• A K Sharma

      Articles written in Journal of Earth System Science

    • Capability ofBhaskara SAMIR to distinguish atmospheric water vapour and liquid water contents

      P C Pandey A K Sharma B S Gohil

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      An environmental model to compute microwave brightness temperatures for downward looking radiometers on board satellite is described. The effects of water vapour, oxygen and clouds on the brightness temperature have been studied for frequencies from 5 to 50 GHz for a standard tropical atmosphere. The effect of look angle on brightness temperture has also been investigated. Based on the model it has been shown that while the radiometers on boardBhaskara at 19·35 and 22·235 GHz are capable of giving the atmospheric water vapour and liquid water contents, the ability to distinguish these quantities is more for the combination of the frequencies 22·235 and 31 GHz.

    • A simulation technique for the determination of atmospheric water content with Bhaskara satellite microwave radiometer (SAMIR)

      P C Pandey A K Sharma B S Gohil

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      A simulation technique has been developed to estimate the integrated atmospheric water content over oceans using the 19·35 and 22·235 GHz brightness temperature data from satellite microwave radiometer (SAMIR) on board the Indian satellite Bhaskara. The results obtained have been compared with those from linear statistical regression and empirical methods as well as from the nearest radiosonde observations. Based on the simulation method, a map of total precipitable water for some of the Bhaskara passes in July 1980 over Bay of Bengal is given. The possible applications of such maps in the study of Indian summar monsoon and boundary layer characteristics have been pointed out.

    • Atmospheric temperature profile for a tropical region from TIROS-N microwave sounding unit

      B S Gohil A K Sharma P C Pandey

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      Atmospheric temperature profiles have been derived using 53·74 GHz, 54·96 GHz and 57·95 GHz channels data from the Microwave Sounding Unit onboard TIROS-N. For this purpose regression coefficients have been derived using MONEX-79 radiosonde data during the period May to July 1979. The temperature profiles derived at a few selected places were closer to radiosonde profiles than the profiles derived using standard regression coefficients for the tropical region supplied by NOAA.

    • Detection of large scale electron density irregularities duringips observations at 103 MHz

      S K Alurkar H O Vats R V Bhonsle A K Sharma

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      Angular displacements in the positions of the quasar 3C 298 were observed during its interplanetary scintillation (ips) observations made using a correlation interferometer at 103 MHz at Thaltej near Ahmedabad. These changes in the apparent positions of the source could be seen as variations in the declination of 3C 298. Two possibilities which might cause such effects are considered; refraction of the radio waves either in the earth’s ionosphere or in the interplanetary medium (ipm) by large scale plasma density inhomogeneities. Order of magnitude calculations for both are presented. Further studies using two-site observations are suggested to decide between the two mechanisms.

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