• K G Vernekar

      Articles written in Journal of Earth System Science

    • MONTBLEX data archival centre

      K G Vernekar S S Aralikatti

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      A co-ordinated project Monsoon Trough Boundary Layer Experiment (MONTBLEX) to study the atmospheric boundary layer in the monsoon trough region was taken up during 1990. 30-m high instrumented towers were erected at Kharagpur, Banaras, Delhi and Jodhpur. Sophisticated equipment like Doppler sodar and Kytoon were used at Kharagpur. Sodars were exposed at Calcutta, Delhi and Jodhpur. ORVSagarkanya cruises were arranged in the Bay of Bengal. The India Meteorological Department set up new surface and radiation observatories and released special radio-sonde, pilot balloons. Using the above mentioned platforms, data were collected during April - September 1990 and after proper editing the entire data were archived at the Indian Institute of Tropical Meteorology, Pune. The DST-MONTBLEX data bank was started at IITM on 25th November 1991. The paper contains the details of this data.

    • A study of turbulent characteristics of atmospheric boundary layer over monsoon trough region using Kytoon and Doppler sodar

      K G Vernekar M N Patil B S Murthy

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      As a part of the MONTBLEX-90 observational programme, Kytoon and Doppler sodar observations were taken at Kharagpur. These data are analysed to study the turbulent characteristics of the atmospheric boundary layer in terms of stability, temperature structure function (CT2) and velocity structure function (Cv2).CT2follows aZ−4/3 law on most of the days, whereas the variation ofCV2is not systematic.CV2andCT2values are found to vary between 10−5−10−1 m4/3s−2 and 10−5−10−2°C2 m−2/3 respectively.

    • Wind profiles in the boundary layer over Kharagpur associated with synoptic scale systems

      D K Paul S P Ghanekar B S Murthy K G Vernekar

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      Doppler sodar wind data for the boundary layer over Kharagpur obtained during MONTBLEX-1990 at a height interval of 30 m from surface up to 1500 m have been analysed for the periods when intense synoptic scale disturbances from north Bay of Bengal moved along the eastern end of the monsoon trough. The variation in the vertical wind profile in the lower boundary layer over Kharagpur during the passage of synoptic scale disturbances has been discussed in the paper. The analysis indicates that the mean winds over Kharagpur veered with height in the lower boundary layer near the surface suggesting divergence over Kharagpur when the system lay south/southwest of the station. No such veering has been noticed when the centre of the system lay very close to the station.

    • Fluxes of heat and momentum over sea surface during the passage of a depression in the north Bay of Bengal

      S Sivaramakrishnan M N Patil K G Vernekar

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      Time variation of surface fluxes of heat, moisture and momentum over a sea station (20°N 89°E) in the north Bay of Bengal has been computed by profile method for the period 18th–25th August 1990 using meteorological data of MONTBLEX-90 from ORVSagarkanya. The fluxes showed synoptic and diurnal variations which are marked during depression (20th–21st August) compared to their variation prior to and after this period. Variations of heat and water vapour fluxes were in phase. Night time fluxes are relatively high compared to day time. Average momentum transfer during depression was two to three times large. Variations in Bowen ratio were relatively large during day time. During depression, it varied between 0·2 in day time and about 0·3 at night and in the undisturbed period between −0·1 and 0·2 during day time and 0·2 and 0·25 at night. The study shows that the assumptionCD=CH=CE of the exchange coefficients normally used in estimating the fluxes by the bulk aerodynamic method is not appropriate becauseCH/CD≈2,CE/CD≈1·5 andCH/CE≈1·4.

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