(1) Seasonality of Heatwaves: Insights from Dynamical Systems Theory and Weather Regimes (2) Serial clustering of multiple impact-related hazards in Germany (3) The impact of volcanic eruptions on cloud properties: A case study of the Raikoke eruption 2019 (4) From fine to giant: Multi-instrument assessment of the particle size distribution of emitted dust during the J-WADI field campaign

 
 

At temperatures between -40°C and 0°C, clouds can be mixed phase, so called because they consist of a mixture of both liquid cloud droplets and ice crystals. This type of cloud is especially poorly represented in climate models. One of the reasons is that both hydrometeors are assumed to be homogeneously mixed in global models, but observations show that ice and liquid are heterogeneously mixed and exist in separate "pockets". This difference in the 3-dimensional spatial distribution of ice and liquid is important to assess and quantify precipitation, cloud processes, radiative properties, and consequently their impact on climate change. The present study aims to better characterize mixed phase clouds and especially the spatial distribution of the thermodynamic phase and understand how meteorology, air parcel transport and aerosols impact it.
 
We defined a parameter to describe the spatial distribution of liquid and ice phases within mixed-phase clouds from observations from the space-based lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarisation). We spatially and temporally collocated the satellite measurements with reanalysis retrievals of aerosol concentration and meteorological parameters from ERA5 (European Centre for Medium-Range Weather Forecasts Reanalysis v5) and MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, version 2) and then applied a multi-linear linear regression fit to quantify the influence of the external parameters on the spatial distribution of the cloud phase up to first order. A second part of the study focuses on ground-based measurements from the North Slope Alaska Station (NSA), where the transport of air parcels is analysed according to cloud type.
 
Focusing on the Arctic region, the results show that temperature is the most important parameter influencing the liquid-ice interface: for example, clouds with a temperature above 265 K have seven times more liquid-ice interfaces and are more homogeneously mixed than clouds with a temperature below 253 K. Black carbon concentration are also important parameters to describe the phase distribution. At NSA, clouds associated with higher transport may be more heterogeneously mixed. The results could be used to refine the parameterisation of clouds in models and their impact on climate change. 

(1) tbd (2) Innovative climate indices to support adaptation strategies at local level - a participatory approach (3) ICON simulations for Swabian MOSES (4) The TEAMx (Multi-scale transport and exchange processes in the atmosphere over mountains – programme and experiment) observational campaign

The stratospheric ozone layer is essential in protecting life on Earth from harmful UV irradiation, and even small changes in ozone layer thickness can cause significant damage to human health and agriculture. Knowing the methods and causes for ozone depletion is therefore critical. As the atmospheric halogen loading moves towards pre-industrial levels in the future, the largest perturbation to the ozone layer could be caused by volcanic eruptions. Large explosive volcanic eruptions have the potential to alter the spatiotemporal profiles of the ozone column through changes in trace gas composition and aerosol loading of the stratosphere. Along with sulfur compounds, volcanic eruptions can inject halogens or water into the stratosphere, potentially leading to sudden and dramatic ozone losses on a hemispheric to global scale. A recent example is the January 15, 2022, Hunga volcanic eruption – the largest eruption in 30 years – injecting a significant amount of water into the stratosphere along with sulfur dioxide, SO2, peaking at a record-high >50 km above the surface.
A 3-D chemistry-climate-aerosol model – SOCOL-AERv2 model (SOCOL = modeling tools for studies of SOlar Climate Ozone Links, AER = 2D aerosol model) – has been used to determine the response of stratospheric ozone to different types of volcanic eruptions in a contemporary atmosphere: water-rich Hunga-like eruptions, eruptions injecting SO2, and eruptions co-injecting halogens into the stratosphere. The dependence on latitude, season, and halogen and water content is discussed as well as the differences in the results for hemispherical and global impacts, comparing the impact of each eruption scenario on the aerosol loading of the atmosphere and stratospheric ozone layer. Changing the climate scenarios, the stratospheric impact of future volcanic eruptions is compared to the contemporary cases as well as comparing the differences between varying climate scenarios for eruptions occurring in the future toward the end of the century.

Since October 2023, a high-resolution urban climate analysis – based on the air flow model FITNAH-3D has been available for Heidelberg, which covers the city area with a spatial resolution of 5 x 5 m.  The results can be used to derive statements about the current microclimatic state and the expected change in the quality of living and local climate comfort for citizens and residents. 
The new screening tool (the so-called climate scanner) allows the display of microclimatic effects of individual measures (tree planting, green facades, etc.) or changes to the position of existing buildings "instantly" via a GIS-interface - without the need for high-performance computing. This enables a fact-based assessment of climate adaptation measures even before the planning process, which in turn prevents costly subsequent adjustments.
The tool is based on an artificial intelligence which is built on a neural network that combines the results of the Heidelberg urban climate analysis with a large number of different urban climate analyses in Germany.

(1) Physical constraints on the stratospheric injection of trace gases from wildfires (2) tbd (3) Assessing the Impacts of Hailstorms in a future climate - first results (4) tbd

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(1) tbd (2) Impacts of Hailstorms on agricultural products (3) tbd (4) tbd