• S S Singh

      Articles written in Journal of Earth System Science

    • Application of semi-implicit scheme of integration to barotropic prediction

      S S Singh A Bandopadhyay

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      Application of a semi-implicit version of primitive equation barotropic model to predict monsoon depressions is proposed. Forecasts upto 48 hr have been quite satisfactory. The results are compared with those obtained from an explicit version of primitive equation barotropic model developed earlier. The flow patterns from these two versions are similar with few exceptions in isolated pockets, however, the forecast movement obtained from the semi-implicit version is comparable or slightly superior to those obtained from the explicit version. The computational time in semi-implicit and explicit schemes is approximately in the ratio of 1∶2.

    • Short range prediction with a multi-level primitive equation model

      S S Singh

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      A five-level primitive equation model in a (x, y, p, t) coordinate system has been developed. A fairly sophisticated scheme of physical processes has been incorporated in the model. The model physics include air-sea interaction, cumulus parametrization, large scale condensation, dry convective adjustment, horizontal and vertical diffusion and simulated radiation. The initial balance between mass and motion fields has been obtained through a dynamic initialization scheme. The model has been integrated upto 48 hr using input data of a case of monsoon depression. The results of initialization and forecast have been presented and discussed. Wind, temperature and vertical velocity fields have been found to retain the observed map features; after the initialization, however, the surface pressure has been considerably modified. The model produced a reasonably good forecast up to 24 hr as far as the flow fields, rainfall region, structure of the depression and the movement of cyclonic circulation were concerned and beyond that damped rapidly. The rainfall rates were underestimated. Some of the shortcomings of the model are also discussed.

    • Cumulus convection and lateral boundary conditions in a limited area model

      E N Rajagopal S S Singh

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      Three versions of Kuo's cumulus parameterization have been tested in a limited area model to investigate their comparative performances. Results show that the version of Anthes produces better forecasts than those produced by other versions. To identify a suitable scheme of lateral boundary conditions for the limited area model, impact of two time-invariant and two time-dependent boundary conditions have been examined. The forecasts suggest that the time-dependent tendency modification scheme, based on large-scale tendencies obtained from observed data, is a better boundary scheme for the model. Furthermore, the forecast produced with the revised version of the model incorporating improved versions of Kuo's scheme and lateral boundary conditions shows an overall improvement.

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