Y. Bhavanikumar

National Atmospheric Research Laboratory

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K. Satheesan

Cochin University of Science and Technology

K. Parameswaran

Vikram Sarabhai Space Centre

K. Raghunath

National Atmospheric Research Laboratory

M. N. Sasi

Vikram Sarabhai Space Centre

Prabha R. Nair

Vikram Sarabhai Space Centre

B. V. Krishna Murthy

SRM University

Geetha Ramkumar

Vikram Sarabhai Space Centre

K. Revathy

SASTRA University

Venkataraman Sivakumar

University of KwaZulu-Natal

S. R. Prabhakaran Nayar

Action Contre la Faim

Cooperative Institutions

Vikram Sarabhai Space Centre

Indian Space Research Organisation

National Atmospheric Research Laboratory

University of Kerala

Indian Institute of Science Bangalore

Sri Venkateswara University

Government of India

Aryabhatta Research Institute of Observational Sciences

Tata Institute of Fundamental Research

Council of Scientific and Industrial Research

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Rayleigh lidar observations of gravity wave characteristics in the middle atmosphere at Gadanki, India (13.5 degrees N, 79.2 degreesE.)

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2002)

K. Parameswaran K. Rajeev M. N. Sasi Geetha Ramkumar B. V. Krishna Murthy

Rayleigh lidar observations of temperature in the stratosphere and mesosphere are carried out an Gadanki from February 29 to March 31, 2000, which provided a powerful means of studying the gravity wave characteristics over the tropical atmosphere during winter. The potential energy per unit mass associated with the gravity wave activity in the upper stratosphere and mesosphere is found to undergo periodic fluctuations, which are closely correlated with the zonal wind fluctuations in the stratosphere produced by the equatorial waves. This provides the first observational evidence for the modulation of the gravity wave activity by the long period equatorial waves over the tropical middle atmosphere. The vertical wave number spectra of gravity waves shows that power spectral density decease with increasing wave number with a slope less than that expected for the saturated gravity wave spectrum in the stratosphere and mesosphere. PSD decreases for vertical wavelengths smaller than about 10 km in the stratosphere while the decrease is observed for the complete range of observed gravity wave spectrum in the mesosphere. A monochromatic upward propagating gravity wave with periodicity of 6 hour, amplitude of about 1 K to 3 K and vertical wavelength of 11 km was observed on 22 March, 2000.

Infragravity wave

Atmospheric wave

Stratopause

Spectral slope

10.1117/12.452784

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Altitude profiles of temperature from 4 to 80 km over the tropics from MST radar and lidar

Journal of Atmospheric and Solar-Terrestrial Physics (2000)

K. Parameswaran M. N. Sasi Geetha Ramkumar Prabha R. Nair V. Deepa

10.1016/s1364-6826(00)00124-3

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Citations (38)

Thin aerosol clouds at tropopause level

B V Krishna Murthy S. R. Prabhakaran Nayar K. Revathy K. Satheesan K. Parameswaran

Aerosol clouds about 2 km below the trop opa use are studi ed usin g th e data from lidar and MST radar at Gadan ki. The cloud shows nuctuation s with time scales as short as 'h h in the backsca tt er ratio. Depolarization factor indicates ic.: crys tal formation when th e cloud is str ong. The MST radar wind data show stro ng turbulence below the cloud level indi ca ti ng. probably, turbulent mixin g /tran sport of wate r vapou r from lower height s to clmJd hei ght s facilitatin g cloud form ation.

Tropopause

Cloud base

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Lidar observed characteristics of the tropical cirrus clouds

Radio Science (2003)

Venkataraman Sivakumar Y. Bhavanikumar P. B. Rao K. Mizutani Teruo Aoki

Using the polarization diversity lidar data collected during March 1998 to April 2001, the characteristics of the tropical cirrus clouds observed over Gadanki (13.5°N; 79.2°E) are presented in this paper. Out of 210 nights of observations during this period, cirrus clouds were observed over the lidar site on 170 nights. The cloud mean height is found to be in the range of 8–17 km with peak occurrence at 13–14 km, just below the tropopause. The cloud thickness has values ranging 0.6–4.2 km with maximum occurrence at 0.9–1.2 km. The scattering ratio and the linear depolarization ratio are in the ranges of 1.14–36 and 0.01–0.75 with peak occurrences seen at 1.14–2 and 0.01–0.05, respectively. The optical depth can be as high as 2, but values less than 0.1 account for most (>80%) of the clouds. The clouds with low optical depth occur most frequently during fall equinox and high optical depth during summer. The formations of thin and thick cirrus clouds are seen to be closely related to the minimum tropospheric temperature and cumulonimbus outflows, respectively.

Cirrus

Tropopause

Depolarization ratio

Ice cloud

10.1029/2002rs002719

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A study of Equartorial wave characteristics using rockets, balloons, lidar and radar

cosp (2002)

M. N. Sasi B. V. Krishna Murthy Geetha Ramkumar K. Satheesan K. Parameswaran

Kelvin wave

Zonal flow (plasma)

Anomaly (physics)

Atmospheric wave

Mean flow

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Citations (2)

Lidar observed characteristics of the tropical cirrus clouds (DOI 10.1029/2002RS002719)

Radio Science (2003)

Venkataraman Sivakumar Y. Bhavanikumar

Cirrus

Source

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Citations (2)

Aerosol Optical Depth, Ozone and Water Vapor Measurements over Gadanki, A Tropical Station in Peninsular India

Aerosol and Air Quality Research (2008)

A. K. Srivastava P. C. S. Devara Y. Jaya Rao Y. Bhavanikumar D. Narayana Rao

This paper reports the results of a study related to the optical and physical characteristics of columnar aerosols and variation in total column ozone (TCO) and precipitable water content (PWC) over Gadanki (13.45°N, 79.18°E), a tropical station in peninsular India, for the first time, using MICROTOPS-II (Microprocessor-based Total Ozone Portable Spectrometer), comprising of both sun photometer and ozonometer. Results show wavelength dependence of AOD, having mean value of ~0.4 (± 0.09) at 500 nm optical channel. Daily mean aerosol size spectra shows, most of the time, power-law distribution. However, its diurnal variations show significant changes in aerosol size spectra modulated by a combination of both power-law and bi-modal distributions. To characterize AOD, the Ångström parameters (i.e., α and β) were used. The day-to-day variations in TCO were found to be in fair agreement with that derived from TOMS satellite data for all the experimental days, having mean observed value of ~253 (± 8) DU over the station. Interestingly, an inverse relationship between TCO and AOD or PWC was observed over the station, on some times of the day, which could be attributed to the mixing of significant fraction of ozone with aerosol and water vapor-rich air mass. However, a significant positive correlation was observed between AOD and PWC.

Sun photometer

Mixing ratio

Precipitable water

10.4209/aaqr.2008.05.0015

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Citations (39)

A study of equatorial wave characteristics using rockets, balloons, lidar and radar

Advances in Space Research (2003)

M. N. Sasi B. V. Krishna Murthy G. Ramkumar K. Satheesan K. Parameswaran

10.1016/s0273-1177(03)00412-5

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Citations (18)

Observational evidences on the influences of tropical lower atmospheric day oscillation on the ionospheric equatorial electrojet

Journal of Atmospheric and Solar-Terrestrial Physics (2005)

T. K. Ramkumar Y. Bhavanikumar D. Narayana Rao S. Gurubaran A. Narendra Babu

Electrojet

Equatorial electrojet

Madden–Julian oscillation

Oscillation (cell signaling)

Quasi-biennial oscillation

10.1016/j.jastp.2005.03.026

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Citations (16)

Equatorial waves in temperature in the altitude range 4 to 70 km

Quarterly Journal of the Royal Meteorological Society (2002)

B. V. Krishna Murthy K. Satheesan K. Parameswaran M. N. Sasi Geetha Ramkumar

Abstract Using altitude profiles of temperature in the range 4 to 70 km derived from Mesosphere–Stratosphere–Troposphere radar and lidar observations at Gadanki (13.5 ° N,79.2 ° E) from 18 January 1999 to 5 March 1999, characteristics of equatorial waves are studied. Two‐dimensional Fourier‐transform analysis of the temperature profiles is carried out to identify the periodicities and their vertical wave numbers. From the characteristics obtained, equatorial slow Kelvin waves with periodicities 15.7 d, 9.4 d, 7.8 d and 6.7 d are identified in the troposphere and stratosphere regions and among these 7.8 d and 6.7 d periodicities are found to penetrate into the mesosphere. Equatorial waves with smaller periodicities in the range 5.2 d to 3.6 d are also observed. The vertical flux of horizontal momentum (zonal) of the identified slow Kelvin‐wave periodicities in the altitude region 4–25 km is estimated. It is found that equatorial waves modulate tropical tropopause temperature and altitude. Copyright © 2002 Royal Meteorological Society.

Tropopause

Kelvin wave

Atmospheric wave

Potential temperature

10.1256/0035900021643700

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Citations (25)