Arctic Ocean acidification over the 21st century co-driven by anthropogenic carbon increases and freshening in the CMIP6 model ensemble Biogeosciences DOI 10.5194/bg-18-2221-2021 17 May 2021 The uptake of carbon, emitted as a result of human activities, results in ocean acidification. We analyse 21st-century projections of acidification in the Arctic Ocean, a region of particular vulnerability, using the latest generation of Earth system models. In this new generation of models there is a large decrease in the uncertainty associated with projections of Arctic Ocean acidification, with freshening playing a greater role in driving acidification than previously simulated. Read more
Airborne measurements of oxygen concentration from the surface to the lower stratosphere and pole to pole Atmospheric Measurement Techniques DOI 10.5194/amt-14-2543-2021 14 May 2021 We describe methods used to make high-precision global-scale airborne measurements of atmospheric oxygen concentrations over a period of 20 years in order to study the global carbon cycle. Our techniques include an in situ vacuum ultraviolet absorption instrument and a pressure- and flow-controlled, cryogenically dried, glass flask sampler. We have deployed these instruments in 15 airborne research campaigns spanning from the Earth’s surface to the lower stratosphere and from pole to pole. Read more
Evaluating stratospheric ozone and water vapour changes in CMIP6 models from 1850 to 2100 Atmospheric Chemistry and Physics DOI 10.5194/acp-21-5015-2021 12 May 2021 Stratospheric ozone and water vapour are key components of the Earth system; changes to both have important impacts on global and regional climate. We evaluate changes to these species from 1850 to 2100 in the new generation of CMIP6 models. There is good agreement between the multi-model mean and observations, although there is substantial variation between the individual models. The future evolution of both ozone and water vapour is strongly dependent on the assumed future emissions scenario. Read more
Diverging land-use projections cause large variability in their impacts on ecosystems and related indicators for ecosystem services Earth System Dynamics DOI 10.5194/esd-12-327-2021 10 May 2021 Many projections of future land-use/-cover exist. We evaluate a number of these and determine the variability they cause in ecosystems and their services. We found that projections differ a lot in regional patterns, with some patterns being at least questionable in a historical context. Across ecosystem service indicators, resulting variability until 2040 was highest in crop production. Results emphasize that such variability should be acknowledged in assessments of future ecosystem provisions. Read more
How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region Weather and Climate Dynamics DOI 10.5194/wcd-2-281-2021 7 May 2021 The interaction of clouds in the trade wind region with the atmospheric flow is complex and at the heart of uncertainties associated with climate projections. In this study, a natural tracer of atmospheric circulation is used to establish a link between air originating from dry regions of the midlatitudes and the occurrence of specific cloud patterns. Two pathways involving transport within midlatitude weather systems are identified, by which air is brought into the trades within 5–10 d. Read more
A process-based evaluation of the Intermediate Complexity Atmospheric Research Model (ICAR) 1.0.1 Geoscientific Model Development DOI 10.5194/gmd-14-1657-2021 3 May 2021 This study conducts an in-depth process-based evaluation of the Intermediate Complexity Atmospheric Research (ICAR) model, employing idealized simulations to increase the understanding of the model and develop recommendations to maximize the probability that its results are correct for the right reasons. The results show that when model skill is evaluated from statistical metrics based on comparisons to surface observations only, such an analysis may not reflect the skill of the model in capturing atmospheric processes like gravity waves and cloud formation. Read more
Similar importance of edaphic and climatic factors for controlling soil organic carbon stocks of the world Biogeosciences DOI 10.5194/bg-18-2063-2021 30 April 2021 Soil organic carbon (SOC) accounts for two-thirds of terrestrial carbon. Yet, the role of soil physicochemical properties in regulating SOC stocks is unclear, inhibiting reliable SOC predictions under land use and climatic changes. Using legacy observations from 141 584 soil profiles worldwide, we disentangle the effects of biotic, climatic and edaphic factors (a total of 31 variables) on the global spatial distribution of SOC stocks in four sequential soil layers down to 2 m. Read more
The behavior of high-CAPE (convective available potential energy) summer convection in large-domain large-eddy simulations with ICON Atmospheric Chemistry and Physics DOI 10.5194/acp-21-4285-2021 28 April 2021 Current state-of-the-art regional numerical weather prediction (NWP) models employ kilometer-scale horizontal grid resolutions, thereby simulating convection within the grey zone. Increasing resolution leads to resolving the 3D motion field and has been shown to improve the representation of clouds and precipitation. Using a hectometer-scale model in forecasting mode on a large domain therefore offers a chance to study processes that require the simulation of the 3D motion field at small horizontal scales. Read more
Do small and large floods have the same drivers of change? A regional attribution analysis in Europe Hydrology and Earth System Sciences DOI 10.5194/hess-25-1347-2021 26 April 2021 Recent studies have shown evidence of increasing and decreasing trends for average floods and flood quantiles across Europe. Studies attributing observed changes in flood peaks to their drivers have mostly focused on the average flood behaviour, without distinguishing small and large floods. This paper proposes a new framework for attributing flood changes to potential drivers, as a function of return period (T), in a regional context. Read more
Interhemispheric transport of metallic ions within ionospheric sporadic E layers by the lower thermospheric meridional circulation Atmospheric Chemistry and Physics DOI 10.5194/acp-21-4219-2021 23 April 2021 Here, we report a study of ionospheric irregularities using scintillation data from COSMIC satellites and identify a large-scale horizontal transport of long-lived metallic ions, combining the simulations of the Whole Atmosphere Community Climate Model with the chemistry of metals and ground-based observations from two meridional chains of stations from 1975–2016. Read more
Observed snow depth trends in the European Alps: 1971 to 2019 The Cryosphere DOI 10.5194/tc-15-1343-2021 9 April 2021 Here, we present an Alpine-wide analysis of snow depth from six Alpine countries – Austria, France, Germany, Italy, Slovenia, and Switzerland – including altogether more than 2000 stations of which more than 800 were used for the trend assessment. Linear trends of monthly mean snow depth between1971 and 2019 showed decreases in snow depth for most stations from November to May. Read more
The enigma of relict large sorted stone stripes in the tropical Ethiopian Highlands Earth Surface Dynamics DOI 10.5194/esurf-9-145-2021 7 April 2021 Large forms of sorted patterned ground belong to the most prominent geomorphic features of periglacial and permafrost environments of the mid-latitudes and polar regions, but they were hitherto unknown in the tropics. Here, we report on relict large sorted stone stripes (up to 1000 m long, 15 m wide, and 2 m deep) on the ca. 4000 m high central Sanetti Plateau of the tropical Bale Mountains in the southern Ethiopian Highlands. Read more
geoChronR – an R package to model, analyze, and visualize age-uncertain data Geochronology DOI 10.5194/gchron-3-149-2021 5 April 2021 Chronological uncertainty is a hallmark of the paleoenvironmental sciences and geosciences. While many tools have been made available to researchers to quantify age uncertainties suitable for various settings and assumptions, disparate tools and output formats often discourage integrative approaches. Here, we describe geoChronR, an open-source R package to facilitate these tasks. Read more
Sensitivities to biological aerosol particle properties and ageing processes: potential implications for aerosol–cloud interactions and optical properties Atmospheric Chemistry and Physics DOI 10.5194/acp-21-3699-2021 2 April 2021 Primary biological aerosol particles (PBAPs), such as bacteria, viruses, fungi, and pollen, represent a small fraction of the total aerosol burden. Given that PBAPs are highly efficient atmospheric ice nuclei (IN) at T > -10 ∘C, we suggest that small changes in their sizes or surface properties due to chemical, physical, or biological processing might translate into large impacts on ice initiation in clouds. Read more
High-resolution optical constants of crystalline ammonium nitrate forinfrared remote sensing of the Asian Tropopause Aerosol Layer Atmospheric Measurement Techniques DOI 10.5194/amt-14-1977-2021 31 March 2021 In this work, we have retrieved the first low-temperature data set of optical constants for crystalline AN in the 800–6000 cm-1 wave number range with a spectral resolution of 0.5 cm-1. We show that our data accurately fit aircraft-borne infrared measurements of ammonium nitrate particles in the upper tropospheric aerosol layer, which is formed during the Asian summer monsoon period. Read more
A statistical–parametric model of tropical cyclones for hazard assessment Natural Hazards and Earth System Sciences DOI 10.5194/nhess-21-893-2021 30 March 2021 We present the formulation of an open-source, statistical–parametric model of tropical cyclones (TCs) for use in hazard and risk assessment applications. We demonstrate the capability of the model to replicate observed behaviour of TCs, including coastal landfall rates which are of significant importance for risk assessments. Read more
A global climatological perspective on the importance of Rossby wavebreaking and intense moisture transport for extreme precipitation events Weather and Climate Dynamics DOI 10.5194/wcd-2-129-2021 29 March 2021 Extreme precipitation events (EPEs) frequently cause flooding with dramatic socioeconomic impacts in many parts of the world.Previous studies considered two synoptic-scale processes, Rossby wave breaking and intense moisture transport, typically in isolation, and their linkage to such EPEs in several regions. This study presents for the first time a global and systematic climatological analysis of these two synoptic-scale processes, in tandem and in isolation, for the occurrence of EPEs. Read more
Characteristics of fragmented aurora-like emissions (FAEs) observed on Svalbard Annales Geophysicae DOI 10.5194/angeo-39-277-2021 26 March 2021 This study analyses the observations of a new type of small-scale aurora-like feature, which is further referred to as fragmented aurora-like emission(s) (FAEs). One possible explanation for this is Farley–Buneman instabilities of strong local currents. In the present study, we provide an overview of the observations and discuss their characteristics and potential generation mechanisms. Read more
Model physics and chemistry causing intermodel disagreement within the VolMIP-Tambora Interactive Stratospheric Aerosol ensemble Atmospheric Chemistry and Physics DOI 10.5194/acp-21-3317-2021 25 March 2021 As part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP), several climate modeling centers performed a coordinated pre-study experiment with interactive stratospheric aerosol models simulating the volcanic aerosol cloud from an eruption resembling the 1815 Mt. Tambora eruption (VolMIP-Tambora ISA ensemble). Read more
Comparison of ozone measurement methods in biomass burning smoke: anevaluation under field and laboratory conditions Atmospheric Measurement Techniques DOI 10.5194/amt-14-1783-2021 24 March 2021 In recent years wildland fires in the United States have had significant impacts on local and regional air quality and negative human health outcomes. Although the primary health concerns from wildland fires come from fine particulate matter (PM2.5), large increases in ozone (O3 have been observed downwind of wildland fire plumes. The chemiluminescence FRM method is highly recommended for accurate measurements of O3 in wildland fire plume studies and at regulatory ambient monitoring sites frequently impacted by wildland firesmoke. Read more