• RAKESH V

      Articles written in Journal of Earth System Science

    • Comparison of the performance of HYBRID ETKF-3DVAR and 3DVAR data assimilation scheme on the forecast of tropical cyclones formed over the Bay of Bengal

      GOVINDAN KUTTY REKHA GOGOI RAKESH V PATERIA M

      More Details Abstract Fulltext PDF

      This study compares the performance of hybrid ensemble transform Kalman filter – three dimensional variational data assimilation (HYBRID) system and three dimensional variational (3DVAR) data assimilation system in Weather Research and Forecasting Model (WRF) in simulating tropical cyclones (TC) formed over the Bay of Bengal. An Ensemble Transform Kalman Filter (ETKF) system updates the ensemble system that provides flow-evolving background error covariance for HYBRID data assimilation system. Results indicate that use of flow-evolving ensemble error covariance in 3DVAR system has systematically reduced the TC position and intensity errors in the analysis; however, adding more weights to the ensemble error covariance term in 3DVAR cost function has not made any significant impact. The 3DVAR analysis depicts a stronger TC vortex with a well pronounced warm core structure as compared to that in HYBRID analysis. The forecasts from HYBRID analysis outperform that from 3DVAR in reducing TC track forecast error. The relative improvement in TC landfall position is 43% and 49% for variously configured HYBRID experiments. The forecasts initiated from HYBRID analysis has higher skill in quantitative precipitation forecasts during TC landfall compared to 3DVAR, which may be attributed to improved track prediction in the HYBRID experiments.

      $\bf{Highlights}$

      $\bullet$ Compared the performance of HYBRID and 3DVAR data assimilation system for Tropical cyclone forecasts.

      $\bullet$ HYBRID has systematically reduced the Tropical cyclone position and intensity errors in the analysis.

      $\bullet$ The forecasts from HYBRID analysis outperform that from 3DVAR in reducing TC track forecast error.

      $\bullet$ The forecasts initiated from HYBRID analysis has higher skill in quantitative precipitation forecasts during Tropical cyclone landfall compared to 3DVAR.

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