Analysis of the ENSO signal in tropospheric and stratospheric temperatures observed by MSU, 1979-2000

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The El Niño-Southern Oscillation (ENSO) signal in the troposphere and lower stratosphere was investigated using Microwave Sounding Unit (MSU) data for the period 1979-2000. Empirical orthogonal functions (EOFs) were computed separately for zonal-mean and eddy temperatures in the Tropics and shown to provide a compact, physically intuitive description of ENSO that captures many of the details of its inception and evolution. Regressions of the MSU data on the principal components (PCs) of the tropical EOFs were then used to estimate the global signal of ENSO. The results show that ENSO accounts for over two-thirds of the temperature variability in the tropical troposphere, where its signature is composed of distinct zonal-mean and eddy patterns whose evolution is not simultaneous. In the tropical stratosphere, and outside the Tropics, ENSO explains a much smaller fraction of the variance (similar to10%), and manifests itself purely in the form of eddy anomaly patterns. The PCs of the eddy EOFs of the tropical stratosphere are almost perfectly correlated with those of the troposphere, suggesting that together the EOFs describe the vertical structure of equatorial waves. Volcanic eruptions and the quasi-biennial oscillation (QBO) are responsible for most of the variability (similar to87%) of the tropical lower stratosphere, and this variability is uncorrelated with ENSO; in the tropical troposphere, the effect of volcanic eruptions is detectable but small, accounting for about 3% of the variance.
© 2004 American Meteorological Society. The National Center for Atmospheric Research is sponsored by the National Science Foundation. We thank Jon Eischeid for his help in obtaining the MSU data used in this paper, and Henry Diaz, Dan Marsh, Bill Randel, and Anne Smith for discussions and suggestions on the original manuscript.
Angell, J. K., 1981: Comparison of variations in atmospheric quantities with sea surface temperature variations in the equatorial eastern Pacific. Mon. Wea. Rev, 109, 230–243. Angell, J. K., 2000a: Tropospheric temperature variations adjusted for El Niño, 1958–1998. J. Geophys. Res, 105, 11841–11849. Angell, J. K., 2000b: Difference in radiosonde temperature trend for the period 1979–1998 of MSU data and the period 1959–1998 twice as long. Geophys. Res., Lett, 27, 2177–2180. Baldwin, M. P., and D. O'Sullivan, 1995: Stratospheric effects of ENSO-related tropospheric circulation anomalies. J. Climate, 8, 649–667. Charney, J. G., and P. G. Drazin, 1961: Propagation of planetary-scale disturbances from the lower into the upper atmosphere. J. Geophys. Res, 66, 83–109. Christy, J. R., and S. J. Drouilhet, 1994: Variability in daily, zonal mean lower-stratospheric temperatures. J. Climate, 7, 106–120. Christy, J. R., and R. T. McNider, 1994: Satellite greenhouse signal. Nature, 367, 325. Christy, J. R., R. W. Spencer, and W. D. Braswell, 2000: MSU tropospheric temperatures: Dataset construction and radiosonde comparisons. J. Atmos. Oceanic Technol, 17, 1153–1170. Díaz, H. F., M. P. Hoerling, and J. K. Eischeid, 2001: ENSO variability, teleconnections and climate change. Int. J. Climatol, 21, 1845–1862. García, R. R., and M. L. Salby, 1987: Transient response to localized episodic heating in the Tropics. Part II: Far-field behavior. J. Atmos. Sci, 44, 499–530. Geisler, J. E., 1981: A linear model of the Walker circulation. J. Atmos. Sci, 38, 1390–1400. Gill, A. E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. Roy. Meteor. Soc, 106, 447–462. Halpert, M. S., and C. F. Ropelewski, 1992: Surface temperature patterns associated with the Southern Oscillation. J. Climate, 5, 577–593. Hamilton, K., 1993: An examination of observed Southern Oscillation effects in the Northern Hemisphere stratosphere. J. Atmos. Sci, 50, 3468–3473. Horel, J. D., and J. M. Wallace, 1981: Planetary-scale atmospheric phenomena associated with the Southern Oscillation. Mon. Wea. Rev, 109, 813–829. Horinouchi, T., and S. Yoden, 1996: Excitation of transient waves by localized episodic heating in the Tropics and their propagation into the middle atmosphere. J. Meteor. Soc. Japan, 74, 189–210. Hoskins, B. J., and D. Karoly, 1981: The steady linear response of a spherical atmosphere to thermal and orographic forcing. J. Atmos. Sci, 38, 1179–1196. Hurrell, J. W., S. J. Brown, K. E. Trenberth, and J. R. Christy, 2000: Comparison of tropospheric temperatures from radiosondes and satellites: 1979–98. Bull. Amer. Meteor. Soc, 81, 2165–2177. Jones, P. D., 1989: The influences of ENSO on global temperatures. Climate Monit, 17, 80–89. Kelly, P. M., and P. D. Jones, 1996: Removal of El Niño–Southern Oscillation signal from the gridded surface air temperature data set. J. Geophys. Res, 101, 19013–19022. Kiladis, G. N., and H. F. Diaz, 1989: Global climatic anomalies associated with extremes in the Southern Oscillation. J. Climate, 2, 1069–1090. Lau, K. M., P. J. Shen, and I. S. Kang, 1994: Multiscale low-frequency circulation modes in the global atmosphere. J. Atmos. Sci, 51, 1169–1193. Michaels, P. J., and P. C. Knappenberger, 2000: Natural signals in the MSU lower troposphere temperature record. Geophys. Res. Lett, 27, 2905–2908. Oort, A. H., and J. J. Yienger, 1996: Observed interannual variability in the Hadley circulation and its connection to ENSO. J. Climate, 9, 2751–2767. Pan, Y. H., and A. H. Oort, 1983: Global climate variations connected with sea surface temperature anomalies in the eastern tropical Pacific Ocean for the 1958–73 period. Mon. Wea. Rev, 111, 1244–1258. Randel, W., R. R. Garcia, and F. Wu, 2002: Time-dependent upwelling in the tropical lower stratosphere estimated from the zonal-mean momentum budget. J. Atmos. Sci, 59, 2141–2152. Rasmusson, E. M., and T. H. Carpenter, 1982: Variations in tropical sea surface temperature and surface wind fields associated with the Southern Oscillation/El Niño. Mon. Wea. Rev, 110, 354–384. Reid, G. C., K. S. Gage, and J. R. McAfee, 1989: The thermal response of the tropical atmosphere to variations in equatorial Pacific sea surface temperature. J. Geophys. Res, 94, 14705–14716. Richman, M. B., 1986: Rotation of principal components. J. Climatol, 6, 293–335. Sato, M., J. E. Hansen, M. P. McCormick, and J. B. Pollack, 1993: Stratospheric aerosol optical depths, 1850–1990. J. Geophys. Res, 98, 22987–22994. Spencer, R. W., and J. R. Christy, 1993: Precision lower stratospheric temperature monitoring with the MSU: Technique, validation and results 1979–1991. J. Climate, 6, 1194–1204. Trenberth, K. E., and J. M. Caron, 2000: The Southern Oscillation revisited: Sea level pressures, surface temperatures and precipitation. J. Climate, 13, 4358–4365. Trenberth, K. E., J. M. Caron, D. P. Stepaniak, and S. Worley, 2002: Evolution of El Niño–Southern Oscillation and global atmospheric surface temperatures. J. Geophys. Res.,107, 4065, doi:10.1029/ 2000JD000298. van Loon, H., and K. Labitzke, 1987: The Southern Oscillation. Part V: The anomalies in the lower stratosphere of the Northern Hemisphere in winter and a comparison with the quasi-biennial oscillation. Mon. Wea. Rev, 115, 357–369. von Storch, H., and F. W. Zwiers, 1999: Statistical Analysis in Climate Research. Cambridge University Press, 484 pp. Wallace, J. M., and D. S. Gutzler, 1981: Teleconnections in the geopotential height field during the Northern Hemisphere winter. Mon. Wea. Rev, 109, 784–812. Wallace, J. M., and F-C. Chang, 1982: Interannual variability of the wintertime polar vortex in the Northern Hemisphere middle stratosphere. J. Meteor. Soc. Japan, 60, 149–155. Xu, J., 1992: On the relationship between the stratospheric quasibiennial oscillation and the tropospheric Southern Oscillation. J. Atmos. Sci, 49, 725–734. Yulaeva, E., and J. M. Wallace, 1994: The signature of ENSO in global temperature and precipitation fields derived from the microwave sounding unit. J. Climate, 7, 1719–1736.