support the convective mixing of dry air and lofted ice. The model provides some insight into the processes affecting the long term trends observed in stratospheric H₂O. Andrews, A E., Boering, K A., Daube, B C., Wofsy, S C., Hintsa, E J., Weinstock, E M., and Bui, T P.: Empirical Age Spectra for the Lower Tropical Stratosphere from In-Situ Observations of CO₂: Implications for Stratospheric Transport, J. Geophys. Res., 104, 26 581–26 595, 1999. Bernath, P F., McElroy, C., Abrams, M., Boone, C., Butler, M., Camy-Peyret, C., Carleer, M., Clerbaux, C., Coheur, P., Colin, R., DeCola, P., DeMazière, M., Drummond, J., Dufour, D., Evans, W., Fast, H., Fussen, D., Gilbert, K., Jennings, D., Llewellyn, E., Lowe, R., Mahieu, E., McConnell, J., McHugh, M., McLeod, S., Michaud, R., Midwinter, C., Nassar, R., Nichitiu, F., Nowlan, C., Rinsland, C., Rochon, Y., Rowlands, N., Semeniuk, K., Simon, P., Skelton, R., Sloan, J., Soucy, M.-A., Strong, K., Tremblay, P., Turnbull, D., Walker, K., Walkty, I., Wardle, D., Wehrle, V., Zander, R., and Zou, J.: Atmospheric Chemistry Experiment (ACE): Mission Overview, Geophys. Res. Lett., 32, L15S01, doi:10.1029/2005GL022386, 2005. Boehm, M T., Verlinde, J., and Ackerman, T P.: On the Maintenance of High Tropical Cirrus, J. Geophys. Res., 104, 24 423–24 433, 1999. Bonazzola, M. and Haynes, P H.: A trajectory-based study of the tropical tropopause region, J. Geophys. Res., 109, D20112, doi10:1029/2003JD000511, 2004. Boone, C D., Nassar, R., Walker, K., Rochon, Y., McLeod, S., Rinsland, C., and Bernath, P.: Retrievals for the Atmospheric Chemistry Experiment Fourier-transform spectrometer, Appl. Optic, 44, 7218–7231, 2005. Brewer, A W.: Evidence for a world circulation provided by the measurements of helium and water vapour distribution in the stratosphere, Q. J. R. Meteor. Soc., 75, 351–363, 1949. Cappa, C D., Hendricks, M B., DePaolo, D J., and Cohen, R C.: Isotopic Fractionation of Water during Evaporation, J. Geophys. Res., 108, 4525, doi:10.1029/2003JD003597, 2003. Danielsen, E F.: A dehydration mechanism for the stratosphere, Geophys. Res. Lett., 9, 605–608, 1982. Danielsen, E F.: In situ evidence of rapid, vertical irreversible transport of lower tropospheric air into the lower stratosphere by convective cloud turrets and by large-scale upwelling in tropical cyclones, J. Geophys. Res., 98, 8665–8681, 1993. Dessler, A E.: The Effect of Deep, Tropical Convection on the Tropical Tropopause Layer, J. Geophys. Res., 107, 4033, doi:10.1029/2001JD000511, 2002. Dessler, A E. and Sherwood, S C.: A model of HDO in the tropical tropopause layer, Atmos. Chem. Phys., 3, 4489–4501, 2003. Dessler, A E., Hanisco, T F., and Füglistaler, S A.: The Effects of Convective Ice Lofting on H₂O and HDO in the TTL and Tropical Lower Stratosphere, J. Geophys. Res., 112, D18309, doi:10.1029/2007JD008609, 2007. Folkins, I. and Martin, R V.: The Vertical Structure of Tropical Convection and its Impact on the Budgets of Water Vapor and Ozone, J. Atmos. Sci., 62, 1560–1573, 2005. Folkins, I., Loewenstein, M., Podolske, J., Oltmans, S J., and Proffit, M.: A Barrier to Vertical Mixing at 14 km in the Tropics: Evidence from Ozonesondes and Aircraft Measurements, J. Geophys. Res., 104, 22 102–22 102, 1999. Folkins, I., Bernath, P., Boone, C., Donner, L J., Lesins, G., Martin, R V., Sinnhuber, B.-M., and Walker, K.: Testing Convective Parameterizations with Tropical Measurements of HNO₃, CO, H₂O, O₃: Implications for the Water Vapor Budget, J. Geophys. Res., 111, D23304, doi:10.1029/2006JD007325, 2006a. Folkins, I., Bernath, P., Boone, C., Lesins, G., Thompson, A M., Walker, K., and White, J C.: Seasonal Cycles of O₃, CO, and Convective Outflow at the Tropical Tropopause, Geophys. Res. Lett., 33, L16802, doi:10.1029/2006GL026602, 2006b. Fueglistaler, S. and Fu, Q.: Impact of Clouds on Radiative Heating Rates in the Tropical Lower Stratosphere, J. Geophys. Res., 111, D23202, doi:10.1029/2006JD007273, 2006. Fueglistaler, S. and Haynes, P H.: Control of Interannual and Longer-Term Variability of Stratospheric Water Vapor, J. Geophys. Res., 110, D08107, doi:10.1029/2005JD006019, 2005. Fueglistaler, S., Wernli, H., and Peter, T.: Tropical troposphere-to-stratosphere transport inferred from trajectory calculations, J. Geophys. Res., 109, D03108, doi:10.1029/2003JD004069, 2004. Fueglistaler, S., Bonazzola, M., Haynes, P H., and Peter, T.: Stratospheric Water Vapor Predicted from the Lagrangian Temperature Histroy of Air Entering the Stratosphere in the Tropics, J. Geophys. Res., 110, D08107, doi:10.1029/2004JD005516, 2005. Gettelman, A., Randel, W J., Wu, F., and Massie, S T.: Transport of water vapor in the tropical tropopause layer, Geophys. Res. Lett., 29, 1009, doi:10.1029/2001GL013818, 2002. Gettelman, A E. and Webster, C R.: Simulations of Water Isotope Abundances in the Upper Troposphere and Lower Stratosphere and Implications for Stratosphere Troposphere Exchange, J. Geophys. Res., 110, D17301, doi:10.1029/2004JD004812, 2005. Grosvenor, D P., Choularton, T W., Coe, H., and Held, G.: A Study of the Effect of Overshooting Deep Convection on the Water Content of the TTL and Lower Stratosphere from Cloud Resolving Model Simulations, Atmos. Chem. Phys., 7, 4977–5002, 2007. Gunson, M R., Abbas, M M., Abrams, M C., Allen, M., Brown, L R., Brown, T L., Chang, A Y., Goldman, A., Irion, F W., Lowes, L L., Mahieu, E., Manney, G L., Michelson, H A., Newchurch, M J., Rinsland, C P., Salawitch, R J., Stiller, G P., Toon, G C., Yung, Y L., and Zander, R.: The Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment: Deployment on the ATLAS Space Shuttle missions, Geophys. Res. Lett., 23, 2333–2336, 1996. Hartmann, D L., Holton, J R., and Fu, Q.: The heat balance of the tropical tropopause, cirrus, and stratospheric dehydration, Geophys. Res. Lett., 28, 1969–1972, 2001. Holton, J R. and Gettelman, A.: Horizontal transport and the dehydration of the stratosphere, Geophys. Res. Lett., 28, 2799–2802, 2001. Holton, J R., Haynes, P H., McIntyre, M E., Douglass, A R., Rood, R B., and Pfister, L.: Stratosphere-troposphere exchange, Rev. Geophys., 33, 403–439, 1995. Jensen, E J. and Pfister, L.: Transport and Freeze-Drying in the Tropical Tropopause Layer, J. Geophys. Res., 109, D02207, doi:10.1029/2003JD004022, 2004. Jensen, E J., Pfister, L., Ackerman, A S., and Tabazedeh, A.: A Conceptual Model of the Dehydration of Air Due to Freeze-Drying by Optically Thin, Laminar Cirrus Rising Slowly Across the Tropical Tropopause, J. Geophys. Res., 106, 17 237–17 252, 2001. Jensen, E J., Smith, J B., Pfister, L., Pittman, J V., Weinstock, E M., Sayres, D S., Herman, R L., Troy, R F., Rosenlof, K., Thompson, T L., A, M, F., Hudson, P K., Cziczo, D J., Heymsfield, A J., Schmitt, C., and Wilson, J C.: Ice Supersaturations Exceeding 100% at the Cold Tropical Tropopause: Implications for Cirrus Formation and Dehydration, Atmos. Chem. Phys., 5, 851–862, 2005. Jensen, E J., Ackerman, A S., and Smith, J A.: Can Overshooting Convection Dehydrate the Tropical Tropopause Layer?, J. Geophys. Res., 112, D11209, doi:10.1029/2006JD007943, 2007. Johnson, D G., Jucks, K W., Traub, W A., and Chance, K V.: Isotopic composition of stratospheric water vapor: Implications for transport, J. Geophys. Res., 106, 12 219–12 226, 2001a. Johnson, D G., Jucks, K W., Traub, W A., and Chance, K V.: Isotopic composition of stratospheric water vapor: Measurements and Photochemistry, J. Geophys. Res., 106, 12 211–12 217, 2001b. Jouzel, J. and Merlivat, L.: Deuterium and Oxygen 18 in Precipitation: Modeling of the Isotopic Effects During Snow Formation, J. Geophys. Res., 99, 11 749–11 757, 1984. Keith, D W.: Stratosphere-troposphere exchange: Inferences from the isotopic composition of water vapor, J. Geophys. Res., 105, 15 167–15 173, 2000. Koop, T., Ng, H P., Molina, L T., and Molina, M J.: A New Optical Technique to Study Aerosol Phase Transitions: The Nucleation of Ice from H₂SO₄ Aerosols, J. Chem. Phys. A., 102, 8924–8931, 1998. Kuang, Z., Toon, G C., Wennberg, P O., and Yung, Y L.: Measured HDO/H₂O ratios across the tropical tropopause, Geophys. Res. Lett., 30, 1372, doi:10.1029/2003GL017023, 2003. Lanzante, J R., Klein, S A., and Seidel, D J.: Temporal Homogenization of Monthly Radiosonde Temperature Data. Part II: Trends, Sensitivities, and MSU Comparison, J. Climate, 16, 241–262, 2003. Livesey, N J.: Data Quality Document for the EOS MLS version 2.2 Level 2 Dataset, Tech. Rep. Tech. Rep., Jet Propulsion Laboratory, 2007. Livesey, N J., Froidevaux, L., Read, W G., Lambert, A., Cofield, R E., Fuller, R A., Jarnot, R F., Jiang, J H., Jiang, Y B., Knosp, B W., Santee, M L., Schwartz, M J., Snyder, W V., Stek, P C., Wagner, P A., Waters, J W., Pumphrey, H C., Avery, M., Browell, E V., Christiensen, L E., Loewenstein, M., Lopez, J D., Sachse, G W., and Webster, C R.: Validation of EOS Microwave Limb Sounder O₃ and CO observations in the upper troposphere / lower stratosphere, J. Geophys. Res., 113, D15S02, doi:10.1029/2007JD008805, in press, 2008. Madden, R A. and Julian, P R.: Observations of the 40–50 Day Tropical Oscillation–A Review, Mon. Weather Rev., 122, 814–837, 1994. McFarquhar, G M. and Heymsfield, A J.: Parameterization of Tropical Cirrus Ice Crystal Size Distributions and Implications for Radiative Transfer: Results from CEPEX, J. Atmos. Sci., 54, 2187–2200, 1997. Mote, P W., Rosenlof, K H., McIntyre, M E., Carr, E S., Gille, J C., Holton, J R., Kinnersley, J S., Pumphrey, H C., III, J. M R., and Waters, J W.: An atmospheric tape recorder: The imprint of tropical tropopause temperatures on stratospheric water vapor, J. Geophys. Res., 101, 3989–4006, 1996. Mote, P W., Dunkerton, T J., McIntyre, M E., Ray, E A., Haynes, P H., and III, J. M R.: Vertical Velocity, Vertical Diffusion, and Dilution by Midlatitude Air in the Tropical Lower Stratosphere, J. Geophys. Res., 103, 8651–8666, 1998. Moyer, E J., Irion, F W., Yung, Y L., and Gunson, M R.: ATMOS stratospheric water and implications for tropospheric-stratospheric transport, Geophys. Res. Lett., 23, 2385–2388, 1996. Nassar, R., Bernath, P F., Boone, C D., Gettelman, A., McLeod, S D., and Rinsland, C P.: Variability in HDO/H₂O Abundance Ratios in the Tropical Tropopause Layer, J. Geophys. Res., 112, D21305, doi:10.1029/2007JD008417, 2007. Nedoluha, G E., Bevilacqua, R M., Gomez, R M., Siskind, D E., Hicks, B C., and III, J. M R.: An evaluation of trends in middle atmospheric water vapor as measured by HALOE, WVMS, and POAM, J. Geophys. Res., 108, 4391, doi:10.1029/2002JD003332, 2003. Notholt, J., Luo, B P., Fueglistaler, S., Weisenstein, D., Rex, M., Lawrence, M G., Bingemer, H., Wohltmann, I., Corti, T., Warneke, T., von Kuhlmann, R., and Peter, T.: Influence of Tropospheric SO₂ Emissions on Particle Formation and the Stratospheric Humidity, Geophys. Res. Lett., 32, L07810, doi:10.1029/2004GL022159, 2005. Pfister, L. and Jensen, E.: Convective Influence Calculations for CR-AVE and TC4, in: 14th Conference on Middle Atmosphere, American Meteorological Society, Portland Oregon, p. P3.12, 2007. Pfister, L., Selkirk, H B., Jensen, E J., Schoeberl, M R., Toon, O B., Browell, E V., Grant, W B., Gary, B., Mahoney, M J., Bui, T V., and Hintsa, E.: Aircraft Observations of Thin Cirrus Clouds near the Tropical Tropopause, J. Geophys. Res., 106, 9765–9786, 2001. Potter, B E. and Holton, J R.: The Role of Mesoscale Convection in the Dehydration of the Lower Tropical Stratosphere, J. Atmos. Sci., 52, 1034–1050, 1995. Randel, W J., Garcia, R R., and Wu, F.: Time-Dependent Upwelling in the Tropical Lower Stratosphere Estimated from the Zonal-Mean Momentum Budget, J. Atmos. Sci., 59, 2141–2152, 2002. Randel, W J., Wu, F., Vömel, H., Nedoluha, G E., and Forster, P.: Decreases in Stratospheric Water Vapor after 2001: Links to Changes in the Tropical Tropopause and the Brewer-Dobson Circulation, J. Geophys. Res., 111, D12312, doi:10.1029/2005JD006744, 2006. Randel, W J., Park, M., Wu, F., and Livesey, N.: A Large Annual Cycle in Ozone above the Tropical Tropopause Linked to the Brewer-Dobson Circulation, J. Atmos. Sci., 64, 4479–4488, 2007. Read, W G., Wu, D L., Waters, J W., and Pumphrey, H C.: Dehydration in the tropical tropopause layer: Implications from the UARS Microwave Limb Sounder, J. Geophys. Res., 109, D06110, doi:10.1029/2003JD004056, 2004. Read, W G., Shippony, Z., and Snyder, W V.: The Clear-Sky Unpolarized Forward Model for the EOS Aura Microwave Limb Sounder (MLS), IEEE Transactions on Geosciences and Remote Sensing: The EOS Aura Mission, 44, 1367–1379, 2006. Read, W G., Bacmeister, J., Cofield, R E., Cuddy, D T., Daffer, W H., Drouin, B J., Fetzer, E., Froidevaux, L., Fuller, R., Herman, R., Jarnot, R F., Jiang, J H., Jiang, Y B., Kelly, K., Knosp, B W., Kovalenko, L J., Lambert, A., Lay, R., Livesey, N J., Liu, H.-C., Loo, M., Manney, G L., Miller, D., Mills, B J., Pickett, H M., Pumphrey, H C., Rosenlof, K H., Sabounchi, X., Santee, M L., Schwartz, M J., Snyder, W V., Stek, P C., Su, H., Takacs, L L., Thurstans, R P., Vömel, H., Wagner, P A., Waters, J W., Weinstock, E M., and Wu, D L.: EOS Aura Microwave Limb Sounder Upper Tropospheric and Lower Stratospheric Humidity Validation, J. Geophys. Res., 112, D24S35, doi:10.1029/2007JD008752, 2007. Read, W G., Schwartz, M J., Lambert, A., Su, H., Livesey, N J., Daffer, W H., and Boone, C D.: The Roles of Convection, Extratropical Mixing, and In-Situ Freeze-drying in the Tropical Tropopause Layer, Atmos. Chem. Phys. Discuss., 8, 3961–4000, 2008. Rodgers, C D.: Characterization and Error Analysis of Profiles Retrieved From Remote Sounding Measurements, J. Geophys. Res., 95, 5587–5595, 1990. Rosenlof, K H.: Seasonal Cycle of the Residual Mean Meridional Circulation in the Stratosphere, J. Geophys. Res., 100, 5173–5191, 1995. Rosenlof, K H. and Reid, G C.: Trends in the Temperature and Water Vapor Content of the Tropical Lower Stratosphere: The Sea-Surface Connection, J. Geophys. Res., 113, D06107, doi:10.1029/2007JD009109, 2008. Rosenlof, K H., Oltmans, S J., Kley, D., III, J. M R., Chiou, E.-W., Chu, W P., Johnson, D G., Kelly, K K., Michelsen, H A., Nedoluha, G E., Remsberg, E E., Toon, G C., and McCormick, M P.: Stratospheric water vapor increases over the past half-century, Geophys. Res. Lett., 28, 1195–1198, 2001. Scherer, M., Vömel, H., Fueglistaler, S., Oltmans, S J., and Staehelin, J.: Trends and Variability of Midlatitude Stratospheric Water Vapor Deduced from the Re-evaluated Boulder Balloon Series and HALOE, Atmos. Chem. Phys., 8, 1390–1402, 2008. Schmidt, G A., Hoffmann, G., Shindell, D T., and Hu, Y.: Modeling Atmospheric Stable Water Isotopes and the Potential for Constraining Cloud Processes and Stratosphere-Troposphere Water Exchange, J. Geophys. Res., 110, D21314, doi:10.1029/2005JD005790, 2005. Schoeberl, M R., Duncan, B N., Douglass, A R., Waters, J., Livesey, N., Read, W., and Filipiak, M.: The Carbon Monoxide Tape Recorder, Geophys. Res. Lett., 33, L12811, doi:10.1029/2006GL026178, 2006. Schoeberl, M R., Ziemke, J R., Bojkov, B., Livesey, N., Duncnan, B., Strahan, S., Froidevaux, L., Kulawik, S., Bhartia, P K., Chandra, S., Levelt, P F., Witte, J C., Thompson, A M., Cuevas, E., Redondas, A., Tarasick, D W., Davis, J., Bodeker, G., Hansen, G., Johnson, B J., Oltmans, S J., Vömel, H., Allaart, M., Kelder, H., Newchurch, M., Godin-Beekmann, S., Ancellet, G., Claude, H., Andersen, S B., Kyrö, E., Parrondos, M., Yela, M., Zablocki, G., Moore, D., Dier, H., von~der Garthen, P., Viatte, P., Stübi, R., Calpini, B., Skrivankova, P., Dorokhov, V., de~Backer, H., Schmidlin, F J., Coetzee, G., Fujiwara, M., Thouret, V., Posny, F., Morris, G., Merrill, J., Leong, C P., Koenig-Langlo, G., and Joseph, E.: A trajectory-based estimate of the tropospheric ozone column using the residual method, J. Geophys. Res., 112, D24S49, doi:10.1029/2007JD008773, 2007. Schwartz, M J., Lambert, Manney, G L., Read, W G., Livesey, N J., Froidevaux, L., Ao, C O., Bernath, P F., Boone, C D., Cofield, R E., Daffer, W H., Drouin, B J., Fetzer, E J., Fuller, R A., Jarnot, R F., Jiang, J H., Jiang, Y B., Knosp, B W., Kruger, K., Li, J.-L F., Mlynczak, M G., Pawson, S., III, J. M R., Santee, M L., Snyder, W V., Stek, P C., Thurstans, R P., Tompkins, A M., Wagner, P A., Walker, K A., Waters, J W., and Wu, D L.: Validation of the Aura Microwave Limb Sounder Temperature and Geopotential Height Measurements, J. Geophys. Res., 113, D15S11, doi:10.1029/2007JD008783, 2008. Seidel, D J., Fu, Q., Randel, W J., and Reichler, T J.: Widening of the Tropical Belt in a Changing Climate, Nature Geoscience, 1, 21–24, \doi10.1038/ngeo.2007.38, 2 December 2007. Sherwood, S C.: A microphysical connection among biomass burning, cumulus clouds, and stratospheric moisture, Science, 295, 1272–1275, 2002. Sherwood, S C. and Dessler, A E.: On the control of stratospheric humidity, Geophys. Res. Lett., 27, 2513–2516, 2000. Sherwood, S C. and Dessler, A E.: A model for transport across the tropical tropopause, J. Atmos. Sci., 58, 765–779, 2001. Sherwood, S C. and Dessler, A E.: Convective mixing near the tropical tropopause: insights from seasonal variations, J. Atmos. Sci., 60, 2674–2685, 2003. Smith, J A., Ackerman, A S., Jensen, E J., and Toon, O B.: Role of Deep Convection in Establishing the Isotopic Composition of Water Vapor in the Tropical Transition Layer, Geophys. Res. Lett., 33, L06812, doi:10.1029/2005GL024078, 2006. Staniforth, A. and Côté, J.: Semi-Langrangian Integration Schemes for Atmospheric Models–A Review, Mon. Weather Rev., 119, 2206–2223, 1991. Wang, P.-H., Minnis, P., McCormick, M P., Kent, G S., and Skeens, K M.: A 6-year climatology of cloud occurrence frequency from Stratospheric Aerosol and Gas Experiment II observations (1985–1990), J. Geophys. Res., 101, 29 407–29 429, 1996. Waters, J W., Froidevaux, L., Harwood, R S., Jarnot, R F., Pickett, H M., Read, W G., Siegel, P H., Cofield, R E., Filipiak, M J., Flower, D A., Holden, J R., Lau, G K., Livesey, N J., Manney, G L., Pumphrey, H C., Santee, M L., Wu, D L., Cuddy, D T., Lay, R R., Lou, M S., Perun, V S., Schwartz, M J., Stek, P C., Thurstans, R P., Boyles, M A., Chandra, K M., Chavez, M C., Chen, G.-S., Chudasama, B V., Dodge, R., Fuller, R A., Girard, M A., Jiang, J H., Jiang, Y., Knosp, B W., LaBelle, R C., Lam, J C., Lee, K A., Miller, D., Oswald, J E., Patel, N C., Pukala, D M., Quintero, O., Scaff, D M., Snyder, W V., Tope, M C., Wagner, P A., and Walch, M J.: The Earth Observing System Microwave Limb Sounder (EOS MLS) on the Aura satellite, IEEE T. Geosci. Remote Sens., The EOS Aura Mission, 44, 1075–1092, 2006. Webster, C R. and Heymsfield, A J.: Water isotope ratios D/H, $^18$O/$^16$O, $^17$O/$^16$O in and out of clouds reveal dehydration pathways and the origin of cirrus, Science, 302, 1742–1745, 2003. Wong, S. and Dessler, A E.: Regulation of H₂O and CO in the Tropical Tropopause Layer by the Madden-Julian Oscillation, J. Geophys. Res., 112, D14305, doi:10.1029/2006JD007940, 2007. Wu, D L., Preusse, P., Eckermann, S., Jiang, J., de~la Torre~Juarez, M., Coy, L., and Wang, D.: Remote Sounding of Atmospheric Gravity Waves with Satellite Limb and Nadir Techniques, Adv. Space Res., 37, 2269–2277, 2006. Zhang, G J. and McFarlane, N A.: Sensitivity of climate simulations to the parameterization of cumulus convection in the Canadian Climate Centre General Circulation Model, Atmos. Ocean., 33, 407–446, 1995. Zhou, X.-L., Geller, M A., and Zhang, M.: Cooling Trend of the Tropical Cold Point Tropopause Temperatures and its Implications, J. Geophys. Res., 106, 1511–1522, 2001.