The European Aerosol Research Lidar Network (EARLINET), part of the Aerosols, Clouds and Trace gases Research Infrastructure (ACTRIS), organized an intensive observational campaign in May 2020, with ...the objective of monitoring the atmospheric state over Europe during the COVID-19 lockdown and relaxation period. Besides the standard operational processing of the lidar data in EARLINET, for seven EARLINET sites having collocated sun-photometric observations in the Aerosol Robotic Network (AERONET), a network exercise was held in order to derive profiles of the concentration and effective column size distributions of the aerosols in the atmosphere, by applying the GRASP/GARRLiC (from Generalized Aerosol Retrieval from Radiometer and Lidar Combined data – GARRLiC – part of the Generalized Retrieval of Atmosphere and Surface Properties – GRASP) inversion algorithm. The objective of this network exercise was to explore the possibility of identifying the anthropogenic component and of monitoring its spatial and temporal characteristics in the COVID-19 lockdown and relaxation period. While the number of cases is far from being statistically significant so as to provide a conclusive description of the atmospheric aerosols over Europe during this period, this network exercise was fundamental to deriving a common methodology for applying GRASP/GARRLiC to a network of instruments with different characteristics. The limits of the approach are discussed, in particular the missing information close to the ground in the lidar measurements due to the instrument geometry and the sensitivity of the GRASP/GARRLiC retrieval to the settings used, especially for cases with low aerosol optical depth (AOD) like the ones we show here. We found that this sensitivity is well-characterized in the GRASP/GARRLiC products, since it is included in their retrieval uncertainties.
The Aerosol, Clouds and Trace Gases Research Infrastructure ACTRIS is currently being developed with support from more than 20 countries and more than 100 research-performing organizations in Europe. ...The pan-European distributed research infrastructure shall provide data and services related to short-lived atmospheric constituents to facilitate high-quality Earth system research in the long term (over at least 20 years). While some of the activities are already in place, ACTRIS functionality will be further ramped up until full operation in 2025. The observation of aerosol, clouds and reactive trace gases with in-situ and remote-sensing techniques in ACTRIS is supported by six Topical Centres, which are responsible for common standards and quality assurance. Free and open virtual access to ACTRIS data is provided by the Data Centre. International users will also have physical access to ACTRIS observatories, atmospheric simulation chambers and mobile platforms as well as remote or physical access to calibration services, digital services and training. Access provision is organized through a single-entry point by the Head Office. In this contribution, the general principles and structure of ACTRIS are introduced, and the observational component related to aerosol remote sensing, which builds on the heritage of the European Aerosol Research Lidar Network (EARLINET) and the European part of the Aerosol Robotic Network (AERONET-Europe), is explained in more detail.
Pollen allergenicity plays an important role on human health and wellness. It is thus of large public interest to increase our knowledge of pollen grain behavior in the atmosphere (source, emission, ...processes involved during their transport, etc.) at fine temporal and spatial scales. First simulations with the Barcelona Supercomputing Center NMMB/BSC-CTM model of
Platanus
and
Pinus
dispersion in the atmosphere were performed during a 5-day pollination event observed in Barcelona, Spain, between 27 – 31 March, 2015. The simulations are compared to vertical profiles measured with the continuous Barcelona Micro Pulse Lidar system. First results show that the vertical distribution is well reproduced by the model in shape, but not in intensity, the model largely underestimating in the afternoon. Guidelines are proposed to improve the dispersion of airborne pollen by numerical prediction models.
As an application of the dimensionless parameterization concept proposed earlier for the characterization of lidar systems, the universal assessment of lidar capabilities in day and night conditions ...is considered. The dimensionless parameters encapsulate the atmospheric conditions, the lidar optical and optoelectronic characteristics, including the photodetector internal noise, and the sky background radiation. Approaches to ensure immunity of the lidar system to external background radiation are discussed.
An improvement of the estimation of mineral dust longwave, direct radiative forcing is presented. It is based on recent developments that combine Sun photometer and multiwavelength lidar data to ...retrieve range‐resolved coarse‐ and fine‐mode extinction coefficients. The forcings are calculated separately for each mode, and their sum is compared to the classical approach in which only the total extinction is considered. The results of four cases of mineral dust intrusion in Barcelona, Spain, show that when the coarse mode predominates, the longwave forcings calculated with the classical approach are underestimated up to 20% near the surface. In all cases the strong coarse‐mode predominance near the surface has also an effect on the forcing in the upper layers.
Key Points
Separated treatment of coarse‐ and fine‐mode particles in a RTMImprovement of the mineral dust longwave, direct radiative forcing estimationIncrease of the longwave forcing when the coarse mode predominates up to 20%
The purpose of the work is to demonstrate real capabilities and to give examples of SiPMs application in lidar technology in both analog and photon counting modes. The experimental research within an ...operating lidar complex adapted to implement the analog mode and photon counting measurements with subsequent inversions of atmospheric extinction and backscattering coefficients was conducted. Theoretical evaluations of potential limitations of atmospheric lidar by use of real day-time background parameters and features of SiPM-photodetectors studied experimentally were carried out with comparison of the extent of sensitivity decreasing for different detectors used and estimations of their operation range reduction.
► We demonstrate real capabilities to use SiPMs as lidar detectors in both analog and photon counting modes. ► We model SiPMs and PMTs as lidar detectors capable to work under intense day-time skylight. ► We examined limitations of SiPMs caused by intense background radiation.
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