Tropospheric gradients provide information on the moisture distribution, whereas zenith total delays provide the overall moisture information along the zenith. When both observations are used together, the model can actuate the moisture fields, correcting their dynamics. Our research shows that, in regions with very few stations, assimilating tropospheric gradients on top of zenith total delay observations can enhance the performance of existing improvements.

Humidity transport from the Earth's surface into the atmosphere is relevant for many processes. However, knowledge of the actual distribution of humidity concentrations is sparse – mainly due to technological limitations. With the lidar presented herein, it is possible to measure humidity concentrations and their vertical fluxes up to altitudes of > 3 km with high spatiotemporal resolution, opening new possibilities for detailed process understanding and, ultimately, better model representation.

Due to the scarcity of offshore in situ observations, alternative data sources are essential for a reliable understanding of offshore winds. Therefore, this study delves into the world of satellite remote sensing (ASCAT) and numerical models (ERA5), exploring their capabilities and limitations in characterising offshore winds. This investigation evaluates these two datasets against measurements from a floating ship-based lidar, collected during a novel measurement campaign in the Baltic Sea.

Ultrafine particles (diameter of less than 100 nm) are suspected to cause significant health effects. Accurately measuring their chemical composition and physical properties in real time is challenging due to their low mass and interference from larger particles. This study proposes a method for the continuous, automated measurement of their composition, tested in a pilot field study to explore their chemical characteristics, physical properties, and sources.

The two ozone instruments of IAGOS (In-service Aircraft for a Global Observation System) have been compared with the Ozone PhotoMeter (OPM) of the World Calibration Center of Ozone Sondes (WCCOS) in an atmospheric simulation chamber under realistic flight conditions of pressure, temperature, and ozone concentrations. The two IAGOS-instruments showed good agreement with the OPM within 5–6 %. The observed differences are small but systematic and reproducible during the intercomparison.

Air pollution management requires accurate determination of emissions and emission ratios of air pollutants. In this paper, we explore a new way to resolve excess mixing ratios in turbulent plumes, which allows aggregation of unbiased ensemble averages of air pollutant ratios that can be compared with emission models. The approach is tested in an urban environment and used to resolve emission patterns of nitrogen oxides and carbon dioxide.