SPALINET: The Spanish and Portuguese Aerosol Lidar Network ,

SPALINET proposes to reinforce and complement the achievement of the goals of EARLINET-ASOS in the following aspects:

• Maintaining quality control of the Spanish and Portuguese lidar stations at the highest possible level by disseminating good practices of control and operation of the systems, along with “end-to-end” verification of specifications.
• Establishing common standards for advanced lidar instruments, to make it possible to improve time coverage, operational procedures, data processing and recovery of optical and microphysical parameters, etc., of interest.
• Establishing data formatting standards to facilitate internal and external access (for example, by atmosphere researchers, climate modellers on regional or global scale, users of satellite data, etc.)
• Serving as an initial nucleus for the development of the Spanish and Portuguese lidar community and stimulating participation in it to improve the spatial coverage of vertical measurements of aerosols in the Spanish and Portuguese territory, thus helping to overcome one of the gaps in the geographical implantation of EARLINET.

Over half of the member instruments of SPALINET work with a CIMEL xun-photometer, most of them belonging to the NASA AERONET (Aerosol RObotic NETwork) network. This network has been supported for around two years by the Spanish network RIMA (Iberian Network of Photometric Measurement of Aerosols). These instruments are a very valuable complement to lidar measurements, since they allow researchers to recover the extinction of aerosols in the atmospheric column (optical thickness) and also to estimate the size distribution of the particles that compose them, also averaged out in the atmospheric column. These parameters are a key factor in validating the lidar data and vertically characterising aerosols observed by means of data fusion.

The goal of SPALINET is the creation of synergy between the ten participating groups, seeking to promote to the full the exchange of information between them to improve and homogenise the specifications of the different units and permitting, in the longer term, the dissemination of this information to new interested groups in Spain and Portugal. The plan is to achieve this goal by means of the following working plan:

Year 1 (2007): Intercomparison of instruments: measurement campaigns

1. Harmonisation of instruments and test procedures.
2. Intercomparison of the various instruments. To do this, a search is made for a test site that is suitable from the points of view of both logistics and the environment: the latter point refers to atmospheric conditions that are appropriate for gathering lidar signals and are characterised by known meteorological processes and aerosols. Finally, the intercomparison exercises are carried out at the chosen point with the maximum number of lidar that can be transported.
3. Creation of a census website of the aerosol lidar instruments in Spain and Portugal with their characteristics, their locations and the goals they cover. This website also serves as a data exchange platform for the tasks carried out within the network.

Year 2 and Year 3 (2008 and 2009): Intercomparison of algorithms

The second and the third year are dedicated to the comparison of the instruments from an algorithmic point of view (elastic and Raman algorithms, respectively):

1. Comparison of the characteristics of the aerosol lidar instruments of the research groups incorporated into the network, in parallel with a comparison of the scientific goals of each group. This series of comparisons leads to the establishment of a list of capacities for each instrument.
2. For groups that use the same inversion methods, a series of common algorithm intercomparison tests is organised. These tests consist in comparing the results obtained by each participant group with the implementation of its algorithm on the basis of synthetic data with different complexities. The results are analysed to estimate the precision of each algorithm. If necessary, the algorithms are optimised to achieve the required precision and the test is repeated.

Year 4 (2010): Drafting of a univocal comparison process and future of SPALINET

1. Drafting of a report which, thanks to the experience gained during the previous three years, reflects a unívocal comparison process of algorithms and instruments with a view to incorporating new participants into the Spanish and Portuguese Aerosol Lidar Network.