Universität zu Köln

Mason, S. L., Chiu, C. J., Hogan, R. J., Moisseev, D. and Kneifel, S. (2018). Retrievals of Riming and Snow Density From Vertically Pointing Doppler Radars. J. Geophys. Res.-Atmos., 123 (24). S. 13807 - 13835. WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-8996

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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.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Mason, S. L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Chiu, C. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hogan, R. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Moisseev, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kneifel, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-161708
DOI:	10.1029/2018JD028603
Journal or Publication Title:	J. Geophys. Res.-Atmos.
Volume:	123
Number:	24
Page Range:	S. 13807 - 13835
Date:	2018
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-8996
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language PARTICLE-SIZE DISTRIBUTION; MIXED-PHASE CLOUDS; ICE WATER-CONTENT; TERMINAL VELOCITIES; ENSEMBLE RETRIEVAL; WAVELENGTH RADAR; FALL VELOCITIES; LIQUID WATER; MICROPHYSICS; SCATTERING Multiple languages Meteorology & Atmospheric Sciences Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/16170