LTE Seminar by Prof. Steve Nesbitt, University of Illinois at Urbana

NASA’s Global Precipitation Measurement (GPM) mission, which launched in early 2014, is tasked to detect and measure precipitation to 65 degrees latitude, where satellite precipitation estimates are highly uncertain. While the remote sensing of rainfall has made significant progress over the last half century or more, the remote sensing of snowfall remains a large challenge. Given the societal impacts of snowfall, as well as its importance in the global water and energy cycle, there is a new impetus to improve snowfall measurements on the ground and from a satellite perspective.
To improve satellite and ground-based measurements of snow, a major push of the GPM Ground Validation (GV) program is to validate spaceborne precipitation retrievals at mid- and high latitudes to constrain and improve satellite precipitation algorithms. Physically-based precipitation retrieval algorithms require knowledge of both the atmospheric and surface contributions to radiative transfer in the microwave. Focusing on the atmospheric portion of the problem, in order to constrain retrieval algorithms, we need to understand both the microphysical properties of precipitation as well as the radiative properties of the particles themselves. However, at high latitudes, few reliable observations exist to routinely measure these properties. Thus our ability to solve the “inverse problem” to retrieve snowfall properties such as mass, habit, and precipitation rate remain poorly constrained. In this presentation, the challenges for measuring snow, as well as important recent progress, will be discussed.