ATHLI16: the ATHens Lidar Intercomparison campaign

Amodeo, Aldo; D’Amico, Giuseppe; Giunta, Aldo; Papagiannopoulos, Nikolaos; Papayannis, A.; Argyrouli, Athina; Mylonaki, Maria; Tsaknakis, G.; Kokkalis, P.; Σουπιωνά, Ουρανία; Tzanis, Chris G.

doi:10.1051/epjconf/201817609008

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…In order to make the lidar products from different systems in EARLINET comparable and to be able to provide qualityassured data sets of network products, specific quality standards have been established (Freudenthaler et al, 2018) and algorithm intercomparison campaigns have been organized (e.g. Amodeo et al, 2018).…”

Section: The Earlinet Productsmentioning

confidence: 99%

Validation of the TROPOMI/S5P aerosol layer height using EARLINET lidars

Michailidis

Koukouli²,

Balis³

et al. 2023

Atmos. Chem. Phys.

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Abstract. The purpose of this study is to investigate the ability of the Sentinel-5P TROPOspheric Monitoring Instrument (TROPOMI) to derive accurate geometrical features of lofted aerosol layers, selecting the Mediterranean Basin as the study area. Comparisons with ground-based correlative measurements constitute a key component in the validation of passive and active satellite aerosol products. For this purpose, we use ground-based observations from quality-controlled lidar stations reporting to the European Aerosol Research Lidar Network (EARLINET). An optimal methodology for validation purposes has been developed and applied using the EARLINET optical profiles and TROPOMI aerosol products, aiming at the in-depth evaluation of the TROPOMI aerosol layer height (ALH) product for the period 2018 to 2022 over the Mediterranean Basin. Seven EARLINET stations were chosen, taking into consideration their proximity to the sea, which provided 63 coincident aerosol cases for the satellite retrievals. In the following, we present the first validation results for the TROPOMI/S5P ALH using the optimized EARLINET lidar products employing the automated validation chain designed for this purpose. The quantitative validation at pixels over the selected EARLINET stations illustrates that the TROPOMI ALH product is consistent with the EARLINET lidar products, with a high correlation coefficient R=0.82 (R=0.51) and a mean bias of -0.51±0.77 km and -2.27±1.17 km over ocean and land, respectively. Overall, it appears that aerosol layer altitudes retrieved from TROPOMI are systematically lower than altitudes from the lidar retrievals. High-albedo scenes, as well as low-aerosol-load scenes, are the most challenging for the TROPOMI retrieval algorithm, and these results testify to the need to further investigate the underlying cause. This work provides a clear indication that the TROPOMI ALH product can under certain conditions achieve the required threshold accuracy and precision requirements of 1 km, especially when only ocean pixels are included in the comparison analysis. Furthermore, we describe and analyse three case studies in detail, one dust and two smoke episodes, in order to illustrate the strengths and limitations of the TROPOMI ALH product and demonstrate the presented validation methodology. The present analysis provides important additions to the existing validation studies that have been performed so far for the TROPOMI S5P ALH product, which were based only on satellite-to-satellite comparisons.

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Section: The Earlinet Productsmentioning

confidence: 99%

Validation of the TROPOMI/S5P aerosol layer height using EARLINET lidars

Michailidis

Koukouli²,

Balis³

et al. 2023

Atmos. Chem. Phys.

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“…Therefore, the corresponding uncertainty of the retrieved LR values is of the order of 11-30%, while the uncertainty for AEβ and AEα ranges between 0.02-0.04 and 0.03-0.08, respectively, as estimated by propagation error calculations. Both lidars are designed according to the optical set-up of a typical EARLINET station [69], following all the EARLINET quality assurance tests and standards [64,70], while the primary aerosol products (αaer and βaer) are retrieved by using the EARLINET Single Calculus Chain (SCC) [65,66].…”

Section: Lidar Systems At the National Technical University Of Athensmentioning

confidence: 99%

Radiative Effect and Mixing Processes of a Long-Lasting Dust Event over Athens, Greece, during the COVID-19 Period

et al. 2021

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We report on a long-lasting (10 days) Saharan dust event affecting large sections of South-Eastern Europe by using a synergy of lidar, satellite, in-situ observations and model simulations over Athens, Greece. The dust measurements (11–20 May 2020), performed during the confinement period due to the COVID-19 pandemic, revealed interesting features of the aerosol dust properties in the absence of important air pollution sources over the European continent. During the event, moderate aerosol optical depth (AOD) values (0.3–0.4) were observed inside the dust layer by the ground-based lidar measurements (at 532 nm). Vertical profiles of the lidar ratio and the particle linear depolarization ratio (at 355 nm) showed mean layer values of the order of 47 ± 9 sr and 28 ± 5%, respectively, revealing the coarse non-spherical mode of the probed plume. The values reported here are very close to pure dust measurements performed during dedicated campaigns in the African continent. By utilizing Libradtran simulations for two scenarios (one for typical midlatitude atmospheric conditions and one having reduced atmospheric pollutants due to COVID-19 restrictions, both affected by a free tropospheric dust layer), we revealed negligible differences in terms of radiative effect, of the order of +2.6% (SWBOA, cooling behavior) and +1.9% (LWBOA, heating behavior). Moreover, the net heating rate (HR) at the bottom of the atmosphere (BOA) was equal to +0.156 K/d and equal to +2.543 K/d within 1–6 km due to the presence of the dust layer at that height. On the contrary, the reduction in atmospheric pollutants could lead to a negative HR (−0.036 K/d) at the bottom of the atmosphere (BOA) if dust aerosols were absent, while typical atmospheric conditions are estimated to have an almost zero net HR value (+0.006 K/d). The NMMB-BSC forecast model provided the dust mass concentration over Athens, while the air mass advection from the African to the European continent was simulated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model.

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“…The EOLE system is based on a pulsed Nd:YAG laser system which emits, simultaneously, high energy pulses at 355, 532, and 1064 nm, with a 10-Hz repetition frequency. The system is designed following the optical set-up (Kokkalis 2017) of a typical member station of the European Aerosol Research Lidar Network (EARLINET), meeting all the quality assurance requirements of the network (Amodeo et al 2018). A 300-mm Cassegrainian telescope collects the backscattered lidar signals, as well as those generated by the spontaneous Raman effect.…”

Section: Lidar Unitmentioning

confidence: 99%

Application and Testing of the Extended-Kalman-Filtering Technique for Determining the Planetary Boundary-Layer Height over Athens, Greece

Kokkalis

Alexiou

Papayannis

et al. 2020

Boundary-Layer Meteorol

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We investigate the temporal evolution of the planetary boundary-layer (PBL) height over the basin of Athens, Greece, during a 6-year period (2011)(2012)(2013)(2014)(2015)(2016), using data from a Raman lidar system. The range-corrected lidar signals are selected around local noon (1200 UTC) and midnight (0000 UTC), for a total of 332 cases: 165 days and 167 nights. In this dataset, the extended-Kalman filtering technique is applied and tested for the determination of the PBL height. Several well-established techniques for the PBL height estimation based on lidar data are also tested for a total of 35 cases. The lidar-derived PBL heights are compared to those derived from radiosonde data. The mean PBL height over Athens is found to be 1617 ± 324 m at 1200 UTC and 892 ± 130 m at 0000 UTC for the period examined, while the mean PBL-height growth rate is found to be 170 ± 64 m h -1 and 90 ± 17 m h -1 during daytime and night-time, respectively.

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ATHLI16: the ATHens Lidar Intercomparison campaign

Cited by 5 publications

References 7 publications

Validation of the TROPOMI/S5P aerosol layer height using EARLINET lidars

Validation of the TROPOMI/S5P aerosol layer height using EARLINET lidars

Radiative Effect and Mixing Processes of a Long-Lasting Dust Event over Athens, Greece, during the COVID-19 Period

Application and Testing of the Extended-Kalman-Filtering Technique for Determining the Planetary Boundary-Layer Height over Athens, Greece

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