EOL Seminar: Understanding the interaction of solar radiation with cirrus ice crystals – implications for the radiative transfer and climate modeling

Date: 
Thursday, June 22, 2017 - 14:00 to 15:00
Location: 
FL2-1022 Large Auditorium
Contact Name: 
Holger Voemel
Contact Email: 
Contact Phone: 
8837

Understanding the interaction of solar radiation with cirrus ice crystals – implications for the radiative transfer and climate modelling

Dr. Emma Järvinen

There exists still a great uncertainty in understanding the magnitude and even the sign of the cirrus short wave radiative effect. Partly, this is due to the difficulties of modelling and para- metrizing the radiative properties of usually non-spherical ice crystals that tend to be found in various shapes and sizes in the atmosphere. Furthermore, recent modelling and laboratory studies have given evidence that including microscale complexities, such as surface rough- ness, will further change the ice crystal light scattering properties. Although, satellite retrieval algorithms already take into account ice crystal complexity, direct in-situ measurements of the microscale structures of natural ice crystals and its influence to their light scattering prop- erties are largely missing. In this talk I will present laboratory and field measurements of ice crystal complexity based on analysis of single particle light scattering patterns. It was found in four airborne measurement campaigns, representing ice clouds from the tropics to arctic, that natural ice crystals are rarely pristine and that their high degree of crystal complexity leads to a similar low asymmetry parameter that appears to be unchanged independent of the measurement location. In the second half of the talk I will discuss the implications of the measured asymmetry parameter for global climate modelling and, at the end of my talk, I will touch the topic of what new possibilities the knowledge of the angular light scattering behav- iour of natural ice crystals could have for improved measurements of ice concentrations in mixed-phase clouds.

Seminar will be webcast at: http://www.fin.ucar.edu/it/mms/fl-live.htm

Thursday, 22 June, 2:00 PM

NCAR-Foothills Laboratory 3450 Mitchell Lane
Bldg 2 Large Auditorium (Rm1022)