613 Seminar: Bastiaan van Diedenhoven

CCSR, Columbia University, NASA/GISS

Realistically representing clouds in climate models remains problematic, partly because of our poor understanding of many key features of cloud formation and evolution. Remote sensing observations are helpful to improve our knowledge of cloud macro- and microphysics, although our current satellite fleet and retrieval techniques are not always sufficient to obtain products accurate and consistent enough to be used for model evaluation. For instance, ice cloud optical thickness and particle size retrievals using visible and shortwave infrared measurements are uncertain because of uncertainties in ice shape. Furthermore, vertical inhomogeneity and multi-layered clouds are problematic for retrievals of, e.g., cloud top height, particle properties and ice thermodynamic phase.

In this talk I will highlight some of the advances that multi-angular, multi-wavelength measurements of total and polarized reflectances at high spatial and angular resolution can contribute to our knowledge of clouds. Such measurements are provided by the airborne Research Scanning Polarimeter (RSP) that has flown in many campaigns and on many different aircraft. The talk will focus on new techniques to retrieve cloud heights of multi-layered systems, thermodynamic phase, ice crystal shape and asymmetry parameter, ice crystal orientation, and ice crystal size and its variation with respect to depth in the cloud top. Aside, I will show that coupling such retrievals with information on atmospheric state, such as relative humidity, buoyancy and wind speed, reveals some interesting variability of cloud properties.


Seminar Series Coordinators