Retrievals of Riming and Snow Density From Vertically Pointing Doppler Radars

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http://hdl.handle.net/10138/307138

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Mason , S L , Chiu , C J , Hogan , R J , Moisseev , D & Kneifel , S 2018 , ' Retrievals of Riming and Snow Density From Vertically Pointing Doppler Radars ' , Journal of Geophysical Research : Atmospheres , vol. 123 , no. 24 , pp. 13807-13834 . https://doi.org/10.1029/2018JD028603

Title: Retrievals of Riming and Snow Density From Vertically Pointing Doppler Radars
Author: Mason, S. L.; Chiu, C. J.; Hogan, R. J.; Moisseev, D.; Kneifel, S.
Contributor: University of Helsinki, Institute for Atmospheric and Earth System Research (INAR)
Date: 2018-12-27
Language: eng
Number of pages: 28
Belongs to series: Journal of Geophysical Research : Atmospheres
ISSN: 2169-897X
URI: http://hdl.handle.net/10138/307138
Abstract: Retrievals of ice and snow are made from Ka- and W-band zenith-pointing Doppler radars at Hyytiala, Finland, during the snow experiment component of the Biogenic Aerosols: Effects on Clouds and Climate (2014) field campaign. In a novel optimal estimation retrieval, mean Doppler velocity is exploited to retrieve a density factor parameter, which modulates the mass, shape, terminal velocity, and backscatter cross sections of ice particles. In a case study including aggregate snow and graupel we find that snow rate and ensemble mean ice density can be retrieved to within 50% of in situ measurements at the surface using dual-frequency Doppler radar retrievals. While Doppler measurements are essential to the retrieval of particle density, the dual-frequency ratio provides a strong constraint on particle size. The retrieved density factor is strongly correlated with liquid water path, indicating that riming is the primary process by which the density factor is modulated. Using liquid water path as a proxy for riming, profiles classified as unrimed snow, rimed snow, and graupel exhibit distinct features characteristic of aggregation and riming processes, suggesting the potential to make estimates of process rates from these retrievals. We discuss the potential application of the technique to future satellite missions. Plain Language Summary Ground-based radar measurements of ice clouds and snow are used to estimate the size, number, and density of snowflakes. Doppler velocity measurements of particle fall speeds are used to estimate the mass and shape of the snow particles. The properties of snow estimated using radar compare well against measurements of particles at the surface and estimates of the amount of liquid water in the atmosphere; the presence of liquid water relates to the potential for riming, in which snowflakes increase in density and fall speed by collecting and freezing liquid droplets. More accurate estimates of snow density from ground-based and satellite radars help to improve global estimates of precipitation and snow accumulation and the representation of clouds and snow in weather and climate models.
Subject: remote sensing
snow
precipitation
optimal estimation
mixed-phase cloud
riming
PARTICLE-SIZE DISTRIBUTION
MIXED-PHASE CLOUDS
ICE WATER-CONTENT
TERMINAL VELOCITIES
ENSEMBLE RETRIEVAL
WAVELENGTH RADAR
FALL VELOCITIES
LIQUID WATER
MICROPHYSICS
SCATTERING
1171 Geosciences
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