Quantifying mountain precipitation gradients in the Everest region (Nepal), based on existing various datasets

Identifying and quantifying mountain precipitation gradients in the Everest region (Nepal), based on existing various datasets

Supervision : Arbindra Khadka, Patrick Wagnon (IGE, Grenoble)

Context and objective

Mountain precipitation is one of the largest unknowns in High Mountain Asia (Immerzeel et al., 2015) due to the paucity of precipitation gauges at high elevation and to the difficulty of accurately measure solid precipitation (gauge catch efficiency) (Khadka et al., 2022). In the Everest Region, the Glacioclim Observatory has a network of different instruments operating since 2012 for the oldest : Geonor rain gauges at 3 sites, from 4200 to 5000 m, able to capture solid precipitation, Campbell SR50 data installed on Mera Glacier at 5360 and 5770 m, able to measure the distance between the sensor and the glacier surface, i.e. the snow accumulation in case of a snowfall, and SnowFox data at 5770 m, able to provide point snow water equivalent. In this area, precipitation has a very large spatial variability with South-to-North horizontal decreasing gradients of precipitation (Sherpa et al., 2017) as well as altitudinal gradients of precipitation, but so far no quantification of such gradients has been done. The objective of this internship is to cross all datasets, potentially including other available datasets (such as stations installed by National Geographic since 2019) to quantify such gradients, within the region of interest.

Specific objectives

Part 1 : quantification of the altitudinal gradient of precipitation at Mera site

Mera Glacier is a Glacioclim benchmark glacier (https://glacioclim.osug.fr). The candidate will use Geonor precipitation datasets available below the glacier at 4900 m, SR50 data useful to quantify snow accumulation in case of snow falls at 2 elevations on the glacier surface, as well as SnowFox data providing measurements of snow water equivalent at the highest station at 5770 m to possibly derive seasonal altitudinal precipitation gradients over the glacier. Deriving snow accumulation from SR50 data or snow water equivalent measurements from SnowFow data is not straightforward and will need some specific work on the data (Gugerli et al., 2019), accounting for the limitations of the measure itself as well as the snow drift.

Part 2 : quantification of the horizontal south-to-north gradient of precipitation

This work relies on Geonor precipitation data, at Khare (4900 m), Pheriche (4200 m) and Pyramide (5000 m). These 3 stations are distributed from South to North over a distance of approximately 25 km, from the wind ward side of the mountain range (directly impacted by the monsoon influx in summer) to the leeward side of the range, much drier. Data are available at hourly time scale, and the candidate will look at the data, from seasonal time scale to the event scale. The aim of this analysis is to quantify the impact of the mountain range on the spatial distribution of precipitation in the upper Everest Region, and to assess horizontal gradients of precipitation as a function of the seasons, or depending on precipitation events. Other stations in the same region (Phortse, Everest Base Camp…) may also be used to complete the dataset, if data are accessible.

Application

We seek for an enthusiastic candidate who is currently enrolled in a Master’s program in atmospheric sciences, earth sciences, or any other related topic. The internship is expected to last for 4 to 6 months. We encourage candidates with interest in quantitative data analysis and with curiosity to explore this rich dataset ! Please provide CV and letter of motivation.

Instruments

Geonor rain gauge : this instrument is equipped with a weighing device and is suitable to measure solid and liquid precipitation https://geonor.com/live/products/weather-instruments/t-200b-weather-precipitation-rain-gauge/

SR50 probe : this instrument is an ultrasonic sensor able to measure the distance between the sensor and the glacier surface, using ultrasonic waves ; https://www.campbellsci.com/sr50a

SnowFox sensor records the intensity of downward-directed secondary cosmic-rays that penetrate the snow pack. This intensity is proportional to the mass of snow traversed by cosmic-rays, and is related to snow water equivalent through a calibration function https://hydroinnova.com/_downloads/snowfox_v1.pdf

Data availability

Glacioclim data : https://glacioclim.osug.fr/Donnees-himalaya
National Geographic data : https://www.nationalgeographic.org/projects/perpetual-planet/everest/weather-data/

References

Gugerli, R., Salzmann, N., Huss, M., and Desilets, D. (2019) : Continuous and autonomous snow water equivalent measurements by a cosmic ray sensor on an alpine glacier, The Cryosphere, 13, 3413–3434, https://doi.org/10.5194/tc-13-3413-2019
Immerzeel W. W., N. Wanders, A. F. Lutz, J. M. Shea, and M. F. P. Bierkens (2015), Reconciling high-altitude precipitation in the upper Indus basin with glacier mass balances and runoff, Hydrol. Earth Syst. Sci., 19, 4673-4687, doi : 10.5194/hess-19-4673-2015
Khadka A, P. Wagnon, F. Brun, D. Shrestha, Y. Lejeune, Y. Arnaud, Evaluation of ERA5-Land and HARv2 reanalysis data at high elevation in the upper Dudh Koshi basin (Everest region, Nepal), J. Applied Meteo. Clim.., 61, 931-954, DOI : 10.1175/JAMC-D-21-0091.1
Sherpa, S. F., P. Wagnon, F. Brun, E. Berthier, C. Vincent, Y. Lejeune, Y. Arnaud, R. Kayastha, A. Sinisalo, Contrasted surface mass balances of debris-free glaciers observed between the southern and the inner parts of the Everest region (2007-2015), J. Glaciol, doi : 10.1017/jog.2017.30, 2017.

Contacts
Arbindra KHADKA : arbindra.khadka univ-grenoble-alpes.fr
Patrick WAGNON : patrick.wagnon univ-grenoble-alpes.fr