How much water does snow contain?
Around 1.2 billion people, or nearly one-sixth of the world, depend on seasonal snow and glaciers for their water supply. For a better understanding of how much water is contained in each winter’s snowfall and how much will be available when it melts in the spring, NASA has launched a seasonal campaign — part of a five-year programme called SnowEx, initiated in 2016-17.
While the geographical focus of SnowEx is North America, NASA’s overall target is optimal strategies for mapping global snow water equivalent (SWE) with remote sensing and models leading to a Decadal Survey “Earth System Explorer” mission. NASA currently has no global satellite mission to track and study SWE. On its website, NASA acknowledges any future snow satellite mission will require observations from an international collection of satellites.
Within its geographic range, SnowEx assesses where snow has fallen, how much there is and how its characteristics change as it melts. It uses airborne measurements, ground measurements and computer modelling. The airborne campaign will fly radar and lidar (light detection and ranging) to measure snow depth, microwave radar and radiometers to measure SWE, optical cameras to photograph the surface, infrared radiometers to measure surface temperature, and hyperspectral imagers for snow cover and composition. Ground teams will measure snow depth, density, accumulation layers, temperature, wetness and snow grain size — the size of a typical particle. This year, real-time computer modelling will be integrated into the campaign as well.