Universität zu Köln

Chellini, Giovanni ORCID: 0000-0002-7303-0468, Gierens, Rosa ORCID: 0000-0002-3879-3099 and Kneifel, Stefan ORCID: 0000-0003-2220-2968 (2022). Ice Aggregation in Low-Level Mixed-Phase Clouds at a High Arctic Site: Enhanced by Dendritic Growth and Absent Close to the Melting Level. J. Geophys. Res.-Atmos., 127 (16). WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-8996

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Abstract

Low-level mixed-phase clouds (MPCs) occur extensively in the Arctic, and are known to play a key role for the energy budget. While their characteristic structure is nowadays well understood, the significance of different precipitation-formation processes, such as aggregation and riming, is still unclear. Using a 3-year data set of vertically pointing W-band cloud radar and K-band Micro Rain Radar (MRR) observations from Ny-angstrom lesund, Svalbard, we statistically assess the relevance of aggregation in Arctic low-level MPCs. Combining radar observations with thermodynamic profiling, we find that larger snowflakes (mass median diameter larger than 1 mm) are predominantly produced in low-level MPCs whose mixed-phase layer is at temperatures between -15 and -10 degrees C. This coincides with the temperature regime known for favoring aggregation due to growth and subsequent mechanical entanglement of dendritic crystals. Doppler velocity information confirms that these signatures are likely due to enhanced ice particle growth by aggregation. Signatures indicative of enhanced aggregation are however not distributed uniformly across the cloud deck, and only observed in limited regions, suggesting a link with dynamical effects. Low Doppler velocity values further indicate that significant riming of large particles is unlikely at temperatures colder than -5 degrees C. Surprisingly, we find no evidence of enhanced aggregation at temperatures warmer than -5 degrees C, as is typically observed in deeper cloud systems. Possible reasons are discussed, likely connected to the ice habits that form at temperatures warmer than -10 degrees C, increased riming, and lack of particle populations characterized by broader size distributions precipitating from higher altitudes.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Chellini, Giovanni UNSPECIFIED orcid.org/0000-0002-7303-0468 UNSPECIFIED Gierens, Rosa UNSPECIFIED orcid.org/0000-0002-3879-3099 UNSPECIFIED Kneifel, Stefan UNSPECIFIED orcid.org/0000-0003-2220-2968 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-664823
DOI:	10.1029/2022JD036860
Journal or Publication Title:	J. Geophys. Res.-Atmos.
Volume:	127
Number:	16
Date:	2022
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-8996
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language RADAR DOPPLER SPECTRA; NY-ALESUND; REFLECTIVITY CALIBRATION; MICROPHYSICAL PROPERTIES; SIZE DISTRIBUTIONS; SNOW MICROPHYSICS; FALL STREAKS; WATER-VAPOR; SURFACE; PRECIPITATION Multiple languages Meteorology & Atmospheric Sciences Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/66482