Constraining snowfall remote sensing using novel high-resolution three-dimensional imaging and mass measurements of hydrometeors in freefall

• Applicant: Dr. Mathias Gergely
• Subject Area: Atmospheric Science
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 254901881

Accurate snowfall retrieval from microwave remote sensing is essential for understanding cloud-precipitation interactions, for weather forecasting and for climate research. However, development of reliable snowfall retrieval algorithms remains severely limited by an absence of detailed snowflake measurements that characterize the natural variability of snowflake mass and three-dimensional (3D) shape. The proposed project aims to (i) obtain these data using novel high-resolution measurement methods and (ii) exploit the measurements to provide look-up tables for the scattering properties of realistic snowflakes.To accomplish these goals, we will acquire the necessary data at an existing mountain laboratory in Utah using a newly developed hotplate device and a recently available automated multi-angle snowflake camera that allows for collecting photographs from multiple directions simultaneously. It is anticipated that each instrument will sample of order one million snowflakes over a single winter season to capture the natural snowflake variability at an unprecedented degree of detail. The modeled scattering properties for these snowflake measurements will be compared to (i) existing microwave scattering calculations for simple idealized snowflake shapes that have been used thus far to approximate real snowflakes and retrieve snowfall from remote-sensing data, and (ii) collocated radar measurements of snowfall. Based on the calculations and experimental validation, we will compile new look-up tables that quantify how the natural variability of snowflake mass and 3D shape relates to microwave remote sensing of clouds and precipitation.

• DFG Programme: Research Fellowships
• International Connection: USA
• Hosts: Professor Timothy Garrett; Professor Gerald Mace