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SUMMARY:Snowfall microphysics: insights gained from Doppler radars - Anne-
 Claire Billault-Roux (LTE - EPFL)
DTSTART:20240712T130000Z
DTEND:20240712T140000Z
UID:TALK218683@talks.cam.ac.uk
CONTACT:Siddharth Gumber
DESCRIPTION:Snowfall is an essential component of the hydrological cycle\,
  as it is involved in most precipitation on Earth\, either directly as sno
 w falling to the ground or indirectly as rain melted from snow. At the sam
 e time\, the ice phase of clouds and precipitation is a key contributor to
  the Earth's radiative budget\, making it a crucial aspect of climate-orie
 nted research.\n\nProperly modeling snowfall for weather and climate appli
 cations requires knowledge of the "microphysics of snowfall"\, that is\, a
  microscale description of snow particles and of the mechanisms by which t
 hey form and grow. Among different approaches to studying snowfall microph
 ysics\, meteorological radars offer decisive insights: the interpretation 
 of radar variables reveals unique information on the microphysical propert
 ies of hydrometeors over large spatial areas and along the vertical dimens
 ion.\nIn this talk\, we investigate snowfall microphysics by relying prima
 rily on measurements from radars transmitting at different frequencies and
  on radar Doppler spectra. The data stems from a multi-sensor dataset of i
 n situ and remote sensing measurements\, which was collected during the IC
 E GENESIS campaign in the Swiss Jura Mountains in January 2021.\n\nBased o
 n these measurements\, we first propose a novel framework to retrieve a nu
 mber of snowfall microphysical properties from dual-frequency radar Dopple
 r spectra\, relying on a two-step\, physics-driven deep learning approach.
  In comparison with existing methods\, this framework relaxes the need for
  certain prior assumptions on microphysical properties\, or on perfect bea
 m alignment and non-turbulent atmosphere. We evaluate the retrieval agains
 t in situ measurements\, and the encouraging (albeit not perfect) results 
 pave the way for advanced characterizations of snowfall properties on larg
 er datasets. Then\, we focus on a specific snowfall event of ICE GENESIS. 
 Through a detailed analysis of multi-frequency and Doppler spectral measur
 ements\, we propose interpretations of the complex signatures observed\, w
 hich reveal the occurrence of distinct ice production and growth processes
 . With this case study\, we further illustrate the relevance of radar meas
 urements to improve our understanding of microphysical processes.\n
LOCATION:BAS Cambridge Seminar Room 1 and Zoom
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