Quantifying the effect of riming on snowfall using ground-based observations

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http://hdl.handle.net/10138/185423

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Moisseev , D , von Lerber , A & Tiira , J 2017 , ' Quantifying the effect of riming on snowfall using ground-based observations ' , Journal of Geophysical Research : Atmospheres , vol. 122 , no. 7 , pp. 4019-4037 . https://doi.org/10.1002/2016JD026272

Title: Quantifying the effect of riming on snowfall using ground-based observations
Author: Moisseev, Dmitri; von Lerber, Annakaisa; Tiira, Jussi
Other contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2017-04-16
Language: eng
Number of pages: 19
Belongs to series: Journal of Geophysical Research : Atmospheres
ISSN: 2169-897X
DOI: https://doi.org/10.1002/2016JD026272
URI: http://hdl.handle.net/10138/185423
Abstract: Ground-based observations of ice particle size distribution and ensemble mean density are used to quantify the effect of riming on snowfall. The rime mass fraction is derived from these measurements by following the approach that is used in a single ice-phase category microphysical scheme proposed for the use in numerical weather prediction models. One of the characteristics of the proposed scheme is that the prefactor of a power law relation that links mass and size of ice particles is determined by the rime mass fraction, while the exponent does not change. To derive the rime mass fraction, a mass-dimensional relation representative of unrimed snow is also determined. To check the validity of the proposed retrieval method, the derived rime mass fraction is converted to the effective liquid water path that is compared to microwave radiometer observations. Since dual-polarization radar observations are often used to detect riming, the impact of riming on dual-polarization radar variables is studied for differential reflectivity measurements. It is shown that the relation between rime mass fraction and differential reflectivity is ambiguous, other factors such as change in median volume diameter need also be considered. Given the current interest on sensitivity of precipitation to aerosol pollution, which could inhibit riming, the importance of riming for surface snow accumulation is investigated. It is found that riming is responsible for 5% to 40% of snowfall mass. The study is based on data collected at the University of Helsinki field station in Hyytiala during U.S. Department of Energy Biogenic Aerosols Effects on Clouds and Climate (BAECC) field campaign and the winter 2014/2015. In total 22 winter storms were analyzed, and detailed analysis of two events is presented to illustrate the study.
Subject: snowfall
riming
precipitation
cloud physics
dual-polarization weather radar
aerosol-cloud-precipitation interaction
T-MATRIX COMPUTATIONS
POLARIMETRIC RADAR
SNOWFLAKE AGGREGATION
SOLID PRECIPITATION
CLOUD MICROPHYSICS
VIDEO DISDROMETER
PART I
ICE
PARTICLES
MASS
114 Physical sciences
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