• Allan, R. P., , K. P. Shine, , A. Slingo, , and J. A. Pamment, 1999: The dependence of clear-sky outgoing long-wave radiation on surface temperature and relative humidity. Quart. J. Roy. Meteor. Soc., 125, 21032126, doi:10.1002/qj.49712555809.

    • Search Google Scholar
    • Export Citation
  • Aumann, H. H., , A. Ruzmaikin, , and A. Behrangi, 2012: On the surface temperature sensitivity of the reflected shortwave, outgoing longwave, and net incident radiation. J. Climate, 25, 65856593, doi:10.1175/JCLI-D-11-00607.1.

    • Search Google Scholar
    • Export Citation
  • Bony, S., , K. M. Lau, , and Y. C. Sud, 1997: On the surface temperature sensitivity of the reflected shortwave, outgoing longwave, and net incident radiation. J. Climate, 10, 20552077, doi:10.1175/1520-0442(1997)010<2055:SSTALS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chaudhuri, P., , and J. S. Marron, 1999: SiZer for exploration of structure in curves. J. Amer. Stat. Assoc., 94, 807823, doi:10.1080/01621459.1999.10474186.

    • Search Google Scholar
    • Export Citation
  • Chung, E.-S., , D. Yeomans, , and B. I. Soden, 2010: An assessment of climate feedback processes using satellite observations of clear-sky OLR. Geophys. Res. Lett., 37, L02702, doi:10.1029/2009GL041889.

    • Search Google Scholar
    • Export Citation
  • Dessler, A. E., 2010: A determination of the cloud feedback from climate variations over the past decade. Science, 330, 15231527, doi:10.1126/science.1192546.

    • Search Google Scholar
    • Export Citation
  • Dessler, A. E., , P. Yang, , J. Lee, , J. Solbrig, , Z. Zhang, , and K. Minschwaner, 2008: An analysis of the dependence of clear-sky top-of-atmosphere outgoing longwave radiation on atmospheric temperature and water vapor. J. Geophys. Res., 113, D17102, doi:10.1029/2008JD010137.

    • Search Google Scholar
    • Export Citation
  • DISC, cited 2013: Aqua AIRS version 6 level 2 data now available. [Available online at disc.sci.gsfc.nasa.gov/datareleases/aqua-airs-version-6.]

  • Du, J., , F. Cooper, , and S. Fueglistaler, 2012: Statistical analysis of global variations of atmospheric relative humidity as observed by AIRS. J. Geophys. Res., 117, D12315, doi:10.1029/2012JD017550.

    • Search Google Scholar
    • Export Citation
  • Fasullo, J. T., , and K. E. Trenberth, 2012: A less cloudy future: The role of subtropical subsidence in climate sensitivity. Science, 338, 792794, doi:10.1126/science.1227465.

    • Search Google Scholar
    • Export Citation
  • Gettelman, A., , W. D. Collins, , E. J. Fetzer, , A. Eldering, , and F. W. Irion, 2006: Climatology of upper-tropospheric relative humidity from the Atmospheric Infrared Sounder and implications for climate. J. Climate, 19, 61046121, doi:10.1175/JCLI3956.1.

    • Search Google Scholar
    • Export Citation
  • Gibbs, J. W., 1876: On the equilibrium of heterogeneous substances. The Collected Works of J. Willard Gibbs, Vol. 2, W. R. Longley and R. G. Van Name, Eds., Yale University Press, 1–531.

  • Hartigan, J. A., , and P. M. Hartigan, 1985: The dip test of unimodality. Ann. Stat., 13, 7084, doi:10.1214/aos/1176346577.

  • Held, I. M., , and B. J. Soden, 2000: Water vapor feedback and global warming. Annu. Rev. Energy Environ., 25, 441475, doi:10.1146/annurev.energy.25.1.441.

    • Search Google Scholar
    • Export Citation
  • Held, I. M., , and K. M. Shell, 2012: Using relative humidity as a state variable in climate feedback analysis. J. Climate, 25, 25782582, doi:10.1175/JCLI-D-11-00721.1.

    • Search Google Scholar
    • Export Citation
  • Inamdar, A. K., , and V. Ramanathan, 1994: Physics of greenhouse effect and convection in warm oceans. J. Climate, 7, 715731, doi:10.1175/1520-0442(1994)007<0715:POGEAC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Kahn, B. H., , A. Gettelman, , E. J. Fetzer, , A. Eldering, , and C. K. Liang, 2009: Cloudy and clear-sky relative humidity in the upper troposphere observed by the A-train. J. Geophys. Res., 114, D00H02, doi:10.1029/2009JD011738.

    • Search Google Scholar
    • Export Citation
  • Manabe, S., , and R. T. Wetherald, 1967: Thermal equilibrium of the atmosphere with a given distribution of relative humidity. J. Atmos. Sci., 24, 241259, doi:10.1175/1520-0469(1967)024<0241:TEOTAW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., 2001: Water’s two height scales: The moist adiabat and the radiative troposphere. Quart. J. Roy. Meteor. Soc., 127, 23532366, doi:10.1002/qj.49712757708.

    • Search Google Scholar
    • Export Citation
  • Minschwaner, K., , and M. B. McElroy, 1992: A model for the energy budget of the atmosphere: Comparison with data from the Earth Radiation Budget Experiment. Planet. Space Sci., 40, 12371250, doi:10.1016/0032-0633(92)90081-X.

    • Search Google Scholar
    • Export Citation
  • Minschwaner, K., , and A. E. Dessler, 2004: Water vapor feedback in the tropical upper troposphere: Model results and observations. J. Climate, 17, 12721282, doi:10.1175/1520-0442(2004)017<1272:WVFITT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Peixoto, J. P., , and A. H. Ort, 1996: The climatology of relative humidity in the atmosphere. J. Climate, 9, 34433463, doi:10.1175/1520-0442(1996)009<3443:TCORHI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Raval, A., , and V. Ramanathan, 1989: Observational determination of the greenhouse effect. Nature, 342, 758761, doi:10.1038/342758a0.

  • Raval, A., , A. H. Ort, , and V. Ramaswamy, 1994: Observed dependence of outgoing longwave radiation on sea surface temperature and moisture. J. Climate, 7, 807821, doi:10.1175/1520-0442(1994)007<0807:ODOOLR>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Read, W. G., and Coauthors, 2007: Aura Microwave Limb Sounder upper tropospheric and lower stratospheric H2O and relative humidity with respect to ice validation. J. Geophys. Res., 112, D24S35, doi:10.1029/2007JD008752.

    • Search Google Scholar
    • Export Citation
  • Risi, C., and Coauthors, 2012: Process-evaluation of tropospheric humidity simulated by general circulation models using water vapor isotopic observations: 2. Using isotopic diagnostics to understand the mid and upper tropospheric moist bias in the tropics and subtropics. J. Geophys. Res., 117, D05304, doi:10.1029/2011JD016623.

    • Search Google Scholar
    • Export Citation
  • Ryoo, J.-M., , T. Igusa, , and D. W. Waugh, 2009: PDFs of tropical tropospheric humidity: Measurements and theory. J. Climate, 22, 33573373, doi:10.1175/2008JCLI2747.1.

    • Search Google Scholar
    • Export Citation
  • Schmetz, J., , and L. van de Berg, 1994: Upper tropospheric humidity observations from Meteosat compared with short-term forecast fields. Geophys. Res. Lett., 21, 573576, doi:10.1029/94GL00376.

    • Search Google Scholar
    • Export Citation
  • Sherwood, S. C., , E. R. Kursinski, , and W. G. Read, 2006: A distribution law for free-tropospheric relative humidity. J. Climate, 19, 62676277, doi:10.1175/JCLI3978.1.

    • Search Google Scholar
    • Export Citation
  • Sherwood, S. C., , W. Ingram, , Y. Tsushima, , M. Satoh, , M. Roberts, , P. L. Vidale, , and P. A. O’Gorman, 2010: Relative humidity changes in a warmer climate. J. Geophys. Res., 115, D09104, doi:10.1029/2009JD012585.

    • Search Google Scholar
    • Export Citation
  • Soden, B. J., , and F. P. Bretherton, 1993: Upper tropospheric relative humidity from the GOES 6.7μm channel method and climatology for July 1987. J. Geophys. Res., 98, 16 66916 688, doi:10.1029/93JD01283.

    • Search Google Scholar
    • Export Citation
  • Spencer, R. W., , and W. D. Braswell, 1997: How dry is the tropical free troposphere? Implications for global warming theory. Bull. Amer. Meteor. Soc., 78, 10971106, doi:10.1175/1520-0477(1997)078<1097:HDITTF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Stephens, G. L., 1990: On the relationship between water vapor over the oceans and sea surface temperature. J. Climate,3, 634–645, doi:10.1175/1520-0442(1990)003<0634:OTRBWV>2.0.CO;2.

  • Su, H., , W. G. Read, , J. H. Jiang, , J. W. Waters, , D. L. Wu, , and E. J. Fetzer, 2006: Enhanced positive water vapor feedback associated with tropical deep convection: New evidence from Aura MLS. Geophys. Res. Lett., 33, L05709, doi:10.1029/2005GL025505.

    • Search Google Scholar
    • Export Citation
  • Susskind, J., , G. Molnar, , L. Iredell, , and N. G. Loeb, 2012: Interannual variability of outgoing longwave radiation as observed by AIRS and CERES. J. Geophys. Res., 117, D23107, doi:10.1029/2012JD017997.

    • Search Google Scholar
    • Export Citation
  • Waliser, D. E., 1996: Formation and limiting mechanisms for very high sea surface temperature: Linking the dynamics and the thermodynamics. J. Climate, 9, 161188, doi:10.1175/1520-0442(1996)009<0161:FALMFV>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Waliser, D. E., , N. E. Graham, , and C. Gautier, 1993: Comparison of the highly reflective cloud and outgoing longwave radiation datasets for use in estimating tropical deep convection. J. Climate, 6, 331353, doi:10.1175/1520-0442(1993)006<0331:COTHRC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Wright, J. S., , A. Sobel, , and J. Galewsky, 2010: Diagnosis of zonal mean relative humidity changes in a warmer climate. J. Climate, 23, 45564569, doi:10.1175/2010JCLI3488.1.

    • Search Google Scholar
    • Export Citation
  • Yang, H., , and R. T. Pierrehumbert, 1994: Production of dry air by isentropic mixing. J. Atmos. Sci., 51, 34373454, doi:10.1175/1520-0469(1994)051<3437:PODABI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Zhang, C., , B. E. Mapes, , and B. J. Soden, 2003: Bimodality in tropical water vapour. Quart. J. Roy. Meteor. Soc., 129, 28472866, doi:10.1256/qj.02.166.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 144 144 33
PDF Downloads 115 115 32

Relative Humidity in the Troposphere with AIRS

View More View Less
  • 1 Jet Propulsion Laboratory, Pasadena, California
© Get Permissions
Restricted access

Abstract

New global satellite data from the Atmospheric Infrared Sounder (AIRS) are applied to study the tropospheric relative humidity (RH) distribution and its influence on outgoing longwave radiation (OLR) for January and July in 2003, 2007, and 2011. RH has the largest maxima over 90% in the equatorial tropopause layer in January. Maxima in July do not arise above 60%. Seasonal variations of about 20% in zonally averaged RH are observed in the equatorial region of the low troposphere, in the equatorial tropopause layer, and in the polar regions. The seasonal variability in the recent decade has increased by about 5% relative to that in 1973–88, indicating a positive trend. The observed RH profiles indicate a moist bias in the tropical and subtropical regions typically produced by the general circulation models. The new data and method of evaluating the statistical significance of bimodality confirm bimodal probability distributions of RH at large tropospheric scales, notably in the ascending branch of the Hadley circulation. Bimodality is also seen at 500–300 hPa in mid- and high latitudes. Since the drying time of the air is short compared with the mixing time of moist and dry air, the bimodality reflects the large-scale distribution of sources of moisture and the atmospheric circulation. Analysis of OLR dependence on surface temperature shows a 0.2 W m−2 K−1 difference in sensitivities between clear-sky and all-sky OLR, indicating a positive longwave cloud radiative forcing. Diagrams of the clear-sky OLR as functions of percentiles of surface temperature and relative humidity in the tropics are designed to provide a new measure of the supergreenhouse effect.

Corresponding author address: Alexander Ruzmaikin, MS 169-506, Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109. E-mail: alexander.ruzmaikin@jpl.nasa.gov

Abstract

New global satellite data from the Atmospheric Infrared Sounder (AIRS) are applied to study the tropospheric relative humidity (RH) distribution and its influence on outgoing longwave radiation (OLR) for January and July in 2003, 2007, and 2011. RH has the largest maxima over 90% in the equatorial tropopause layer in January. Maxima in July do not arise above 60%. Seasonal variations of about 20% in zonally averaged RH are observed in the equatorial region of the low troposphere, in the equatorial tropopause layer, and in the polar regions. The seasonal variability in the recent decade has increased by about 5% relative to that in 1973–88, indicating a positive trend. The observed RH profiles indicate a moist bias in the tropical and subtropical regions typically produced by the general circulation models. The new data and method of evaluating the statistical significance of bimodality confirm bimodal probability distributions of RH at large tropospheric scales, notably in the ascending branch of the Hadley circulation. Bimodality is also seen at 500–300 hPa in mid- and high latitudes. Since the drying time of the air is short compared with the mixing time of moist and dry air, the bimodality reflects the large-scale distribution of sources of moisture and the atmospheric circulation. Analysis of OLR dependence on surface temperature shows a 0.2 W m−2 K−1 difference in sensitivities between clear-sky and all-sky OLR, indicating a positive longwave cloud radiative forcing. Diagrams of the clear-sky OLR as functions of percentiles of surface temperature and relative humidity in the tropics are designed to provide a new measure of the supergreenhouse effect.

Corresponding author address: Alexander Ruzmaikin, MS 169-506, Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109. E-mail: alexander.ruzmaikin@jpl.nasa.gov
Save