The implantation of CE318-T photometers on offshore and coastal platforms constitutes a major turning point for atmospheric and ocean color applications.

Keywords : Aerosols, photometer, water radiance, monitoring, ocean properties, ocean color, Earth observation, remote sensing, CAL/VAL, SeaPRISM.

17th December 2021

The main substances that affect the color of the ocean include dissolved organic matter, living phytoplankton with chlorophyll pigments, and non-living particles like marine snow and mineral sediments. Ocean color data have a critical role in operational observation systems monitoring coastal eutrophication, harmful algal blooms, and sediment plumes. Scientists rely on satellite observations to monitor Ocean Color (OC) parameters, such as chlorophyll a concentration (Chla) and inherent optical properties of water (IOP), to better understand the role of the ocean in the Earth’s climate.

However, the current satellite measurement systems can provide only coarse spatial resolution, with relevant lack of data.

Thus, AERONET Ocean Color saw the light of day in 2002. This new component of AERONET (NASA AErosol RObotic NETwork) aims at providing more data concerning satellites measurements as there is a lack of insights in the monitoring of marine aerosols and water radiance. Since 2002, more than 31 OC measurement sites have been integrated on the network through offshore fixed platforms and coastal platforms all around the world.

Its particularity is that the measurements are taken from the radiance emerging from the sea using CE318-TV12-OC (SeaPRISM) Cimel photometers. By measuring the water radiance from the sea with instruments installed on coastal/offshore platforms or boats, Cimel improves the accuracy of satellites measurements. AERONET decided in 2015, after full validation, to accept only the CE318-T for new photometers entering the network. Below is a representative drawing of the measurement principle of the CE318-TV12-OC (SeaPRISM) photometer:

Figure 1: Measurement principle of the Cimel CE318-TV12-OC (SeaPRISM).

Many missions are conducted by AERONET-OC to collect ocean color data and measurements. Below, one of these campaigns conducted on an offshore platform (AAOT) in the Adriatic Sea.

Figure 2: AERONET OC site located in the Acqua Alta Oceanographic Tower (AAOT) in the Gulf of Venice in the Northern Adriatic Sea in July 2018.

Figure 3: Measurements performed at AERONET-OC AAOT – Scatterplot of LIOP WN(λ) versus LChla WN(λ).

Click Here to read the article!

Citation: Zibordi, Giuseppe, Brent N. Holben, Marco Talone, Davide D’Alimonte, Ilya Slutsker, David M. Giles, and Mikhail G. Sorokin. «Advances in the Ocean Color Component of the Aerosol Robotic Network (AERONET-OC)”, Journal of Atmospheric and Oceanic Technology 38, 4 (2021): 725-746, accessed Sep 17, 2021,

ATTO project

ATTO: the Amazon Tall Tower Observatory, an Amazon research project

Keywords : ATTO, Aerosols, Photometer, Atmosphere

The Amazon Tall Tower Observatory (ATTO) is the world’s highest research facility located in the middle of the Amazon rainforest in northern Brazil. It is a research site with a 325 meters tower for atmospheric observations.

This joint German-Brazilian project was launched in 2008 in order to further the understanding of the Amazon rainforest and its interaction with the soil beneath and the atmosphere above. This is made possible by recording continuously meteorological, chemical and biological data such as greenhouse gases or aerosols.

Scientists and researchers on site hope to gain insights into how the Amazon interacts with the atmosphere and the soil. This region is very important for the global climate as Saharan dust, biomass smoke from Africa, urban and marine aerosols come from long distances due to the winds. It is vital to get a better understanding of this area for environmental decisions.

On this gigantic tower, a CE318-T photometer is installed at 210 meters from the ground and allows a more efficient calculation of the quantity of aerosols present in the air around this site. The photometer uses NASA’s AERONET calibration system to collect the most reliable data possible.

Cimel photometer on the tower (© NASA AERONET)

At the core of the project is to learn more about biogeochemical cycles, the water cycle and energy fluxes in the Amazon. The goal is to determine their impact on global climate and how they are influenced by the changing climate and land-use change.

ATTO teams strive to close a gap in the global climate monitoring network and want to improve climate prediction models and to recognize the importance of the Amazon within the climate system.

Thanks to our sun-photometer, the scientists on site were able to collect information on daily mean AOD values at 550 nm wavelength.  These data allowed us to analyze the soils present in the atmosphere of the Amazon forest. Here some results of the ATTO project with our sun-photometer between August and September 2019.

Citation: Hassan Bencherif, Nelson Bègue, Damaris Kirsch Pinheiro, David Du Preez, Jean-Maurice Cadet, et al.. Investigating the Long-Range Transport of Aerosol Plumes Following the Amazon Fires (August 2019): A Multi-Instrumental Approach from Ground-Based and Satellite Observations. Remote Sensing, MDPI, 2020, Advances in Remote Sensing of Biomass Burning, 12 (22), pp.3846.

Read the article here!

If you want to discover or learn more about this major project, visit:

RIMA NASA-AERONET network : Long-term monitoring of aerosol properties

UVa - Proyecto Aeropa

RIMA NASA-AERONET network: Long-term monitoring of aerosol properties

RIMA (Red Ibérica de Medida fotométrica de Aerosoles) is a scientific network for the long-term monitoring of columnar aerosol properties based on sun-photometer measurements. RIMA is federated to AERONET (AErosol RObotic NETwork), a NASA program in collaboration with the University of Lille (LOA). According to the AERONET aims, the scientific objectives of RIMA involve the characterization of aerosols for climate studies, the validation of satellite products and the synergies with other measurements and data correlation.

RIMA follows all AERONET protocols (calibration, measurements, data policy, etc.) and its sites and data are available through the AERONET web site. The key task of calibration and the network management are carried out by the Group of Atmospheric Optics of the University of Valladolid (GOA-UVa) and master instruments are calibrated at the high-mountain facility CIAI (Izaña Atmospheric Research Center, AEMET) in collaboration with PHOTONS and CIAI-AEMET. Large support is obtained from the AERONET (NASA) and PHOTONS (University of Lille). The calibration facility used by CIMEL for photometers in Izaña is important thanks to its pure sky and its absolute zero which allows a perfect calibration of those solutions since 2006.

A software named Caelis was recently developed by GOA as a service to the RIMA community with the aim to facilitate the network management and the control of the site instruments and measurements. This tool relies on a powerful relational data base which represents a great potential for the scientific work as well.

Keywords: Aerosols, AERONET, Calibration, Sun/Sky/Lunar Multispectral Photometer, Earth observation, Atmospheric monitoring, Satellite CAL/VAL

Acronyms :

  • CIAI: Centro de Investigación Atmosférica de Izaña
  • GOA-Uva: Grupo de Optica Atmosférica – Universidad de Valladolid
  • LOA: Laboratoire d’Optique Atmosphérique

Citation : Toledano, C. & Cachorro, Victoria & Berjón, Alberto & Frutos Baraja, A. & Fuertes, David & González, R. & Torres, Benjamin & Rodrigo, R. & Bennouna, Yasmine & Martín, L. & Guirado-Fuentes, Carmen. (2011). RIMA-AERONET network: Long-term monitoring of aerosol properties. Optica Pura y Aplicada. 44. 629-633.


Aerosol optical depth comparison between GAW-PFR and AERONET-Cimel radiometers from long-term (2005–2015) 1 min synchronous measurements

CE318-T Izaña

Aerosol optical depth comparison between GAW-PFR and AERONET-Cimel radiometers from long-term (2005–2015) 1 min synchronous measurements

August 9, 2019

A comprehensive comparison of more than 70 000 synchronous 1 min aerosol optical depth (AOD) data from three Global Atmosphere Watch precision-filter radiometers (GAW-PFR), traceable to the World AOD reference, and 15 Aerosol Robotic Network Cimel radiometers (AERONET-Cimel), calibrated individually with the Langley plot technique, was performed for four common or “near” wavelengths, 380, 440, 500 and 870 nm, in the period 2005–2015.

The goal of this study is to assess whether, despite the marked technical differences between both networks (AERONET, GAW-PFR) and the number of instruments used, their long-term AOD data are comparable and consistent.

The percentage of data meeting the World Meteorological Organization (WMO) traceability requirements (95 % of the AOD differences of an instrument compared to the WMO standards lie within specific limits) is >92 % at 380 nm, >95 % at 440 nm and 500 nm, and 98 % at 870 nm, with the results being quite similar for both AERONET version 2 (V2) and version 3 (V3). For the data outside these limits, the contribution of calibration and differences in the calculation of the optical depth contribution due to Rayleigh scattering and O3 and NO2 absorption have a negligible impact. For AOD >0.1, a small but non-negligible percentage (∼1.9 %) of the AOD data outside the WMO limits at 380 nm can be partly assigned to the impact of dust aerosol forward scattering on the AOD calculation due to the different field of view of the instruments. Due to this effect the GAW-PFR provides AOD values, which are ∼3 % lower at 380 nm and 2 % lower at 500 nm compared with AERONET-Cimel. The comparison of the Ångström exponent (AE) shows that under non-pristine conditions (AOD >0.03 and AE <1) the AE differences remain <0.1. This long-term comparison shows an excellent traceability of AERONET-Cimel AOD with the World AOD reference at 440, 500 and 870 nm channels and a fairly good agreement at 380 nm, although AOD should be improved in the UV range.

Citation: Cuevas, E., Romero-Campos, P. M., Kouremeti, N., Kazadzis, S., Räisänen, P., García, R. D., Barreto, A., Guirado-Fuentes, C., Ramos, R., Toledano, C., Almansa, F., and Gröbner, J.: Aerosol optical depth comparison between GAW-PFR and AERONET-Cimel radiometers from long-term (2005–2015) 1 min synchronous measurements, Atmos. Meas. Tech., 12, 4309–4337,, 2019.


Sunbelt Spectra comparison with Standard ASTM G173: the Chilean case

Sunbelt Spectra comparison with Standard ASTM G173: the Chilean case

December, 2017

Two spectra of solar direct normal irradiance (including circumsolar) are estimated based on spatio-temporal averages of the relevant atmospheric parameters extracted from two different databases: MODIS satellite sensor retrievals and AERONET sun photometer network. The satellite database is used to calculate an average spectrum for the area of the Atacama Desert. The AERONET database is used for two purposes: (i) to apply bias-removal linear methods to correct the MODIS parameters over Atacama, and (ii) to calculate an average local spectrum for the Paranal station. The SMARTS radiative transfer model is used to obtain the three spectra developed in this study. Both the Atacama and Paranal spectra are compared against each other and also to the world reference, ASTM G173. In one of the cases, significant differences are found for short wavelengths. In order to quantify the relative importance of these spectral differences, the propagation of errors due to the use of each spectrum is evaluated for CSP applications over the Atacama Desert, considering twelve different scenarios involving the reflectance, transmittance or absorptance of various materials.

Citation: Marzo, Aitor & Polo, Jesus & Wilbert, Stefan & Gueymard, Chris & Jessen, Wilko & Ferrada, Pablo & Alonso-Montesinos, Joaquín & Ballestrín, Jesús. (2017). Sunbelt Spectra comparison with Standard ASTM G173: the Chilean case. AIP Conference Proceedings. 2033. 10.1063/1.5067195.


Image source: Pixabay

A 10-year characterization of the Saharan Air Layer lidar ratio in the subtropical North Atlantic

A 10-year characterization of the Saharan Air Layer lidar ratio in the subtropical North Atlantic

May 10, 2019

Particle extinction-to-backscatter ratio (lidar ratio) is a key parameter for a correct interpretation of elastic lidar measurements. Of particular importance is the determination of the lidar ratio of the Saharan Air Layer mineral dust transported into the free troposphere over the North Atlantic region. The location of the two sun photometer stations managed by the Izaña Atmospheric Research Centre (IARC) on the island of Tenerife and a decade of available micropulse lidar (MPL) data allow us to determine the lidar ratio under almost pure-dust conditions. This result can be considered representative of the Saharan dust transported westward over the North Atlantic in the subtropical belt.

Three different methods have been used to calculate the lidar ratio in this work: (1) using the inversion of sky radiance measurements from a sun–sky photometer installed at the Izaña Observatory (2373 m a.s.l.) under free-troposphere conditions; (2) the one-layer method, a joint determination using a micropulse lidar sited at the Santa Cruz de Tenerife sea-level station and photometric information considering one layer of aerosol characterized by a single lidar ratio; and (3) the two-layer method, a joint determination using the micropulse lidar and photometric information considering two layers of aerosol with two different lidar ratios. The one-layer method only uses data from a co-located photometer at Santa Cruz de Tenerife, while the two-layer conceptual approach incorporates photometric information at two heights from the observatories of Izaña and Santa Cruz de Tenerife. The almost pure-dust lidar ratio retrieval from the sun–sky photometer and from the two-layer method give similar results, with lidar ratios at 523 nm of 49 ± 6 and 50 ± 11 sr. These values obtained from a decade of data records are coincident with other studies in the literature reporting campaigns in the subtropical North Atlantic region. This result shows that the two-layer method is an improved conceptual approach compared to the single-layer approach, which matches the real lower-troposphere structure well. The two-layer method is able to retrieve reliable lidar ratios and therefore aerosol extinction profiles despite the inherent limitations of the elastic lidar technique.

We found a lack of correlation between lidar ratio and Ångström exponent (α), which indicates that the dust lidar ratio can be considered independent of dust size distribution in this region. This finding suggests that dust is, under most atmospheric conditions, the predominant aerosol in the North Atlantic free troposphere, which is in agreement with previous studies conducted at the Izaña Observatory.

Citation: Berjón, A., Barreto, A., Hernández, Y., Yela, M., Toledano, C., and Cuevas, E.: A 10-year characterization of the Saharan Air Layer lidar ratio in the subtropical North Atlantic, Atmos. Chem. Phys., 19, 6331-6349,, 2019.


Photo credits: NASA-GSFC

Aerosol measurements with shipborne sun-sky-lunar photometer and collocated multiwavelength Raman polarization lidar over the Atlantic Ocean

Aerosol measurements with shipborne sun-sky-lunar photometer and collocated multiwavelength Raman polarization lidar over the Atlantic Ocean

A shipborne sun-sky-lunar photometer was tested in two trans-Atlantic cruises aboard the German research vessel Polarstern from 54° N to 54° S. A full diurnal cycle of mixed dust-smoke episode measured with shipborne CE318-T is presented for the first time. Latitudinal distribution of AOD from the shipborne CE318-T, Raman lidar and MICROTOPS II shows the same trend with high values at 0 ~ 20° N dust transported belt and low values at Southern Hemisphere. Coefficient of determination for the linear regression between MICROTOPS II and shipborne sun-sky-lunar photometer was 0.993 for AOD at 500 nm and 0.896 for Ångström exponent at 440–870 nm.

Citation: Yin, Zhenping & Ansmann, Albert & Baars, Holger & Martin, Radenz & Jimenez, Cristofer & Engelmann, Ronny & Seifert, Patric & Herzog, Alina & Ohneiser, Kevin & Hanbuch, Karsten & Blarel, L & Goloub, Philippe & Dubois, Gael & Victori, Stephane & Maupin, Fabrice. (2019). Aerosol measurements with shipborne sun-sky-lunar photometer and collocated multiwavelength Raman polarization lidar over the Atlantic Ocean. Atmospheric Measurement Techniques Discussions. 1-21. 10.5194/amt-2019-132.  


Photo: Alfred Wegener Institute/Stefan Hendricks