[1] We summarize our Raman lidar observations which were carried out in Europe, Asia, and Africa during the past 10 years, with focus on particle extinction-to-backscatter ratios (lidar ratios) and Angstrom exponents. For the first time, we present statistics on lidar ratios for almost all climatically relevant aerosol types solely based on Raman lidar measurements. Sources of continental particles were in North America and Europe, the Sahara, and south and Southeast and east Asia. The North Atlantic Ocean, and the tropical and South Indian Ocean were the sources of marine particles. The statistics are complemented with lidar ratios describing aged forest fire smoke and pollution from polar regions (Arctic haze) after long-range transport. In addition, we present particle Angstrom exponents for the wavelength range from 355 to 532 nm and from 532 to 1064 nm. We compare our data set of lidar ratios to the recently published AERONET (Aerosol Robotic Network) lidar ratio climatology. That climatology is based on aerosol scattering modeling in which AERONET Sun photometer observations serve as input. Raman lidar measurements of extinction-to-backscatter ratios of Saharan dust and urban aerosols differ significantly from the numbers obtained with AERONET Sun photometers. There are also differences for some of the Angstrom exponents. Further comparison studies are needed to reveal the reason for the observed differences.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006JD008292

Aerosol-type-dependent lidar ratios observed with Raman lidar

The European Aerosol Research Lidar Network, EARLINET, was founded in 2000 as a research project for establishing a quantitative, comprehensive, and statistically significant database for the horizontal, vertical, and tempo- ral distribution of aerosols on a continental scale. Since then EARLINET has continued to provide the most extensive col- lection of ground-based data for the aerosol vertical distribu- tion over Europe. This paper gives an overview of the network's main de- velopments since 2000 and introduces the dedicated EAR- LINET special issue, which reports on the present innova- tive and comprehensive technical solutions and scientific re- sults related to the use of advanced lidar remote sensing tech- niques for the study of aerosol properties as developed within the network in the last 13 years. Since 2000, EARLINET has developed greatly in terms of number of stations and spatial distribution: from 17 sta- tions in 10 countries in 2000 to 27 stations in 16 countries in 2013. EARLINET has developed greatly also in terms of technological advances with the spread of advanced multi- wavelength Raman lidar stations in Europe. The develop- ments for the quality assurance strategy, the optimization of instruments and data processing, and the dissemination of data have contributed to a significant improvement of the net- work towards a more sustainable observing system, with an increase in the observing capability and a reduction of oper- ational costs. Consequently, EARLINET data have already been ex- tensively used for many climatological studies, long-range transport events, Saharan dust outbreaks, plumes from vol- canic eruptions, and for model evaluation and satellite data validation and integration. Future plans are aimed at continuous measurements and near-real-time data delivery in close cooperation with other ground-based networks, such as in the ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) www.actris.net, and with the modeling and satellite commu- nity, linking the research community with the operational world, with the aim of establishing of the atmospheric part of the European component of the integrated global observ- ing system.

https://www.dwd.de/DWD/forschung/projekte/ceilomap/files/amt-7-2389-2014.pdf

EARLINET: towards an advanced sustainable European aerosol lidar network

CO2, CH4, and N2O are recognised as the most important greenhouse gases, the concentrations of which increase rapidly through human activities. Space-borne integrated path differential absorption lidar allows global observations at day and night over land and water surfaces in all climates. In this study we investigate potential sources of measurement errors and compare them with the scientific requirements. Our simulations reveal that moderate-size instruments in terms of telescope aperture (0.5–1.5 m) and laser average power (0.4–4 W) potentially have a low random error of the greenhouse gas column which is 0.2% for CO2 and 0.4% for CH4 for soundings at 1.6 μm, 0.4% for CO2 at 2.1 μm, 0.6% for CH4 at 2.3 μm, and 0.3% for N2O at 3.9 μm. Coherent detection instruments are generally limited by speckle noise, while direct detection instruments suffer from high detector noise using current technology. The wavelength selection in the vicinity of the absorption line is critical as it controls the height region of highest sensitivity, the temperature cross-sensitivity, and the demands on frequency stability. For CO2, an error budget of 0.08% is derived from our analysis of the sources of systematic errors. Among them, the frequency stability of ± 0.3 MHz for the laser transmitter and spectral purity of 99.9% in conjunction with a narrow-band spectral filter of 1 GHz (FWHM) are identified to be challenging instrument requirements for a direct detection CO2 system operating at 1.6 μm.

/pdf/space-borne-remote-sensing-of-co2-ch4-and-n2o-by-integrated-3enyvm8kyj.pdf

Space-borne remote sensing of CO2, CH4, and N2O by integrated path differential absorption lidar: a sensitivity analysis

. Airborne lidar and in-situ measurements of aerosols and trace gases were performed in volcanic ash plumes over Europe between Southern Germany and Iceland with the Falcon aircraft during the eruption period of the Eyjafjalla volcano between 19 April and 18 May 2010. Flight planning and measurement analyses were supported by a refined Meteosat ash product and trajectory model analysis. The volcanic ash plume was observed with lidar directly over the volcano and up to a distance of 2700 km downwind, and up to 120 h plume ages. Aged ash layers were between a few 100 m to 3 km deep, occurred between 1 and 7 km altitude, and were typically 100 to 300 km wide. Particles collected by impactors had diameters up to 20 μm diameter, with size and age dependent composition. Ash mass concentrations were derived from optical particle spectrometers for a particle density of 2.6 g cm−3 and various values of the refractive index (RI, real part: 1.59; 3 values for the imaginary part: 0, 0.004 and 0.008). The mass concentrations, effective diameters and related optical properties were compared with ground-based lidar observations. Theoretical considerations of particle sedimentation constrain the particle diameters to those obtained for the lower RI values. The ash mass concentration results have an uncertainty of a factor of two. The maximum ash mass concentration encountered during the 17 flights with 34 ash plume penetrations was below 1 mg m−3. The Falcon flew in ash clouds up to about 0.8 mg m−3 for a few minutes and in an ash cloud with approximately 0.2 mg m−3 mean-concentration for about one hour without engine damage. The ash plumes were rather dry and correlated with considerable CO and SO2 increases and O3 decreases. To first order, ash concentration and SO2 mixing ratio in the plumes decreased by a factor of two within less than a day. In fresh plumes, the SO2 and CO concentration increases were correlated with the ash mass concentration. The ash plumes were often visible slantwise as faint dark layers, even for concentrations below 0.1 mg m−3. The large abundance of volatile Aitken mode particles suggests previous nucleation of sulfuric acid droplets. The effective diameters range between 0.2 and 3 μm with considerable surface and volume contributions from the Aitken and coarse mode aerosol, respectively. The distal ash mass flux on 2 May was of the order of 500 (240–1600) kg s−1. The volcano induced about 10 (2.5–50) Tg of distal ash mass and about 3 (0.6–23) Tg of SO2 during the whole eruption period. The results of the Falcon flights were used to support the responsible agencies in their decisions concerning air traffic in the presence of volcanic ash.

/pdf/airborne-observations-of-the-eyjafjalla-volcano-ash-cloud-3dz485lnbg.pdf

Airborne observations of the Eyjafjalla volcano ash cloud over Europe during air space closure in April and May 2010

A deeper understanding of long-term ozone trends and periods of significant ozone depletion as well as of the anthropogenic greenhouse effect requires the concerted actions of experimenters and modelers. With respect to observations, atmospheric constituents need to be measured simultaneously and on a global basis. Fourier-transform infrared spectrometers are especially suited for this measurement task. Apromising and challenging branch of Fourier-transform infrared spectroscopy is its application to limb-emission sounding by the use of cryogenic instrumentation. This method allows the measurements to be made independently of the time of the day. The MIPAS (Michelson interferometer for passive atmospheric sounding) balloon-borne (MIPAS-B) and space-based (MIPAS-S) experiments apply this technique. While the MIPAS-B instrument has already been used for several years for stratospheric process studies, the MIPAS-S instrument is in development for the European Space Agency's ENVISAT mission. Instrumental aspects of these MIPAS experiments are highlighted, the most important results in ozone research achieved with MIPAS-B are reviewed, and a brief overview of the scientific capabilities of the MIPAS space experiment is given.

Remote sensing of vertical profiles of atmospheric trace constituents with MlPAS limb-emission spectrometers.

The prime aim of the Atmospheric Dynamics Mission is to demonstrate measurements of vertical wind profiles from space. Extensive studies conducted by the European Space Agency over the past 15 years have culminated in the selection of a high-performance Doppler wind lidar based on direct-detection interferometric techniques. Such a system, with a pulsed laser operating at 355-nm wavelength, would utilize both Rayleigh scattering from molecules and Mie scattering from thin cloud and aerosol particles; measurement of the residual Doppler shift from successive levels in the atmosphere provides the vertical wind profiles. The lidar would be accommodated on a satellite flying in a sun-synchronous orbit, at an altitude of ~400 km, providing near-global coverage; target date for launch is in 2007. Processing of the backscatter signals will provide about 3000 globally distributed wind profiles per day, above thick clouds or down to the surface in clear air, at typically 200-km separation along the satellite track...

The atmospheric dynamics mission for global wind field measurement

The global observation of profiles of the atmospheric wind speed is the highest-priority unmet need for global numerical weather prediction. Satellite Doppler lidar is the most promising candidate to meet the requirements on global wind profile observations with high vertical resolution, precision, and accuracy. The European Space Agency (ESA) decided to implement a Doppler wind lidar mission called the Atmospheric Dynamics Mission Aeolus (ADM-Aeolus) to demonstrate the potential of the Doppler lidar technology and the expected impact on numerical weather forecasting. An airborne prototype of the instrument on ADM-Aeolus was developed to validate the instrument concept and retrieval algorithms with realistic atmospheric observations before the satellite launch. It is the first airborne direct-detection Doppler lidar for atmospheric observations, and it is operating at an ultraviolet wavelength of 355 nm. The optical design is described in detail, including the single-frequency pulsed laser and th...

/pdf/the-airborne-demonstrator-for-the-direct-detection-doppler-1ke8occ5y4.pdf

The Airborne Demonstrator for the Direct-Detection Doppler Wind Lidar ALADIN on ADM-Aeolus. Part I: Instrument Design and Comparison to Satellite Instrument

The Adm-Aeolus Mission - the First Wind-Lidar in Space

The Michelson interferometer for passive atmospheric sounding (MIPAS) is a high resolution Fourier-transform spectrometer to measure concentration profiles of stratospheric constituents on a global scale. It observes the atmospheric emissions from the earth horizon (limb) throughout the thermal infrared region (685 - 2410 cm-1, 14.6 - 4.15 micrometers ), which allows the simultaneous measurement of more than 20 key trace gases, including the complete NOy-family and several CFCs. MIPAS is selected as an ESA-payload for the Envisat-1 project of the Polar Orbiting Earth-observation Mission POEM. Launch is planned for 1998.

Michelson interferometer for passive atmospheric sounding (MIPAS): a high-resolution limb sounder for the European Polar Platform

The Atmospheric Dynamics Mission ADM-Aeolus of the European Space Agency ESA will be the first lidar mission to sense the global wind field from space. It is based on an incoherent Doppler lidar operating at 355 nm with a two-interferometer receiver for aerosol and molecular return. The launch is planned for October 2007 and the nominal operation time is 3 years. An airborne instrument demonstrator is under development for ground and airborne campaigns envisaged in the years 2005 and 2006. An overview of the ADM, the campaign objectives, and the results of the development of the airborne demonstrator are shown.

/pdf/development-of-an-airborne-demonstrator-for-adm-aeolus-and-fsu3zawaq6.pdf

Martin Endemann

Papers

The atmospheric dynamics mission for global wind field measurement

The Airborne Demonstrator for the Direct-Detection Doppler Wind Lidar ALADIN on ADM-Aeolus. Part I: Instrument Design and Comparison to Satellite Instrument

The Adm-Aeolus Mission - the First Wind-Lidar in Space

Michelson interferometer for passive atmospheric sounding (MIPAS): a high-resolution limb sounder for the European Polar Platform

Development of an Airborne Demonstrator for ADM-AEOLUS and Campaign Activities