Browsing by Author "Pawar, S.D."

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    A laboratory investigation of electrical influence on the freezing of water drops: A cloud physics perspective
    (Springer, 2021) Mudiar, Dipjyoti; Pawar, S.D.; Hazra, Anupam; Gangane, Abhijeet; Gopalakrishnan, V.; Lal, D.M.; Srivastava, Manoj K
    Electro-crystallization, the freezing of water droplet induced by an electric field has been investigated by many investigators previously. But disagreements regarding the cause of freezing still persist in the literature. A cloud chamber of the internal dimension of 1 ft � 1 ft has been designed to study electro-crystallization of �mm� size pure water drops. More than 150 experiments have been performed in the chamber in the absence and presence of an electric field. Preliminary results suggest that in normal conditions, maximum drops freeze in the temperature ranging from ?10� to �15�C, consistent with the previous laboratory studies. When the drops are subjected to an electric field of magnitude 2�5 kV cm?1, the drops are observed to freeze in a much warmer temperature ranging from �6� to �10�C indicating an electric field induced crystallization. No movement of the drops is observed during the freezing, which suggests that the freezing may be initiated by absorption of the latent heat of fusion by the Nylon wire where the drops are kept suspended. The implication of the electrically induced freezing from the perspective of cloud physics also has been discussed. � 2021, Indian Academy of Sciences.
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    Lightning and precipitation: The possible electrical modification of observed raindrop size distributions
    (Elsevier Ltd, 2021) Mudiar, Dipjyoti; Pawar, S.D.; Hazra, Anupam; Gopalkrishnan, V.; Lal, D.M.; Chakravarty, Kaustav; Domkawale, Manoj A.; Srivastava, Manoj K.; Goswami, B.N.; Williams, Earle
    Many studies of cloud electrification have suggested that the presence of precipitation in the mixed phase region of the cloud is essential for charge separation and lightning initiation in clouds. However, observations of the rain gush phenomenon, a transient amplification in near-surface intensity after an overhead lightning also suggest that the lightning discharge can substantially enhance precipitation intensity at the ground. But the microphysical link between lightning and enhanced precipitation intensity after lightning is not well understood. With the observation of a transient amplification in the rain intensity and broadening of the corresponding Raindrop Size distribution (RDSD) after the lightning, it is inferred here that the lightning-induced atmospheric ions and prevailing electrical forces may potentially modulate the RDSD as well as the rain intensity by influencing the collision-coalescence process and the growth rate of raindrops after lightning. The time delay between the lightning and subsequent increase in rain intensity at the Earth's surface was observed to be between 2-4 min. Also, a good correlation was observed between the variations in lightning frequency and the rain intensity during thunderstorms with an average time lag of 4 min. Piepgrass et al. (1982) have reported a good correlation between lightning frequency and rainfall when the precipitation lagged the lightning by times of 4 and 9 min. These observations indicate that the association between lightning frequency and rainfall with 4-min time lag (the shorter one) may be a result of the lightning-induced growth of raindrops below the melting layer rather than the enhancement in precipitation in the mixed phase region of cloud. The new knowledge, coupled with our related work (MUDIAR et al., 2018) on stratiform clouds provides a compelling basis for the parameterization of the electrical processes in weather/climate models. � 2021
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    Role of Electrical Effects in Intensifying Rainfall Rates in the Tropics
    (John Wiley and Sons Inc, 2022) Mudiar, Dipjyoti; Hazra, Anupam; Pawar, S.D.; Karumuri, Rama Krishna; Konwar, Mahen; Mukherjee, Subrata; Srivastava, Manoj K.; Goswami, B.N.; Williams, Earle
    In the backdrop of a significant improvement in weather prediction with Numerical Weather Prediction models, quantitative prediction of the intensity of heavy rainfall events and associated disasters has remained a challenge. Encouraged by the recent emergence of compelling observational evidence for a significant electrical influence on cloud/rain microphysical processes (Mudiar, Pawar, Gopalakrishnana et�al.,�2021, https://doi.org/10.1029/2021gl093577), here we propose a hypothesis that the modification of the raindrop size distribution (RDSD) towards larger drop sizes facilitated by cloud electric fields could be one factor responsible for realistic rainfall intensity in weather/climate models. The robustness of the proposed hypothesis is confirmed through a series of simulations of strongly electrified rain events with the Weather Research and Forecasting model incorporating the electrically modified RDSD parameters in the model physics. Our results indicate a possible roadmap for improving hazard prediction associated with extreme rainfall events in weather prediction models. � 2021. American Geophysical Union. All Rights Reserved.