GCPEx Science Goals

Falling snow is critically important for society in terms of freshwater resources, atmospheric water and energy cycles, and ecosystems. However, there are few archives of falling snow around the world that can be used to improve measurements from satellites. GCPEx will make detailed in situ observations of cloud and frozen precipitation microphysics to improve these databases.

Falling snow represents a primary contribution to regional atmospheric and terrestrial water budgets, particularly at high latitudes. While often overlooked, precipitation falling in the form of snow is critically important for society and the Earth’s climate, geologic and ecosystems. Snowpacks store freshwater and reflect incoming radiation energy. Falling snow disrupts transportation systems and contributes to the overall precipitation record. Yet despite their importance for human activity and understanding the Earth system, detailed descriptions of the microphysical properties (composition and structure) of frozen precipitation systems and regimes are under-represented in the available ground-validation archives. These archives are of critical importance for building the algorithms that translate what satellites’ observe from space to meaningful estimations of falling snow on Earth’s surface.

GCPEx will address these issues by making detailed in situ observations of cloud and frozen precipitation microphysics in coordination with:

  1. A ground-based Polarimetric C-band Doppler radar (King City).
  2. A primary heavily instrumented ground site (CARE), containing particle measurement instrumentation, snow water equivalent measurements, upward pointed radars and downward-looking radiometers.
  3. Four secondary ground sample locations (SGSL) with additional ground instrumentation, including particle measurement and snow-water equivalent measurements together with vertically-pointing radar.
  4. The NASA DC-8 aircraft with radiometer channels from 50-183 GHz, and radar channels at Ku and Ka-band.
  5. The University of North Dakota (UND) Citation aircraft and the Canadian National Research Council Convair 580 aircraft with in situ particle sensors. 

These ground and aircraft instrument measurements will be coordinated to:

  • Evaluate the falling snow detection characteristics of current and future spaceborne instrumentation,
  • Document the macro- and microphysical properties snowfall with detailed ground and airborne active and passive observations of lake effect and synoptic snow events (and any other occurring snow events, e.g., blizzards),
  • Establish the implications of variability in the snow, surface, and environmental characteristics for the accuracy in satellite-based snow detection and estimation at high latitudes,
  • Explore methods for improving these estimates using future satellite instrumentation and focused cloud-resolving model experiments, and
  • If the measurements exist, extend these analyses to mixed-phase, wet snow events.

It is anticipated that the data collected during GCPEx will provide an invaluable resource for resolving challenges in current satellite snow detection and estimation. The eventual outcome of this effort will be to help improve our understanding of frozen precipitation processes in high-latitude environments and their importance in the context of the global hydrological cycle.

Next Topic: Measuring Frozen Precipitation from Space