613 Seminar: Jie Gong

USRA and the Climate & Radiation Laboratory

Cloud processes play an instrumental role in determining the TOA and surface radiation budget as well as the precipitation characteristics. In particular, cloud ice processes are arguably among the most poorly understood, in part due to various ice crystal types and sizes, as well as multiple pathways in ice particle formation and evolution. While ice microphysical processes themselves cannot be readily observed from space, the integrated effects of these processes (e.g., cloud and precipitation structures, microphysical/macrophysical properties) can be inferred using remote sensing techniques.
The launch of the Global Precipitation Measurement (GPM) core satellite in February 2014 enables new investigations of microphysical properties of frozen particles and their connection to surface precipitations. Conically polarimetric scanning at high microwave frequencies (89 and 166 GHz) from the GPM’s Microwave Imager (GMI) enhances sensitivity to frozen precipitation particle scattering and preserves the polarimetric information from ice clouds and floating snowflakes. Moreover, the procession orbit design of GPM also provides us an opportunity to study the diurnal change of ice microphysics.
In this talk, I will present our recent investigation on GMI’s 89 and 166 GHz polarimetric difference (PD) measurements. The link between PD signals and ice microphysical properties, including ice crystal orientation, shape, size and mixing will be hypothesized and studied one by one using the radiative transfer models (RTMs). The diurnal cycle of PD in the tropics will also be presented, which leads the diurnal change of ice cloud mass and occurring frequency by ~ 3 hrs. This implies the important role that ice microphysics play in the formation and dissipation processes of ice clouds and frozen precipitation.

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