Universität zu Köln

Falconi, Marta Tecla, von Lerber, Annakaisa ORCID: 0000-0003-2890-1217, Ori, Davide ORCID: 0000-0002-9964-2200, Marzano, Frank Silvio and Moisseev, Dmitri ORCID: 0000-0002-4575-0409 (2018). Snowfall retrieval at X, Ka and W bands: consistency of backscattering and microphysical properties using BAECC ground-based measurements. Atmos. Meas. Tech., 11 (5). S. 3059 - 3080. GOTTINGEN: COPERNICUS GESELLSCHAFT MBH. ISSN 1867-8548

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Abstract

Radar-based snowfall intensity retrieval is investigated at centimeter and millimeter wavelengths using co-located ground-based multi-frequency radar and video-disdrometer observations. Using data from four snowfall events, recorded during the Biogenic Aerosols Effects on Clouds and Climate (BAECC) campaign in Finland, measurements of liquid-water-equivalent snowfall rate S are correlated to radar equivalent reflectivity factors Z(e), measured by the Atmospheric Radiation Measurement (ARM) cloud radars operating at X, Ka and W frequency bands. From these combined observations, power-law Z(e)-S relationships are derived for all three frequencies considering the influence of riming Using microwave radiometer observations of liquid water path, the measured precipitation is divided into lightly, moderately and heavily rimed snow. Interestingly lightly rimed snow events show a spectrally distinct signature of Z(e)-S with respect to moderately or heavily rimed snow cases. In order to understand the connection between snowflake microphysical and multi-frequency backscattering properties, numerical simulations are performed by using the particle size distribution provided by the in situ video disdrometer and retrieved ice particle masses. The latter are carried out by using both the T-matrix method (TMM) applied to soft-spheroid particle models with different aspect ratios and exploiting a pre-computed discrete dipole approximation (DDA) database for rimed aggregates. Based on the presented results, it is concluded that the soft-spheroid approximation can be adopted to explain the observed multifrequency Z(e)-S relations if a proper spheroid aspect ratio is selected. The latter may depend on the degree of riming in snowfall. A further analysis of the backscattering simulations reveals that TMM cross sections are higher than the DDA ones for small ice particles, but lower for larger particles. The differences of computed cross sections for larger and smaller particles are compensating for each other. This may explain why the soft-spheroid approximation is satisfactory for radar reflectivity simulations under study.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Falconi, Marta Tecla UNSPECIFIED UNSPECIFIED UNSPECIFIED von Lerber, Annakaisa UNSPECIFIED orcid.org/0000-0003-2890-1217 UNSPECIFIED Ori, Davide UNSPECIFIED orcid.org/0000-0002-9964-2200 UNSPECIFIED Marzano, Frank Silvio UNSPECIFIED UNSPECIFIED UNSPECIFIED Moisseev, Dmitri UNSPECIFIED orcid.org/0000-0002-4575-0409 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-185893
DOI:	10.5194/amt-11-3059-2018
Journal or Publication Title:	Atmos. Meas. Tech.
Volume:	11
Number:	5
Page Range:	S. 3059 - 3080
Date:	2018
Publisher:	COPERNICUS GESELLSCHAFT MBH
Place of Publication:	GOTTINGEN
ISSN:	1867-8548
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute for Geophysics and Meteorology
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language RADAR REFLECTIVITY; SIZE SPECTRA; SCATTERING; PARTICLE; CALIBRATION; SIGNATURES; AGGREGATE; MATRIX Multiple languages Meteorology & Atmospheric Sciences Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/18589