ABSTRACT

The humble snowflake, oft noted for its unparalleled beauty and elegance, also plays a critical role in ensuring our continued survival as a species. Falling snow is a truly global phenomenon -- and has direct dynamic and physical impacts on the atmosphere and surface. In the colder regions of the Earth, whether by latitude or elevation, snow reaching the surface has a tendency to accumulate. For many regions of the world, the seasonal accumulation and subsequent melt of snowpack provides freshwater resources needed for human survival. In warmer climes, snow melts before reaching the surface, continuing its path as a raindrop -- collecting together to become streams, rivers, and lakes. The formation of snowflakes, in transition from vapor to ice, and the melting of snowflakes have direct observable impacts on the heating or cooling through energy exchange with the atmosphere where these processes occur. This, in turn, modifies the circulation of the atmosphere. As we turn our collective focus more toward understand a changing climate, the need for measuring falling snow becomes increasingly evident and relevant. In this talk, the allegory of a single snowflake progressing through its life-cycle is used to relate the story of scientific progress in the measurement of falling snow. There are challenges and obstacles that make precise and accurate measurements of falling snow difficult, particularly due to the wide variations manifested in the shape, size, and composition of individual snowflakes. I'll discuss how these individual characteristics, when integrated together, form the familiar phenomenon of snowfall -- and describe the relevant current and planned approaches for in situ and remote sensing.

About the Speaker:

Dr. Benjamin Johnson received his Bachelor of Science degree in Physics from Oklahoma State University in 1998, a Master of Science degree in Atmospheric Sciences from Purdue University in December 2001, and completed his Ph.D. degree in December 2007 from the University of Wisconsin-Madison.

He is currently a Research Associate in JCET. His research interests cover a broad spectrum of precipitation cloud modeling, radiative transfer, cloud microphysics, and radar/radiometer remote sensing from air, space, and ground. Dr. Johnson is focusing on combined dual-frequency radar and multi-channel radiometer retrievals of frozen and mixed-phase precipitation at microwave frequencies in the 10 to 340 GHz range, with a focus on the Global Precipitation Mission (GPM) science objectives.

He is also a member of the GPM combined radar/radiometer algorithm development team, and is actively involved in developing improved retrieval algorithms for snowfall using passive microwave and radar remote sensing methods.