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      https://www.ias.ac.in/article/fulltext/jess/130/0082

    • Keywords

       

      Unified model; orographic rain; categorical verification; extreme rain; rainfall forecast; NWP.

    • Abstract

       

      Prediction of heavy/extreme rains is still a challenge, even for the most advanced state-of-the-art high-resolution Numerical Weather Prediction (NWP) modelling systems. Hydrological models use the rainfall forecasts from the NWP models as input. This study evaluates the performance of the UK Met Office Unified Model (UM) in predicting the rainfall exceeding 80th and 90th percentiles. Such high rainfall amounts occur over the Western Ghats (WGs) and North East (NE) India mainly due to the forced ascent of air parcels. Apart from the significant upgrades in the UM's dynamical core, the model features an increased horizontal grid (40–10 km) and vertical resolution (50–70 levels). The prediction skill of heavy rainfall events improves with an increased horizontal resolution of the model. The probability of detection (POD), false alarm ratio (FAR), and critical success index (CSI) are the verification metrics used. As per these metrics, model rainfall forecasts have improved during 2007–2018 (increase in CSI from 0.29 to 0.38, POD from 0.45 to 0.55, and decrease in FAR from 0.55 to 0.45). Additionally, to verify extreme and rare events, the symmetric extremal dependence index (SEDI) is also used. SEDI also shows an increase from 0.47 to 0.62 and 0.16 to 0.41 over WGs and NE India during the study period, suggesting an improved skill of predicting heavy rains over the mountains. The improved forecast performance is consistent and relatively higher over WGs than over NE states.

    • Author Affiliations

       

      KULDEEP SHARMA1 RAGHAVENDRA ASHRIT1 SUSHANT KUMAR1 SEAN MILTON2 EKKATTIL N RAJAGOPAL1 ASHIS K MITRA1

      1. National Centre for Medium Range Weather Forecasting, Ministry of Earth Sciences, A-50, Sector-62, Noida 201 309, India.
      2. Met Office, FitzRoy Road, Exeter Devon, EX1 3PB, UK.
    • Dates

       
    • Supplementary Material

       
  • Journal of Earth System Science | News

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