Summary
During the last phase of the Indian Middle Atmosphere Programme everyday launchings of high altitude balloons were carried out at three locations i.e. Trivandrum (8.5°N, 77.5°E), Hyderabad (17.2°N, 78.3°E) and Bhubaneshwar (21.3°N, 85.5°E) for measuring winds and temperature between 1 and 30 km altitude in a campaign mode from 23 January 1989 to 31 March 1989. The data thus obtained have been examined to determine the characteristics of tropical/equatorial waves. Spectral analysis of the time series (68 points) of both zonal and meridional wind components using Maximum Entropy Method (MEM) reveal the presence of waves with periods between 4–30 days.
Strong oscillations centered around 5 days and 18 days seem to dominate in the upper troposphere and lower stratosphere at all the three stations. While 5 day wave has an amplitude of about 2 m/s, the 18 day wave has an amplitude between 8–10 m/s in the zonal and 5–6 m/s in meridional component around tropopause. Its amplitude is maximum over Hyderabad and decreases somewhat on either side i.e. over Trivandrum and Bhubaneshwar. Weekly rocket wind data from Balasore near Bhubaneshwar show that 18–20 day wave continues to propagate vertically in the altitude range of 30–60 km. Temperature data also exhibits similar oscillations with amplitude of about 1 K for 4–5 day wave and 2–3 K for 18 day wave maximising just above tropopause (∼ 18 km).
It is found that some of the observed wave modes, particularly the 18 day wave have characteristics matching those of forced Rossby wave rather than Kelvin wave while the 5 day and 9 day waves have characteristics matching those of mixed Rossby-gravity waves. The latter may be generated due to convective forcing in the troposphere while the former may be penetrating from the midlatitudes.
Similar content being viewed by others
References
Andrews, D. G., Holton, J. R., Leovy, C. B., 1987:Middle Atmosphere Dynamics. Orlando, Florida, U.S.A.: Academic Press.
Akaike, H., 1969: Fitting autoregressive models for prediction.Ann. Inst. Stat. Math.,21, 243–247.
Barrodale, I., Erickson, R. E., 1980: Algorithms for least squares linear prediction and maximum entropy method. Part I—Theory.Geophysics,40, 420–446.
Chen, T.-C., 1987: 30–50 day oscillations of 200-mb temperature and 850-mb height during the 1979 northern summer.Mon. Wea. Rev.,115, 1589–1605.
Cornish, C. R., Larsen, M. F., 1985: A review of synoptic scale wave perturbations in the equatorial stratosphere.J. Atmos. Terr. Phys.,47, 769–780.
Depradine, C. A., 1981: Waves at 200-mb during GATE.Mon. Wea. Rev. USA,109, 975–982.
Devarajan, M., Reddy, C. A., Ragava Reddi, C., 1985: Rockei observations of Kelvin waves in the upper stratosphere over India.J. Atmos. Sci.,42, 1873–1879.
Fein, J. S., Stephens, P. L., Loughran, K. S., 1983: The Global Atmospheric Research Programme: 1979–1982.Rev. Geophys Space Phys.,21, 1076–1096.
Hartmann, D. L., Gross, J. R., 1988: Seasonal variability of the 40–50 day oscillations in wind and rainfall in the tropics.J. Atmos. Sci.,45, 2680–2702.
Hayashi, Y., 1974: Spectral analysis of tropical disturbances appearing in GFDL general circulation model.J. Atmos. Sci.,31, 180–218.
Holton, J. R., 1972: Waves in the equatorial stratosphere generated by tropospheric heat sources.J. Atmos. Sci.,29, 368–375.
Holton, J. R., 1975:The Dynamic Meteorology of the Stratosphere and Mesosphere. Meteorol. Monograph No. 37, Am. Meteor. Soc., Boston, Massachusetts.
Knutson, T. R., Weickmann, K. M., Kutzbach, J. F., 1986: Global scale intraseasonal oscillations of outgoing longwave radiation and 250-mb zonal wind during northernhemisphere summer.Mon. Wea. Rev.,114, 605–623.
Krishnamurti, T. N., Gadgil, S., 1985: On the structure of 30–50 day mode over the globe during the FGGE.Tellus,37A, 336–360.
Krishnamurthy, B. V., Indukumar, S., Reddi, C. R., Raghavarao, R., Rama, G. V., 1986: Results of equatorial wave campaign of IMAP in May–June 1984.Indian J. Radio Space Phys.,15, 125–138.
Longuet-Higgins, M. S., 1968: The eigne functions of Laplace tidal equations over a sphere.Phil. Trans. Roy. Soc. London (Ser. A),26A, 511–607.
Lau, K.-M., Chan, P. H., 1986: Aspects of 40–50 day oscillation during the Northern summer as inferred from outgoing lonwave radiation.Mon. Wea. Rev.,114, 1334–1367.
Lau, K.-M., Phillips, T., 1986: Coherent fluctuations of extratropical geopotential height and tropical convections in intraseasonal time scales.J. Atmos. Sci.,43, 1164–1181.
Lindzen, R. S., Tsay, C.-Y., 1985: Wave structure of the tropical stratosphere over the Marshall Islands area during 1 April–1 July 1958.J. Atmos. Sci.,32, 2008–2021.
Matsuno, T., 1966: Quasi-geostrophic motions in the equatorial area.J. Meteor. Soc. Japan,44, 25–43.
Maruyama, T., 1969: Long term behaviour of Kelvin waves and mixed-Rossby gravity waves.J. Meteor. Soc. Japan.,47, 245–254.
Madden, R. A., Julian, P. R., 1971: Detection of 40–50 day oscillation in the zonal wind in the tropical Pacific.J. Atmos. Sci.,28, 702–708.
Madden, R. A., Julian, P. R., 1972: Description of global scale circulation cells in the tropics with 40–50 day period.J. Atmos. Sci.,29, 1109–1123.
Madden, R. A., 1986: Seasonal variations of the 40–50 day oscillation in the tropics.J. Atmos. Sci.,43, 3138–3158.
Murakami, T., 1972: Equatorial tropospheric waves induced by diabatic heat sources.J. Atmos. Sci.,29, 827–836.
Murakami, M., 1979: Large scale aspects of deep convective activity over the GATE area.Mon. Wea. Rev.,107, 994–1013.
Nagpal, O. P., Raghavarao, R., 1991: On the wave forcing of the semi-annual zonal wind oscillation.J. Atmos. Terr. Phys.,53, 1181–1193.
Raghavarao, R., Suhasini, R., Sridharan, R., Krishnamurthy, B. V., Nagpal, O. P., 1990: Vertical structure and characteristics of 23–60 day (zonal) oscillations over tropical latitudes during the winter months of 1986: Results of equatorial wave campaign—II.Proc. Indian Acad. Sci.,99, 413–423.
Reed, R. J., 1981: Upper tropospheric waves in the subtropical pacific during SOP-I of FGGE and their interaction with the ICCZ, Paper presented at the IAMAP Symp. on the general circulation of atmosphere II—Tropical aspects, Hamburg, FRG. 17–19 Aug 1981.
Salby, M. L., 1984: Survey of planetary-scale travelling waves: The state of theory and observations.Rev. Geophys. Space Phys.,22, 209–236.
Salby, M. L., Hartmann, D. L., Bailey, P. B., Gille, J. C., 1984: Evidence for equatorial Kelvin modes in Nimbus-7 LIMS.J. Atmos. Sci.,41, 220–235.
Simmons, A. J., 1982: The forcing of stationary wave motions by tropical diabatic heating.Quart. J. Roy. Meteor. Soc.,108, 503–534.
Schodel, J. P., Munk, J. W., 1972: Methoden zur Untersuchung der spektralen Frequenzerverteilung von Schwerewellen in der Ionosphere.Z. Geophys.,38, 169.
Wallace, J. M., 1973: General circulation of the tropical lower stratosphere.Rev. Geophys. Space Phys.,11, 191–222.
Wallace, J. M., Kousky, V. E., 1968: Observational evidence of Kelvin waves in the tropical atmosphere.J. Atmos. Sci.,25, 900–907.
Wallace, J. M., Chang, H-R., 1988: Equatorial energy accumulation and emanation regions: Impact of zonally varying basic state.J. Atmos. Sci.,45, 803–829.
Webster, P. J., Holton, J. R., 1982: Cross equatorial response to mid latitude forcing in a zonally varying basic state.J. Atoms. Sci.,39, 722–733.
Yanai, M., 1966: Stratospheric wave disturbances propagating over the equatorial pacific.J. Meteor. Soc. Japan.,44, 291–294.
Yasunari, T., 1981: Structure of an Indian summer monsoon system with around 40 day period.J. Meteor. Soc. Japan.,59, 336–354.
Zangvil, A., 1977: On the presentation and interpretation of spectra of long scale disturbances.Mon. Wea. Rev.,105, 1469–1472.
Zangvil, A., Yanai, M., 1980: Upper tropospheric waves in the tropics. Part-I: Dynamical analysis in the wave number-frequency domain.J. Atmos. Sci.,37, 283–298.
Author information
Authors and Affiliations
Additional information
With 15 Figures
Rights and permissions
About this article
Cite this article
Dhaka, S.K., Kumar, A. & Nagpal, O.P. Some studies of tropical/equatorial waves over Indian Tropical Middle Atmosphere: Results of tropical wave campaign. Meteorl. Atmos. Phys. 51, 25–39 (1993). https://doi.org/10.1007/BF01080878
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF01080878