Forecasting extreme precipitation event over Munsiyari (Uttarakhand) using 3DVAR data assimilation in mesoscale model
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Forecasting extreme precipitation event over Munsiyari (Uttarakhand) using 3DVAR data assimilation in mesoscale model N NARASIMHA RAO1,* , M S SHEKHAR1 and G P SINGH2 1 Snow 2
and Avalanche Study Establishment (DRDO), Chandigarh, India. Department of Geophysics, Institute of Science, Banaras Hindu University, Varanasi, India. *Corresponding author. e-mail: [email protected] MS received 1 September 2019; revised 6 November 2019; accepted 13 November 2019
A localized extreme precipitation event occurred over Munsiyari (Uttarakhand, India) on 2nd July 2018 causing Cash Coods, landslides and damage to the hydropower project. A preliminary study has been carried out by using Weather Research and Forecasting (WRF) model with three-dimensional variation data assimilation technique (3DVAR) to examine the feasibility of the model to predict the localized phenomena. Sensitivity experiments were carried out with two different microphysics in the model. Results show that P3 1-category plus double moment cloud water microphysics scheme with 3DVAR in WRF simulates the quantity of precipitation closer to the observed precipitation over Munsiyari. The vertical velocity and relative humidity were also simulated well during 3DVAR data assimilation as compared to without data assimilation over study region. Keywords. Extreme precipitation; WRF; WSM6 and P3 microphysics; 3D-Var; Himalaya.
1. Introduction Extreme precipitation events, now-a-days, have become more concern, particularly over the Indian Himalayan region in the context of present climate change and global warming. Study shows increase in temperature and decrease in precipitation over Western Himalayan region due to global warming and regional climate change (Shekhar et al. 2010). The source of many important rivers such as the Ganga and Yamuna, which feeds water to different parts of the country, it becomes necessary to predict the spatial as well as temporal spread of precipitation more accurately. The southern part of the Indian Western Himalaya and Central Himalaya experience enormous amount of rainfall during southwest monsoon season particularly in July and August months. The extreme precipitation events
in the form of cloudbursts, squall lines, strong winds, thunderstorms, snowfall, hailstorms and storm surges trigger Cash Coods, soil erosion, landslides, etc., resulting huge human causalities, loss of properties and aAect the economy of the country. The climatology for different categories of extreme events over Western Himalaya during winter has been recently studied by Shekhar et al. (2017). By using the observed precipitation data in their study, they have shown that rainy days have decreased and duration of dry spell has increased over the Western Himalayan region. Lack of dense observatory network over Western and Central Himalaya makes it very difBcult to understand the climate of these regions which in turn makes it difBcult to predict the extreme events more eAectively either
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