A Case Study on Assessing Cumulonimbus Induced Flight Vulnerabilities Over the Nepalese Himalayan Terrain
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Pure and Applied Geophysics
A Case Study on Assessing Cumulonimbus Induced Flight Vulnerabilities Over the Nepalese Himalayan Terrain ANANT CHANDRA,1,2 SATYAJIT GHOSH,1,3
NEELAY DOSHI,1 SUSHRUT DESHPANDE,1 and SIDDHARTH GUMBER1
Abstract—With a boom in the tourist industry both in India and adjoining Nepal, middle-class tourists from the Indian subcontinent have started routinely flying over the Himalayan terrain over the last decade. This influx of tourists stretches its aviation sector, in a country with some of the most vulnerable airports. The Himalayan terrain plays a key role in shaping weather systems over the region which has witnessed several aircraft crashes. Tourists in Nepal routinely fly 19-seater aircrafts such as the Beechcraft 1900D for a joy ride over the Himalayan range and are particularly vulnerable. This paper assesses the risks and vulnerabilities associated with such short duration flights starting from Kathmandu and covering parts of the Himalayan region. The region experiences deep cumulonimbus clouds which form over a period of a few days and are ubiquitous during the monsoon season (June to September). The vertical extent of such clouds ranges from 2 km upwards to up to the tropopause. This paper first assesses cumulonimbus mediated hazards along flight routes with thunderstorm activity and then details a critique on the hazard tied down to secondary effects i.e. deposition of supercooled droplets on a Beechcraft 1900D. In particular, the paper explores the role of cumulonimbus induced icing on the aircraft surfaces which can severely affect tourist flights over this part of the developing world. Keywords: Aircraft icing, cumulonimbus clouds, Himalayas, Nepalese aviation, Beechcraft 1900D, WRF, aviation meteorology.
1. Introduction The Himalayan region experiences one of the most intense thunderstorm activities in the world (Zipser et al. 2006). During the monsoon season, warm moist air from the Indian ocean encounters the Himalayan range and is forced to rise up (orographic
1
School of Mechanical Engineering, Vellore Institute of Technology, Vellore 632 014, India. E-mail: [email protected] 2 School of Aerospace and Mechanical Engineering, TU Delft, Delft, The Netherlands. 3 Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK.
lifting). The subsequent cooling of this air results in the formation of large convective clouds initiating thunderstorm activity. Several flights within this Himalayan country, including scenic mountain flights flying across this terrain are severely affected (see Fig. 1). These short-duration flights are here to stay, at least for the coming several decades boosting Nepal’s economy. With some reduction in snow cover, this region is already experiencing the ravages of global warming (Bastola 2017). Rise in global temperatures may lead to more intense hydrological cycles which in turn would lead to an increase in the frequency of convective clouds and precipitation (Fowler and Hennessy 1995). Additio
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