If you are interested in the zoom link, please contact alexander.siebelts@partner.kit.edu .

Even in a warming world, extreme winter weather events like cold air outbreaks still occur and have high socioeconomic costs, but they remain a challenge to forecast skillfully in the subseasonal-to-seasonal timeframe (i.e., 2-8 weeks). In this talk, I will discuss recent work by the Applied Climate Dynamics Group at the University of Oklahoma to improve our dynamical understanding of the evolution of cold air outbreaks in the central United States and then use this knowledge to improve skill in subseasonal predictions of those events. We use a combination of observations and numerical modeling experiments to show why we should care about intraseasonal variability in the stratosphere to improve our forecast skill, including considering different types of stratosphere-troposphere coupling outside of the “classical” paradigm. Additionally, we will highlight particular precursor flow patterns in the upper troposphere (so-called blocking patterns) which were key for skillful 3+ week forecasts of the February 2021 North American Cold Air Outbreak and could be exploited for long-lead predictions of future cold air outbreaks.

(1) Master thesis: Modelling of the sea surface temperature impact on the land-sea breeze over West Africa (2) Convection permitting scale climate ensembles (3) tbd (4) Organization of SIP processes in convective clouds

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If you are interested in the zoom link, please contact vdurlich@gmail.com .

(1) Forecast uncertainty growth in warm conveyor belts in neural network weather prediction model (2) tbd (3) Master Thesis: Impact of climate change on the Rossby wave activity over the Northern Hemisphere and impacts to temperature Extremes over Europe (4) tbd

 
 

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Mesoscale processes like cold pools and gust fronts occur everywhere on Earth and they are an essential element of severe storms. But now we realize that they might also be relevant for climate. The multi-scale interactions in which mesoscale processes are interwoven, from the mm-scale of rain drops to the large-scale circulation, were long out of the range accessible to both traditional Earth system models and high-resolution large-eddy simulations. Emerging tools like global coupled storm-resolving simulations, together with new observations and innovative methods to extract process-oriented products now offer the basis for critical advances in understanding the role of mesoscale processes for the radiative budget and hydrological cycle. In this presentation, I will show recent results demonstrating the importance of shallow mesoscale circulations and cold pools for cloud amount and cloud organization in the trades, and discuss two new tools that we’re developing to advance the physical understanding of the role of mesoscale processes for the fate of trade cumulus clouds. 
Mesoscale processes like cold pools and gust fronts occur everywhere on Earth and they are an essential element of severe storms. But now we realize that they might also be relevant for climate. The multi-scale interactions in which mesoscale processes are interwoven, from the mm-scale of rain drops to the large-scale circulation, were long out of the range accessible to both traditional Earth system models and high-resolution large-eddy simulations. Emerging tools like global coupled storm-resolving simulations, together with new observations and innovative methods to extract process-oriented products now offer the basis for critical advances in understanding the role of mesoscale processes for the radiative budget and hydrological cycle. In this presentation, I will show recent results demonstrating the importance of shallow mesoscale circulations and cold pools for cloud amount and cloud organization in the trades, and discuss two new tools that we’re developing to advance the physical understanding of the role of mesoscale processes for the fate of trade cumulus clouds. 
 

If you are interested in the zoom link, please contact miriam.bentke@student.kit.edu .

(1) Master Thesis: Impact of climate change on the Rossby wave activity over the Northern Hemisphere and impacts to temperature Extremes over Europe (2) Master Thesis: Physical constraints on the emission of water vapor and ash from Hunga Tonga eruption January 2022 (3) tbd (4) tbd

The moisture content and vertical distribution in the extratropical UTLS is important for radiative properties in particular with a perspective to anticipated change of tropopause height and moisture content due to rising greenhouse gas concentrations. We present a Lagrangian perspective on various processes that control the extratropical UTLS moisture content including deep convection and warm-conveyor belts as well as cloud and mixing processes close to the local tropopause. The analysis combines various data sources on UTLS moisture including high-resolution ICON simulation and ERA5, but also observational data from aircraft and satellite. 
 

If you are interested in the zoom link, please contact tabea.unser@student.kit.edu .

The top of the atmosphere reflectivity of the planet, depends in part, on the optical properties of aerosol in the atmosphere. Frequently atmospheric chemists use chemical proxies for aerosol and here we describe a series of experiment using optical trapping with material extracted from atmospheric filter samples. The experiments demonstrating to a first approximation that organic matter may for core-shell morphologies, have refractive indexes that vary with location and that thin films on aerosol have chemical removal rates comparable to mechanical removal rates from the atmosphere. Basic radiative transfer modelling also demonstrates that thin organic films on atmospheric aerosol may have appreciable effects on planetary reflectivity. We will also show some early data that near-field scattering effects between pairs of aerosol particles predicted by theory (T-matrix) may not agree with experiment.

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