An analysis of snow cover changes in the Himalayan region using MODIS snow products and in-situ temperature data

Abstract

Amidst growing concerns over the melting of the Himalayas' snow and glaciers, we strive to answer some of the questions related to snow cover changes in the Himalayan region covering Nepal and its vicinity using Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover products from 2000 to 2008 as well as in-situ temperature data from two high altitude stations and net radiation and wind speed data from one station. The analysis consists of trend analysis based on the Spearman's rank correlation on monthly, seasonal and annual snow cover changes over five different elevation zones above 3,000 m. There are decreasing trends in January and in winter for three of the five elevation zones (all below 6,000 m), increasing trends in March for two elevation zones above 5,000 m and increasing trends in autumn for four of the five elevation zones (all above 4,000 m). Some of these observed trends, if continue, may result in changes in the spring and autumn season river flows in the region. Dominantly negative correlations are observed between the monthly snow cover and the in-situ temperature, net radiation and wind speed from the Pyramid station at 5,035 m (near Mount Everest). Similar correlations are also observed between the snow cover and the in-situ temperature from the Langtang station at 3,920 m elevation. These correlations explain some of the observed trends and substantiate the reliability of the MODIS snow cover products.

Review of studies on land use and land cover change in Nepal

“…These mapping exercises indicated that remote-sensing (RS) data and geographic information system (GIS) tools are more reliable for snow cover mapping. Further snow cover and glacier change research has been carried out using various methods, datasets and techniques in Nepal in a major part of the Himalayan regions (Armstrong 2010;Bolch et al 2012), as well as at the national level (Shrestha and Joshi 2009;Bajracharya et al 2014) or at a smaller scale (Maskey et al 2011;Shrestha et al 2012;Kuhle 2014;Shea et al 2014). The overall small-scale mapping of various classes of LULC in Nepal is summarized in the Table 2, with LULC categories, spatial and temporal coverage, sources of data and references.…”

“…This has been verified by the Himalayan region annual glacier retreat rate, reported as 0.3−1m, the highest rate in the world (Dyurgerov and Meier 2005). Many studies (regional, national and small-scale) have been carried out on Nepal's snow/glacier cover changes Kadota et al 1997;Nie et al 2010;Lamsal et al 2011;Maskey et al 2011;Bolch et al 2012;Bajracharya et al 2014), which all examine the changing situation of snow/glacier cover in the country.…”

“…The MODIS base snow cover seasonal mapping shows the trend of snow cover rate decreasing in January and increasing in March between 2000 and 2008 (Maskey et al 2011), although significant errors in estimating seasonal snow cover occurred because of cloud during the period of analysis (Shrestha and Joshi 2009). The historical age of ice glaciations in Nepal's various mountains has been well documented (Kuhle 2006a;b), while another study of snow cover covering 30 years in the Sagarmatha (Everest) National park area identified an increasing trend, where snow cover was 34.2% in 197834.2% in and 39.8% in 200934.2% in (Midriak 2009).…”

Climate and topographic controls on snow cover dynamics in the Hindu Kush Himalaya

“…June-August and autumn, i.e. September-November) following schema adopted by Immerzeel et al, 2009 andMaskey et al, 2011. Intra-annual variability is important for water users like hydropower sector and farming community to understand the changes and adapt, average monthly SCAs spanning a 10-year period were plotted, and variations within individual months were captured by standard deviations (SDs) using 10 sets of monthly average SCAs.…”

Hydrological Modelling and data assimilation of Satellite Snow Cover Area using a Land Surface Model, VIC

“…The study also aims at estimating snowmelt runoff contribution to the annual discharge at the Thalot site. MOD10A2 comes in a spatial resolution of 500*500 m 2 in every 8-day period that begins on the first day of each year and extends to the first few days of the next year, (Maskey et al, 2011).…”