Factors affecting the solar spectral ultraviolet (UV) irradiance at Thessaloniki, Greece were investigated using measurements with single- and double-monochromator Brewer spectroradiometer, which started operating respectively in 1989 and 1993 and continue up to the present. The two data records were quality controlled, homogenized and finally merged into one dataset, which was used in the analysis. Subsets of these data corresponding to different solar zenith angles (SZAs) and to cloud-free skies were used to quantify the long-term changes in surface UV irradiance at different wavelengths, and the importance of the factors responsible for these changes is discussed. It is shown that the calculated UV changes vary with SZA due to the different atmospheric path of the photons and the dependence of the diffuse to direct irradiance ratio on the SZA. The effect of total ozone and aerosols on UV irradiance is examined and the corresponding radiation amplification factors (RAFs) at the various wavelengths are calculated. The observed changes in UV irradiance due to ozone are smaller than those expected for the changes in total ozone, suggesting that the influence of the ozone is masked by other factors. An important finding of this study is that the improvement in air quality at Thessaloniki, during the period under examination, is the main reason for the observed increase in solar UV irradiance.

In this work, collocated lidar–radar observations are used to retrieve the vertical profiles of cloud properties above the Eastern Mediterranean. Measurements were performed in the framework of the PRE-TECT experiment during April 2017 at the Greek atmospheric observatory of Finokalia, Crete. Cloud geometrical and microphysical properties at different altitudes were derived using the Cloudnet target classification algorithm. We found that the variable atmospheric conditions that prevailed above the region during April 2017 resulted in complex cloud structures. Mid-level clouds were observed in 38% of the cases, high or convective clouds in 58% of the cases, and low-level clouds in 2% of the cases. From the observations of cloudy profiles, pure ice phase occurred in 94% of the cases, mixed-phase clouds were observed in 27% of the cases, and liquid clouds were observed in 8.7% of the cases, while Drizzle or rain occurred in 12% of the cases. The significant presence of Mixed-Phase Clouds was observed in all the clouds formed at the top of a dust layer, with three times higher abundance than the mean conditions (26% abundance at −15 °C). The low-level clouds were formed in the presence of sea salt and continental particles with ice abundance below 30%. The derived statistics on clouds’ high-resolution vertical distributions and thermodynamic phase can be combined with Cloudnet cloud products and lidar-retrieved aerosol properties to study aerosol-cloud interactions in this understudied region and evaluate microphysics parameterizations in numerical weather prediction and global climate models.

The aim of this paper is to apply a new lane separation methodology for the maritime sector emissions attributed to the different vessel types and marine traffic loads in the Mediterranean and the Black Sea defined via the European Marine and Observation Data network (EMODnet), developed in 2016. This methodology is implemented for the first time on the Copernicus Atmospheric Monitoring Service Global Shipping (CAMS-GLOB-SHIP v2.1) nitrogen oxides (NO_X) emissions inventory, on the Sentinel-5 Precursor Tropospheric Monitoring Instrument (TROPOMI) nitrogen dioxide (NO₂) tropospheric vertical column densities, and on the LOTOS-EUROS (Long Term Ozone Simulation—European Operational Smog) CTM (chemical transport model) simulations. By applying this new EMODnet-based lane separation method to the CAMS-GLOB-SHIP v2.1 emission inventory, we find that cargo and tanker vessels account for approximately 80% of the total emissions in the Mediterranean, followed by fishing, passenger, and other vessel emissions with contributions of 8%, 7%, and 5%, respectively. Tropospheric NO₂ vertical column densities sensed by TROPOMI for 2019 and simulated by the LOTOS-EUROS CTM have been successfully attributed to the major vessel activities in the Mediterranean; the mean annual NO₂ load of the observations and the simulations reported for the entire maritime EMODnet-reported fleet of the Mediterranean is in satisfactory agreement, 1.26 ± 0.56 × 10¹⁵ molecules cm⁻² and 0.98 ± 0.41 × 10¹⁵ molecules cm⁻², respectively. The spatial correlation of the annual maritime NO₂ loads of all vessel types between observation and simulation ranges between 0.93 and 0.98. On a seasonal basis, both observations and simulations show a common variability. The wintertime comparisons are in excellent agreement for the highest emitting sector, cargo vessels, with the observations reporting a mean load of 0.98 ± 0.54 and the simulations of 0.81 ± 0.45 × 10¹⁵ molecules cm⁻² and correlation of 0.88. Similarly, the passenger sector reports 0.45 ± 0.49 and 0.39 ± 0.45 × 10¹⁵ molecules cm⁻² respectively, with correlation of 0.95. In summertime, the simulations report a higher decrease in modelled tropospheric columns than the observations, however, still resulting in a high correlation between 0.85 and 0.94 for all sectors. These encouraging findings will permit us to proceed with creating a top-down inventory for NO_x shipping emissions using S5P/TROPOMI satellite observations and a data assimilation technique based on the LOTOS-EUROS chemical transport model.

The eVe lidar is a scanning system that can perform combined linear/circular polarization and Raman measurements at 355 nm and consists of the European Space Agency’s (ESA) reference aerosol lidar system. eVe was deployed in the ASKOS campaign, which was held in Cabo Verde during the summer/autumn of 2021 and 2022, for the validation of the aerosol products of the ESA’s Aeolus mission. During the campaign, eVe performed routine linear/circular depolarization measurements during Aeolus overpasses as well as dual-field-of-view measurements for the investigation of multiple scattering effects on dust layers. Herein, we present an overview of the acquired measurements and findings.

Spectral measurements of surface solar irradiance in the ultraviolet are conducted at the Laboratory of Atmospheric Physics (LAP), Aristotle University of Thess