Do changing circulation types raise the frequency of summertime thunderstorms and large hail in Europe?

We study the role of changes in circulation type frequency on the evolution of summertime thunderstorm and large hail frequency across Europe since 1950 until 2020 to find out if they are responsible for the changes that an additive regression convective hazard models model (AR-CHaMo) predicts to have happened. To define circulation types, the 500 hPa geopotential height anomaly field on each day was clustered into 14 distinct patterns using principal component analysis and k-means clustering. We show that lightning and hail occurrence, both observed and modeled by AR-CHaMo, strongly depend on the circulation type, with a higher frequency observed in poleward flow downstream of a trough and on the lee side of mountains. AR-CHaMo predicts strong increases in hail frequency across central parts of Europe to have occurred in the 1950–2020 period. During this period, changes in circulation type frequency are small and only significant for 2 of the 14 clusters. The trends in both lightning and hail frequency to be expected if they were solely determined by circulation patterns, are small, with typical values of 1%–3% per decade relative to the mean, whereas the trends expected by AR-CHaMo are on the order of 4%–10% in most areas. Across many regions, the sign of the changes does not agree in sign, in particular across European Russia where circulation types have become more favorable for lightning and hail, but a decreasing probability was modeled by AR-CHaMo. We conclude that changing circulation types are, in general, not responsible for changes in thunderstorm and hail frequency, which included the strong increase of conditions favorable for large hail in central Europe

Assessment of Urban CO2 Measurement and Source Attribution in Munich Based on TDLAS-WMS and Trajectory Analysis

Anthropogenic carbon dioxide (CO2) emissions mainly come from cities and their surrounding areas. Thus, continuous measuring of CO2 in urban areas is of great significance to studying human CO2 emissions. We developed a compact, precise, and self-calibrated in-situ CO2/H2O sensor based on TDLAS (tunable diode laser absorption spectroscopy), WMS (wavelength modulation spectroscopy), and VCSEL (vertical-cavity surface-emitting laser). Multi-harmonic detection is utilized to improve the precision of both measurements to 0.02 ppm for CO2 and 1.0 ppm for H2O. Using the developed sensor, we measured CO2 concentrations continuously in the city center of Munich, Germany, from February 2018 to January 2019. Urban CO2 concentrations are strongly affected by several factors, including vegetation photosynthesis and respiration (VPR), planetary boundary layer (PBL) height, and anthropogenic activities. In order to further understand the anthropogenic contribution in terms of CO2 sources, the HySPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model was applied to calculate six-hour backward trajectories. We analyzed the winter CO2 with the trajectory clustering, PSCF (potential source contribution function), and CWT (concentration weighted trajectory) methods, and found that local emissions have a great impact on urban CO2 concentration, with main emission sources in the north and southeast directions of the measurement site. In situations with an uneven trajectory distribution, PSCF proves somewhat superior in predicting the potential emission sources compared to CWT

Documentation of sediment cores during SONNE Expedition SO228 from the western tropical Pacific

The core descriptions (chapter 7) summarize the most important results of the analysis of each sediment core following procedures applied during ODP/IODP expeditions. All cores were opened, described, and color-scanned. In the core descriptions the first column displays the lithological data that are based on visual analysis of the core and are supplemented by information from binocular and smear slide analyses. The sediment classification largely follows ODP/IODP convention. Lithological names consist of a principal name based on composition, degree of lithification, and/or texture as determined from visual description and microscopic observations. In the structure column the intensity of bioturbation together with individual or special features (turbidites, volcanic ash layers, plant debris, shell fragments, etc.) is shown. The hue and chroma attributes of color were determined by comparison with the Munsell soil color charts and are given in the color column in the Munsell notation. A GretagMacbethTM Spectrolino spectrophotometer was used to measure percent reflectance values of sediment color at 36 wavelength channels over the visible light range (380-730 nm) on all of the cores. The digital reflectance data of the spectrophotometer readings were routinely obtained from the surface (measured in 1 cm steps) of the split cores (archive half). The Spectrolino is equipped with a measuring aperture with folding mechanism allowing an exact positioning on the split core and is connected to a portable computer. The data are directly displayed within the software package Excel and can be controlled simultaneously. From all the color measurements, for each core the red/blue ratio (700 nm/450 nm) and the lightness are shown together with the visual core description. The reflectance of individual wavelengths is often significantly affected by the presence of minor amounts of oxyhydroxides or sulphides. To eliminate these effects, we used the red/blue ratio and lightness