Fakultät Naturwissenschaften

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Biologie, Ernährungs-wissenschaften und Lebensmittelwissenschaften sind die Schwerpunkte der Fakultät. Die Forschung befasst sich mit Schlüsselthemen der Life Sciences.

Homepage: https://natur.uni-hohenheim.de/

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Analysis of secondary inorganic aerosols over the greater Athens area using the EPISODE–CityChem source dispersion and photochemistry model
(2024) Myriokefalitakis, Stelios; Karl, Matthias; Weiss, Kim A.; Karagiannis, Dimitris; Athanasopoulou, Eleni; Kakouri, Anastasia; Bougiatioti, Aikaterini; Liakakou, Eleni; Stavroulas, Iasonas; Papangelis, Georgios; Grivas, Georgios; Paraskevopoulou, Despina; Speyer, Orestis; Mihalopoulos, Nikolaos; Gerasopoulos, Evangelos
Secondary inorganic aerosols (SIAs) are major components of fine particulate matter (PM 2.5), having substantial implications for climate and air quality in an urban environment. In this study, a state-of-the-art thermodynamic model has been coupled to the source dispersion and photochemistry city-scale chemistry transport model EPISODE–CityChem, which is able to simulate pollutants at a horizontal resolution of 100m×100m, to determine the equilibrium between the inorganic gas and aerosol phases over the greater Athens area, Greece, for the year 2019. In agreement with in situ observations, sulfate ( SO42-) is calculated to have the highest annual mean surface concentration (2.15  ± 0.88  µgm-3) among SIAs in the model domain, followed by ammonium ( NH4+; 0.58  ± 0.14  µgm-3) and fine nitrate ( NO3-; 0.24  ± 0.22  µgm-3). Simulations denote that NO3-formation strongly depends on the local nitrogen oxide emissions, along with the ambient temperature, the relative humidity, and the photochemical activity. Additionally, we show that anthropogenic combustion sources may have an important impact on the NO3-formation in an urban area. During the cold period, the combined effect of decreased temperature in the presence of non-sea-salt potassium favors the partitioning of HNO3in the aerosol phase in the model, raising the NO3-formation in the area. Overall, this work highlights the significance of atmospheric composition and the local meteorological conditions for the equilibrium distribution of nitrogen-containing semi-volatile compounds and the acidity of inorganic aerosols, especially in urban areas where atmospheric trace elements from natural and anthropogenic sources coexist.
On the temperature stability requirements of free-running Nd:YAG lasers for atmospheric temperature profiling through the rotational Raman technique
(2024) Zenteno-Hernández, José Alex; Comerón, Adolfo; Dios, Federico; Rodríguez-Gómez, Alejandro; Muñoz-Porcar, Constantino; Sicard, Michaël; Franco, Noemi; Behrendt, Andreas; Di Girolamo, Paolo
We assess the temperature stability requirements of unseeded Nd:YAG lasers in lidar systems for atmospheric temperature profiling through the rotational Raman technique. Taking as a reference a system using a seeded laser assumed to emit pulses of negligible spectral width and free of wavelength drifts, we estimate first the effect of the pulse spectral widening of the unseeded laser on the output of the interference filters, and then we derive the limits of the allowable wavelength drift for a given bias in the temperature measurement that would add to the noise-induced uncertainty. Finally, using spectroscopic data, we relate the allowable wavelength drift to allowable temperature variations in the YAG rod. We find that, in order to keep the bias affecting atmospheric temperature measurements smaller than 1 K, the Nd:YAG rod temperature should also be kept within a variation range of 1 K.
The ATMONSYS water vapor DIAL: advanced measurements of short-term variability in the planetary boundary layer
(2025) Speidel, Johannes; Vogelmann, Hannes; Behrendt, Andreas; Lange, Diego; Mauder, Matthias; Reichardt, Jens; Wolz, Kevin
High-resolution measurements of water vapor concentrations and their transport throughout the turbulent planetary boundary layer (PBL) and beyond are key for an enhanced understanding of atmospheric processes. This study presents data from the mobile Atmospheric Monitoring System (ATMONSYS) Differential Absorption Lidar (DIAL), operated with a novel titanium sapphire (Ti:Sa) laser concept, for the first time. The ATMONSYS DIAL aims to resolve turbulence throughout the PBL with a sampling frequency of 10 sand vertical resolutions of less than 200 m. General measuring capabilities during high-noon, clear-sky, summer conditions with a maximum vertical measurement range of >3 km and statistical uncertainties of <5 % are demonstrated. The analysis of turbulence spectra shows good agreement with Kolmogorov's law, demonstrating the system's capability to resolve turbulence. However, deviations from Kolmogorov behavior are observed at certain frequency ranges. By combining the ATMONSYS DIAL with an adjacent high-quality Doppler wind lidar, some of these deviations are mitigated in the co-spectra due to independent noise from both instruments. However, intermediate deviations from Kolmogorov behavior persist, likely due to surrounding surface heterogeneities. The agreement of the co-spectra with Kolmogorov's law at the highest frequencies demonstrates that the ATMONSYS DIAL is capable of resolving turbulent latent energy fluxes down to the measurement's Nyquist frequency of 5×10-2Hz. A system cross-intercomparison of the ATMONSYS DIAL with two adjacent water vapor Raman lidars and radiosondes shows overall good agreement between the sensors, despite minor DIAL deficiencies under certain conditions with broken clouds passing over the lidar. The observed profile-to-profile DIAL fluctuations and sensor-to-sensor deviations, in combination with low statistical uncertainty, highlight the advantage of humidity lidars, such as the ATMONSYS DIAL, in capturing both short-term and small-scale dynamics of the lowermost atmosphere.

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