Uncertainty in aerosol–cloud radiative forcing is driven by clean conditions Atmospheric Chemistry and Physics DOI 10.5194/acp-23-4115-2023 21 April 2023 The impact of aerosols on clouds is one of the largest uncertainties in the human forcing of the climate. Aerosol can increase the concentrations of droplets in clouds, but observational and model studies produce widely varying estimates of this effect. We show that these estimates can be reconciled if only polluted clouds are studied, but this is insufficient to constrain the climate impact of aerosol. The uncertainty in aerosol impact on clouds is currently driven by cases with little aerosol. Read more
A multi-disciplinary analysis of the exceptional flood event of July 2021 in central Europe – Part 2: Historical context and relation to climate change Natural Hazards and Earth System Sciences DOI 10.5194/nhess-23-1287-2023 19 April 2023 Heavy precipitation in July 2021 led to widespread floods in western Germany and neighbouring countries. The event was among the five heaviest precipitation events of the past 70 years in Germany, and the river discharges exceeded by far the statistical 100-year return values. Simulations of the event under future climate conditions revealed a strong and non-linear effect on flood peaks: for +2K global warming, an 18% increase in rainfall led to a 39% increase of the flood peak in the Ahr river. Read more
Brief communication: On the extremeness of the July 2021 precipitation event in western Germany Natural Hazards and Earth System Sciences DOI 10.5194/nhess-23-1227-2023 17 April 2023 Estimating the severity of a rainfall event based on the damage caused is easy but highly depends on the affected region. A less biased measure for the extremeness of an event is its rarity combined with its spatial extent. In this brief communication, we investigate the sensitivity of such measures to the underlying dataset and highlight the importance of considering multiple spatial and temporal scales using the devastating rainfall event in July 2021 in central Europe as an example. Read more
Investigation of links between dynamical scenarios and particularly high impact of Aeolus on numerical weather prediction (NWP) forecasts Author(s): Anne Martin, Martin Weissmann, and Alexander Cress Weather and Climate Dynamics DOI 10.5194/wcd-4-249-2023 14 April 2023 Global wind profiles from the Aeolus satellite mission are an important recent substitute for the Global Observing System, showing an overall positive impact on numerical weather prediction forecasts. This study highlights atmospheric dynamic phenomena constituting pathways for significant improvement of Aeolus for future studies, including large-scale tropical circulation systems and the interaction of tropical cyclones undergoing an extratropical transition with the midlatitude waveguide. NWP) forecasts Author(s): Anne Martin, Martin Weissmann, and Alexander Cress">Read more
The new Kr-86 excess ice core proxy for synoptic activity: West Antarctic storminess possibly linked to Intertropical Convergence Zone (ITCZ) movement through the last deglaciation Climate of the Past DOI 10.5194/cp-19-579-2023 12 April 2023 It is unclear how different components of the global atmospheric circulation, such as the El Niño effect, respond to large-scale climate change. We present a new ice core gas proxy, called krypton-86 excess, that reflects past storminess in Antarctica. We present data from 11 ice cores that suggest the new proxy works. We present a reconstruction of changes in West Antarctic storminess over the last 24000 years and suggest these are caused by north–south movement of the tropical rain belt. ITCZ) movement through the last deglaciation">Read more
Reproducible and relocatable regional ocean modelling: fundamentals and practices Geoscientific Model Development DOI 10.5194/gmd-16-1481-2023 10 April 2023 The aim is to increase the capacity of the modelling community to respond to societally important questions that require ocean modelling. The concept of reproducibility for regional ocean modelling is developed: advocating methods for reproducible workflows and standardised methods of assessment. Then, targeting the NEMO framework, we give practical advice and worked examples, highlighting key considerations that will the expedite development cycle and upskill the user community. Read more
Influence of ozone and humidity on PTR-MS and GC-MS VOC measurements with and without a Na2S2O3 ozone scrubber Atmospheric Measurement Techniques DOI 10.5194/amt-16-1179-2023 7 April 2023 Atmospheric ozone can induce artefacts in volatile organic compound measurements. Laboratory tests were made using GC-MS and PTR-MS aircraft systems under tropospheric and stratospheric conditions of humidity and ozone, with and without sodium thiosulfate filter scrubbers. Ozone in dry air produces some carbonyls and degrades alkenes. The scrubber lifetime depends on ozone concentration, flow rate and humidity. For the troposphere with scrubber, no significant artefacts were found over 14 d. PTR-MS and GC-MS VOC measurements with and without a Na2S2O3 ozone scrubber">Read more
A climate-conditioned catastrophe risk model for UK flooding Natural Hazards and Earth System Sciences DOI 10.5194/nhess-23-891-2023 5 April 2023 We present and validate a model that simulates current and future flood risk for the UK at high resolution (~ 20-25 m). We show that UK flood losses were ~ 6 % greater in the climate of 2020 compared to recent historical values. The UK can keep any future increase to ~ 8 % if all countries implement their COP26 pledges and net-zero ambitions in full. However, if only the COP26 pledges are fulfilled, then UK flood losses increase by ~ 23 %, and potentially by ~ 37 % in a worst-case scenario. Read more
Performance of the flood warning system in Germany in July 2021 – insights from affected residents Natural Hazards and Earth System Sciences DOI 10.5194/nhess-23-973-2023 3 April 2023 In July 2021 intense rainfall caused devastating floods in western Europe with 184 fatalities in the German federal states of North Rhine-Westphalia (NW) and Rhineland-Palatinate (RP), calling their warning system into question. An online survey revealed that 35 % of respondents from NW and 29 % from RP did not receive any warning. Many of those who were warned did not expect severe flooding, nor did they know how to react. The study provides entry points for improving Germany’s warning system. Read more
Reconciling the paradox of soil organic carbon erosion by water Biogeosciences DOI 10.5194/bg-20-635-2023 31 March 2023 The direction and magnitude of the net erosion-induced land–atmosphere C exchange have been the topic of a big scientific debate for more than a decade now. Many have assumed that erosion leads to a loss of soil carbon to the atmosphere, whereas others have shown that erosion ultimately leads to a carbon sink. Here, we show that the soil carbon erosion source–sink paradox is reconciled when the broad range of temporal and spatial scales at which the underlying processes operate are considered. Read more
