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Since its establishment in 2000, EARLINET (European Aerosol Research Lidar NETwork) has provided, through its database, quantitative aerosol properties, such as aerosol backscatter and aerosol extinction coefficients, the latter only for stations able to retrieve it independently (from Raman or high-spectral-resolution lidars). These coefficients are stored in terms of vertical profiles, and the EARLINET database also includes the details of the range resolution of the vertical profiles. In fact, the algorithms used in the lidar data analysis often alter the spectral content of the data, mainly acting as low-pass filters to reduce the high-frequency noise. Data filtering is described by the digital signal processing (DSP) theory as a convolution sum: each filtered signal output at a given range is the result of a linear combination of several signal input data samples (relative to different ranges from the lidar receiver), and this could be seen as a loss of range resolution of the output signal. Low-pass filtering always introduces distortions in the lidar profile shape. Thus, both the removal of high frequency, i.e., the removal of details up to a certain spatial extension, and the spatial distortion produce a reduction of the range resolution. This paper discusses the determination of the effective resolution (ERes) of the vertical profiles of aerosol properties retrieved from lidar data. Large attention has been dedicated to providing an assessment of the impact of low-pass filtering on the effective range resolution in the retrieval procedure.

The financial support for EARLINET by the European Union under grant RICA 025991 in the Sixth Framework Programme is gratefully acknowledged. Since 2011 EARLINET has been integrated in the ACTRIS Research Infrastructure Project supported by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262254. The authors acknowledge the ESA financial support under the ESRIN contract 21769/08/I-OL and 22202/09/I-EC. Additional financial support has been received from the Andalusia Regional Government through project P10-RNM-6299 and from the Spanish Ministry of Science and Technology through projects CGL2010-18782, and CSD2007-00067.

This work was supported by CEA (Commissariat à l’Énergie Atomique) and CEREA joint laboratory École des Ponts ParisTech – EDF R&D. We thank all participants of the EARLINET network and MISTRALS/ChArMEx (Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/) for the 72 h continuous measurements. Forecasts and near-real-time quick looks for the lidar measurement alert have been provided by the MISTRALS/ChArMEx Operating Center (http://choc.sedoo.fr/) set-up at OMP (L’Observatoire Midi-Pyrénées), Toulouse. Lidar measurements are supported by the 7th Framework Programme project Aerosols, Clouds, and Trace Gases Research InfraStructure (ACTRIS) network (grant agreement no. 262254). The Barcelona EARLINET lidar team thanks the Spanish Ministry of Economy and Competitivity and European Regional Development (FEDER) funds through project TEC2012-34575 and Scientific and Technological Infrastructure project UNPC10-4E-442, as well as the Spanish Ministry of Science and Innovation and FEDER funds under projects CGL2011-13580-E/CLI and CGL2011-16124-E/CLI.

Global climatological distributions of key aerosol quantities (extinction, optical depth, mass, and surface area density) are shown in comparison with results from a three-dimensional global model including stratospheric and tropospheric aerosol components. Large increases of anthropogenic sulfur production at tropical latitudes by developing countries may explain these rather large predicted changes of stratospheric sulfate.

In the framework of ACTRIS (Aerosols, Clouds, and Trace Gases Research Infrastructure Network) summer 2012 measurement campaign (8 June–17 July 2012), EARLINET organized and performed a controlled exercise of feasibility to demonstrate its potential to perform operational, coordinated measurements and deliver products in near-real time. Eleven lidar stations participated in the exercise which started on 9 July 2012 at 06:00 UT and ended 72 h later on 12 July at 06:00 UT. For the first time, the single calculus chain (SCC) – the common calculus chain developed within EARLINET for the automatic evaluation of lidar data from raw signals up to the final products – was used. All stations sent in real-time measurements of a 1 h duration to the SCC server in a predefined netcdf file format. The pre-processing of the data was performed in real time by the SCC, while the optical processing was performed in near-real time after the exercise ended. 98 and 79 % of the files sent to SCC were successfully pre-processed and processed, respectively. Those percentages are quite large taking into account that no cloud screening was performed on the lidar data. The paper draws present and future SCC users' attention to the most critical parameters of the SCC product configuration and their possible optimal value but also to the limitations inherent to the raw data. The continuous use of SCC direct and derived products in heterogeneous conditions is used to demonstrate two potential applications of EARLINET infrastructure: the monitoring of a Saharan dust intrusion event and the evaluation of two dust transport models. The efforts made to define the measurements protocol and to configure properly the SCC pave the way for applying this protocol for specific applications such as the monitoring of special events, atmospheric modeling, climate research and calibration/validation activities of spaceborne observations.

Water vapour (H2O) is one of the operationallyretrieved key species of the Michelson Interferometer forPassive Atmospheric Sounding (MIPAS) instrument aboardthe Environmental Satellite (ENVISAT) which was launchedinto its sun-synchronous orbit on 1 March 2002 and operateduntil April 2012. Within the MIPAS validation activities,independent observations from balloons, aircraft, satellites,and ground-based stations have been compared to EuropeanSpace Agency (ESA) version 4.61 operational H2Odata comprising the time period from July 2002 until March2004 where MIPAS measured with full spectral resolution.No significant bias in the MIPAS H2O data is seen in thelower stratosphere (above the hygropause) between about15 and 30 km. Differences of H2O quantities observed byMIPAS and the validation instruments are mostly well withinthe combined total errors in this altitude region. In the upperstratosphere (above about 30 km), a tendency towardsa small positive bias (up to about 10 %) is present in theMIPAS data when compared to its balloon-borne counterpartMIPAS-B, to the satellite instruments HALOE (HalogenOccultation Experiment) and ACE-FTS (AtmosphericChemistry Experiment, Fourier Transform Spectrometer),and to the millimeter-wave airborne sensor AMSOS (AirborneMicrowave Stratospheric Observing System). In themesosphere the situation is unclear due to the occurrenceof different biases when comparing HALOE and ACE-FTSdata. Pronounced deviations between MIPAS and the correlativeinstruments occur in the lowermost stratosphere and upper troposphere, a region where retrievals of H2O are mostchallenging. Altogether it can be concluded that MIPAS H2Oprofiles yield valuable information on the vertical distributionof H2O in the stratosphere with an overall accuracy ofabout 10 to 30% and a precision of typically 5 to 15% –well within the predicted error budget, showing that theseglobal and continuous data are very valuable for scientificstudies. However, in the region around the tropopause retrievedMIPAS H2O profiles are less reliable, suffering froma number of obstacles such as retrieval boundary and cloudeffects, sharp vertical discontinuities, and frequent horizontalgradients in both temperature and H2O volume mixing ratio(VMR). Some profiles are characterized by retrieval instabilities.

This paper introduces the Atmospheric Measurement Techniques special issue on tropospheric profiling, which was conceived to host full papers presenting the results shown at the 9th International Symposium on Tropospheric Profiling (ISTP9). ISTP9 was held in L'Aquila (Italy) from 3 to 7 September 2012, bringing together 150 scientists representing of 28 countries and 3 continents. The tropospheric profiling special issue collects the highlights of ISTP9, reporting recent advances and future challenges in research and technology development.

One of the techniques adopted by the Pierre Auger Observatory to detect ultra high energy cosmic rays is based on air fluorescence detection. The knowledge of atmospheric properties during data acquisition is of primary importance. Together with other instruments, a system of four steerable elastic LIDARs, currently in operation, and a Raman LIDAR, that has taken data for about one year, provide measurements of the cloud coverage and of the aerosol optical transmission. This paper describes the hardware designs, the operational procedures, and the analyses performed on the collected data: aerosol optical properties and their vertical distributions.

EARLINET has been collecting high quality aerosol optical profiles over Europe since 2000. The comparison with automatic collected dataset of aerosol optical depth (AOD) from AERONET and MODIS demonstrates the effectiveness of EARLINET regular measurement schedule for climatological studies. The analysis of optical properties in the local boundary layer indicates that the general decrease of AOD observed by different platforms over Europe in the last decade could be due to the modification of aerosol properties (towards less absorbing and larger particles) in the lower troposphere.

We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays.