NA1: ACTRIS Management and coordination
WP2 WPleader:

  • The overall objective of this activity is to improve the observations of the vertical aerosol distribution by means of a network of advanced and coordinated lidar stations in such a way that the data they provide can be efficiently integrated with those contributed by other parts of the whole ACTRIS infrastructure. To this end, the following specific objectives are defined:
  • To enhance the shared scientific and technological knowledge on remote sensing of vertical aerosol profiles among the participants and to provide an interface to the rest of ACTRIS, as well as to the external scientific community, through exchange of expertise with focus on the strengthening of the whole ACTRIS infrastructure observing capabilities.
  • To assure the highest quality for lidar data through direct intercomparison campaigns and quality assurance internal check-up procedures. This will increase the throughput of lidar contribution to ACTRIS and will allow to improve the aerosol lidar techniques by checking and approving new methodologies and technologies.
  • To define a set of extended (beyond current EARLINET) standards for lidar-instrument capabilities and aerosol-profile products, as well as to improve the present EARLINET retrieval capabilities and to allow the end user to fully exploit lidar products
Description of work

The existing EARLINET infrastructure consists of 26 advanced aerosol lidar stations (at least five others are expected to join in the near future) distributed over Europe and has already provided the world largest database so far on aerosol four-dimensional (space-time) distribution at continental scale. The goal of this networking activity is to blend the EARLINET infrastructure, from a scientific and structural point of view, to the whole ACTRIS community and to provide effective means to reinforce it for remote sensing of vertical aerosol profiles on continental scale. Within ACTRIS the remote sensing of vertical aerosol distributions by coordinated advanced lidar stations spanning the European continent will be improved in coordination with WP6 to ensure a smooth integration of the results provided by the lidar observations with those coming from other parts of the whole infrastructure to achieve a synergistic effect enhancing its overall capabilities and usefulness. EARLINET database will be continuously updated and data will be accessible through WP18 (MPG). Due to the specific topics of WP20 and WP22, a special interaction of this networking activity with those joint research activities will be ensured. The activity will be implemented through the following tasks linked to the objectives stated in the previous section (task leader (underlined) and main participants are indicated in parentheses):

Task2.1: Exchange of expertise (UPC + all)
This task is intended as the backbone of the networking activity, allowing the participants to interact exchanging their expertise, discussing new ideas and concepts, sharing the outcomes of the other tasks, and facilitating ways for training and providing critical insight to (young) scientists. In addition it must also provide a means of interfacing with the participants in the other networking and joint research activities of the project on a more focused way than in the General Assembly and, to some extent, reaching out to the external scientific and technical community, as well as the general public. It is also expected that, this task may help originating technological developments with a measurable impact on the European industry. The task will mainly be structured in a series of technical workshops, one per year, during the full project duration. The workshops will be organized around a specific and well-defined set of topics (like for instance user requirements, instrument and data analysis optimization, etc.). The attendance of the workshops will consist of all the partners involved in long-term lidar observations and of other partners in ACTRIS more directly concerned by the workshop topics, as identified by the ACTRIS Executive Steering Committee. Scientific or technical external stakeholders (for example members of the passive and active Earth observation satellite community) can also be invited to the whole workshop or part of it. In particular, during the second and fourth years the workshops will be open to representatives of other lidar networks (in the framework of GALION) and of end users (atmospheric scientists, meteorologists, modellers, etc). An important expected outcome of the workshops is the effective training of (students and young) researchers on aerosol remote sensing lidar techniques, and synergies with other aerosol remote and in-situ measurement techniques included in ACTRIS. To facilitate an effective flow of scientific and technical information, all the material presented in the workshops will be made available to the ACTRIS partners through the project website. The workshops will be organised under the auspices of the Executive ACTRIS Steering Committee, which will be in charge of overseeing their synergies with the whole ACTRIS community, but will otherwise completely be under the responsibility of the EARLINET community both for the scientific and logistical organisation. In particular, UPC will coordinate this task and each EARLINET station participating in ACTRIS will be actively involved in the organization of this activity.

Task 2.2: Quality Assurance (LMU, CNR + all )
The main objective of this task is to assure along the time the quality of the measurements for all the EARLINET and other (ACTRIS or external) lidar stations, and approving new techniques and technologies. In this respect, it is expected that ACTRIS will improve significantly aerosol lidar techniques, will have a positive impact on the quality of lidar products and can be regarded as the worldwide knowledge base for aerosol lidar profiling quality-assurance techniques. Key sub-tasks to achieve the objective are direct lidar system inter-comparisons against approved reference systems, controlled regular internal quality checks, as explained in what follows.

Task 2.2.1: Intercomparison campaigns will be performed during the second and fourth years of the project for lidar sites of partners not belonging to EARLINET and for lidar systems (EARLINET or not) that have been significantly upgraded or to which new techniques are being applied. For these intercomparison campaigns the reference lidar systems from CNR and LMU will be used. As a part of transnational access, the possibility of intercomparison campaigns with the reference system located in Potenza (CNR) for lidar systems from institutions not participating in ACTRIS will be offered.

Task 2.2.2: Internal quality check-ups for the hardware will be performed regularly for all the lidar stations in EARLINET (minimum one per year) and for the non-EARLINET partner stations wishing to track their lidar hardware status. The internal quality assurance checks will be based on well established tools previously developed, tested and documented under the FP6 project EARLINET-ASOS (contract No. 025991 (RICA)), not excluding new developments that may be generated within ACTRIS. The following internal checkup tests are considered as mandatory (full documentation is currently available in the internal part of the EARLINET web page and will be made available to the ACTRIS partners):
- Telecover test: to detect optical misalignment and to check the full overlap range of lidar systems.
- Rayleigh fit: to check the goodness of lidar signal in the far range.
- Dark measurement: to detect distortions of lidar signal produced by electromagnetic interference and/or stray light.
- Trigger delay check: to measure the delay between the laser pulse emission and the effective start of the acquisition. LMU will be responsible for supervising these tests in order to: - collect all the results and to document them in a homogeneous way on the project website,
- assist partners in the correct use of the tests, - assist partners in the interpretation of unexpected results,
- find solutions and adaptation of the tests for newly arising problems or new partners,
- compare the results from different systems with respect to commonalities and differences,
- issue recommendations for best solutions for new systems or system upgrades.

Task 2.2.3: High-level quality check on the lidar data and products.
The main specific goals, under CNR responsibility, are: - definition of a set of parameters for both lidar raw data and final aerosol products that can be used as a standard to assess their quality. - implementation of procedures for the quality check of both lidar raw data and final products according to the defined standard. Although the activities of this task are under the responsibility of LMU and CNR and coordinated by them, all the ACTRIS lidar community and the partners more closely affected by their outcomes will actively participate in their specific definition, implementation, and in the discussion of the partial results in the workshops of task 2.1.

Task 2.3: Improvement of lidar techniques and data analysis for aerosol characterization (CNR, IFT, LMU, CNISM)
In the framework of EARLINET the definition of a standard set of main aerosol optical parameters (aerosol extinction and backscatter coefficient profiles, lidar ratio, Ångström exponent) was performed. A standardization was also implemented both at instrument and algorithm levels. In particular a Single Calculus Chain (SCC) was developed in the EARLINET-ASOS project, providing all the EARLINET partners with the possibility to analyse their data in an automatic way from raw lidar signals to final products. Even if the standard set of final-product parameters currently generated by the EARLINET SCC provides a quite complete optical characterization of atmospheric aerosol, there is a strong demand from the scientific community for the addition to the standard set of other significant parameters such as aerosol depolarization ratio, layer geometrical and optical properties, and uncertainties in the product parameters. These issues are addressed in this task through the following sub-tasks, for which responsible partners are also indicated in parentheses:

Task 2.3.1: Definition of new aerosol parameters to be included in the EARLINET standard set and of related quality-assurance procedures:
- aerosol depolarization ratio. Critical evaluation of different calibrations techniques taking into account the different experimental setups within EARLINET. Definition of standards for the calibration of aerosol depolarization ratio. Implementation of procedures to calibrate and calculate the aerosol depolarization ratio (CNR, CNISM).
- aerosol layer geometrical properties. Development of fully automated procedures to characterize the aerosol layers in terms of height and thickness and to obtain the PBL height (IFT).
- aerosol layer optical properties. Development of fully automated procedures to characterize the aerosol layers and PBL in terms of mean optical properties: extinction, backscatter, lidar ratio, Ångström exponent, depolarization ratio, and optical depth (IFT).
- product uncertainties. Critical evaluation of different techniques to calculate the statistical and systematic uncertainties on products. Definition of standards for uncertainty calculation for the different EARLINET lidar systems. Implementation of procedures for the error calculation on lidar data (CNR)
- cloud masking. Critical evaluation of existing algorithms to cloud mask the lidar data. Particular efforts will be devoted to full automate the separation of clouds with respect the aerosol layers (CNR, IFT).

Task 2.3.2 Development of a web graphic interface to improve the user-friendliness of the Single Calculus Chain and to manage the set of experimental parameters needed to perform lidar analysis. (CNR)
Task 2.3.3: Detailed documentation transferring to both internal and external users the information needed to fully exploit lidar products and making easier their use from scientific community (CNR, IFT).
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