Veranstaltungskalender

Volcanism is a major driver of climate variability and has played a critical role in the long-term evolution of Earth’s atmosphere and habitability through the release of gases including sulfur species, water, carbon dioxide, and halogens. In this talk, I will summarize my work on volcanic radiative forcing exerted by volcanic eruptions of different magnitudes in the past and in the future. The general mechanisms by which volcanic eruptions affect climate are well understood today. Until recently, research efforts have mainly been focused on the direct radiative, dynamical and chemical effects of sulfate aerosol particles formed by large-magnitude explosive eruptions such as Mt. Pinatubo in 1991. However, eruptions much smaller in magnitude than 1991 Mt. Pinatubo routinely decrease the transparency of the stratosphere to a degree that a cooling effect is discernible in upper tropospheric temperature measurements. I will make a case for the need to include these small-magnitude eruptions in climate model simulations. In addition, I will show that global warming can affect both eruptive column dynamics and the volcanic sulfate aerosol lifecycle and thus the radiative forcing and climate effects of future volcanic eruptions. 

(1) Investigating Arctic Multilayer Clouds with K-means Clustering (2) Simulating the size sorting of hydrometeors with P3 microphysics in a supercell case of the RELAMPAGO-CACTI campaign (3) Ein Experiment mit der senseBox zur Aufzeichnung von Wetterphänomenen für Physiklehramtskandidat:innen (4) Assessing the aerosol direct radiative effect - a radiation multiple call scheme implemented to ICON-ART

The turbulent mixing of clouds with their environment decreases cloud amount, and hence the ability of clouds to reflect solar radiation. Because the mixing increases with the droplet and hence aerosol concentration, this interaction is known to affect the role of clouds in the climate system, although its magnitude is hard to constrain. In this talk, I will review several mechanisms by which the droplet concentration affects the turbulent mixing of clouds and their environment, and discuss some associated problems. Ultimately, I will use ensembles of large-eddy simulations to derive a heuristic model by which the effect of aerosol-mediated mixing on clouds can be assessed. 

(1) Convective storms in a changing climate (2) tbd (3) Analysis and correction of MJO related errors in subseasonal ECMWF ensemble forecasts (4) tbd
 

(1) tbd (2) Serial clustering of multiple impact-related hazards in Germany (3) tbd (4) tbd

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

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