A 6-year lidar survey reveals enhanced rockwall retreat and modified rockfall magnitudes/frequencies in deglaciating cirques Earth Surface Dynamics DOI 10.5194/esurf-8-753-2020 8 October 2020 Rockfall size and frequency in two deglaciating cirques in the Central Alps, Austria, is analysed based on 6-year rockwall monitoring with terrestrial lidar (2011–2017). The erosion rates derived from this dataset are very high due to a frequent occurrence of large rockfalls in freshly deglaciated areas. The results obtained are important for rockfall hazard assessments, as, in rockwalls affected by glacier retreat, historical rockfall patterns are not good predictors of future events. Read more
Current glacier recession causes significant rockfall increase: the immediate paraglacial response of deglaciating cirque walls Earth Surface Dynamics DOI 10.5194/esurf-8-729-2020 8 October 2020 Climate warming is causing significant ice surface lowering even in the uppermost parts of alpine glaciers. Using terrestrial lidar, we quantify rockfall in freshly exposed cirque walls. During 6-year monitoring (2011–2017), an extensive dataset was established and over 600 rockfall events identified. Drastically increased rockfall activity following ice retreat can clearly be observed as 60 % of the rockfall volume detached from less than 10 m above the glacier surface. Read more
A Bayesian framework for emergent constraints: case studies of climate sensitivity with PMIP Climate of the Past DOI 10.5194/cp-16-1715-2020 6 October 2020 Interest in past climates as sources of information for the climate system has grown in recent years. In particular, studies of the warm mid-Pliocene and cold Last Glacial Maximum showed relationships between the tropical surface temperature of the Earth and its sensitivity to an abrupt doubling of atmospheric CO 2 . In this study, we develop a new and promising statistical method and obtain similar results as previously observed, wherein the sensitivity does not seem to exceed extreme values. Read more
Vertical profiles of light absorption and scattering associated with black carbon particle fractions in the springtime Arctic above 79∘ N Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10545-2020 6 October 2020 Black carbon is a factor in the warming of the Arctic atmosphere due to its ability to absorb light, but the uncertainty is high and few observations have been made in the high Arctic above 80° N. We combine airborne and ground-based observations in the springtime Arctic, at and above 80° N, with simulations from a global model to show that light absorption by black carbon may be much larger than modelled. However, the uncertainty remains high. Read more
Comparing secondary organic aerosol (SOA) volatility distributions derived from isothermal SOA particle evaporation data and FIGAERO–CIMS measurements Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10441-2020 1 October 2020 We compared the volatility distributions of secondary organic aerosol (SOA) constituents estimated from isothermal evaporation experiments from either particle size change data, by process modelling and global optimization, or from mass spectrometer data with positive matrix factorization analysis. Our results show that, despite the two very different estimation methods, the volatility distributions are comparable if uncertainties are taken into account. Read more
Predicting the morphology of ice particles in deep convection using the super-droplet method:development and evaluation of SCALE-SDM 0.2.5-2.2.0, -2.2.1, and -2.2.2 Geoscientific Model Development DOI 10.5194/gmd-13-4107-2020 1 October 2020 Using the super-droplet method, we constructed a detailed numerical model of mixed-phase clouds based on kinetic description and subsequently demonstrated that a large-eddy simulation of a cumulonimbus which predicts ice particle morphology without assuming ice categories or mass–dimension relationships is possible. Our results strongly support the particle-based modeling methodology’s efficacy for simulating mixed-phase clouds. Read more
A compact QCL spectrometer for mobile, high-precision methane sensing aboard drones Atmospheric Measurement Techniques DOI 10.5194/amt-13-4715-2020 29 September 2020 We describe a lightweight (2 kg) mid-IR laser spectrometer for airborne, in situ atmospheric methane (CH 4 ) measurements. The instrument, based on an open-path circular multipass cell, provides fast response (1 Hz) and sub-parts-per-billion precision. It can easily be mounted on a drone, giving access to highly resolved 4D (spatial and temporal) data. The performance was assessed during field deployments involving artificial CH 4 releases and vertical concentration gradients in the PBL. Read more
Using constructed soils for green infrastructure – challenges andlimitations SOIL DOI 10.5194/soil-6-413-2020 29 September 2020 The goal of this study was to discuss current methods to create soils adapted for various green infrastructure (GI) designs. Investigating these new soils for several design categories of GI will provide technical information for management and design agencies. Moreover, these studies can serve as pioneer experiments to prevent recurring errors and, thus, provide improved plant growth practices. Results show that these constructed soils have a high potential to provide multiple soil functions. Read more
HyLands 1.0: a hybrid landscape evolution model to simulate the impact of landslides and landslide-derived sediment on landscape evolution Geoscientific Model Development DOI 10.5194/gmd-13-3863-2020 24 September 2020 Landslides shape the Earth’s surface and are a dominant source of terrestrial sediment. Rivers, then, act as conveyor belts evacuating landslide-produced sediment. Understanding the interaction among rivers and landslides is important to predict the Earth’s surface response to past and future environmental changes and for mitigating natural hazards. We develop HyLands, a new numerical model that provides a toolbox to explore how landslides and rivers interact over several timescales. Read more
Quantifying burning efficiency in megacities using the NO2/CO ratio fromthe Tropospheric Monitoring Instrument (TROPOMI) Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10295-2020 24 September 2020 Rapid urbanization has increased the consumption of fossil fuel, contributing the degradation of urban air quality. Burning efficiency is a major factor determining the impact of fuel burning on the environment. We quantify the burning efficiency of fossil fuel use over six megacities using satellite remote sensing data. City governance can use these results to understand air pollution scenarios and to formulate effective air pollution control strategies. Read more
Fire Weather Index: the skill provided by the European Centre for Medium-Range Weather Forecasts ensemble prediction system Natural Hazards and Earth System Sciences DOI 10.5194/nhess-20-2365-2020 22 September 2020 Forecasting of daily fire weather indices driven by the ECMWF ensemble prediction system is shown to have a good skill up to 10 d ahead in predicting flammable conditions in most regions of the world. The availability of these forecasts through the Copernicus Emergency Management Service can extend early warnings by up to 1–2 weeks, allowing for greater proactive coordination of resource-sharing and mobilization within and across countries. Read more
The value of remote marine aerosol measurements for constraining radiative forcing uncertainty Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10063-2020 22 September 2020 The amount of energy reflected back into space because of man-made particles is highly uncertain. Processes related to naturally occurring particles cause most of the uncertainty, but these processes are poorly constrained by present-day measurements. We show that measurements over the Southern Ocean, far from pollution sources, efficiently reduce climate model uncertainties. Our results pave the way to designing experiments and measurement campaigns that reduce this uncertainty even further. Read more
Lessons from a high-CO2 world: an ocean view from ∼3 million years ago Climate of the Past DOI 10.5194/cp-16-1599-2020 17 September 2020 We examine the sea-surface temperature response to an interval of climate ~ 3.2 million years ago, when CO 2 concentrations were similar to today and the near future. Our geological data and climate models show that global mean sea-surface temperatures were 2.3 to 3.2 ºC warmer than pre-industrial climate, that the mid-latitudes and high latitudes warmed more than the tropics, and that the warming was particularly enhanced in the North Atlantic Ocean. Read more
A semi-empirical potential energy surface and line list for H216O extending into the near-ultraviolet Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10015-2020 17 September 2020 Water vapour has a complex spectrum and absorbs from the microwave to the near-UV where it dissociates. There is limited knowledge of the absorption features in the near-UV, and there is a large disagreement for the available models and experiments. We created a new ab initio model that is in good agreement with observation at 363 nm. At lower wavelengths, our calculations suggest that the latest experiments overestimate absorption. This has implications for trace gas retrievals in the near-UV. Read more
Revisiting global satellite observations of stratospheric cirrus clouds Atmospheric Chemistry and Physics DOI 10.5194/acp-20-9939-2020 15 September 2020 Cirrus clouds appearing in the upper troposphere and lower stratosphere have important impacts on the radiation budget and climate change. We revisited global stratospheric cirrus clouds with CALIPSO and for the first time with MIPAS satellite observations. Stratospheric cirrus clouds related to deep convection are frequently detected in the tropics. At middle latitudes, MIPAS detects more than twice as many stratospheric cirrus clouds due to higher detection sensitivity. Read more
Groundwater storage dynamics in the world’s large aquifer systems fromGRACE: uncertainty and role of extreme precipitation Earth System Dynamics DOI 10.5194/esd-11-755-2020 15 September 2020 Recent assessments of the sustainability of global groundwater resources using the Gravity Recovery and Climate Experiment (GRACE) satellites assume that the underlying trends are linear. Here, we assess recent changes in groundwater storage (ΔGWS) in the world’s large aquifer systems using an ensemble of GRACE datasets and show that trends are mostly non-linear. Non-linearity in ΔGWS derives, in part, from the episodic nature of groundwater replenishment associated with extreme precipitation. Read more
Inconsistencies between chemistry–climate models and observed lower stratospheric ozone trends since 1998 Atmospheric Chemistry and Physics DOI 10.5194/acp-20-9737-2020 10 September 2020 Recent lower stratospheric ozone decreases remain unexplained. We show that chemistry–climate models are not generally able to reproduce mid-latitude ozone and water vapour changes. Our analysis of observations provides evidence that climate change may be responsible for the ozone trends. While model projections suggest that extratropical ozone should recover by 2100, our study raises questions about their efficacy in simulating lower stratospheric changes in this region. Read more
Climatic information archived in ice cores: impact of intermittency and diffusion on the recorded isotopic signal in Antarctica Climate of the Past DOI 10.5194/cp-16-1581-2020 10 September 2020 The isotopic composition in ice cores from Antarctica is usually interpreted as a temperature proxy. Using a forward model, we show how different the signal in ice cores and the actual climatic signal are. Precipitation intermittency and diffusion do indeed affect the archived signal, leading to the reshuffling of the signal which limits the ability to reconstruct high-resolution climatic variations with ice cores. Read more
Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period Climate of the Past DOI 10.5194/cp-16-1565-2020 8 September 2020 We identify signatures of large bipolar volcanic eruptions in Greenland and Antarctic ice cores during the last glacial period, which allows for a precise temporal alignment of the ice cores. Thereby the exact timing of unexplained, abrupt climatic changes occurring during the last glacial period can be determined in a global context. The study thus provides a step towards a full understanding of elements of the climate system that may also play an important role in the future. Read more
ESD Ideas: Global climate response scenarios for IPCC assessments Earth System Dynamics DOI 10.5194/esd-11-751-2020 8 September 2020 Policy making on climate change routinely employs socioeconomic scenarios to sample the uncertainty in future forcing of the climate system, but the Intergovernmental Panel on Climate Change has not employed similar discrete scenarios to sample the uncertainty in the global climate response. Here, we argue that to enable risk assessments and development of robust policies this gap should be addressed, and we propose a simple methodology. Read more