Research Areas

ATMOSPHERIC AEROSOLS

From November 2023 to the end of February 2024, during its voyage to Antarctica, the crew of PERSEVERANCE conducted approximately 150 photometric measurements using the Calitoo handheld photometer provided by the Laboratoire d’Optique Atmosphérique.

Illustration of measurements taken on board the PERSEVERANCE with the Calitoo photometer

This instrument provides access to the optical extinction depth of atmospheric particles (AOD) at 3 wavelengths (465, 540, and 619 nm). The AOD (or Aerosol Optical Depth) represents the integral of the aerosol extinction coefficient over the entire atmospheric column. This quantity is related to the extinction or attenuation of the direct solar beam by scattering (the dominant process) and absorption (the minor process) of aerosols.

Its spectral variation depends primarily on particle size and, to a lesser extent, on their shape and chemical nature. Approximately 90% of the acquired data are of good quality. Among the 10% of rejected data are the first few days, affected by thin high-altitude clouds and solar elevations that were too low (<10°), which the observers, still familiarizing themselves with the instrument, had probably not noticed. Some anomalous data, detected by unstable triplets/doublets, were also rejected. The geographical distribution of the data is presented in Figures 2 and 3. It reflects the spatial and temporal variability of aerosols present throughout the atmospheric column. Except in cases of high-altitude transport (free troposphere or stratosphere), aerosols are located in the planetary boundary layer, whose height varies with season and various meteorological factors.

Spatio-temporal variability of AOD measured from PERSEVERANCE (11/2023-02/2024). Map generated with GPSvisualizer: https://www.gpsvisualizer.com/map_input?form=data

The filtered and corrected data can be downloaded at the following link:

PERSEVERANCE CAMPAIGN 11/2023-02/2024-CNRS/U-LILLE-LOA

Analysis of the PERSEVERANCE data indicates that no remarkable aerosol events affected the regions crossed by the PERSEVERANCE at the time of its passage. One recommendation would be to increase the density of observations as soon as meteorological conditions permit (in particular, the systematic taking of 3 consecutive measurements, allowing for better detection of contamination from thin high-altitude clouds). It is also desirable to continue measurements during future campaigns and, eventually, to conduct them from the Polar POD to complement the aerosol profile measurements of the automatic lidar planned for this platform. A marine version of the AERONET automatic photometer now exists. A feasibility test during a future campaign could be considered.

Finally, to briefly illustrate the value of this type of observation for space applications. Satellite observation in these remote regions remains difficult to evaluate and sometimes very imprecise depending on the sensors considered and cloud cover. The following figures present AOD maps derived from the American MODIS spectrometer for 01/30 and 02/01/2024.

MODIS AOD at 550 nm (01/30/2024). Source NASA-Worldview

A new stage in the collaboration with the University of Lille was reached with the installation of an automated photometer on the aft gantry. A preliminary visit took place in April 2024 during the vessel’s technical shutdown, followed by numerous iterations for an installation completed in March 2025. This type of instrument had never before been deployed on a sailing vessel.

PERSEVERANCE is the first sailing vessel equipped with a solar photometer and, as such, is now integrated into the AERONET (AErosol RObotic NETwork) network in its maritime component. This international program, coordinated by NASA and the PHOTONS project (PHOtométrie pour le Traitement Opérationnel de Normalisation Satellitaire — University of Lille, CNES, CNRS-INSU), brings together ground-based and shipborne remote sensing instruments dedicated to the study of atmospheric aerosols.

The PERSEVERANCE participates more specifically in the Maritime Aerosol Network (MAN), a branch of the AERONET network dedicated to collecting aerosol optical depth (AOD) measurements over the oceans. Measurements are carried out using a Microtops II photometer, regularly used aboard research or commercial vessels to improve oceanic coverage of atmospheric data.

This type of mission enables the acquisition of valuable data in maritime regions often poorly covered by fixed ground stations. Observations are processed and classified according to the quality levels defined by AERONET (levels 1.0 to 2.0), then made available to the scientific community via the AERONET and PHOTONS platforms.

“The AERONET network has enabled, since 1993, the measurement, study, and understanding, from the ground through passive remote sensing, of the variability of aerosol parameters, the detection of potential changes, and assistance in quantifying their multiple impacts on air quality and climate. The measured variables are widely used for satellite validations, models, aerosol climatologies, and instrumental synergies . ” excerpt from the CNRS website.

Organizational and data flow diagram: data are recorded locally on the onboard PC, then automatically transmitted to LOA (Lille) at hourly intervals, subject to connection availability.

The contribution of PERSEVERANCE is part of the network’s overall objective: to provide a homogeneous, long-term, and open-access database for the validation of satellite sensors, the study of climate processes related to aerosols, and collaboration between laboratories worldwide.

Real-time monitoring of measurements acquired by PERSEVERANCE: website