In the past, the possibility to retrieve the total column of water vapour (TCWV) from the thermal infrared (TIR) day and night measurements above water surfaces of the dual-view Along Track Scanning Radiometers (ATSR) has been demonstrated, and an algorithm, named Advanced InfrarRed Water Vapour Estimator (AIRWAVE), was developed and successfully applied to the measurements of the (A)ATSR instrument series. A similar instrument, the Sea and Land Surface Temperature Radiometer (SLSTR), is currently operating on board the Sentinel 3 satellite series. In this paper, we demonstrate that the AIRWAVE algorithm can be successfully applied to the SLSTR instrument to obtain reliable TCWV measurements. The steps performed for upgrading the algorithm are thoroughly described. The new AIRWAVE algorithm makes use of parameters computed offline with a state-of-the-art radiative transfer model using the most recent spectroscopic data and continuum model. For the parameters calculation, a new climatology capable of representing the average atmospheric and sea surface status during SLSTR measurements has been developed. The new algorithm, named AIRWAVE-SLSTR, has been implemented in both IDL and Python languages. In the frame of an EUMETSAT contract, AIRWAVE-SLSTR has been applied to a full year of SLSTR measurements (2021) and the retrieved TCWV have been validated with the help of both satellite- and ground-based measurements. The correlation of the retrieved TCWV with satellite MW measurements is 0.94 and the average bias is of the order of 0.66 kg/m${}^2$. When compared to ground-based measurements, the average correlation is 0.93 and the bias −0.48 kg/m${}^2$. The obtained accuracy is well within the requirements set for both numerical weather predictions (1–5 kg/m${}^2$) and for coastal altimetry applications (1.8–3 kg/m${}^2$). Therefore, the AIRWAVE-SLSTR algorithm can be safely applied to obtain a long time series of reliable TCWV above water surfaces.

We report the installation and first two years of operation of an EM27/SUN Fourier transform spectrometer at the CNR-ISAC facility in Bologna, Italy, the first instrument of its kind operating in the Po Valley, one of the European region mostly affected by anthropogenic pollution. The instrument is integrated into the COCCON network and it retrieves total columns and column-averaged dry air mole fractions of CO₂, CH₄, CO, and H₂O using the PROFFAST processing chain as per standardized COCCON protocols. The data is filtered with the fitted solar gas shift in the O₂ absorption band for quality controls, and here we study the seasonality of the retrieved products. To assess the relationship between column-integrated and near-surface measurements, we present a case-study comparison against a co-located Cavity Ring-Down Spectroscopy analyzer for CO₂ and CH₄ over a single day, using ceilometer-derived Mixed Aerosol Layer height to interpret the differing diurnal variability between the two techniques, with CRDS showing substantially larger amplitude swings driven by boundary-layer dynamics and surface emission/sink processes. We further validate the EM27/SUN against TROPOMI satellite retrievals of XCH₄ and total-column CO over the full observing period, finding low systematic biases (-0.13% and 0.60% respectively) consistent with satellite mission requirements and comparable to TCCON stations at similar latitudes. As a case-study, we show that both instruments jointly detected an anomalous CO enhancement in July-August 2024 attributable to long-range transport of Canadian wildfires smoke, illustrating the capability of ground-based FTIR observations to identify high-altitude pollution intrusions undetectable by in-situ instrumentation alone. These results establish the EM27/SUN in Bologna as a robust reference for satellite validation and a valuable tool for characterizing atmospheric transport events in the Po Valley.

Long-term observations of black carbon (BC) are essential for assessing the effectiveness of air-quality and climate policies and for understanding the potential feedback of climate change. We present an 18-year dataset (2007–2024) of equivalent black carbon (eBC) mass concentration derived from the aerosol absorption coefficient measured at the Monte Cimone WMO/GAW Global Station (CMN, 2165 m a.s.l.), a key high-altitude observatory in the Mediterranean climate-change hotspot. The dataset is accompanied by detailed description of: i) the infrastructural evolution, including instrumentation and sampling system; ii) the definition of quality assurance protocol and data treatment; iii) the definition of the uncertainties. This documentation provides a comprehensive description and quantification of the data reliability over 18 years of measurements, necessary for the scientific valorisation of the dataset. Applications of the dataset demonstrate: i) a statistically significant decline in eBC concentrations over the last two decades ii) a strong linkage between eBC variability and boundary-layer dynamics when combined with ERA5 reanalysis; iii) a variable agreement with FLEXPART simulations across temporal scales, supporting its use for model evaluation. The dataset, openly available through the ITINERIS HUB, provides one of the longest continuous eBC records in the Mediterranean troposphere and represents a valuable resource for climate studies, trend assessments, and multi-station integration within ACTRIS and GAW.

We report the installation and first two years of operation of an EM27/SUN Fourier transform spectrometer at the CNR-ISAC facility in Bologna, Italy, the first instrument of its kind operating in the Po Valley, one of the European regions most affected by anthropogenic pollution. The instrument is integrated into the COCCON network, and it retrieves total columns and column-averaged dry-air mole fractions of CO₂, CH₄, CO, and H₂O using the PROFFAST processing chain as per standardized COCCON protocols. The data are quality-controlled using the fitted solar gas shift in the O₂ absorption band, and the seasonality of the retrieved products is investigated. To explore the relationship between column-integrated and near-surface measurements, we present an illustrative one-day comparison with a co-located cavity ring-down spectroscopy analyzer for CO₂ and CH₄, using the ceilometer-derived mixed aerosol layer height to interpret the different diurnal variability between the two techniques, with the CRDS showing substantially larger amplitude swings driven by boundary-layer dynamics and surface emission/sink processes. We further compare the EM27/SUN with TROPOMI satellite retrievals of XCH₄ and total-column CO over the full observing period, obtaining low systematic biases (0.01% and 0.60%, respectively) consistent with satellite mission requirements and comparable to those reported for TCCON stations at similar latitudes. As a case study, we show that both instruments captured an anomalous CO enhancement in July 2024 that is consistent with long-range transport of Canadian wildfire emissions, illustrating the potential of ground-based FTIR observations to identify high-altitude pollution intrusions that may not be detected by in situ instrumentation alone. These results demonstrate the potential of the EM27/SUN measurements in Bologna as a reference dataset for satellite validation and as a complementary tool for investigating atmospheric transport events in the Po Valley.