Mission of the TC

The mission of the Centre for Aerosol Remote Sensing (CARS) is to offer operation support to ACTRIS National Facilities operating aerosol remote sensing instrumentation:

  • aerosol high-power aerosol lidars
  • automatic low-power lidars and ceilometers
  • automatic sun/sky/polarized/lunar photometer.

Additionally, the Centre for Aerosol Remote Sensing offers specialized services for the above instruments and related ACTRIS variables, to ACTRIS users of various types: academia, business, industry and public services.

What the TC offers

CARS offers operation support to ACTRIS National Facilities, as well as specialized services to ACTRIS users:

  • Training and consultancy for setting up and running an aerosol remote sensing station
  • Measurement and data procedures and tools for QA/QC of the lidar and photometer measurements
  • Measurement and data quality monitoring, including calibration of photometers, characterization of lidar optical blocks, direct comparison with reference systems, support for debugging, upgrading and optimizing the instruments
Operation support for ACTRIS National Facilities

CARS provides operation support to ACTRIS National Facilities having the “Aerosol remote sensing” certificate. Part of the operation support is provided on schedule, part on demand. Requests for operation support should be addressed directly to CARS.
The complete list of operation support can be found here: Operation support for ACTRIS National Facilities

Specialized services for ACTRIS users

CARS is providing services to users on demand. Requests should be addressed through SAMU (link to SAMU page).
The complete list of specialized services can be found here: Specialized services for ACTRIS users

 

Variables & measurement techniques

The focus of the Centre for Aerosol Remote Sensing is on measuring with high accuracy the optical properties of tropospheric and low stratospheric aerosols, and potentially derive their microphysical properties. CARS involves aerosols column and aerosol profiling measurement techniques as well as their synergetic uses at ground-based level.

 

 

Variable

Data product level

Requirement

Aerosol high-power lidar

Sun/sky/lunar photometer

Attenuated backscatter profile

L1, L2

Minimum

X

 

Volume depolarization profile

L1, L2

Minimum

X

 

Particle backscatter coefficient profile

L1, L2

Minimum

X

 

Particle extinction coefficient profile

L1, L2

Minimum

X

 

Lidar ratio profile

L1, L2

Minimum

X

 

Ångström exponent profile

L1, L2

Optimum

X

 

Backscatter-related Ångström exponent profile

L1, L2

Optimum

X

 

Particle depolarization ratio profile

L1, L2

Minimum

X

 

Particle layer geometrical properties (height and thickness)

L1, L2

Minimum

X

 

Particle layer optical properties (extinction, backscatter, lidar ratio, Ångström exponent, depolarization ratio, optical depth)

L1, L2

Minimum

X

 

Column integrated extinction

L1, L2

Minimum

X

X

Planetary boundary layer height

L1, L2

Optimum

X

 

Spectral Downward Sky Radiances

L1

Minimum

 

X

Direct Sun/Moon Extinction Aerosol Optical Depth (column)

L1

Minimum

 

X

Aerosol columnar  properties

L2

Minimum

X

X

Aerosol profile microphysical and optical properties

L2

Minimum

X

X

 

Aerosol profile observations

Aerosol profile observations are covered in ACTRIS by automatic low-power lidars and high-power lidars. Due to the differences at the hardware level (e.g. laser power and sounding wavelengths), the data products which can be retrieved from these measurement techniques are essentially different.

  • Automatic low-power lidars and ceilometers (ALC) are currently used to provide aerosol layering and attenuated backscatter at one wavelength, information which is used in combination with cloud radars and microwave radiometers to complete the cloud classification at the ACTRIS Cloud Remote Sensing National Facilities. In addition, these parameters could be used to study fog formation that is of great importance for visibility studies. The temporal coverage and low overlap of low power lidar instruments is a valuable add-on used to study the diurnal variation of aerosol layers and to trigger advanced measurements performed using high-power lidar instruments. Even single wavelength low-power lidars are able to detect high resolution dynamics of aerosol layers.
  • Aerosol high-power aerosol lidars (AHL) are aerosol lidar which thanks to the higher power can provide besides the same quantities reported for the ALL, more quantitative information about the aerosol optical properties. In particular, AHL used to provide profile aerosol optical properties (aerosol backscatter coefficient, aerosol extinction coefficient and aerosol linear depolarization ratio) at one or more wavelengths, allowing subsequent calculation of several spectral parameters (Angstrom exponents, lidar ratios) of the lofted aerosol layers, and therefore aerosol typing.
Aerosol column observations

Aerosol column observations are covered in ACTRIS by automatic sun/sky/lunar photometers (ASP). The state-of-the-art photometric measurement techniques and associated retrieval techniques provide aerosol properties both directly (e.g. daytime and night time spectral extinction AOD and daytime downward sky angular, spectral and polarized radiance) and indirectly (size distribution, refractive indexes, single scattering albedo, spherical fraction, scattering properties (Dubovik et al., 2000, 2014). 

Synergies between aerosol profile and column observations

Synergies between aerosol profile and column observations are being greatly developed within ACTRIS-1/2 to provide higher-level aerosol variables such as daytime extinction, backscatter, absorption and mass concentration (total, fine, coarse) and columnar aerosols optical and microphysical properties.

 

Our Units & Teams

ARS is organized in 8 Units which are grouped in 3 clusters, one cluster for each measurement technique covered by CARS.

Organigram

Our Facilities


Mobile instruments


These instruments can be deployed at the user site for direct comparison with user’s field instruments

  • Reference AHL (mobile): 3 mobile aerosol lidars, various channel setups 
  • Field automatic sun/sky/lunar photometer: a dedicated set of reference mobile sun/sky/moon photometers to be in volved in field campaign or inter-comparison exercises


Fixed reference instruments


These instruments are operated at CARS’ locations and are used for direct comparison with user’s field instruments.

  • Reference AHL (fixed): 4 multiwavelength lidar, Raman or HSRL, 3 beta + 2 alpha + 3 delta, dynamic range 200 m to 20 km; complemented by ancillary instrumentation (meteorology)
  • Modular lidar set-up: 1 modular lidar to set-up different lidar configurations: aerosol fluorescence; tropospheric aerosol optical properties; temperature with rotational Raman from troposphere to stratosphere; liquid water content; HSRL configuration.
  • Reference automatic low-power lidars: most commonly used types of low-power lidars
  • Master automatic sun/sky/lunar photometer: reference sun/sky/moon photometers to enable calibration transfer, by 3 lines, of about 10 x (robot + data logger) each, to receive field instruments to be calibrated in AOD (absolute error < 0.01) and tested


Laboratories


CARS hosts several laboratories for characterization of instruments and components, and calculation of calibration and correction factors.

  • Optical laboratory: configurable setups to determine the relevant optical parameters for lidar characterization
  • Laboratory and outdoor equipment ASP: calibrated integrating spheres for sky radiance calibration (relative error < 3%), specific linear polarizing system to calibrate polarization (absolute error < 0.005), thermal chambers to measure temperature sensitivity, solar simulator to adjust solar tracking system, mobile reference photometer for internal and external radiance traceability between calibration, spectrometers to control filter transmission, sky-imager and lidar as complementary instruments.
National Institute of R&D for Optoelectronics (INOE)

INOE is a public research institute under the coordination of the Romanian Ministry for Research, Innovation and Digitalization. The Remote Sensing Department has multidisciplinary expertise and laboratories, spanning from laboratory/in-situ chemical analysis to remote sensing of the atmosphere. INOE is hosting one Unit which is responsible for the QA/QC of the aerosol high-power lidar measurements (CARS-AHL-INOE), and currently ensures the leadership of CARS.

Meteorological Institute of the Ludwig-Maximilians-University (LMU)

LMU is the oldest university in Bavaria, and one of the largest of Germany covering the full spectrum of science with a strong emphasis on natural sciences. The Meteorological Institute is part of the Faculty of Physics. Research focus include radiative transfer modelling and remote sensing (active and passive). It is a key partner of ACTRIS (EARLINET) since the beginning. LMU is hosting two Units: a) a Unit responsible for the QA/QC of the aerosol high-power lidar measurements (CARS-AHL-LMU); b) a Unit responsible for the QA/QC of the automatic low-power lidar and ceilometer measurements (CARS-ALC-LMU).

National Research Council of Italy (CNR)

CNR is the main public research performing organization in Italy, reporting directly to the Ministry of the Education, University and Research. The activities will be specifically performed at the Institute of Methodologies for Environmental Analysis (IMAA). CNR-IMAA has a long expertise in atmospheric research developing methodologies to integrate data from active and passive instruments and to validate models and participates among the others in the following projects: ACTRIS, ACTRIS-2, ACTRIS-PPP, ENVRIplus, EUNADICS, EARLINET, EARLINET-ASOS, GEOMON. CNR-IMAA is hosting one Unit which is responsible for the QA/QC of the aerosol high-power lidar measurements (CARS-AHL-CNR).

Hohenpeissenberg Meteorological Observatory, Deutscher Wetterdienst (HPB-DWD)

HPB-DWD performs research and monitoring of climate and atmospheric composition, which covers meteorology, ozone, precipitation radar, GAW global station, and greenhouse gases within ICOS. The Hohenpeissenberg Meteorological Observatory has contributed in QA/QC by intercomparison experiments and standardization for reactive trace gases VOC and NOx, and remote sensing of aerosol by ceilometers and lidars. HPB-DWD is hosting one Unit which is responsible for the QA/QC of the automatic low-power lidar and ceilometer measurements (CARS-ALC-DWD).

CNRS-Laboratoire d’Optique Atmospherique (LOA-CNRS)

LOA is a joint CNRS and University of Lille research laboratory. Its expertise in aerosols widely covers aerosols remote sensing field both from ground-based observation, as pilot of AERONET network in France and Europe, and satellite observation, as PI of POLDER/PARASOL space missions from CNES and the future 3MI aerosol mission from EUMETSAT. The Laboratoire d’Optique Atmospherique expertise also includes the development and implementation of high-performance aerosol retrieval algorithms such as GRASP. LOA-CNRS is hosting one Unit which is responsible for the QA/QC of the automatic sun/sky/lunar photometer measurements (CARS-ASP-CNRS), and currently ensures the co-leadership of CARS.

University of Valladolid (UVA)

The University of Valladolid was founded in the XIII century and is one of the oldest universities in Europe. The Group of Atmospheric Optics (GOA) belongs to the Optics Department of the Science Faculty, and has a long record in atmospheric research by optical methods for more than 20 years. Since 2006 the GOA group operates an AERONET calibration facility, in close collaboration with AERONET headquarters in NASA, the Laboratory of Atmospheric Optics in Lille and the Izaña Atmospheric Research Center. GOA is hosting one Unit which is responsible for the QA/QC of the automatic sun/sky/lunar photometer measurements (CARS-ASP-UVA).

Izaña Atmospheric Research Center (AEMET-IARC)

The Izaña Atmospheric Research Center (IARC) is part of the State Meteorological Agency of Spain (AEMET). IARC has multidisciplinary expertise and laboratories, therefore contributes to WMO-GAW Programme since 1989, and to other international networks and programs as NDACC, BSRN, AERONET, GAW-PFR. Its main Observatory (Izaña Atmospheric Observatory) dates back to 1916, with uninterrupted meteorological and climatological observations. AEMET-IARC is hosting one Unit which is responsible for the QA/QC of the automatic sun/sky/lunar photometer measurements (CARS-ASP-AEMET).