4  Data

Author

Bowen Wu, Jiahao Tong

The analysis utilizes three main types of satellite data from Google Earth Engine and one self uploaded shapefile:

4.1 Study Area

  • Center point: Mount Everest (86.9252°E, 27.98833°N)

  • Analysis buffer: 10-15km radius

  • Includes multiple climbing routes (shapefile import from private asset)

var routes = ee.FeatureCollection("projects/ee-wbwhaha/assets/Everest");

4.2 Temperature Data

  • Source:

    • MODIS MOD11A2 dataset

  • Temporal resolution: 8-day composite

  • Spatial resolution: 1km

  • Time period: February 18, 2011 - March 30, 2025

  • Variables:

    • Daytime Land Surface Temperature (LST_Day_1km)
    • Nighttime Land Surface Temperature (LST_Night_1km)

  • Data processing:

    • For more LST algorithms details (here)[https://lpdaac.usgs.gov/documents/119/MOD11_ATBD.pdf]. \[ \text{Temperature (°C)} = \text{Raw Value} \times 0.02 - 273.15 \]

4.3 Terrain Data

  • Source:

    • USGS/SRTMGL1_003 dataset
    • NASA/NASADEM_HGT/001 dataset

  • Spatial resolution: 30m

  • Variables:

    • DEM (the elevation data)
    • Slope (identifying steep areas >20 degrees, calculated from DEM)
    • Aspect (terrain orientation, calculated from DEM)

  • Data processing:

    • For each route, the system creates a line geometry
    • Along this line, 100 equidistant points are sampled
    • At each point, the elevation value is extracted from the DEM
    • The resulting elevation values are stored as a feature property

4.4 Snow Cover Data

  • Source:

    • Sentinel-2 imagery

  • Temporal resolution: 5-10 days (depending on satellite overpasses)

  • Spatial resolution: 10m (Bands 3, 4, 8) and 20m (Band 11)

  • Time period: January 2015 - Present

  • Variables:

    • Band 3 (Green): Used in NDSI calculation to detect snow
    • Band 11 (SWIR): Used in NDSI calculation to detect snow
    • Snow Class: Derived from the NDSI and snow fraction (classified into 4 categories: < 25%, 25–50%, 50–75%, > 75% snow cover)

  • Data processing:

    • NDSI is calculated using the formula: \[ \text{NDSI} = \frac{\text{Band 3} - \text{Band 11}}{\text{Band 3} + \text{Band 11}} \]

    • Snow fraction is calculated using a neighborhood mean reducer over a 10-pixel radius

    • Snow cover classes are derived by categorizing the snow percentage into four classes