K. Sen Gupta
Vikram Sarabhai Space Centre
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Featured researches published by K. Sen Gupta.
Boundary-Layer Meteorology | 1992
J. Winston Jeeva Prakash; K. Narayanan Nair; K. Sen Gupta; P. K. Kunhikrishnan
An investigation has been made of the structure of sea-breeze fronts observed at Thumba mostly during the months of December to April using data from a Doppler SODAR and in situ measurements of wind components, humidity and temperature. The study shows that the vertical wind structure observed in the SODAR height range provides a distinct signature of the passage of a front and that the intensity of the front is decided by the intensity and direction of the prevailing winds as well as the amount of rotation of the wind vector during the onset of the sea-breeze. Spectral analyses of vertical winds during the passage of the front reveal a dominant periodicity of about 6 min for strong sea-breeze fronts.
Boundary-Layer Meteorology | 2003
D. Bala Subrahamanyam; K. Sen Gupta; T. K. Mandal
The upper air data collected from the balloon-borne GLASS Sondes launched from the Oceanic Research Vessel (ORV) Sagar Kanya during the Intensive Field Phase of the Indian Ocean experiment (INDOEX, IFP-99;SK-141 Cruise) are utilized forstudying the variability in the mixed-layer heights observed over the western tropical Indian Ocean and central Arabian Sea. During the entire cruise, typical daytime convective mixed-layer heights (roughly corresponding to 1400 LT) obtained from θV and q profiles, were observed to be in the range 200–900 m. Shallowmixed -layer heights are observed, in general, over the Inter-Tropical Convergence Zone (ITCZ). Over the central Arabian Sea, vertical profiles of θV and q demonstrate a double mixed-layer structure of the marine atmospheric boundary layer (MABL), which gradually disappears close to the Indian coastline.
Journal of Atmospheric and Solar-Terrestrial Physics | 1997
K. Parameswaran; K. Rajeev; K. Sen Gupta
Abstract Aerosol number densities in the lower troposphere measured by a bistatic CW lidar are used to study their altitude structure in the nocturnal mixing region and its association with stratified turbulence. In the early night hours the aerosol concentration shows a maximum just above the daytime Thermal Internal Boundary Layer. This maximum disappears in the late night hours. The integrated aerosol content in the first 1 km shows a general decrease during the post-midnight hours. Stratified aerosol layers are observed in the nocturnal mixing region during the post-midnight period. The association between these stratified aerosol layers and the prevailing atmospheric stability condition in this region is studied using the altitude profiles of different meteorological parameters obtained from pilot balloon and tethered balloonsonde observations.
Boundary-Layer Meteorology | 1994
J. Winston Jeeva Prakash; K. Sen Gupta; K. Narayanan Nair; P. K. Kunhikrishnan
Surface-layer features with different prevailing wind directions for two distinct seasons (Southwest Monsoon and Northeast Monsoon) on the west coast of India are studied using data obtained from tower-based sensors at a site located about 500 m from the coast. Only daytime runs have been used for the present analysis. The surface boundary-layer fluxes have been estimated using the eddy correlation method. The surface roughnessz0 obtained using the stability-corrected wind profiles (Paulson, 1970) has been found to be low for the Southwest monsson season. For the other season,z0 is relatively high. The drag coefficientCD varies with height in the NE monsoon season but not in the season with lowz0. This aspect is reflected in the wind profiles for the two seasons and is discussed in detail. The scaling behaviour of friction velocityu* and the turbulence intensity of longitudinal, lateral and vertical winds σu, σv and σw, respectively) are further examined to study their dependence on fetch. Our study shows that for the non-dimensional case, σu/u* and σv/u* do not show any surface roughness dependence in either season. On the other hand, for σw/u* for the season with lowz0, the values are seen to agree well with that of Panofskyet al. (1977) for homogeneous terrain whereas for the other season with highz0, the results seem to conform more to the values observed by Smedman and Högström (1983) for coastal terrain. The results are discussed in the light of observations by other investigators.
Planetary and Space Science | 1972
B. V. Krishna Murthy; K. Sen Gupta
The phenomenon of the sudden disappearance of equatorial sporadic E at two stations, namely, Trivandrum and Kodaikanal is studied. It is established that whenever there is a sudden disappearance of Es, there is a depression in the horizontal magnetic field (H) range. Electron velocities during the presence and absence of sporadic E have been estimated. These results show that the irregularities responsible for sporadic E are present even when the electron velocities are less than the ion thermal velocity.
Atmospheric Research | 1986
K. Sen Gupta; P. K. Kunhikrishnan; V. Radhika; K. Narayanan Nair
Abstract A simple method is described for estimating the sensible heat flux by using a Doppler sodar system and a thermal probe. This method, which can be applied to a convective boundary layer in morning hours, is based on knowing the zero heat flux level from the reflectivity and the vertical wind speed.
Planetary and Space Science | 1973
K. Sen Gupta; B. V. Krishna Murthy
Abstract The effects of E -region electric fields on F -region parameters like height of constant electron density contours ( h N ) and semi-thickness, at an equatorial station, Trivandrum, are investigated. The E -region east-west electric field ( E y ) has been deduced using the horizontal magnetic field values from the ground magnetograms. It is found that the semi-thickness parameter and h N follow closely the E -region electric field ( E y ) variations in the forenoon and noon periods. In the afternoon, it is shown that there is close association between h N and E y , when the electric field variations are large. On a day-to-day basis also, h N and the E -region electric field show very good correlation in the forenoon and noon hours. It is also shown that higher levels are affected more than the lower levels in the F -region by E y .
Journal of Atmospheric and Solar-Terrestrial Physics | 1972
B. V. Krishna Murthy; K. Sen Gupta
Abstract A method of estimating the F-region vertical velocities from electron density-true height profiles is presented. The conditions under which this method is applicable are discussed. Using this method some nighttime velocity height-profiles are estimated and presented.
Boundary-Layer Meteorology | 2002
Prakash M. Ramchandran; Radhika Ramchandran; K. Sen Gupta; Shailesh Patil; P. N. Jadhav
Quarterly Journal of the Royal Meteorological Society | 1993
J. Jeeva Winston Prakash; Radhika Ramchandran; K. Narayanan Nair; K. Sen Gupta; P. K. Kunhikrishnan