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Atmospheric Measurement Techniques

Detecting layer height of smoke aerosols over vegetated land and water surfaces via oxygen absorption bands: hourly results from EPIC/DSCOVR in deep space

Detecting aerosol layer height from space is challenging. The traditional method relies on active sensors such as lidar that provide the detailed vertical structure of the aerosol profile but is costly with limited spatial coverage (more than 1 year is needed for global coverage). Here we developed a passive remote sensing technique that uses backscattered sunlight to retrieve smoke aerosol layer height over both water and vegetated surfaces from a sensor 1.5 million kilometers from the Earth.

Hydrology and Earth System Sciences

Technical note: A microcontroller-based automatic rain sampler for stable isotope studies

Most commercial automatic rain samplers are costly and do not prevent evaporation from the collection bottles. Hence, we have developed a microcontroller-based collector enabling timer-actuated integral rain sampling. The simple, low-cost device is robust and effectively minimizes post-sampling evaporation. The excellent performance of the collector during an evaporation experiment in a lab oven suggests that even multi-week field deployments in warm climates are feasible.

Solid Earth

Induced seismicity in geologic carbon storage

To meet the goal of the Paris Agreement to limit temperature increase below 2 ºC, geologic carbon storage (GCS) will be necessary at the gigatonne scale. But to successfully deploy GCS, seismicity induced by CO₂injection should be controlled and maintained below a threshold that does not generate nuisances to the population. We conclude that felt induced seismicity can be minimized provided that a proper site characterization, monitoring and pressure management are performed.

Atmospheric Chemistry and Physics

Aerosol pH and its driving factors in Beijing

Aerosol acidity plays a key role in secondary aerosol formation. To provide a more comprehensive reference for aerosol pH and a basis for controlling secondary aerosol generation, this study used the latest data covering four seasons and different particle sizes to obtain the characteristics of aerosol pH and explore the main factors affecting aerosol pH and gas–particle partitioning in the Beijing area.

Earth System Dynamics

Including the efficacy of land ice changes in deriving climate sensitivity from paleodata

Processes causing the same global-average radiative forcing might lead to different global temperature changes. We expand the theoretical framework by which we calculate paleoclimate sensitivity with an efficacy factor. Applying the revised approach to radiative forcing caused by CO₂and land ice albedo perturbations, inferred from data of the past 800 000 years, gives a new paleo-based estimate of climate sensitivity.

Atmospheric Measurement Techniques

A sampler for atmospheric volatile organic compounds by copter unmanned aerial vehicles

Volatile organic compound (VOC) emissions influence air quality and particulate distributions, particularly in major source regions such as the Amazon. A sampler for collecting VOCs from an unmanned aerial vehicle (UAV) is described. Field tests of its performance and an initial example data set collected in the Amazon are also presented. The low cost, ease of use, and maneuverability of UAVs give this method the potential to significantly advance knowledge of the spatial distribution of VOCs.

Natural Hazards and Earth System Sciences

Analysis of an extreme weather event in a hyper-arid region using WRF-Hydro coupling, station, and satellite data

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-19-1129-2019
13 June 2019

The work addresses the need for reliable precipitation forecasts in hyper-arid environments through state-of-the-art hydro-meteorological modeling. Accounting for land–atmosphere interactions in the applied model is shown to improve the accuracy of precipitation output. The chain of events controlling the soil moisture–precipitation feedback are diagnosed and verified by in situ observations and satellite data.

Atmospheric Chemistry and Physics

Global distribution of methane emissions, emission trends, and OH concentrations and trends inferred from an inversion of GOSAT satellite data for 2010–2015

We use 2010–2015 satellite observations of atmospheric methane to improve estimates of methane emissions and their trends, as well as the concentration and trend of tropospheric OH (hydroxyl radical, methane’s main sink). We find overestimates of Chinese coal and Middle East oil/gas emissions in the prior estimate. The 2010–2015 growth in methane is attributed to an increase in emissions from India, China, and areas with large tropical wetlands. The contribution from OH is small in comparison.

Biogeosciences

Responses of an abyssal meiobenthic community to short-term burial with crushed nodule particles in the south-east Pacific

To elucidate the potential effects of crushed nodule particle deposition on abyssal meiobenthos, we covered abyssal soft sediment in the Peru Basin (4200 m depth) with approximately 2 cm of this nodule material for 11 d. About half of the meiobenthos migrated from the sediment into the added material, and nematode feeding type proportions in that added layer were altered. These results considerably contribute to our understanding of the short-term responses of deep-sea meiobenthos to burial.

Atmospheric Measurement Techniques

Aerosol size distributions during the Atmospheric Tomography Mission (ATom): methods, uncertainties, and data products

From 2016 to 2018 a NASA aircraft profiled the atmosphere from 180 m to ~12 km from the Arctic to the Antarctic over both the Pacific and Atlantic oceans. This program, ATom, sought to sample atmospheric chemical composition to compare with global climate models. We describe the how measurements of particulate matter were made during ATom, and show that the instrument performance was excellent. Data from this project can be used with confidence to evaluate models and compare with satellites.

Solid Earth

The Bortoluzzi Mud Volcano (Ionian Sea, Italy) and its potential for tracking the seismic cycle of active faults

The Ionian Sea in southern Italy is at the center of active convergence between the Eurasian and African plates, with many known M_w > 7.0 earthquakes. Here, a recently discovered mud volcano (called the Bortoluzzi Mud Volcano or BMV) was surveyed during the Seismofaults 2017 cruise (May 2017). The BMV is the active emergence of crustal fluids probably squeezed up during the seismic cycle. As such, the BMV may potentially be used to track the seismic cycle of active faults.

Climate of the Past

Glacial CO₂ decrease and deep-water deoxygenation by iron fertilization from glaciogenic dust

Proxy records of glacial oxygen change provide constraints on the contribution of the biological pump to glacial CO₂ decrease. Here, we report our numerical simulation which successfully reproduces records of glacial oxygen changes and shows the significance of iron supply from glaciogenic dust. Our model simulations clarify that the enhanced efficiency of the biological pump is responsible for glacial CO₂ decline of more than 30 ppm and approximately half of deep-ocean deoxygenation.

Geoscience Communication

Telling the boiling frog what he needs to know: why climate change risks should be plotted as probability over time

Humanity’s situation with respect to climate change is sometimes likened to that of a frog in a slow-boiling pot of water. But are we telling the frog what he needs to know? Most climate science is communicated to governments in the form of predictions of what is most likely to happen. I argue it should instead answer the following questions: what is the worst that could happen, and how likely will that become as time goes by? The risks and need to act will then become much clearer to see.

Ocean Science

Impacts of Three Gorges Dam’s operation on spatial–temporal patterns of tide–river dynamics in the Yangtze River estuary, China

In this study, we assessed the impacts of the world’s largest dam, the Three Gorges Dam (TGD), on tide–river dynamics and concluded that the strongest impacts occurred during autumn and winter due to the TGD’s operation. The results obtained will hopefully enhance our understanding of the impacts of large-scale human interventions on estuarine hydrodynamics and guide effective and sustainable water management in the Yangtze River estuary and other estuaries with substantial freshwater discharge.

The Cryosphere

Recrystallization processes, microstructure and crystallographic preferred orientation evolution in polycrystalline ice during high-temperature simple shear

Ice mechanics is an important tool to better predict the response of glaciers or polar ice sheets to climate variations. Nevertheless our current predictive abilities are limited as the microscale mechanisms responsible for ice creep are poorly identified. We show in this study, using state-of-the-art experimental techniques, which recrystallization processes control ice deformation. This will allow realistic simulations, necessary to predict the long-term effects on ice landmasses.

Atmospheric Chemistry and Physics

Photooxidants from brown carbon and other chromophores in illuminated particle extracts

We measured hydroxyl radical (^•OH), singlet oxygen (¹O₂*), and organic triplets (³C*) in illuminated aqueous particle extracts. After measuring the impact of dilution on oxidant concentrations, we extrapolated our results to predict them in ambient particles –¹O₂* and³C* concentrations appear to be greatly enhanced, while^•OH appears largely unchanged. Two of these oxidants (¹O₂*,³C*) are not yet included in atmospheric models, and our results make it possible to include them in the future.

Atmospheric Chemistry and Physics

Northern Hemisphere continental winter warming following the 1991 Mt. Pinatubo eruption: reconciling models and observations

This study provides compelling new evidence that the surface winter warming observed over the Northern Hemisphere continents following the 1991 eruption of Mt. Pinatubo was, very likely, completely unrelated to the eruption. This result has implications for earlier eruptions, as the evidence presented here demonstrates that the surface signal of even the very largest known eruptions may be swamped by the internal variability at high latitudes.

Solid Earth

Time-lapse gravity and levelling surveys reveal mass loss and ongoing subsidence in the urban subrosion-prone area of Bad Frankenhausen, Germany

Subrosion, i.e. the underground leaching of soluble rocks, causes disastrous sinkhole events worldwide. We investigate the accompanying mass transfer using quarter-yearly time-lapse gravity campaigns over 4 years in the town of Bad Frankenhausen, Germany. After correcting for seasonal soil water content, we find evidence of underground mass loss and attempt to quantify its amount. This is the first study of its kind to prove the feasibility of this approach in an urban area.

Atmospheric Chemistry and Physics

Quantifying variations in shortwave aerosol–cloud–radiation interactions using local meteorology and cloud state constraints

Aerosols are released by natural and human activities. When aerosols encounter clouds they interact in what is known as the indirect effect. Brighter clouds are expected due to the microphysical response; however, certain environments can trigger a modified response. Limits on the stability, humidity, and cloud thickness are applied regionally to investigate local cloud responses to aerosol, resulting in a range of indirect effects that would result in significant cooling or slight warming.

Hydrology and Earth System Sciences

Using a coupled agent-based modeling approach to analyze the role of risk perception in water management decisions

This study applies a two-way coupled agent-based model (ABM) with a river-reservoir management model (RiverWare) to analyze the role of risk perception in water management decisions using the Bayesian inference mapping joined with the cost–loss model. The calibration results capture the dynamics of historical irrigated area and streamflow changes and suggest that the proposed framework improves the representation of human decision-making processes compared to conventional rule-based ABMs.

Atmospheric Chemistry and Physics

Heterogeneous sulfate aerosol formation mechanisms during wintertime Chinese haze events: air quality model assessment using observations of sulfate oxygen isotopes in Beijing

Sulfate is a key species contributing to particle formation and growth during wintertime Chinese haze events. This study combines observations and modeling of oxygen isotope signatures in sulfate aerosol to investigate its formation mechanisms, with a focus on heterogeneous production on aerosol surface via H₂O₂, O₃, and NO₂ and trace metal catalyzed oxidation. Contributions from different formation pathways are presented.

Biogeosciences

Reciprocal bias compensation and ensuing uncertainties in model-based climate projections: pelagic biogeochemistry versus ocean mixing

Anthropogenic greenhouse gas emissions trigger complex climate feedbacks. Output form Earth system models provides a basis for related political decision-making. One challenge is to arrive at reliable model parameter estimates for the ocean biogeochemistry module. We illustrate pitfalls through which flaws in the ocean module are masked by wrongly tuning the biogeochemistry and discuss ensuing uncertainties in climate projections.

Natural Hazards and Earth System Sciences

Summertime precipitation extremes in a EURO-CORDEX 0.11° ensemble at an hourly resolution

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-19-957-2019
2 May 2019

A state-of-the-art regional climate model ensemble for Europe is investigated for extreme precipitation intensities. The models poorly reproduce short duration events of less than a few hours. Further, there is poor connection to some known hotspots for extreme cases. The model performance is much improved at 12 h durations. Projected future increases scale with seasonal mean temperature change, within a range from a few percent to over 10 percent per degree Celsius.

Atmospheric Chemistry and Physics

Vertical and horizontal distribution of submicron aerosol chemical composition and physical characteristics across northern India during pre-monsoon and monsoon seasons

Our study, for the first time, presents measurements of aerosol chemical composition and physical characteristics across northern India in the pre-monsoon and monsoon seasons of 2016 using the FAAM BAe-146 UK research aircraft. Across northern India, an elevated aerosol layer dominated by sulfate aerosol exists that diminishes with monsoon arrival. The Indo-Gangetic Plain (IGP) boundary layer is dominated by organics, whereas outside the IGP sulfate dominates with increased scattering aerosol.

Hydrology and Earth System Sciences

Controls on spatial and temporal variability in streamflow and hydrochemistry in a glacierized catchment

Hydrometric and geochemical dynamics are controlled by interplay of meteorological conditions, topography and geological heterogeneity. Nivo-meteorological indicators (such as global solar radiation, temperature and decreasing snow depth) explain monthly conductivity and isotopic dynamics best. These insights are important for better understanding hydrochemical responses of glacierized catchments under a changing cryosphere.

The Cryosphere

Winter tourism under climate change in the Pyrenees and the French Alps: relevance of snowmaking as a technical adaptation

This study investigates the snow reliability of 175 ski resorts in the Pyrenees (France, Spain and Andorra) and the French Alps under past and future conditions (1950–2100) using state-of-the-art climate projections and snowpack modelling accounting for snow management, i.e. grooming and snowmaking. The snow reliability of ski resorts shows strong elevation and regional differences, and our study quantifies changes in snow reliability induced by snowmaking under various climate scenarios.

The Cryosphere

Uncertainty quantification of the multi-centennial response of the Antarctic ice sheet to climate change

Using probabilistic methods, we quantify the uncertainty in the Antarctic ice-sheet response to climate change over the next millennium under the four RCP scenarios and parametric uncertainty. We find that the ice sheet is stable in RCP 2.6 regardless of parametric uncertainty, while West Antarctica undergoes disintegration in RCP 8.5 almost regardless of parametric uncertainty. We also show a high sensitivity of the ice-sheet response to uncertainty in sub-shelf melting and sliding conditions.

Earth System Dynamics

ESD Ideas: Propagation of high-frequency forcing to ice age dynamics

We demonstrate here that nonlinear character of ice sheet dynamics, which was derived naturally from the conservation laws, is an effective means for propagating high-frequency forcing upscale.

The Cryosphere

Modelling the future evolution of glaciers in the European Alps under the EURO-CORDEX RCM ensemble

Glaciers in the European Alps play an important role in the hydrological cycle, act as a source for hydroelectricity and have a large touristic importance. We model the future evolution of all glaciers in the Alps with a novel model that combines both ice flow and melt processes. We find that under a limited warming scenario about one-third of the present-day ice volume will still be present by the end of the century, while under strong warming more than 90 % of the volume will be lost by 2100.

Atmospheric Chemistry and Physics

A new description of probability density distributions of polar mesospheric clouds

In this paper we present a new description of statistical probability density functions (pdfs) of polar mesospheric clouds (PMC). We derive a new class of pdfs that describes successfully the probability statistic of ALOMAR lidar observations of different ice parameters. As a main advantage the new method allows us to connect different observational PMC distributions of lidar and satellite data, and also to compare with distributions from ice model studies.

The Cryosphere

Pathways of ice-wedge degradation in polygonal tundra under different hydrological conditions

We studied the stability of ice wedges (massive bodies of ground ice in permafrost) under recent climatic conditions in the Lena River delta of northern Siberia. For this we used a novel modelling approach that takes into account lateral transport of heat, water, and snow and the subsidence of the ground surface due to melting of ground ice. We found that wetter conditions have a destabilizing effect on the ice wedges and associated our simulation results with observations from the study area.

Geoscientific Model Development

Terrainbento 1.0: a Python package for multi-model analysis in long-term drainage basin evolution

Terrainbento 1.0 is a Python package for modeling the evolution of the surface of the Earth over geologic time (e.g., thousands to millions of years). Despite many decades of effort by the geomorphology community, there is no one established governing equation for the evolution of topography. Terrainbento 1.0 thus provides 28 alternative models that support hypothesis testing and multi-model analysis in landscape evolution.

Atmospheric Chemistry and Physics

Permafrost nitrous oxide emissions observed on a landscape scale using the airborne eddy-covariance method

As frozen soil, called permafrost, increasingly thaws over the years, scientists have put much effort into understanding how this may increase carbon emissions, which would exacerbate climate change. Our work supports the emerging view that these efforts should also include nitrous oxide (N₂O), a more potent greenhouse gas. Using a low-flying aircraft to study thousands of acres of Alaskan permafrost, we observed average N₂O emissions higher than typically assumed for regions such as this.

Geoscientific Model Development

Devito (v3.1.0): an embedded domain-specific language for finite differences and geophysical exploration

This paper presents Devito, a Python-based software. The aim of this software is to provide a high-level simple interface to users for the description and discretization of the mathematical definition of the physics. This research initially started as an attempt to improve research time, portability, and performance in exploration geophysics. We present the latest version of the software that is already making an impact in academics and industry.

Biogeosciences

Carbon cycling in the North American coastal ocean: a synthesis

We review and synthesize available information on coastal ocean carbon fluxes around North America (NA). There is overwhelming evidence, compiled and discussed here, that the NA coastal margins act as a sink. Our synthesis shows the great diversity in processes driving carbon fluxes in different coastal regions, highlights remaining gaps in observations and models, and discusses current and anticipated future trends with respect to carbon fluxes and acidification.

Climate of the Past

The 4.2 ka BP Event in the Mediterranean region: an overview

The Mediterranean region has returned some of the clearest evidence of a climatically dry period occurring approximately 4200 years ago. We reviewed selected proxies to infer regional climate patterns between 4.3 and 3.8 ka. Temperature data suggest a cooling anomaly, even if this is not uniform, whereas winter was drier, along with dry summers. However, some exceptions to this prevail, where wetter condition seems to have persisted, suggesting regional heterogeneity.

Biogeosciences

On the role of soil water retention characteristic on aerobic microbial respiration

Soil water is a medium from which microbes acquire resources and within which they are able to move. Occupancy and availability of water and oxygen gas in soils are mutually exclusive. In addition, as soil dries the remaining water is held with an increasing degree of adhesive energy, which restricts microbes’ ability to extract resources from water. We introduce a mathematical model that describes these interacting effects and organic matter decomposition.

Hydrology and Earth System Sciences

Geostatistical interpolation by quantile kriging

Many variables, e.g., in hydrology, geology, and social sciences, are only observed at a few distinct measurement locations, and their actual distribution in the entire space remains unknown. We introduce the new geostatistical interpolation method ofquantile kriging, providing an improved estimator and associated uncertainty. It can also host variables, which would not fulfill the implicit presumptions of the traditional geostatistical interpolation methods.

Natural Hazards and Earth System Sciences

Exposure-based risk assessment and emergency management associated with the fallout of large clasts at Mount Etna

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-19-589-2019
20 March 2019

The fallout of large clasts (> 5 cm) from the margins of eruptive plumes can damage local infrastructure and severely injure people close to the volcano. Even though this potential hazard has been observed at many volcanoes, it has often been overlooked. We present the first hazard and risk assessment of large-clast fallout from eruptive plumes and use Mt Etna (Italy) as a case study. The use of dedicated shelters in the case of an explosive event that occurs with no warning is also evaluated.

The Cryosphere

Evaluation of CloudSat snowfall rate profiles by a comparison with in situ micro-rain radar observations in East Antarctica

Evaluation of the vertical precipitation rate profiles of CloudSat radar by comparison with two surface-based micro-rain radars (MRR) located at two antarctic stations gives a near-perfect correlation between both datasets, even though climatic and geographic conditions are different for the stations. A better understanding and reassessment of CloudSat uncertainties ranging from −13 % up to +22 % confirms the robustness of the CloudSat retrievals of snowfall over Antarctica.

Climate of the Past

Pleistocene glacial history of the New Zealand subantarctic islands

The New Zealand subantarctic islands, in the Pacific sector of the Southern Ocean, provide valuable records of past environmental change. We find that the Auckland Islands hosted a small ice cap around 384 000 years ago, but that there was little glaciation during the Last Glacial Maximum, around 21 000 years ago, in contrast to mainland New Zealand. This shows that the climate here is susceptible to changes in regional factors such as sea-ice expanse and the position of ocean fronts.

Atmospheric Chemistry and Physics

Trends in global tropospheric ozone inferred from a composite record of TOMS/OMI/MLS/OMPS satellite measurements and the MERRA-2 GMI simulation

Both a 38-year merged satellite record of tropospheric ozone from TOMS/OMI/MLS/OMPS and a MERRA-2 GMI model simulation show large increases of 6–7 Dobson units from the Near East to India–East Asia and eastward over the Pacific. These increases in tropospheric ozone are attributed to increases in pollution over the region over the last several decades. Secondary 38-year increases of 4–5 Dobson units with both GMI model and satellite measurements occur over central African–tropical Atlantic.

Hydrology and Earth System Sciences

Attributing the 2017 Bangladesh floods from meteorological and hydrological perspectives

In August 2017 Bangladesh faced one of its worst river flooding events in recent history. For the large Brahmaputra basin, using precipitation alone as a proxy for flooding might not be appropriate. In this paper we explicitly test this assumption by performing an attribution of both precipitation and discharge as a flooding-related measure to climate change. We find the change in risk to be of similar order of magnitude (between 1 and 2) for both the meteorological and hydrological approach.

Hydrology and Earth System Sciences

Effects of univariate and multivariate bias correction on hydrological impact projections in alpine catchments

Several multivariate bias correction methods have been developed recently, but only a few studies have tested the effect of multivariate bias correction on hydrological impact projections. This study shows that incorporating or ignoring inter-variable relations between air temperature and precipitation can have a notable effect on the projected snowfall fraction. The effect translated to considerable consequences for the glacio-hydrological responses and streamflow components of the catchments.

Climate of the Past

Late Miocene–Pliocene climate evolution recorded by the red clay cover on the Xiaoshuizi planation surface, NE Tibetan Plateau

Multiple proxies for the XSZ planation surface reveal that the climate was dry and stable during the late Miocene but became intermittently humid with more seasonality at 4.7–3.9 Ma. Regional climatic differences between the central and western CLP reveal that expansion of the paleo-EASM occurred during the early Pliocene. The warming of the high northern latitudes in response to the closure of the Panama Seaway may have been responsible for the thermodynamical enhancement of the paleo–EASM.

Geoscientific Model Development

The Open Global Glacier Model (OGGM) v1.1

Mountain glaciers are one of the few remaining subsystems of the global climate system for which no globally applicable community-driven model exists. Here we present the Open Global Glacier Model (OGGM; www.oggm.org), developed to provide a modular and open-source numerical model framework for simulating past and future change of any glacier in the world.

Hydrology and Earth System Sciences

Conservative finite-volume forms of the Saint-Venant equations for hydrology and urban drainage

A new derivation of the equations for one-dimensional open-channel flow in rivers and storm drainage systems has been developed. The new approach solves some long-standing problems for obtaining well-behaved solutions with conservation forms of the equations. This research was motivated by the need for highly accurate models of large-scale river networks and the storm drainage systems in megacities. Such models are difficult to create with existing equation forms.

Hydrology and Earth System Sciences

Seasonal origins of soil water used by trees

We used stable isotopes of xylem water to study differences in the seasonal origin of water in more than 900 individual trees from three dominant species in 182 Swiss forested sites. We discovered that midsummer transpiration was mostly supplied by winter precipitation across diverse humid climates. Our findings provide new insights into tree vulnerability to droughts, transport of water (and thus solutes) in soils, and the climatic information conveyed by plant-tissue isotopes.

The Cryosphere

The Reference Elevation Model of Antarctica

The Cryosphere
DOI 10.5194/tc-13-665-2019
26 February 2019

The Reference Elevation Model of Antarctica (REMA) is the first continental-scale terrain map at less than 10 m resolution, and the first with a time stamp, enabling measurements of elevation change. REMA is constructed from over 300 000 individual stereoscopic elevation models (DEMs) extracted from submeter-resolution satellite imagery. REMA is vertically registered to satellite altimetry, resulting in errors of less than 1 m over most of its area and relative uncertainties of decimeters.

Atmospheric Measurement Techniques

Revisiting the differential freezing nucleus spectra derived from drop-freezing experiments: methods of calculation, applications, and confidence limits

The abundance of freezing nuclei in water samples is routinely determined by experiments involving the cooling of sample drops and observing the temperatures at which the drops freeze. This is used for characterizing the nucleating abilities of materials in laboratory preparations or to determine the numbers of nucleating particles in rain, snow, river water or other natural waters. The evaluation of drop-freezing experiments in terms of differential nucleus spectra is advocated in the paper.