• B Venkateswara Rao

      Articles written in Journal of Earth System Science

    • Equatorial wave activity during 2007 over Gadanki, a tropical station

      Salauddin Mohammad Gopa Dutta B Venkateswara Rao P Vinay Kumar

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      ECMWF Re-Analysis (ERA-interim) data of winds for the year 2007 between the pressure levels 1 and 1000 hPa (0–49 km) have been analyzed for equatorial wave activity over a tropical station Gadanki (13.5°N, 79.2°E). Available wind observations made by MST radar located at the same site have also been used to investigate the wave activity in the troposphere and lower stratosphere. Waves in the period bands 7–10, 12–15 and 20–30 d are observed. Temporal variability of the wave activity has been investigated by constructing wavelet spectra. The longer period waves show strong seasonal variability with maximum and minimum activities during winter and summer months respectively. Short period activity is more prominent during June–July–August in the tropospheric region. The waves are found to be generated in the troposphere by wind shear and convection. Propagation of the waves to higher altitudes is found to depend strongly on background zonal wind and phase of the quasi-biennial oscillation (QBO). The waves are inhibited to propagate through the negative wind shear zone. Meridional waves might be generated by non-linear wave CISK.

    • Numerical simulation and observations of very severe cyclone generated surface wave fields in the north Indian Ocean

      P Sirisha P G Remya T M Balakrishnan Nair B Venkateswara Rao

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      Accurate wave forecast is most needed during tropical cyclones as it has adverse effects on the entire marine activities. The present work evaluates the performance of a wave forecasting system under very severe cyclonic conditions for the Indian Ocean. The wave model results are validated separately for the deep water and shallow water using in-situ observations. Satellite altimeter observations are also utilized for validation purpose. The results show that the model performance is accurate (SI < 26% and correlation > 0.9) and consistent during very severe cyclones (categories 4 and 5). The power of the cyclone waves which hit in the eastern Indian coastal region is also analysed and it reveals that the coastal region which lies on the right side of the cyclone track receives high amount wave energy throughout the cyclone period. The study also says that the abnormal waves mostly present on the right side of the track.

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