Evaluating the impact of topography on the initiation of Nor’westers over eastern India

Abstract

Pre-monsoon thunderstorms are catastrophic and frequent over eastern and north-eastern India. The Chhota Nagpur plateau (CNP) believes to be the triggering platform for thunderstorms over east India. This study attempted to determine the influence of the CNP topography on thunderstorm formation and propagation by observing the changes in the values of thermodynamic indices over eastern India. The work attempted ten cases of thunderstorms in multiple simulations, i.e. each case simulated three times with varying elevations of CNP topography (in total 30 simulations) by Advanced Weather Research and Forecasting (WRF–ARW) model. Our analysis revealed that when the elevation of topography of the CNP changes (increases/decreases), the characteristics of several thermodynamic indices alter considerably (with values changing from negative to the positive side for some indices). We found the Cross Total Index (CTI) shows considerable differences in all the thunderstorm simulations, and the values are higher in the increased CNP topography (∼ −4 to 6 °C). However, the Humidity Index (HI) (∼ −10 to 15 °C) and Convective INhibition (CIN) (∼ −200 to 200 J/Kg) values depict considerable changes in decreased topography. The results are crucial to understanding and quantifying the role of CNP in pre-monsoon thunderstorms over east India.

Keywords:

• Thunderstorms
• topography
• numerical simulation
• thermodynamic indices
• CNP

Acknowledgments

The authors are thankful to India Meteorology Department for providing the thunderstorm information for the present study. Mr. Rajesh Kumar Sahu wants to acknowledge the National Institute of Technology Rourkela for providing research facilities.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The datasets utilised in this article are freely accessible through the following sites: http://weather.uwyo.edu/upperair/sounding.html, https://mosdac.gov.in/ and https://rda.ucar.edu/datasets/ds083.2/#!description. The numerical model used in the study is available freely at https://www.mmm.ucar.edu/models/wrf. All other analysed datasets generated for this study are included in the article.

Additional information

Funding

Authors want to acknowledge the Science and Engineering Research Board (SERB), Department of Science and Technology, Govt. of India for providing the funding [project-funding code: DST/SERB/ECR/2017/001361].