Events

The intensification of extreme precipitation in a warming climate has been shown in observations and climate models to follow approximately theoretical Clausius-Clapeyron scaling. However, larger changes have been indicated in events of short-duration which frequently trigger flash floods or landslides, causing loss of life. At the same time heatwaves and associated droughts and water shortages are increasing in frequency. Together these provide cascading impacts on water quality, agricultural production and other societal necessities. Continental-scale convection-permitting climate models (CPCMs) and new observational datasets provide the state-of-the-art in understanding future changes to extreme weather (rainfall, wind, hail, lightning) and their compounding effects with global warming. But climate models are underestimating the rate of change of warming in the real world, and the increase in associated extreme weather events due to their poor representation of dynamical circulation changes and feedbacks from land, ocean and ice dynamics. It will be argued that a shift in focus is needed from our reliance on climate models towards embedding different lines of evidence in a transdisciplinary storylines approach. Ultimately we must work together across disciplines to address these rapid changes and co-create actionable information that can be quickly embedded into policy and practice, using this approach to improve both early warning systems and projections of extreme weather events for climate adaptation.

(1) Getting Aerosol Effects into Parameterized Convection - How emulation of Cloud Resolving Models helps to represent Aerosol Cloud Interactions in parametrized convection in a coarse resolution model (2) The TEAMx (Multi-scale transport and exchange processes in the atmosphere over mountains – programme and experiment) observational campaign (3) AIRflows first results - spatially resolved wind measurements at 100 m resolution (4) Characteristics of diabatically driven high-impact cyclones over Europe

The Aeolus wind lidar satellite was launched in 2018 with the aim to mitigate the lack of global wind profile observations for NWP models. The satellite provided unprecedented direct wind profile observations for a period of nearly 5 years. By now various NWP centers conducted data denial experiments that demonstrate a remarkable impact of Aeolus on forecast skill and according to ECMWF the satellite has the largest impact per satellite.
While the overall beneficial impact has now been proven by various studies, the mechanisms leading to forecast improvements still remain to be investigated as the satellite only adds a comparably low number of observations to the global observing system and the observations were associated with relatively high errors (~ 5 m/s for most observations) and low spatial resolution (~100 km for most observations).
Largest improvements were found in the tropics and studies indicate that the improvements are associated with a better representation of tropical waves as well as the correction of systematic structural errors in current NWP models.  This is likely related to the ability of Aeolus to provide wind profile observations in contrast to most other tropical wind observations that are restricted to a single layer as e.g. atmospheric motion vectors. In midlatitudes, there is indication that the largest forecast improvements were associated with the excitation of Rossby wave packets, but details on if and how Aeolus can constrain divergent upper-level winds are still under investigation.
The talk summarizes the status of impact studies with the Aeolus satellite with a particular focus on gaps in our understanding that need to be resolved in view of a planned follow-on European wind lidar satellite mission.

 
 

Multi-Pressure Chemical Ionization Mass Spectrometry & Uronium CIMS: Novel ionization approaches to achieve comprehensive sensitivity with a single mass spectrometer
The chemical diversity among atmospheric trace gases demands different chemical ionization strategies under various pressures to enable comprehensive mass spectrometric analysis. For instance, organic acids and highly oxygenated compounds are detected sensitively via near-atmospheric pressure ionization in negative mode (e.g., using NO3-, Br-, I-). Certain low-polarity volatile organic compounds (VOCs), on the other hand, are effectively ionized by positive mode ion attachment. Meanwhile, minimally polar molecules often require non-selective positive mode ionization (e.g., proton-transfer reaction, PTR) at low pressure to suppress matrix effects (notably humidity). By combining these approaches, one can achieve a near-complete sensitivity to atmospheric trace constituents.
In the first part of the talk, I will elaborate on multi-pressure chemical ionization mass spectrometry (MPCIMS), the combination of high- and low-pressure ionization schemes within a single instrument, which enables the quantification of the full distribution of precursor molecules and their oxidation reaction products from the same stream of gas. We demonstrate the performance of the new methodology in a laboratory experiment employing a-pinene, a monoterpene relevant to atmospheric particle formation, where MPCIMS allows to measure the spectrum of compounds ranging from the volatile precursor hydrocarbon to highly functionalized condensable reaction products.
Second, I discuss uronium as an efficient and robust reagent cation for the ionization of VOCs at atmospheric IMR pressures. Urea, a solid chemical safe to humans with a negligible vapor pressure under normal circumstances, is sublimated from the solid phase under x-ray irradiation to form the uronium ion. We determine the calibration factors for VOCs, amines, and DMSO under different humidities in calibration experiments, interpret the ionization efficiencies using theory, and show results of test measurements of different chemical systems. Beyond the favorable sensitivities allowing detection at the low ppq level - attainable due to uronium’s applicability at atmospheric IMR pressure and a tendency to form strongly bound ion-molecular clusters – and low susceptibility to humidity changes, the marked benefit of uronium CIMS lies in the trivial handling of the reagent supply and long-term stability of the ion production system. The combination of favorable performance and easy handling render uronium CIMS promising to become a go-to method for ultra-sensitive positive mode chemical ionization.

The mesosphere and lower thermosphere at 50-200 km altitude is subject to highly dynamical physical and chemical processes that are driven by solar and magnetospheric forcing from above and by meteorological disturbances from below. This layer is of increasing societal relevance as its weather directly affects the functionality of ground- and space-based communication and navigation systems, and the lifetime and trajectories of low-earth-orbiting satellites and (re-)entering objects. Gravity waves are essential for coupling all atmospheric layers, from the troposphere to the thermosphere, but are difficult to treat in numerical models. I will present successful multidecadal simulation results as well as case studies conducted at km-resolution, where gravity waves are explicitly resolved. More broadly, I will discuss perspectives and challenges in high-resolution whole atmosphere modelling from both the technical and scientific perspective.

(1) Forecast Dispersion and Sensitivity in observation-perturbed ensembles of data-driven weather prediction models (2) Impacts of Hailstorms on agricultural products (3) Drought propagation: A search for extreme events and its impact on the Rhine River Basin