AERONET Sun Photometer – NASA Aerosol Monitoring Network

The AERONET (AErosol RObotic NETwork) Sun Photometer deployed at the ENGEOS Lab is part of NASA’s globally standardized network for ground-based aerosol monitoring and characterization. It provides long-term, high-quality observations of aerosol optical and microphysical properties that are essential for climate research, satellite product validation, and air quality assessments.

ENGEOS Lab operates a Cimel CE318-T Sun–Sky–Lunar Multispectral Photometer, integrated into the NASA AERONET network.

AERONET is a global federation of ground-based remote sensing aerosol networks coordinated by NASA and PHOTONS (PHOtométrie pour le Traitement Opérationnel de Normalisation Satellitaire – University of Lille 1, CNES, and CNRS-INSU), supported by a wide range of international agencies, universities, and scientists.

Instrument Overview – Cimel CE318-T

The CE318-T is a next-generation, solar-powered photometer capable of measuring:

• Direct Sun irradiance
• Sky Radiance in multiple directions
• Lunar observations for nighttime aerosol retrievals

This upgraded version has been operational at ENGEOS Lab since March 2020, succeeding the original CE318 model installed in June 2012.

Technical Specifications:

• Spectral Range: 340–1640 nm
• Standard Wavelengths: 440, 670, 870, 940, 1020 nm
• AOD Accuracy: 0.01–0.02 (Holben et al., 2001)
• Measurement Interval: Every 10 seconds; AOD reported every 15 minutes

By measuring sunlight attenuation and scattering at specific wavelengths, the instrument enables:

• Aerosol Optical Depth (AOD) retrieval
• Cloud-screened observations
• Derivation of aerosol microphysical properties, such as:

• Particle size distribution
• Single-scattering albedo
• Asymmetry parameter
• Complex refractive index

Sky radiance measurements at scattering angles ≥120° enable advanced inversion algorithms for aerosol characterization.

Applications at ENGEOS Lab:

• Validation of satellite aerosol products (e.g., MODIS, VIIRS, CALIPSO)
• Desert dust climatology and aerosol dynamics over hyper-arid environments
• Air quality monitoring in urban and remote locations
• Support for regional climate modeling and field campaigns

The relevance of AERONET measurements in the UAE is well demonstrated in regional studies, including Nelli et al. (2020), which highlight the value of AOD and microphysical retrievals for advancing aerosol research in desert climates.

All data from the ENGEOS AERONET station are processed, quality-controlled, and publicly released by NASA Goddard Space Flight Center, accessible via the AERONET data portal.

Figure 4. AERONET Sun Photometer.