A novel post-processing algorithm for Halo Doppler lidars

Vakkari, Ville; Manninen, Antti; O’Connor, Ewan; Schween, Jan H.; Zyl, P. G. van; Marinou, Eleni

doi:10.5194/amt-12-839-2019

Cited by 35 publications

(39 citation statements)

References 29 publications

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“…The Streamline Pro is designed without moving parts on the outside, which limits the scanning to a cone of 20° from vertical. All Stream Line variants can be used for depolarization ratio measurements, but an important difference between XR and other Stream Line versions is that the XR background noise level cannot be determined as accurately in the near range as for the non-XR versions (Vakkari et al, 2019). This difference is attributed to the more sensitive amplifier used in the Stream Line XR (Vakkari et al, 2019).…”

Section: Halo Doppler Lidarmentioning

confidence: 99%

“…A background check to determine background noise level is performed automatically once per hour. We post-processed SNR according to Vakkari et al (2019), which is essential to be able to further reduce the instrumental noise floor by averaging the SNR.…”

Section: Halo Doppler Lidarmentioning

confidence: 99%

“…CC BY 4.0 License. Now, recently developed post-processing (Vakkari et al, 2019) allows the utilization of significantly weaker signals from Halo Doppler lidars than previously. Therefore, the main aim of this paper is to assess the capabilities of Halo Doppler lidars in providing particle linear depolarization ratio measurements at 1565 nm wavelength.…”

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confidence: 99%

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Aerosol particle depolarization ratio at 1565 nm measured with a Halo Doppler lidar

Vakkari¹,

Baars²,

Bohlmann³

et al. 2020

Preprint

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Abstract. Depolarization ratio is a valuable parameter for lidar-based aerosol categorization. Usually, aerosol particle depolarization ratio is determined at relatively short wavelengths of 355 nm and/or 532 nm, but some multi-wavelength studies including longer wavelengths indicate strong spectral dependency. Here, we investigate the capabilities of Halo Photonics Stream Line Doppler lidars to retrieve the particle linear depolarization ratio at 1565 nm wavelength. We utilize collocated measurements with another lidar system, PollyXT at Limassol, Cyprus, and at Kuopio, Finland, to compare the depolarization ratio observed by the two systems. For mineral dust-dominated cases we find typically a little lower depolarization ratio at 1565 nm than at 355 nm and 532 nm. However, for dust mixed with other aerosol we find higher depolarization ratio at 1565 nm. For polluted marine aerosol we find marginally lower depolarization ratio at 1565 nm compared to 355 nm and 532 nm. For mixed spruce and birch pollen we find a little higher depolarization ratio at 1565 nm compared to 532 nm. Overall, we conclude that Halo Doppler lidars can provide particle linear depolarization ratio at 1565 nm wavelength at least in the lowest 2–3 km above ground.

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Section: Halo Doppler Lidarmentioning

confidence: 99%

Section: Halo Doppler Lidarmentioning

confidence: 99%

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Aerosol particle depolarization ratio at 1565 nm measured with a Halo Doppler lidar

Vakkari¹,

Baars²,

Bohlmann³

et al. 2020

Preprint

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“…A Halo Photonics Stream Line pulsed Doppler LiDAR [39] was located at 8 m above sea level at Utö, and a 15 • elevation angle velocity azimuth display (VAD) scan was configured with 24 azimuthal directions every 15 min. The radial resolution of the measurement was 30 m, and the integration time per beam was 7 s. Raw data were post-processed according to [40], and a signal-to-noise ratio threshold of −23 dB was applied to the radial measurements before wind retrieval from the VAD. The three first range gates were excluded from the analysis, and thus, horizontal winds were available from 35 m above sea level at a 7.8 m height resolution.…”

Section: Utömentioning

confidence: 99%

Looking for an Offshore Low-Level Jet Champion among Recent Reanalyses: A Tight Race over the Baltic Sea

et al. 2020

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With an increasing interest in offshore wind energy, focus has been directed towards large semi-enclosed basins such as the Baltic Sea as potential sites to set up wind turbines. The meteorology of this inland sea in particular is strongly affected by the surrounding land, creating mesoscale conditions that are important to take into consideration when planning for new wind farms. This paper presents a comparison between data from four state-of-the-art reanalyses (MERRA2, ERA5, UERRA, NEWA) and observations from LiDAR. The comparison is made for four sites in the Baltic Sea with wind profiles up to 300 m. The findings provide insight into the accuracy of reanalyses for wind resource assessment. In general, the reanalyses underestimate the average wind speed. The average shear is too low in NEWA, while ERA5 and UERRA predominantly overestimate the shear. MERRA2 suffers from insufficient vertical resolution, which limits its usefulness in evaluating the wind profile. It is also shown that low-level jets, a very frequent mesoscale phenomenon in the Baltic Sea during late spring, can appear in a wide range of wind speeds. The observed frequency of low-level jets is best captured by UERRA. In terms of general wind characteristics, ERA5, UERRA, and NEWA are similar, and the best choice depends on the application.

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“…CC BY 4.0 License. The measurements were post-processed according to Vakkari et al (2019) and the attenuated backscatter (β) was calculated from signal-to-noise ratio (SNR) taking into account the telescope focus (infinity). The uncertainties in radial velocity and β were calculated according to O'Connor et al (2010).…”

Section: Halo Doppler Lidarmentioning

confidence: 99%

Winter atmospheric boundary layer observations over sea ice in the coastal zone of the Bothnian Bay (Baltic Sea)

Wenta¹,

Brus²,

Doulgeris³

et al. 2020

Preprint

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Abstract. The Hailuoto Atmospheric Observations over Sea ice (HAOS) campaign took place at the westernmost point of Hailuoto island (Finland) between 27 February and 2 March 2020. The aim of the campaign was to obtain atmospheric boundary layer (ABL) observations over seasonal sea ice in the Bay of Bothnia. Throughout 4 days both fixed-wing and quad-propeller rotorcraft unmanned aerial vehicles (UAV) were deployed over the sea ice to measure the properties of the lower ABL and to obtain accompanying high-resolution aerial photographs of the underlying ice surface. Additionally, a 3D sonic anenometer, an automatic weather station and a Halo Doppler lidar were installed on the shore to collect meteorological observations. During the UAV flights, measurements of temperature, relative humidity and atmospheric pressure were collected at 4 different altitudes between 25 m and 100 m, over an area of ~ 1.5 km2 of sea ice, located 1.1–1.3 km offshore from the Hailuoto Marjaniemi pier, together with orthomosaic maps of the ice surface below. Altogether the obtained dataset consists of 27 meteorological flights, 4 photogrammetry missions and continuous measurements of atmospheric properties from ground-based stations located at the coast. The acquired observations have been quality controlled and post processed and are available through the PANGAEA repository (https://doi.pangaea.de/10.1594/PANGAEA.918823, Wenta et al., 2020).

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A novel post-processing algorithm for Halo Doppler lidars

Cited by 35 publications

References 29 publications

Aerosol particle depolarization ratio at 1565 nm measured with a Halo Doppler lidar

Aerosol particle depolarization ratio at 1565 nm measured with a Halo Doppler lidar

Looking for an Offshore Low-Level Jet Champion among Recent Reanalyses: A Tight Race over the Baltic Sea

Winter atmospheric boundary layer observations over sea ice in the coastal zone of the Bothnian Bay (Baltic Sea)

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