A machine-learning-based cloud detection and thermodynamic-phaseclassification algorithm using passive spectral observations Atmospheric Measurement Techniques DOI 10.5194/amt-13-2257-2020 21 May 2020 A machine-learning (ML)-based approach that can be used for cloud mask and phase detection is developed. An all-day model that uses infrared (IR) observations and a daytime model that uses shortwave and IR observations from a passive instrument are trained separately for different surface types. The training datasets are selected by using reference pixel types from collocated space lidar. The ML approach is validated carefully and the overall performance is better than traditional methods. Read more
The catastrophic thermokarst lake drainage events of 2018 in northwestern Alaska: Fast-forward into the future The Cryosphere DOI 10.5194/tc-2020-106 21 May 2020 Northwestern Alaska has been highly affected by changing climatic patterns with new temperature and precipitation maxima over the recent years. In particular, the Baldwin and northern Seward peninsulas are characterized by an abundance of thermokarst lakes that are highly dynamic and prone to lake drainage, like many other regions at the southern margins of continuous permafrost. We used Sentinel-1 synthetic aperture radar (SAR) and Planet CubeSat optical remote sensing data to analyze recently observed widespread lake drainage. Read more
Quantification of seasonal and diurnal dynamics of subglacial channels using seismic observations on an Alpine glacier The Cryosphere DOI 10.5194/tc-14-1475-2020 19 May 2020 Our study addresses key questions on the subglacial drainage system physics through a novel observational approach that overcomes traditional limitations. We conducted, over 2 years, measurements of the subglacial water-flow-induced seismic noise and of glacier basal sliding speeds. We then inverted for the subglacial channel’s hydraulic pressure gradient and hydraulic radius and investigated the links between the equilibrium state of subglacial channels and glacier basal sliding. Read more
Summarizing the state of the terrestrial biosphere in few dimensions Biogeosciences DOI 10.5194/bg-17-2397-2020 19 May 2020 To closely monitor the state of our planet, we require systems that can monitor the observation of many different properties at the same time. We create indicators that resemble the behavior of many different simultaneous observations. We apply the method to create indicators representing the Earth’s biosphere. The indicators show a productivity gradient and a water gradient. The resulting indicators can detect a large number of changes and extremes in the Earth system. Read more
Intercomparison of wind observations from the European Space Agency’s Aeolus satellite mission and the ALADIN Airborne Demonstrator Atmospheric Measurement Techniques DOI 10.5194/amt-13-2075-2020 14 May 2020 This work reports on the first airborne validation campaign of ESA’s Earth Explorer mission Aeolus, conducted in central Europe during the commissioning phase in November 2018. After presenting the methodology used to compare the data sets from the satellite, the airborne wind lidar and the ECWMF model, the wind results from the underflights performed are analyzed and discussed, providing a first assessment of the accuracy and precision of the preliminary Aeolus wind data. Read more
The acidity of atmospheric particles and clouds Atmospheric Chemistry and Physics DOI 10.5194/acp-20-4809-2020 14 May 2020 Acid rain is recognized for its impacts on human health and ecosystems, and programs to mitigate these effects have had implications for atmospheric acidity. Historical measurements indicate that cloud and fog droplet acidity has changed in recent decades in response to controls on emissions from human activity, while the limited trend data for suspended particles indicate acidity may be relatively constant. This review synthesizes knowledge on the acidity of atmospheric particles and clouds. Read more
Drainage divide networks – Part 2: Response to perturbations Earth Surface Dynamics DOI 10.5194/esurf-8-261-2020 12 May 2020 Drainage divides are believed to provide clues about divide migration and the instability of landscapes. Here, we present a novel approach to extract drainage divides from digital elevation models and to order them in a drainage divide network. We present our approach by studying natural and artificial landscapes generated with a landscape evolution model and disturbed to induce divide migration. Read more
The benefits to climate science of including early-career scientists asreviewers Geoscience Communication DOI 10.5194/gc-3-89-2020 12 May 2020 Early-career scientists (ECSs) are rarely invited to act as peer reviewers. Participating in a group peer review of the IPCC Special Report on Ocean and Cryosphere in a Changing Climate, PhD students spent more time reviewing than more established scientists and provided a similar proportion of substantive comments. By soliciting and including ECSs in peer review, the scientific community would reduce the burden on more established scientists and may improve the quality of that process. Read more
Brief communication: Residence time of energy in the atmosphere Nonlinear Processes in Geophysics DOI 10.5194/npg-27-235-2020 30 April 2020 We deduce that after a global thermal perturbation, the Earth’s atmosphere would need about a couple of months to come back to equilibrium. Read more
Drainage divide networks – Part 1: Identification and ordering in digital elevation models Earth Surface Dynamics DOI 10.5194/esurf-8-245-2020 30 April 2020 Drainage divides are believed to provide clues about divide migration and the instability of landscapes. Here, we present a novel approach to extract drainage divides from digital elevation models and to order them in a drainage divide network. We present our approach by studying natural and artificial landscapes generated with a landscape evolution model and disturbed to induce divide migration. Read more
Authigenic formation of Ca–Mg carbonates in the shallow alkaline LakeNeusiedl, Austria Biogeosciences DOI 10.5194/bg-17-2085-2020 29 April 2020 Dolomite (CaMg(CO 3 ) 2 ) is supersaturated in many aquatic settings (e.g., seawater) on modern Earth but does not precipitate directly from the fluid, a fact known as the dolomite problem. The widely acknowledged concept of dolomite precipitation involves microbial extracellular polymeric substances (EPSs) and anoxic conditions as important drivers. In contrast, results from Lake Neusiedl support an alternative concept of Ca–Mg carbonate precipitation under aerobic and alkaline conditions. Read more
Oxygen and sulfur mass-independent isotopic signatures in black crusts: thecomplementary negative Δ33S reservoir of sulfate aerosols? Atmospheric Chemistry and Physics DOI 10.5194/acp-20-4255-2020 27 April 2020 Given their critical impact on radiative forcing, sulfate aerosols have been extensively studied using their isotope signatures (δ 34 S, ∆ 33 S, ∆ 36 S, δ 18 O, and ∆ 17 O). A striking observation is that ∆ 33 S > 0 ‰, implying a missing reservoir in the sulfur cycle. Here, we measured ∆ 33 S < 0 ‰ in black crust sulfates (i.e., formed on carbonate walls) that must therefore result from distinct chemical pathway(s) compared to sulfate aerosols, and they may well represent this complementary reservoir. Read more
Surface water and groundwater: unifying conceptualization and quantification of the two “water worlds” Hydrology and Earth System Sciences DOI 10.5194/hess-24-1831-2020 27 April 2020 We present a blueprint for a unified modelling framework to quantify chemical transport in both surface water and groundwater systems. There has been extensive debate over recent decades, particularly in the surface water literature, about how to explain and account for long travel times of chemical species that are distinct from water flow (rainfall-runoff) travel times. We suggest a powerful modelling framework known to be robust and effective from the field of groundwater hydrology. Read more
Statistical estimation of global surface temperature response to forcing under the assumption of temporal scaling Earth System Dynamics DOI 10.5194/esd-11-329-2020 23 April 2020 This paper presents efficient Bayesian methods for linear response models of global mean surface temperature that take into account long-range dependence. We apply the methods to the instrumental temperature record and historical model runs in the CMIP5 ensemble to provide estimates of the transient climate response and temperature projections under the Representative Concentration Pathways. Read more
Technical note: Preparation and purification of atmospherically relevant α-hydroxynitrate esters of monoterpenes Atmospheric Chemistry and Physics DOI 10.5194/acp-20-4241-2020 23 April 2020 This report describes a simple, safe and effective method to prepare nitrate esters of terpenes (carene, limonene, perillic alcohol, beta-pinene and alpha-pinene) which are key oxidation products in the atmosphere. These compounds are implicated in the formation of secondary organic aerosols. A compilation of the relevant spectroscopic data has been presented. The availability of these compounds and their characterization data will enable further study of the structure–reactivity relationships. Read more
Run-up, inundation, and sediment characteristics of the 22 December 2018 Sunda Strait tsunami, Indonesia Natural Hazards and Earth System Sciences DOI 10.5194/nhess-20-933-2020 21 April 2020 This article reports the results of a field survey carried out in the disaster area of the December 2018 Sunda Strait tsunami, Indonesia. It provides data covering run-up heights, inundations, tsunami directions, and sediment characteristics. The data can be used for the validation of hydrodynamic models, and they contribute to a better understanding of the Sunda Strait tsunami caused by the Anak Krakatau volcano. In addition, they are important for spatial planning and mitigation efforts. Read more
Supercooled liquid water cloud observed, analysed, and modelled at the top ofthe planetary boundary layer above Dome C, Antarctica Atmospheric Chemistry and Physics DOI 10.5194/acp-20-4167-2020 21 April 2020 Thin (~ 100 m) supercooled liquid water (SLW, water staying in liquid phase below 0 °C) clouds have been detected, analysed, and modelled over the Dome C (Concordia, Antarctica) station during the austral summer 2018–2019 using observations and meteorological analyses. The SLW clouds were observed at the top of the planetary boundary layer and the SLW content was always strongly underestimated by the model indicating an incorrect simulation of the surface energy budget of the Antarctic Plateau. Read more
Ramped thermal analysis for isolating biologically meaningful soil organic matter fractions with distinct residence times SOIL DOI 10.5194/soil-6-131-2020 16 April 2020 Soils contain one of the largest and most dynamic pools of carbon on Earth, yet scientists still struggle to understand the reactivity and fate of soil organic matter upon disturbance. In this study, we found that with increasing thermal stability, the turnover time of organic matter increased from decades to centuries with a concurrent shift in chemical composition. In this proof-of-concept study, we found that ramped thermal analyses can provide new insights for understanding soil carbon. Read more
Baroclinic and barotropic instabilities in planetary atmospheres: energetics, equilibration and adjustment Nonlinear Processes in Geophysics DOI 10.5194/npg-27-147-2020 16 April 2020 Baroclinic and barotropic instabilities are well known as the processes responsible for the production of the most important energy-containing eddies in the atmospheres and oceans of Earth and other planets. Linear and nonlinear instability theories provide insights into when such instabilities may occur, grow to a large amplitude and saturate, with examples from the laboratory, simplified numerical models and planetary atmospheres. We conclude with a number of open issues for future research. Read more
Description and Evaluation of the specified-dynamics experiment in the Chemistry-Climate Model Initiative Atmospheric Chemistry and Physics DOI 10.5194/acp-20-3809-2020 9 April 2020 Atmospheric composition is strongly influenced by global-scale winds that are not always properly simulated in computer models. A common approach to correct for this bias is to relax or nudge to the observed winds. Here we systematically evaluate how well this technique performs across a large suite of chemistry–climate models in terms of its ability to reproduce key aspects of both the tropospheric and stratospheric circulations. Read more