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Opis: Imaging Atmospheric Cherenkov Telescope (IACT) systems are used in high-energy astrophysics to detect and study gamma-ray sources in the universe. These telescopes measure properties of cosmic gamma rays using Cherenkov radiation emitted by secondary particles produced after interacting with the Earth’s atmosphere. Atmospheric monitoring is crucial for the proper operation of IACT systems. A number of remote sensing and in situ methods are used to understand and correct the effects of the atmosphere on the propagation of Cherenkov radiation from its origin to the telescope. Failure to do so greatly decreases IACT performance, particularly, their energy resolution and threshold. Lidar systems can be used to measure atmospheric optical depth profiles, which are essential for IACT calibration. The main aim of this thesis is to demonstrate that a prototype lidar for the north-ern site of the Cherenkov Telescope Array Observatory (CTAO), which is a next-generation IACT now under construction, has hardware and software capabilities that would lead to the construction of CTAO Raman lidar. Due to specific require-ments of the CTAO, a Raman lidar, which can provide better atmospheric parameter accuracy, will be used for the first time in an IACT system. In 2021-2022 the BRL was deployed to the future CTAO-North site at the Roque de los Muchachos observatory, La Palma, for testing in its actual operating conditions. During a year and a half long test period, it underwent a number of tests, including manual and remote operation under various environmental conditions. These included hot summers, cold winters, rain, snow, ice, and strong winds, but also some more exotic events, such as desert sand intrusions (Calima) and volcanic eruptions. The latter two are presented in this work as test cases for atmospheric characterization. Since the main goal of a CTAO lidar is the optical depth measurements, the BRL does not have the full set of features for aerosol characterization. While it can yield the ˚Angstr¨om exponent and lidar ratio, it does not provide depolarization informa-tion, which is one of the key components for aerosol typing. As the atmosphere at La Palma was found to be more complex than initially anticipated, we present the benefits of including depolarization capability by using a conceptually similar Raman lidar system specifically designed for aerosol characterization. We present the results of a campaign focused on the determination of bioaerosol capabilities to act as cloud condensation nuclei and ice-nucleating particles in mixed-phase clouds, where depo-larization information was used to determine the thermodynamic phase of the cloud.
Ključne besede: Cherenkov Telescope Array Observatory, Raman Lidar, atmospheric optical depth, aerosol characterization, Cumbre Vieja, Calima
Objavljeno v RUNG: 23.10.2023; Ogledov: 282; Prenosov: 4
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Opis: Light aircraft (WT10 - experimental) with position and windspeed variables provided by onboard GPS, as well as additional meteorological sensors. The aircraft was mounted with a: a sunshine pyranometer type SPN1 (Delta-T Devices Ltd), a polar integrating nephelometer AURORA 4000 (Ecotech Pty Ltd), and had a dual sampling line aircraft for measurements at the fine and coarse fraction of the absorption by two Continuous Light Absorption Photometer (CLAPS, by Haze Instruments d.o.o.) and the particle size distribution by two optical particle counters (OPC, model 11D, GRIMM Technologies). The pyranometer provides measurements of the global, direct and diffuse irradiance for a radiation spectrum range between 400 and 2700nm with a 1s time resolution. The polar integrating nephelometer measures the scattering coefficients of particles at three wavelengths (450, 525 and 635 nm) and multiple angles (two selected for the campaign: 0, 90deg) with a 5s time resolution. The CLAP photometers measure the absorption coefficient by aerosol particles at three wavelengths (467, 529 and 653 nm) with a 1s time resolution. The OPC measurements provide the number and mass concentration of aerosol particles for 31 bins in the size range between 0.253 and 35.15 micrometers with a 6s time resolution. The 2021 and 2022 campaigns are found at: http://www.worldgreenflight.com/glwf.php#to-2021 http://www.worldgreenflight.com/glwf.php#to-2022-jatac
Ključne besede: Aeolus satellite, Saharan dust, aerosol, calibration, validation
Objavljeno v RUNG: 27.09.2023; Ogledov: 402; Prenosov: 5
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Ključne besede: black carbon, brown carbon, carbonaceous aerosol, wildfire, air quality, CASS
Objavljeno v RUNG: 06.06.2023; Ogledov: 691; Prenosov: 6
Celotno besedilo (18,34 MB)

Ključne besede: local air quality, aerosol measurements, perception, heating habits
Objavljeno v RUNG: 27.02.2023; Ogledov: 687; Prenosov: 0
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Opis: Since 2007, a series of ESA supported airborne campaigns have been essential to the development of the Aeolus Doppler Wind Lidar satellite mission, which was successfully launched on 22 September 2018 and is providing a novel wind and aerosol profile data. A core element of the Aeolus Cal/Val activities is DLR’s A2D wind lidar on-board the DLR Falcon aircraft, an airborne demonstrator for the Aeolus ALADIN satellite instrument flown in combination with the 2-µm Doppler Wind Lidar reference system. Following the pre-launch WindVal-I and –II campaigns in 2015 and 2016, a number of calibration and validation campaigns have been successfully implemented: WindVal-III providing early Cal/Val results in November 2018 only three months after the Aeolus launch, AVATAR-E in May 2019 focussing on the Cal/Val over Central Europe, and AVATAR-I in September 2019 providing Cal/Val information in the North Atlantic and Arctic flying from Iceland. The airborne validation is also being supported through balloon flights in the tropical UTLS and lower stratosphere in the frame of the CNES Stratéole-2 stratospheric balloon activities. In the frame of the ESA supported pre-Stratéole-2 campaign, eight stratospheric balloons have been launched from the Seychelles in November/December 2019 providing unique upper level wind data for the Aeolus validation. The largest impact of the Aeolus observations is expected in the Tropics, and in particular over the Tropical oceans, where only a limited number of wind profile information is provided by ground based observations. Aeolus provides key direct measurements which are of importance to correctly constrain the wind fields in models. In addition, Aeolus observations have the potential to further enhance our current knowledge on aerosols and clouds by globally providing optical properties products that include atmospheric backscatter and extinction coefficient profiles, lidar ratio profiles and scene classification. In the tropics, a particularly interesting case is the outflow of Saharan dust and its impact on micro-physics in tropical cloud systems. The region off the coast of West Africa allows the study of the Saharan Aerosol layer, African Easterly Waves and Jets, Tropical Easterly Jet, as well as the deep convection in ITCZ. Together with international partners, ESA is currently implementing a Tropical campaign in July 2020 with its base in Cape Verde that comprises both airborne and ground-based activities addressing the tropical winds and aerosol validation, as well as science objectives. The airborne component includes the DLR Falcon-20 carrying the A2D and 2-µm Doppler Wind lidars, the NASA P-3 Orion with the DAWN and HALO lidar systems, the APR Ku-, Ka- and W-band Doppler radar and drop sondes, and a Slovenian small aircraft providing in-situ information from aethalometers, nephelometers and optical particle counters. The ground-based component led by the National Observatory of Athens is a collaboration of European teams providing aerosol and cloud measurements with a range of lidar, radar and radiometer systems, as well as a drone providing in-situ aerosol observations. In addition, the participation airborne capabilities by NOAA and LATMOS/Meteo France are currently being investigated. This paper will provide a summary of the Aeolus campaign focussing on the planned tropical campaign.
Ključne besede: Aeolus satellite, ALADIN, aerosol, validation
Objavljeno v RUNG: 23.08.2022; Ogledov: 977; Prenosov: 44
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