Articles written in Journal of Earth System Science

    • Impact of high resolution land surface initialization in Indian summer monsoon simulation using a regional climate model

      C K Unnikrishnan M Rajeevan S Vijaya Bhaskara Rao

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      The direct impact of high resolution land surface initialization on the forecast bias in a regional climatemodel in recent years over Indian summer monsoon region is investigated. Two sets of regional climatemodel simulations are performed, one with a coarse resolution land surface initial conditions and secondone used a high resolution land surface data for initial condition. The results show that all monsoonyears respond differently to the high resolution land surface initialization. The drought monsoon year2009 and extended break periods were more sensitive to the high resolution land surface initialization.These results suggest that the drought monsoon year predictions can be improved with high resolutionland surface initialization. Result also shows that there are differences in the response to the land surfaceinitialization within the monsoon season. Case studies of heat wave and a monsoon depression simulationshow that, the model biases were also improved with high resolution land surface initialization. Theseresults show the need for a better land surface initialization strategy in high resolution regional modelsfor monsoon forecasting.

    • Sensitivity to initial conditions on the simulation of extratropical cyclone ‘Gong’ formed over North Atlantic


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      The role of initial conditions (ICs) in the simulation of severe winter storm ‘Gong’ formed over North Atlantic is studied. The life cycle of Gong started at 1800 UTC of 16–0600 UTC of 22 January, 2013, with CSLP of 972 hPa. The gusty wind (${\sim}$33 ms$^{-1}$) and torrential rainfall of ${\sim}$90 mm d$^{-1}$ recorded over several major cities of the Iberian peninsula. Five numerical experiments were performed with the WRF model by initializing at 0600 UTC of 16, 1800 UTC of 16, 0600 UTC of 17, 1800 UTC of 17, and 0600 UTC of 18 January, 2013. Our results suggest that significant differences are seen among the experiments, particularly with the ICs of 0600 UTC 17 January, 2013, which represent the quick movement of Gong with a slight underestimation of intensity. The experiment with IC 0600 UTC on 18 January, 2013 produced the best simulation as compared to the observations. The simulated track, intensity, wind flow, and rainfall were well agreeing with the observations. The 12-h average track errors were ranging from 95 to 332 km with 24-, 36-, 48-, 60-, and 72-h lead time. The Q-vectors of Gong with the WRF model with 24-h lead time produced minimum errors.


      $\bullet$ Sensitivity of initial and boundary conditions (ICs) are studied for an extra-tropical cyclone (ETC, Gong (2013)) over North Atlantic Ocean using WRF model.

      $\bullet$ Movement (track) and synoptic feature of Gong have been evaluated with observations. WRF could simulate the characteristics throughout life cycle of Gong.

      $\bullet$ The model attained intense stage was well simulated.

      $\bullet$ Cyclogenesis and Q-Vector for Gong are sensitive to the ICs and model could simulate better with 48-h lead time.

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