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Retrievals of ice microphysical properties using dual-wavelength polarimetric radar observations during stratiform precipitation events

Tetoni, Eleni and Ewald, Florian and Hagen, Martin and Köcher, Gregor and Zinner, Tobias and Groß, Silke Martha (2022) Retrievals of ice microphysical properties using dual-wavelength polarimetric radar observations during stratiform precipitation events. Atmospheric Measurement Techniques (AMT), 15 (13), pp. 3969-3999. Copernicus Publications. doi: 10.5194/amt-15-3969-2022. ISSN 1867-1381.

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Official URL: https://amt.copernicus.org/articles/15/3969/2022/amt-15-3969-2022.html

Abstract

Ice growth processes within clouds affect the type and amount of precipitation. Hence, the importance of an accurate representation of ice microphysics in numerical weather and numerical climate models has been confirmed by several studies. To better constrain ice processes in models, we need to study ice cloud regions before and during monitored precipitation events. For this purpose, two radar instruments facing each other were used to collect complementary measurements. The C-band POLDIRAD weather radar from the German Aerospace Center (DLR) in Oberpfaffenhofen and the Ka-band MIRA-35 cloud radar from the Ludwig Maximilians University of Munich (LMU) were used to monitor stratiform precipitation in the vertical cross-sectional area between the two instruments. The logarithmic difference of radar reflectivities at two different wavelengths (54.5 and 8.5 mm), known as the dual-wavelength ratio, was exploited to provide information about the size of the detected ice hydrometeors, taking advantage of the different scattering behavior in the Rayleigh and Mie regime. Along with the dual-wavelength ratio, differential radar reflectivity measurements from POLDIRAD provided information about the apparent shape of the detected ice hydrometeors. Scattering simulations using the T-matrix method were performed for oblate and horizontally aligned prolate ice spheroids of varying shape and size using a realistic particle size distribution and a well-established mass–size relationship. The combination of dual-wavelength ratio, radar reflectivity, and differential radar reflectivity measurements as well as scattering simulations was used for the development of a novel retrieval for ice cloud microphysics. The development of the retrieval scheme also comprised a method to estimate the hydrometeor attenuation in both radar bands. To demonstrate this approach, a feasibility study was conducted on three stratiform snow events which were monitored over Munich in January 2019. The ice retrieval can provide ice particle shape, size, and mass information which is in line with differential radar reflectivity, dual-wavelength ratio, and radar reflectivity observations, respectively, when the ice spheroids are assumed to be oblates and to follow the mass–size relation of aggregates. When combining two spatially separated radars to retrieve ice microphysics, the beam width mismatch can locally lead to significant uncertainties. However, the calibration uncertainty is found to cause the largest bias for the averaged retrieved size and mass. Moreover, the shape assumption is found to be equally important to the calibration uncertainty for the retrieved size, while it is less important than the calibration uncertainty for the retrieval of ice mass. A further finding is the importance of the differential radar reflectivity for the particle size retrieval directly above the MIRA-35 cloud radar. Especially for that observation geometry, the simultaneous slantwise observation from the polarimetric weather radar POLDIRAD can reduce ambiguities in retrieval of the ice particle size by constraining the ice particle shape.

Item URL in elib:https://elib.dlr.de/188172/
Document Type:Article
Title:Retrievals of ice microphysical properties using dual-wavelength polarimetric radar observations during stratiform precipitation events
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Tetoni, EleniDLR, IPAhttps://orcid.org/0000-0003-3441-8803UNSPECIFIED
Ewald, FlorianDLR, IPAhttps://orcid.org/0000-0002-5899-0890UNSPECIFIED
Hagen, MartinDLR, IPAhttps://orcid.org/0000-0003-4714-0775UNSPECIFIED
Köcher, GregorLudwig-Maximilians-Universität München, Munich, Germanyhttps://orcid.org/0000-0003-1586-6774UNSPECIFIED
Zinner, TobiasLudwig-Maximilians-Universität München, Munich, GermanyUNSPECIFIEDUNSPECIFIED
Groß, Silke MarthaDLR, IPAhttps://orcid.org/0000-0002-7467-9269UNSPECIFIED
Date:5 July 2022
Journal or Publication Title:Atmospheric Measurement Techniques (AMT)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:15
DOI:10.5194/amt-15-3969-2022
Page Range:pp. 3969-3999
Publisher:Copernicus Publications
ISSN:1867-1381
Status:Published
Keywords:dual-wavelength radar method, polarimetry, ice microphysics, ice scattering simulations
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Atmospheric and climate research
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Lidar
Deposited By: Tetoni, Eleni
Deposited On:07 Sep 2022 08:24
Last Modified:19 Oct 2023 12:50

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