Location and Configuration

Initially, BAQUNIN was centered in the Rome metropolitan area, one of Europe’s most densely populated regions (≈4.3 million inhabitants). This area features complex orography: Rome lies along the Tiber valley, bordered by the Apennines (north) and Alban Hills (south) and to the west, terrain slopes toward the Tyrrhenian Sea, 27 km from the city center.

The first configuration included three observation stations: Atmospheric Physics Laboratory (APL, Sapienza University, urban), CNR-ISAC Tor Vergata (semi-rural) and CNR-IIA Montelibretti (rural). Each site hosts BAQUNIN instruments alongside existing observatories for meteorology and atmospheric composition. The suite includes active and passive remote sensing systems and surface instruments for retrieving key parameters on gases and aerosols. Most devices are installed at APL, with a Pandora-2S dual spectrometer at each site. Numerical simulations of meteorological fields are produced using the WRF model.

Since 2025, BAQUNIN has expanded its observational capacity by installing additional instruments in “associated observatories”, namely at San Pietro Capofiume (Bologna), Aosta, and in Milan for a mid-term campaign (12 months). This extension aims to strengthen monitoring of the Po Valley, one of the most polluted areas in Europe, and to study the transport of pollutants to surrounding regions. Furthermore, these sites provide valuable data for satellite calibration and validation over areas with different and more complex orographic and meteorological conditions, enhancing the representativeness of BAQUNIN observations.

In addition, BAQUNIN collaborates with ENEA Lampedusa and Thule (Greenland) sites in activities ranging from instrument upgrades and retrieval code improvements to data harmonization, dissemination, and archiving, as well as supporting joint measurement campaigns across the different sites.

Network Integration

Thanks to its strategic location and diverse instrumentation, BAQUNIN is a certified node in major national and international networks:

• Pandonia Global Network, PGN
• Skynet 
• European Skynet Radiometers, ESR 
• Aerosol Robotic Network, AERONET
• European Brewer Network, EUBREWNET 
• COllaborative Carbon Column Observing Network , COCCON 
• Osservatorio Milano Duomo, OMD
• Sardegna Clima

Data Management

BAQUNIN products originate from multiple instruments and processing chains, requiring harmonization of naming conventions, units, and metadata. Native datasets are converted to netCDF following GEOMS standards. Final products are disseminated via the BAQUNIN website and ESA’s EVDC portal (ESA Validation Data Center).

Research Activities

Current activities include:

• Synergistic interpretation of remote sensing data for air quality assessment
• Investigation of PBL meteorology and local-scale dynamics
• Analysis of aerosol transport and its impact on atmospheric composition
• Development of LIDAR systems and retrieval algorithms
• Intercomparison of instruments within global networks
• Satellite calibration/validation in urban, semi-rural, and rural contexts
The consortium also organizes measurement campaigns with national and international partners and offers hosting opportunities for external instruments at the APL site.
ESA and EUMETSAT Support
BAQUNIN was initiated under ESA’s IDEAS+ contract (2015) and continued through the IDEAS-QA4EO framework (2019), focusing on:
• Night-time aerosol and trace gas retrievals
• Improved aerosol retrievals using NO₂ corrections
• Urban NO₂ imaging via AOTF-based cameras
• UAV-based BRDF observations
• Ground-based validation of satellite cloud masks
BAQUNIN maintains and operates its scientific suite, organizes collocation campaigns, and contributes to these projects. Additionally, the consortium now supports EUMETSAT’s Fiducial Reference Measurements for Copernicus Aerosol Cal/Val Activities, reinforcing BAQUNIN’s role in European atmospheric research.