• Asnani, G. C. 1993. Tropical Meteorology. Vol. 1 and Vol. 2, self-published by Prof. G. C. Asnani ℅ IITM, India, 1202 pp.

  • Balsley, B. B., W. L. Ecklund, D. A. Carter, A. C. Riddle, and K. S. Gage. 1988. Average vertical motions in the tropical atmosphere observed by a radar wind profiler on Pohnpei (7°N latitude, 157°E longitude). J. Atmos. Sci. 45:396405.

    • Search Google Scholar
    • Export Citation
  • Dutta, G., B. Bapiraju, P. Balasubramanyam, and H. Aleem Basha. 1999. VHF radar observations of gravity waves at a low latitude. Ann. Geophys. 17:10121019.

    • Search Google Scholar
    • Export Citation
  • Fukao, S., M. F. Larsen, M. D. Yamanaka, H. Furukawa, T. Tsuda, and S. Kato. 1991. Observations of a reversal in long-term average vertical velocities near the jet stream wind maximum. Mon. Wea. Rev. 119:14791489.

    • Search Google Scholar
    • Export Citation
  • Gage, K. S., J. R. McAfee, D. A. Carter, W. L. Ecklund, A. C. Riddle, G. C. Reid, and B. B. Balsley. 1991. Long-term mean vertical motion over the tropical Pacific: Wind-profiling Doppler radar measurements. Science 254:17711773.

    • Search Google Scholar
    • Export Citation
  • Godbole, R. V. 1977. The composite structure of the monsoon depression. Tellus 29:2540.

  • Holton, J. R. 1979. An Introduction to Dynamic Meteorology. 2d ed. Academic Press, 391 pp.

  • Hoppe, U. P. and D. C. Fritts. 1995. On the downward bias in vertical velocity measurements by VHF radars. Geophys. Res. Lett. 22:619622.

    • Search Google Scholar
    • Export Citation
  • Jagannadha Rao, V. V. M., M. Venkat Ratnam, and D. Narayana Rao. 2002. Study of mean vertical motions over Gadanki (13.5°N, 79.2°E), a tropical station, using Indian MST radar. Radio Sci., in press.

    • Search Google Scholar
    • Export Citation
  • Koteswaram, P. 1958. The easterly jet stream in the Tropics. Tellus 10:4357.

  • Krishnamurti, T. N. and L. Bounoua. 1996. An Introduction to Numerical Weather Prediction Techniques. CRC Press, 293 pp.

  • Krishna Reddy, K. Coauthors,. 2000. A brief climatology of vertical velocities and small-scale gravity wave activity in the lower stratosphere and troposphere as observed by the Indian MST radar. Proc. Ninth Int. Workshop on Technical and Scientific Aspects of MST Radar Combined with COST 76 Final Profiler Workshop, Toulouse, France, Cooperation on Science and Technology, 198–201.

    • Search Google Scholar
    • Export Citation
  • Kuo, F-S., H-W. Shen, I-J. Fu, J-K. Chao, J. Rottger, and C-H. Liu. 1985. Altitude dependence of vertical velocity spectra observed by VHF radar. Radio Sci. 20:13491354.

    • Search Google Scholar
    • Export Citation
  • Larsen, M. F. and J. Rottger. 1991. VHF radar measurements of in-beam incidence angles and associated vertical-beam radial velocity corrections. J. Atmos. Oceanic Technol. 8:477490.

    • Search Google Scholar
    • Export Citation
  • Larsen, M. F. and R. D. Palmer. 1997. A relationship between horizontal flow gradients, in-beam incidence angles, and vertical velocities. Radio Sci. 32:12691277.

    • Search Google Scholar
    • Export Citation
  • Larsen, M. F., J. Rottger, and D. N. Holden. 1987. Direct measurements of vertical-velocity power spectra with the Sousy-VHF-Radar wind profiler system. J. Atmos. Sci. 44:34423448.

    • Search Google Scholar
    • Export Citation
  • Larsen, M. F., J. Rottger, and T. S. Dennis. 1988. A comparison of operational analyses and VHF wind profiler vertical velocities. Mon. Wea. Rev. 116:4859.

    • Search Google Scholar
    • Export Citation
  • May, P. T., S. Fukao, T. Tsuda, T. Sato, and S. Kato. 1988. The effect of thin scattering layers on the determination of wind by Doppler radars. Radio Sci. 23:8394.

    • Search Google Scholar
    • Export Citation
  • McAfee, J. R., K. S. Gage, and R. G. Strauch. 1994. Examples of vertical velocity comparison from collocated VHF and UHF profilers. Radio Sci. 29:879880.

    • Search Google Scholar
    • Export Citation
  • Nagpal, O. P., D. Praveen Kumar, and S. K. Dhaka. 1994. Characteristics of tropospheric gravity waves by Indian MST radar: ST mode operation. Ind. J. Radio Space Phys. 23:611.

    • Search Google Scholar
    • Export Citation
  • Narayana Rao, D., S. Thulasiraman, S. Vijaya Bhaskara Rao, T. Narayana Rao, P. Kishore, M. Venkat Ratnam, and K. Krishna Reddy. 2000. VHF radar observations of tropical easterly jet stream over Gadanki. Adv. Space Res. 26:943946.

    • Search Google Scholar
    • Export Citation
  • Narayana Rao, T. N., D. Narayana Rao, and S. Raghavan. 1999. Tropical-precipitating systems observed with Indian MST radar. Radio Sci. 34:11251139.

    • Search Google Scholar
    • Export Citation
  • Nastrom, G. D. and J. M. Warnock. 1994. Vertical motions estimated using data from a single station and a form of the adiabatic method. J. Appl. Meteor. 33:6573.

    • Search Google Scholar
    • Export Citation
  • Nastrom, G. D., W. L. Ecklund, and K. S. Gage. 1985. Direct measurement of large scale vertical velocities using clear air Doppler radars. Mon. Wea. Rev. 113:708718.

    • Search Google Scholar
    • Export Citation
  • Nastrom, G. D., W. L. Clark, K. S. Gage, T. E. VanZandt, J. M. Warnock, R. Creasy, and P. M. Pauley. 1994. Case studies of vertical velocity seen by the Flatland Radar compared with indirectly compared values. J. Atmos. Oceanic Technol. 11:1421.

    • Search Google Scholar
    • Export Citation
  • Rao, P. B., A. R. Jain, P. Kishore, P. Balamuralidhar, S. H. Damle, and G. Viswanathan. 1995. Indian MST radar. 1. System description and sample vector wind measurements in ST mode. Radio Sci. 30:11251138.

    • Search Google Scholar
    • Export Citation
  • Rottger, J. and M. F. Larsen. 1990. UHF/VHF radar techniques for atmospheric research and wind profiler applications. Radar in Meteorology, D. Atlas, Ed., Amer. Meteor. Soc., 235–281.

    • Search Google Scholar
    • Export Citation
  • Sato, T. 1989. Radar principles. Handbook for MAP, S. Fukao, Ed., Vol. 30, International School on Atmospheric Radar, 19–53.

  • Yoe, J. G. and R. Ruster. 1992. VHF Doppler radar observations of vertical velocities in the vicinity of the jet stream. Mon. Wea. Rev. 120:23782382.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 191 46 0
PDF Downloads 76 31 1

Mean Vertical Velocities Measured by Indian MST Radar and Comparison with Indirectly Computed Values

V. V. M. Jagannadha RaoDepartment of Physics, Sri Venkateswara University, Tirupati, India

Search for other papers by V. V. M. Jagannadha Rao in
Current site
Google Scholar
PubMed
Close
,
D. Narayana RaoDepartment of Physics, Sri Venkateswara University, Tirupati, India

Search for other papers by D. Narayana Rao in
Current site
Google Scholar
PubMed
Close
,
M. Venkat RatnamDepartment of Physics, Sri Venkateswara University, Tirupati, India

Search for other papers by M. Venkat Ratnam in
Current site
Google Scholar
PubMed
Close
,
K. MohanDepartment of Physics, Sri Venkateswara University, Tirupati, India

Search for other papers by K. Mohan in
Current site
Google Scholar
PubMed
Close
, and
S. Vijaya Bhaskar RaoDepartment of Physics, Sri Venkateswara University, Tirupati, India

Search for other papers by S. Vijaya Bhaskar Rao in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Mean vertical velocities and their variations observed with Indian mesosphere–stratosphere–troposphere (MST) radar located at Gadanki (13.5°N, 79.2°E), a tropical station in India, are presented. In this study, a comparison has been made between Indian MST radar–measured vertical velocities and those computed by radiosonde data using kinematic and adiabatic methods. From this study, it is observed that the signs of vertical motion estimated by the kinematic method agree well with MST-radar values, although the magnitudes differ, except in a small region where radar vertical velocity changes in sign from negative to positive in the lower troposphere during monsoon months. This upward motion in this season is attributed to horizontal convergence due to change in wind direction that is not observed in radiosonde data when averaged, because of poor height resolution of the radiosonde (500 m or more varying with height) as compared with the radar range resolution (150 m). Profiles of vertical velocities computed using the kinematic method tend to approach the shape of radar vertical velocity profiles as the separation of the radiosonde network decreases. The vertical velocities computed using the adiabatic method are found to be small and are attributed to a small tilt in isentropic surfaces caused by small latitudinal temperature gradients commonly observed in the Tropics; they also may be partly due to neglect of diabatic heating. The bias between radar and radiosonde vertical velocities tends to decrease when the time used for averaging of MST radar data is approximately 6 h (before and after 3-h average).

Corresponding author address: Prof. D. Narayana Rao, Department of Physics, Sri Venkateswara University, Tirupati 517 502, India. profdnrao2001@yahoo.com

Abstract

Mean vertical velocities and their variations observed with Indian mesosphere–stratosphere–troposphere (MST) radar located at Gadanki (13.5°N, 79.2°E), a tropical station in India, are presented. In this study, a comparison has been made between Indian MST radar–measured vertical velocities and those computed by radiosonde data using kinematic and adiabatic methods. From this study, it is observed that the signs of vertical motion estimated by the kinematic method agree well with MST-radar values, although the magnitudes differ, except in a small region where radar vertical velocity changes in sign from negative to positive in the lower troposphere during monsoon months. This upward motion in this season is attributed to horizontal convergence due to change in wind direction that is not observed in radiosonde data when averaged, because of poor height resolution of the radiosonde (500 m or more varying with height) as compared with the radar range resolution (150 m). Profiles of vertical velocities computed using the kinematic method tend to approach the shape of radar vertical velocity profiles as the separation of the radiosonde network decreases. The vertical velocities computed using the adiabatic method are found to be small and are attributed to a small tilt in isentropic surfaces caused by small latitudinal temperature gradients commonly observed in the Tropics; they also may be partly due to neglect of diabatic heating. The bias between radar and radiosonde vertical velocities tends to decrease when the time used for averaging of MST radar data is approximately 6 h (before and after 3-h average).

Corresponding author address: Prof. D. Narayana Rao, Department of Physics, Sri Venkateswara University, Tirupati 517 502, India. profdnrao2001@yahoo.com

Save