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Observing wind, aerosol particles, cloud and precipitation: Finland's new ground-based remote-sensing network

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Author(s): A. Hirsikko | E. J. O'Connor | M. Komppula | K. Korhonen | A. Pfüller | E. Giannakaki | C. R. Wood | M. Bauer-Pfundstein | A. Poikonen | T. Karppinen | H. Lonka | M. Kurri | J. Heinonen | D. Moisseev | E. Asmi | V. Aaltonen | A. Nordbo | E. Rodriguez | H. Lihavainen | A. Laaksonen | K. E. J. Lehtinen | T. Laurila | T. Petäjä | M. Kulmala | Y. Viisanen

Journal: Atmospheric Measurement Techniques Discussions
ISSN 1867-8610

Volume: 6;
Issue: 4;
Start page: 7251;
Date: 2013;
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ABSTRACT
The Finnish Meteorological Institute, in collaboration with the University of Helsinki, has established a new ground-based remote-sensing network in Finland. The network consists of five topographically, ecologically and climatically different sites distributed from southern to northern Finland. The main goal of the network is to monitor air pollution and boundary layer properties in near real time, with a Doppler lidar and ceilometer at each site. In addition to these operational tasks, two sites are members of the Aerosols, Clouds, and Trace gases Research InfraStructure Network (ACTRIS); a Ka-band Doppler cloud radar at Sodankylä will provide cloud retrievals within CloudNet, and a multi-wavelength Raman lidar, POLLYXT (POrtabLe Lidar sYstem eXTended), in Kuopio provides optical and microphysical aerosol properties through EARLINET (European Aerosol Research Lidar Network to Establish an Aerosol Climatology). Three C-band weather radars are located in the Helsinki metropolitan area and are deployed for operational and research applications. We carried out two inter-comparison campaigns to investigate the Doppler lidar performance. The aims of the campaigns were to compare the backscatter coefficient and retrieved wind profiles, and to optimise the lidar sensitivity through adjusting the telescope focus and data-integration time to ensure enough signals in low-aerosol-content environments. The wind profiles showed good agreement between different lidars. However, due to inaccurate telescope focus setting and varying receiver sensitivity, backscatter coefficient profiles showed disagreement between the lidars. Harsh Finnish winters could pose problems, but, due to the built-in heating systems, low ambient temperatures had no, or only a minor, impact on the lidar operation: including scanning-head motion. However, accumulation of snow and ice on the lens has been observed, which can lead to formation of a water/ice layer thus attenuating the signal inconsistently. Thus, care must be taken to ensure continuous snow removal.
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