Ground Validation

By Ellen Gray, NASA Goddard Space Flight Center Original www.nasa.gov Press Release (published 1/12/12) Beginning Jan. 17, NASA will fly an airborne science laboratory above Canadian snowstorms to tackle a difficult challenge facing the upcoming Global Precipitation Measurement (GPM) satellite mission -- measuring snowfall from space. GPM is an international satellite mission that will set a new standard for precipitation measurements from space, providing next-generation observations of worldwide rain and snow every three hours. It is also the first mission designed to detect falling snow...

The GCPEx observing strategy framework is designed to use a combination of multi-frequency radar, particle imaging and water equivalent-measuring surface instrumentation in conjunction with airborne dual-frequency radar, high frequency radiometer and in situ microphysics observations arranged in stacked altitude patterns to provide the most complete coupled sampling of surface and in-cloud microphysical properties possible. The resulting 3D volumes will be combined to provide a fundamental description of snowfall physics at the ground and through the atmospheric column, and to create an...

The primary objectives of GCPEx are to obtain coordinated high quality in situ and remote sensing observations of falling snow events in a northern latitude climate. Such systems are prevalent in the Ontario region in the December- February timeframe where monthly mean snowfall amounts are approximately 40, 30 and 25 cm/month for December, January and February, respectively. Furthermore, the primary choice for DC-8 operations (Bangor, Maine) will allow potential sampling of Nor’Eastern Blizzards and heavy snow events over St. Johns Newfoundland (site of current NCAR snowfall measurements...

To augment the observations and provide additional test cases for synthetic algorithm development and satellite simulator testing, a number of modeling activities are also planned. Cloud resolving model simulate frozen precipitation events using the GSFC-Weather Research and Forecasting (WRF) will be performed, initialized and forced by appropriate NWP forecast models. The GSFC WRF has single-moment Goddard Microphysics and spectral-bin microphysics. All of the microphysical schemes have their own set of unique capabilities and assumptions, and all will be tested by the GPM groups. In turn...

Frozen precipitation is particularly difficult to measure from space due to the wide variability in snowflake shapes and behavior. Snowflakes can have different impacts on the active and passive instruments signals compared to liquid precipitation, which is further complicated by a weak signal to noise ratio resulting from different scattering properties of liquid verses frozen precipitation. In recent years, the capability to quantify liquid precipitation from space has been greatly enhanced with the addition of several measurement capabilities from low-Earth orbit, most notably from passive...

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...