The Weather Hazards Associated with the US-Bangla Aircraft Accident at the Tribhuvan International Airport, Nepal (original) (raw)
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Journal of Applied Meteorology and Climatology, 2017
Nepal has been the location of a series of fatal aircraft accidents, raising serious concerns about civil aviation security and the safety of passengers. However, significant studies on weather patterns associated with the airports and air routes of the Himalayan complex terrain and their implications for aviation activities are yet to be carried out. The present study numerically reconstructs the prevailing weather conditions and puts forward some possible causes behind the most recent fatal aircraft accident in the foothills of the western Nepal Himalaya at 0730 UTC (1315 LST) 16 February 2014. The weather patterns have been numerically simulated at 1-km2 horizontal grid resolution using the Weather Research and Forecasting (WRF) modeling system. The reconstructed weather situation shows the existence of a low-level cloud ceiling, supercooled cloud water and hail, trapped mountain waves, supercritical descent of a strong tail wind, and the development of turbulence at the altitude...
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The main meteorological features of the central Kathmandu valley, Nepal were investigated by means of the dataset recorded by the automated meteorological observatory of Tri-Chandra Multiple Campus (1295m a.s.l. and 27.708217oN, and 85.315369oE) from May 2018 to April 2021. Initially, this observatory was installed for laboratory work with promoting clean energy resources by phasing out mercury instruments, since the onset of the coronavirus pandemic the growing importance of having resilience in the meteorological observation system has been more clearly demonstrated. Now, this automated real-time meteorological observatory becomes a backbone of our academic system, whereby students and teachers can have direct access to the data source and can self-analyze the prevailing atmospheric condition. As the detailed picture of the seasonal and diurnal cycle of meteorological parameters over the central Kathmandu valley, Ranipokhari premises, has been unavailable, this study tries to outl...
Pre-Monsoon Thunderstorms in Nepal
— During the pre-monsoon months in Nepal, severe thunder and hailstorms cause significant property and agricultural damage in addition to loss of life from lightening. Forecasting thunderstorm severity remains a challenge even in wealthy, developed countries that have modern meteorological data gathering infrastructure, such as Doppler Radar. This study attempts to isolate the specific and unique characteristics of the two hailstorms that might explain their severity. The primary data sources for this investigation included Infrared Satellite images, which illustrated the sequences of convective activity, and original archived ESRL India and China upper air data, which were used for synoptic and mesoscale analyses. Keywords—Pre-Monsoon Thunderstorms, Heat Lows.
A Meteorological Analysis from the Southern Slope of Mt. Everest, Nepal
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Mt. Everest is the highest mountain in the world, with an elevation ending at 8848.86 m above sea level, providing unique opportunity for direct observation of the upper troposphere. Utilizing the data from recently established five automatic weather stations (AWSs) network along the Everest climbing route, as part of the National Geographic and Rolex Perpetual Planet Expedition to Mount Everest 2019, from June 2019 to May 2020, this study investigates the meteorological environment over the southern slope of the Mt. Everest. Precipitation, temperature, radiations (income and outgoing short wave and long wave radiation), wind speed and direction along with derived variables like Lapse Rate, Precipitation Gradient, 6.11 hPa Isoline, and zero-degree Isotherm are analyzed with the aim of understanding altitudinal variation. Precipitation is mainly concentrated in monsoon with highest in Phortse (530 mm). Analysis of temperature lapse rate shows the highest lapse rate (-5.6 ℃ km-1) in m...
Winter-time Hydraulic Jump over the Pokhara Valley, Nepal
Journal of Nepal Physical Society, 2023
The Pokhara Valley is set to be one of the aviation hubs of Nepal with the opening of an international airport. The complex mid-hill mountainous topography of the Gangi-Himalaya and the characteristic wind system of the valley make safe aviation rather challenging over the valley. This study using the Weather Research and Forecasting modeling system shows that hydraulic jump-like phenomena occur regularly during winter in the western and central part of the Pokhara Valley during late afternoon/early evening when the airport may remain relatively busy. The jump occurs over the western part of the valley when the regional southwesterly plain to mountain wind via the Putalibazar Valley intrudes into the Valley crossing the Deurali-Mattikhan hill. The jump-like flow is accompanied by the formation of a mild reverse roller above the jump region and the head-on convergence with the northeasterly katabatic/drainage wind from Parche-Namarjung along the southeast-northwest oriented valley axis generating an updraft of as much as 0.4 to 0.8 m s-1. The southwesterly overrides northeasterly generating clockwise vertical rotors and high turbulence over the northeastern region of the valley. An early prediction of possible wind hazards at high spatiotemporal resolutions are highly desired to make aviation activities in the region safer for civil aviation.
2022
Atmospheric turbulence is a primary meteorological hazard to en-route air traffic. The role of Clear Air Turbulence (CAT) for various processes in the atmosphere is still ambiguous. An Air India flight AI462 encountered severe CAT on 19 April 2018. The present study simulates the CAT event and is focused on understanding and investigating favourable conditions for the occurrence of CAT. Weather Research and Forecasting (WRF) Model V4.0.3 has been used to simulate the turbulence. The 6-hourly NCEP FNL Operational Global Analysis data at 0.25° X 0.25° resolution is taken as input to provide the model's initial and lateral boundary conditions. For simulating the atmospheric environments at the time of the event, Yonsei University Scheme, WSM 3-Class Simple Ice Scheme, Kain-Fritsch (New-Eta) Scheme, Rapid Radiative Transfer Model (RRTM) Scheme, and Revised MM5 Monin-Obukhov Scheme are used. This study shows that Vertical Velocity, Geopotential Thickness, Wind Shear and Bulk Richards...
Thunderstorm characteristics in Nepal during the pre-monsoon season 2012
Atmospheric Research, 2014
A training period of lightning location data usage has been carried out in Nepal during the pre-monsoon season April-June 2012. The training was one part of a Finnish-Nepalese Project (FNEP) between the Department of Hydrology and Meteorology of Nepal (DHM) and the Finnish Meteorological Institute (FMI). FNEP aimed for the development of operational meteorological readiness in a developing country such as Nepal. The lightning location training included the introduction to lightning location techniques and principles and the actual hands-on training for the operational DHM forecasters. The lightning location system used was the Vaisala long range Global Lightning Dataset 360 (GLD360), which has practically a global coverage. During the three months of training, a dataset of Nepalese lightning was also collected, indicating the pre-monsoon thunderstorm characteristics of Nepal.
Journal of Applied Meteorology, 2003
Air pollution transport in Kathmandu valley has been investigated in reference to the observed concentration distribution of NO2 and SO2 and numerical simulation of local flow fields. The spatial distributions of NO2 and SO2 were measured in two ways: one is a 3-weeks average during 18 February to 11 March and the 1-day average on 12 April 2001 at identical sites with passive samplers. Using the PSU-NCAR Mesoscale Model MM5, initializing with ECMWF meteorological fields, meteorological conditions over Kathmandu valley has been simulated. The simulation reasonably reproduced the characteristic late wintertime meteorological conditions of the valley as inferred from the surface observations at the Airport as well as Sodar observation. The simulation results suggest that intrusion of the cooler air masses into the valley in the afternoon resulted in shallow stablelayer, in the lower part of which thermal internal boundary layer developed over Kathmandu valley. Pictures of smoke taken during the observation period confirmed that the shallow stable layer suppressed the vertical dispersion and trapped the air pollutants below 200 meters. The observed spatial distribution of NO2 and SO2 well coincided with the spatial patterns of the shallow southwesterly and northwesterly afternoon winds, intruding and merging into the westerly wind in the Basin. This suggested their major role in valley's air pollution transport thereby causing relatively high concentration in the downwind eastern area of the valley. These southwesterly and northwesterly winds are thought to be the valley winds from the southern plain area and western valley effectively channeled by underlying river gorge and low-mountain passes respectively.