ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-30-1623-2012 Intraseasonal oscillation (ISO) in the MLT zonal wind over Kolhapur (16.8° N) and Tirunelveli (8.7° N) Rokade M. V. 1 Kondala Rao R. 2 Nikte S. S. 1 Ghodpage R. N. 3 Patil P. T. 3 Sharma A. K. 1 Gurubaran S. 4 Earth and Space Science Laboratory, Department of Physics, Shivaji University Kolhapur, 416004, India Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India Medium Frequency Radar, Indian Institute of Geomagnetism, Shivaji University Campus, Kolhapur, 416004, India Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli, 627 011, India 05 12 2012 30 12 1623 1631 Copyright: © 2012 M. V. Rokade et al. 2012 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/30/1623/2012/angeo-30-1623-2012.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/30/1623/2012/angeo-30-1623-2012.pdf

Simultaneous observations of the mean zonal winds at 88 km obtained by the medium-frequency (MF) radars at Kolhapur (16.8° N, 74.2° E) and Tirunelveli (8.7° N, 77.8° E) have been used to study the intraseasonal oscillation (ISO) in the MLT region. The influences of the intraseasonal variations in the lower tropospheric convective activity associated with the Madden-Julian oscillations on the latitudinal behavior of intraseasonal oscillations (ISO) of the zonal winds in the equatorial mesosphere and lower thermosphere (MLT) have been studied. The ISO activity in the lower tropospheric convective activity is examined by employing outgoing long wave radiation (OLR) as a proxy for deep convective activity occurring in the tropical lower atmosphere. The ISO activity in the zonal wind over TIR is more correlated with that in the convective activity compared to the ISO over KOL. The latitudinal and temporal variabilities of the ISO in MLT zonal winds are explained in terms of the intraseasonal variabilities in the convective activity.

 References Baldwin, M. P., Baldwin, M. P., Gray, L. J., Dunkerton, T. J., Hamilton, K., Haynes, P. H., Randel, W. J., Holton, J. R., Alexander, M. J., Hirota, I., Horinouchi, T., Jones, D. B. A., Kinnersley, J. S., Marquardt, C., Sato, K., and Takahashi, M.: The quasi-biennial oscillation, Rev. Geophys., 39, 179–229, 2001. Burrage, M. D., Vincent, R. A., Mayr, H. G., Skinner, W. R., Arnold, N. F., and Hays, P. B.: Long-term variability in the equatorial middle atmosphere zonal wind, J. Geophys. Res., 101, 12847–12854, 1996. Dunkerton, T. J.: On the role of the Kelvin wave in the westerly phase of the semimmual zonal wind oscillation, J. Atmos. Sci., 36, 32–41, 1979. Dunkerton, T. J.: Theory of the mesopause semiannual oscillation, J. Atmos. Sci., 41, 1755–1764, 1982. Dunkerton, T. J.: The role of gravity waves in the quasibiennial oscillation, J. Geophys. Res., 102, 26053–26076, <a href="http://dx.doi.org/10.1029/96JD02999">https://doi.org/10.1029/96JD02999</a>, 1997. Ebdon, R. A.: Notes on the wind flow at 50 mb in tropical and sub-tropical regions in January 1957 and January 1958, Q. J. Roy. Meteorol. Soc., 86, 540–542, 1960. Eckermann, S. D. and Vincent, R. A.: First observations of intraseasonal oscillations in the equatorial mesosphere and lower thermosphere, Geophys. Res. Lett., 21, 265–268, 1994. Eckermann, S. D., Rajopadhyaya, D. K., and Vincent, R. A.: Intraseasonal wind variability in the equatorial mesosphere and lower thermosphere: Long-term observations from the central Pacific, J. Atmos. Terr. Phys., 59, 603–627, 1997. Garcia, R. R.: The role of equatorial waves in the semiannual oscillation of the middle atmosphere, in Atmospheric Science Across the Stratopause, Geophys. Monogr. Ser., vol. 123, pp. 161–176, Washington, D.C., 2000. Garcia, R. R., Dunkerton, T. J., Lieberman, R. S., and Vincent, R. A.: Climatology of the semiannual oscillation of the tropical middle atmosphere, J. Geophys. Res., 102, 26019–26032, 1997. Garcia, R. R., Lieberman, R. S., Russell, J. M., and Mlynczak, M. G.: Large-Scale Waves in the Mesosphere and Lower Thermosphere Observed by SABER, JAS, May 2005. Hamilton, K. P.: Rocketsonde observations of the mesospheric semiannual oscillation at Kwajalein, Atmos. Ocean., 20, 281–286, 1982. Hendon, H. H. and Salby, M. L.: The life cycle of the Madden-Julian Oscillation, J. Atmos. Sci., 51, 2225–2237, 1994. Hendon, H. H. and Woodberry, K.: The diurnal cycle of tropical convection, J. Geophys. Res., 98, 16623–16637, <a href="http://dx.doi.org/10.1029/93JD00525">https://doi.org/10.1029/93JD00525</a>, 1993. Hirota, I.: Equatorial waves in the upper stratosphere and mesosphere in relation to the semiannual oscillation of the zonal wind, J. Atmos. Sci., 35, 714–722, 1978. Isoda, F., Tsuda, T., Nakamura, T., Murayama, Y., Igarashi, K., Vincent, R. A., Reid, I. M., Nuryanto, A., and Manurung, S. L.: Long-period wind oscillations in the mesosphere and lower thermosphere at Yamagawa (30 N, 131 E), Pontianak (0 N, 109 E) and Christmas Island (2 N, 157 W), J. Atmos. Sol. Terr. Phys., 64, 1055–1067, 2002. Isoda, F., Tsuda, T., Nakamura, T., Vincent, R. A., Reid, I. M., Achmad, E., Sadewo, A., and Nuryanto, A.: Intraseasonal oscillations of the zonal wind near the mesopause observed with medium-frequency and meteor radars in the tropics, J. Geophys. Res., 109, D21108, <a href="http://dx.doi.org/10.1029/2003JD003378">https://doi.org/10.1029/2003JD003378</a>, 2004. Knutson, T. R. and Kutzbach, J. E.: Global-scale intraseasonal oscillations of outgoing longwave radiation and 250 mb zonal wind during Northern Hemisphere summer, Mon. Weather Rev., 114, 605–623, 1986. Kovalam, S., Vincent, R. A., Reid, I. M., Tsuda, T., Nakamura, T., Nuryanto, A., and Wiryosumarto, H.: Longitudinal variations in planetary wave activity in the equatorial mesosphere, Earth Planets Space, 51, 665–674, 1999. Kumar, K. and Jain, A. R.: Latitudinal variations of 30–70&nbsp;day period waves over the tropical Indian zone, J. Atmos. Terr. Phys., 56, 1135–1145, 1994. Kumar, K. K., Antonia, T. M., Ramkumar, G., Deepa, V., Gurubaran, S., and Rajaram, R.: On the tropospheric origin of mesosphere and lower thermosphere wind variability, J. Geophys. Res., 112, D07109, <a href="http://dx.doi.org/10.1029/2006JD007962">https://doi.org/10.1029/2006JD007962</a>, 2007. Lau, K. M. and Chan, P. H.: Aspects of the 40–50&nbsp;day oscillation during the northern winter as inferred from outgoing longwave radiation, Mon. Weather Rev., 113, 1889–1909, 1985. Lau, K. M. and Waliser, D. E.: Intraseasonal Variability in the Atmosphere-Ocean Climate System, 474 pp., Springer Praxis, New York, 2004. Lieberman, R. S.: Intraseasonal variability of high-resolution Doppler Imager winds in the equatorial mesosphere and lower thermosphere, J. Geophys. Res., 103, 11221–11228, <a href="http://dx.doi.org/10.1029/98JD00532">https://doi.org/10.1029/98JD00532</a>, 1998. Lindzen, R. S. and Holton, J. R.: A theory of the quasi-biennial oscillation, J. Atmos. Sci., 25, 1095–1107, 1968. Madden, R. A. and Julian, P. R.: Detection of a 40–50 day oscillation of the zonal wind in the tropical Pacific, J. Atmos. Sci., 28, 702–708, 1971. Madden, R. A. and Julian, P. R.: Description of global-scale circulation cells in the tropics with a 40–50 day period, J. Atmos. Sci., 29, 1109–1123, 1972. Madden, R. A. and Julian, P. R.: Observations of the 40–50-day tropical oscillation: A review, Mon. Weather Rev., 122, 814–837, 1994. Matthews, A. J.: Propagation mechanism for the Madden-Julian Oscillation, Q. J. Roy. Meteorol. Soc., 126, 2637–2651, 2000. Matsuno, T.: Quasi-geostrophic motions in the equatorial area, J. Meteorol. Soc. Jpn., 44, 25–43, 1966. Miyoshi, Y. and Fujiwara, H.: Excitation mechanism of intraseasonal oscillation in the equatorial mesosphere and lower thermosphere, J. Geophys. Res., 111, D14108, <a href="http://dx.doi.org/10.1029/2005JD006993">https://doi.org/10.1029/2005JD006993</a>, 2006. Mota Lima, L., Alves, E. de Oliveira, Medeiros, A. F., Buriti, R. A., Batista, P. P., Clemesha, B. R., and Takahashi, H.: 3–4&nbsp;day Kelvin waves observed in the MLT region at 7.4° S Brazil, Geofísica Internacional, 47, 153–160, 2008. Nagpal, O. P. and Raghavarao, R.: On the wave forcing of the semiannual zonal wind oscillation, J. Atmos. Terr. Phys., 53, 1181–1193, 1991. Nagpal, O. P., Dhaka, S. K., and Srivastav, S. K.: Wave characteristics in the troposphere and stratosphere over the Indian tropics during the DYANA campaign, J. Atmos. Terr. Phys., 56, 1117–1133, 1994. Nakazawa, T.: Intraseaonal variations in OLR in the tropics during the FGGE year, J. Meteorol. Soc. Jpn., 64, 17–34, 1986. Rajaram, R. and Gurubaran, S.: Seasonal variabilities of low-latitude mesospheric winds, Ann. Geophys., 16, 197–204, <a href="http://dx.doi.org/10.1007/s00585-998-0197-4">https://doi.org/10.1007/s00585-998-0197-4</a>, 1998. Rao, R. K., Gurubaran, S., Sathishkumar, S., Sridharan, S., Nakamura, T., Tsuda, T., Takahashi, H., Batista, P. P., Clemesha, B. R., Buriti, R. A., Pancheva, D. V., and Mitchell, N. J.: Longitudinal varibility in intraseasonal oscillation in the tropical mesosphere and lower thermosphere region, J. Geophys. Res., 114, D19110, <a href="http://dx.doi.org/10.1029/2009JD011811">https://doi.org/10.1029/2009JD011811</a>, 2009. Reed, R. J., Campbell, W. J., Rasmussen, L. A., and Rogers, R. G.: Evidence of a downward propagating annual wind reversal in the equatorial stratosphere, J. Geophys. Res., 66, 813–818, 1961. Riggin, D., Fritts, D. C., Tsuda, T., Nakamura, T., and Vincent, R. A.: Radar observations of a 3-day Kelvin wave in the equatorial mesosphere, J. Geophys. Res., 102, 26141–26157, 1997. Sridharan, S., Gurubaran, S., and Rajaram, R.: QBO influences on the variability of planetary waves in the equatorial mesopause region, Earth Planets Space, 55, 687–696, 2003. Sridharan, S., Tsuda, T., and Gurubaran, S.: Radar observations of long-term variability of mesosphere and lower thermosphere winds over Tirunelveli (8.7° N, 77.8° E), J. Geophys. Res., 112, D23105, <a href="http://dx.doi.org/10.1029/2007JD008669">https://doi.org/10.1029/2007JD008669</a>, 2007. Stockwell, R. G., Mansinha, L., and Lowe, R. P.: Localization of the Complex Spectrum: The <i>S</i> Transform, IEEE transactions on signal processing, 44, no. 4, April 1996. Tsutsumi, M., Tsuda, T., Nakamura, T., and Fukao, S.: Wind velocity and temperature fluctuations due to a 2-day wave observed with radio meteor echoes, J. Geophys. Res., 101, 9425–9432, 1996. Vincent, R. A.: Long-motions in the equatorial mesosphere, J. Atmos. Sol. Terr. Phys., 55, 1067–1080, 1993. Vincent, R. A. and Lesicar, D.: Dynamics of the equatorial mesosphere: First results with a new generation partial reflection radar, Geophys. Res. Lett., 18, 825–828, <a href="http://dx.doi.org/10.1029/91GL00768">https://doi.org/10.1029/91GL00768</a>, 1991. Yang, G., Hoskins, B., and Slingo, J.: Convectively Coupled Equatorial Waves. Part I: Horizontal and Vertical Structures, JAS, November 2006. Yoshida, S., Tsuda, T., Shimizu, A., and Nakamura, T.: Seasonal variations of 3.0– 3.8-day ultra-fast Kelvin waves observed with a meteor wind radar and radiosonde in Indonesia, Earth Planets Space, 51, 675–684, 1999. Zhang, C.: Madden-Julian oscillation, Rev. Geophys., 43, RG2003, <a href="http://dx.doi.org/10.1029/2004RG000158">https://doi.org/10.1029/2004RG000158</a>, 2005. Ziemke, J. R. and Stanford, J. L.: One-to-two month oscillations: Observed high-latitude tropospheric and stratospheric response to tropical forcing, J. Atmos. Sci., 48, 1336–1347, 1991.