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The almost six-years long database of aerosol and cloud vertical profiles provided by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) is at the present the longest database of aerosol optical properties at global scale. This database is a unique tool for the characterization of aerosol 4D distribution at global scale. However, CALIPSO has a small footprint and a revisiting time of 16 days, and therefore how well these measurements represent the atmospheric conditions of a surrounding area over a longer time is a big issue to be investigated. Because of its geographic coverage and the large number of advanced Raman aerosol lidars, EARLINET, the European Aerosol Research Lidar Network, offers a unique opportunity for the validation and full exploitation of the CALIPSO mission. CALIPSO Level 2 and Level 3 data products are investigated in terms of their representativeness by comparison with EARLINET measurements. Comparisons for the Level 2 profiles available in both version 2 (40 km as horizontal resolution) and version 3 (5 km) releases highlight the issue of finding a best compromise between the high resolution and the high signal-to-noise ratio. Representativeness of monthly averages provided in Level 3 data is investigated using EARLINET-CALIPSO correlative measurements. The study will furthermore benefit from the availability of the 12-years long-term database of EARLINET climatological data available from May 2000.

Cuatro sistemas lidar Raman multifrecuencia (Madrid, Granada, Barcelona y Evora), tomaron medidas simultaneamente a un sistema de referencia (Potenza) para verificar su funcionamiento durante la campana de intercomparacion: SPALI10, (SPAin Lidar Intercomparison 2010) que tuvo lugar en Madrid entre el 18 de Octubre y el 5 de Noviembre de 2010. Estos sistemas lidar Raman multifrecuencia proporcionan propiedades opticas de los aerosoles con resolucion vertical. Los perfiles suministrados por los sistemas lidar se compararon con informacion complementaria proporcionada por otra instrumentacion, tal como la distribucion de tamanos de los aerosoles medida de manera continua a nivel de superficie o la caracterizacion de la columna de aerosoles obtenida por fotometros solares. El amplio conjunto de medidas obtenido durante la campana SPALI10 permite evaluar algunos aspectos de las propiedades opticas y microfisicas de los aerosoles resueltos en altura. En este trabajo se discuten algunos detalles relevantes observados al intercomparar los resultados proporcionados por los diferentes instrumentos.

At the end of May 2008 one of the strongest Saharan dust outbreaks ever reached Central Europe. This event gave us the opportunity to extend our series of studies on Saharan dust characterization, which includes measurements near the source (SAMUM‐1, Morocco) and in the regime of mid range transport (SAMUM‐2, Cape Verde). The optical properties of the aerosol particles as a function of time and height are derived from data of the two Raman depolarization‐lidar systems MULIS and POLIS at Munich and Maisach (Germany), respectively. Measurements include the extensive properties of the particles, backscatter coefficient bp and extinction coefficient ap, and the intensive particle properties, linear depolarization ratio dp and lidar ratio Sp. All quantities are derived at two wavelengths, l = 355 nm and l = 532 nm. The focus of the study is on the intensive properties, for which we found on average dp = 0.30 at 355 nm and dp = 0.34 at 532 nm. The systematic errors were typically larger than the dp‐difference at the two wavelengths. With respect to the lidar ratio, we found Sp = 59 sr for both wavelengths, with an uncertainty range between ±4 sr and ±10 sr. These values are quite similar to the results from the SAMUM campaigns. Thus, our results suggest that the intensive optical properties of Saharan dust do not change significantly if the transport time is less than one week. However, more case studies in the far‐range regime are required to scrutinize this statement. To further refine conclusions with respect to the wavelength dependence of dp a further reduction of the errors is desired.

The particle linear depolarization ratio δp of Saharan dust, marine aerosols and mixtures of biomass-burning aerosols from southern West Africa and Saharan dust was determined at three wavelengths with three lidar systems during the SAharan Mineral dUst experiMent 2 at the airport of Praia, Cape Verde, between 22 January and 9 February 2008. The lidar ratio Sp of these major types of tropospheric aerosols was analysed at two wavelengths. For Saharan dust, we find wavelength dependent mean particle linear depolarization ratios δp of 0.24–0.27 at 355 nm, 0.29–0.31 at 532 nm and 0.36–0.40 at 710 nm, and wavelength independent mean lidar ratios Sp of 48–70 sr. Mixtures of biomass-burning aerosols and dust show wavelength independent values of δp and Sp between 0.12–0.23 and 57–98 sr, respectively. The mean values of marine aerosols range independent of wavelength for δp from 0.01 to 0.03 and for Sp from 14 to 24 sr.DOI: 10.1111/j.1600-0889.2011.00556.x

Aerosol Robotic Network (AERONET) Sun photometer observations were carried out at Ouarzazate, Morocco, during the Saharan Mineral Dust Experiment (SAMUM) 2006. Data from one measurement day, 19 May 2006, are used to derive particle optical and microphysical parameters with AERONET's latest version of lightâ��scattering model for nonâ��spherical particle geometry. In our analysis we also make use of a novel measurement channel at 1638 nm wavelength. We compare the results to data products obtained by airborne highâ��spectralâ��resolution lidar, several groundâ��based Raman lidar, and airborne and groundâ��based in situ measurement platforms. We chose that specific measurement day because the dust plume was vertically well mixed. Extinction coefficients from AERONET Sun photometer and lidar observations and in situ measurements agree well. ��ngstr�¶m exponents from Sun photometer and lidar are in close agreement, too. Airborne in situ measurements of dust particle size distributions show larger effective radii than inferred from the AERONET data. Complex refractive indices that are derived with the AERONET algorithm differ from the values obtained with different independent techniques employed in our study. The singleâ��scattering albedo was derived from the airborne observations of particle size distributions and complex refractive indices. Singleâ��scattering albedo differs to the value inferred from the AERONET data. The differences may be attributed to the different effective radii that we obtained from the various techniques. The differences between the data products from the various measurement platforms, however, cannot be generalized, as we could only test data for one measurement day. An analysis of additional measurements is under way.

The European Aerosol Research Lidar Network, EARLINET, performs correlative observations during CALIPSO overpasses based on a sophisticated measurement strategy since June 2006. Within a dedicated activity supported by the European Space Agency (ESA), sixteen EARLINET stations contributed about 1500 measurements during an intensive observational period from May 2008 to October 2009. From these measurements, we establish a long-term aerosol and cloud database of correlative EARLINET-CALIPSO observations. This database shall provide a basis for homogenizing long-term space-borne observations conducted with different lidar instruments operating at different wavelengths on various platforms over the next decade(s). The database is also used to study the quality and representativeness of satellite lidar cross sections along an orbit against long-term lidar network observations on a continental scale.

The high variability of tropospheric aerosols, both in space and time, is the main cause of the high uncertainty about radiative forcing related to tropospheric aerosols and their interaction with clouds. Because of the lack of high resolution aerosol global vertical profiles, the vertical mixing has not been considered so far in studies of spatial and temporal variability. The CALIPSO mission provides the first opportunity to investigate the 4-D aerosol and cloud fields in detail. However, because of the CALIOP small footprint and the revisit time of 16 days, correlative ground-based lidar observations are necessary in order to investigate the representativeness of these satellite observations. EARLINET, the European Aerosol Research Lidar Network, started correlative measurements for CALIPSO in June 2006, right after the CALIPSO launch. An integrated study of CALIPSO and EARLINET correlative measurements opens new possibilities for spatial (both horizontal and vertical) and temporal representativeness investigation of polar-orbit satellite measurements also in terms of revisit time.

In June 2006, the satellite-borne lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) began its observations onboard CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations; Winker et al., 2007). This date is regarded the starting point of a unique long-term, global, 4-dimensional aerosol and cloud data set. The forthcoming missions ADM-Aeolus (Atmospheric Dynamics Mission; Stoffelen et al., 2005; Ansmann et al., 2006) of the European Space Agency ESA and EarthCARE (Earth Clouds, Aerosols, and Radiation Explorer) of ESA and the Japan Aerospace Exploration Agency JAXA (ESA, 2004), with their lidar instruments ALADIN (Atmospheric Laser Doppler Lidar Instrument) and ATLID (Atmospheric Lidar), respectively, will continue such kind of observations. It is expected that the long-term data set gained in this way will substantially improve our knowledge on the role of aerosols and clouds in the Earth's climate system.

The talk explains how aerosol-free regions in a lidar signal can be determined by means of the so-called Rayleigh-fit. Criteria based on statistical analyses of the residuals are proposed and explained in detail, which allow to assess the quality of the Rayleigh-fit. Some of the methods can be used to develop quantitative criteria for the uncertainty in the retrieved reference value for the lidar signal inversion.

The European Aerosol Research LIdar NETwork (EARLINET) is an aerosol lidar network on a continental scale. EARLINET is now a leading network in qualitycontrolled quantitative aerosol profiling performing a schedule of routine measurements and presently consists of 28 stations distributed over Europe. The construction of an un-biased spatio-temporal database of vertical profiles of aerosol optical properties on a regional scale for climate and air quality research is the main objective of EARLINET and is accomplished through application of Raman lidars. One of the tasks in the EC-funded project EARLINET-ASOS is to optimize individual instruments with the aim of homogenization of aerosol data products over the network and increased data coverage by automation. This task is approached by selection of optimal solutions existing in the pool of individual stations. This is done for components, subsystems as well as for system integration. In system integration emphasis lies on automation to reduce the amount of manpower needed, to improve temporal coverage, and to make performance independent from individual operators. The procedure to perform these tasks is outlined and the set of tools enabling the assessment of performance under development is described.

A test is described, which serves as a self-check of theoptical part of a lidar system. Several lidar signals usingdifferent parts of the lidar telescope are compared.Differences in these signals indicate range dependenttransmission changes of the optical receiver, resultingin signal distortion. A systematic approach includingcomparison with ray tracing simulations of the opticalsystem can point out causes of the deviations.

It is shown that a tilted slit in the focal plane of the lidar telescope limits the telescopes field of view efficiently and suppresses the background in the lidar signal by up to an order of magnitude better than a circular diaphragm.

EARLINET (European Aerosol Research Lidar Network to Establish an Aerosol Climatology) is a joint project of 19 lidar groups operating aerosol lidar systems at 21 stations over a large part of Europe, plus one group focussing on mathematical problems associated with the retrieval of aerosol properties from lidar observations. The main goal of EARLINET is to establish a comprehensive statistically representative data set of the aerosol vertical distribution. For this purpose, each lidar group performs vertical aerosol soundings on a routine basis three times a week on preselected days and times. Additionally several special measurements (e.g. on Saharan dust, temporal cycles, rural and urban differences, long and medium range transport) are part of the project.