Early instrumental meteorological measurements in Switzerland Climate of the Past DOI 10.5194/cp-15-1345-2019 22 July 2019 The 18th and early 19th centuries saw pronounced climatic variations with impacts on the environment and society. Although instrumental meteorological data for that period exist, only a small fraction has been the subject of research. This study provides an overview of early instrumental meteorological records in Switzerland resulting from an archive survey and demonstrates the great potential of such data. It is accompanied by the online publication of the imaged data series and metadata. Read more
Converging photospheric vortex flows close to the polarity inversion line of a fully emerged active region Annales Geophysicae DOI 10.5194/angeo-37-603-2019 22 July 2019 We describe a technique used to locate and classify critical points in 2-D flow fields at the solar photosphere obtained from the evolution of the line-of-sight magnetic field in a region close to the magnetic polarity inversion line of a fully emerged active region. We apply this technique to locate a particular kind of critical point associated to vortex flows, which are considered important, since they can twist and interweave the foot points of flux tubes and generate magnetic reconnection. Read more
Towards monitoring localized CO2 emissions from space: co-located regional CO2 and NO2 enhancements observed by the OCO-2 and S5P satellites Atmospheric Chemistry and Physics DOI 10.5194/acp-19-9371-2019 22 July 2019 The quantification of anthropogenic emissions with current CO2 satellite sensors is difficult, but NO2 is co-emitted, making it a suitable tracer of recently emitted CO2. We analyze enhancements of CO2 and NO2 observed by OCO-2 and S5P and estimate the CO2plume cross-sectional fluxes that we compare with emission databases. Our results demonstrate the usefulness of simultaneous satellite observations of CO2 and NO2 as envisaged for the European Copernicus anthropogenic CO2 monitoring mission Read more
Brief communication: Updated GAMDAM glacier inventory over high-mountain Asia The Cryosphere DOI 10.5194/tc-13-2043-2019 19 July 2019 The Glacier Area Mapping for Discharge from the Asian Mountains (GAMDAM) glacier inventory was updated to revise the underestimated glacier area in the first version. The total number and area of glaciers are 134 770 and 100 693 ± 11 790 km2 from 453 Landsat images, which were carefully selected for the period from 1990 to 2010, to avoid mountain shadow, cloud cover, and seasonal snow cover. Read more
Quantification of water vapour transport from the Asian monsoon to the stratosphere Atmospheric Chemistry and Physics DOI 10.5194/acp-19-8947-2019 12 July 2019 We investigate the transport pathways of water vapour from the upper troposphere in the Asian monsoon region to the stratosphere. In the employed chemistry-transport model we use a tagging method, such that the impact of different source regions on the stratospheric water vapour budget can be quantified. A key finding is that the Asian monsoon (compared to other source regions) is very efficient in transporting air masses and water vapour to the tropical and extratropical stratosphere. Read more
Evaluating post-glacial bedrock erosion and surface exposure duration by coupling in situ optically stimulated luminescence and 10Be dating Earth Surface Dynamics DOI 10.5194/esurf-7-633-2019 11 July 2019 Assessing the impact of glaciation at the Earth’s surface requires simultaneous quantification of the impact of climate variability on past glacier fluctuations and on bedrock erosion. Here we present a new approach for evaluating post-glacial bedrock surface erosion in mountainous environments by combining two different surface exposure dating methods. This approach can be used to estimate how bedrock erosion rates vary spatially and temporally since glacier retreat in an alpine environment. Read more
Dissolved organic matter at the fluvial–marine transition in the Laptev Sea using in situ data and ocean colour remote sensing Biogeosciences DOI 10.5194/bg-16-2693-2019 11 July 2019 In this article, we present the variability and characteristics of dissolved organic matter at the fluvial–marine transition in the Laptev Sea from a unique dataset collected during 11 Arctic expeditions. We develop a new relationship between dissolved organic carbon (DOC) and coloured dissolved organic matter absorption, which is used to estimate surface water DOC concentration from space. We believe that our findings help current efforts to monitor ongoing changes in the Arctic carbon cycle. Read more
Atmospheric measurements of the terrestrial O2:CO2 exchange ratio of a midlatitude forest Atmospheric Chemistry and Physics DOI 10.5194/acp-19-8687-2019 10 July 2019 Predictions of global warming require predictions of how much CO2 will be taken up by the oceans, how much by land plants, and how much will stay in the atmosphere. Measurements of atmospheric oxygen (O2) help with these predictions if we also know the ratio of O2 release to CO2 uptake in land plants. We have measured this ratio in a midlatitude forest and find a lower value than the one in wide use. If truly applicable, our results call for a modest adjustment in the global carbon budget. Read more
Evaluation of global simulations of aerosol particle and cloud condensation nuclei number, with implications for cloud droplet formation Atmospheric Chemistry and Physics DOI 10.5194/acp-19-8591-2019 8 July 2019 Effects of aerosols on clouds are important for climate studies but are among the largest uncertainties in climate projections. This study evaluates the skill of global models to simulate aerosol, cloud condensation nuclei (CCN) and cloud droplet number concentrations (CDNCs). Model results show reduced spread in CDNC compared to CCN due to the negative correlation between the sensitivities of CDNC to aerosol number concentration (air pollution) and updraft velocity (atmospheric dynamics). Read more
Flood risk in a range of spatial perspectives – from global to local scales Natural Hazards and Earth System Sciences DOI 10.5194/nhess-19-1319-2019 5 July 2019 Considering flood risk composed of hazard, exposure, and vulnerability from global to local scales, this paper reviews and presents increasing observed flood losses and projections of flood hazard and losses. We acknowledge existence of multiple driving factors and of considerable uncertainty, in particular with regards to projections for the future. Finally, this paper analyses options for flood risk reduction from a global framework to regional and local scales. Read more
Description of a formaldehyde retrieval algorithm for the Geostationary Environment Monitoring Spectrometer (GEMS) Atmospheric Measurement Techniques DOI 10.5194/amt-12-3551-2019 4 July 2019 The Geostationary Environment Monitoring Spectrometer (GEMS) will be launched by South Korea in 2019, and it will measure radiances ranging from 300 to 500 nm every hour with a fine spatial resolution of 7 km x 8 km over Seoul in South Korea to monitor column concentrations of air pollutants including O3, NO2, SO2, and HCHO, as well as aerosol optical properties. This paper describes a GEMS formaldehyde retrieval algorithm including a number of sensitivity tests for algorithm evaluation. Read more
Converting snow depth to snow water equivalent using climatological variables The Cryosphere DOI 10.5194/tc-13-1767-2019 4 July 2019 We present a new statistical model for converting snow depths to water equivalent. The only variables required are snow depth, day of year, and location. We use the location to look up climatological parameters such as mean winter precipitation and mean temperature difference (difference between hottest month and coldest month). The model is simple by design so that it can be applied to depth measurements anywhere, anytime. The model is shown to perform better than other widely used approaches. Read more
Emission of trace gases and aerosols from biomass burning – an updated assessment Atmospheric Chemistry and Physics DOI 10.5194/acp-19-8523-2019 4 July 2019 Biomass burning is one of the largest sources of atmospheric pollutants worldwide. This paper presents an up-to-date compilation of emission factors for over 120 trace gas and aerosol species from the different forms of open vegetation fires and domestic biofuel use, based on an analysis of over 370 published studies. Using these emission factors and current global burning activity data, the annual emissions of important species released by the various types of biomass burning are estimated. Read more
Mid-Holocene climate change over China: model–data discrepancy Climate of the Past DOI 10.5194/cp-15-1223-2019 2 July 2019 The mid-Holocene has been an excellent target for comparing models and data. This work shows that, over China, all the ocean–atmosphere general circulation models involved in PMIP3 show a very large discrepancy with pollen data reconstruction when comparing annual and seasonal temperature. It demonstrates that to reconcile models and data and to capture the signature of seasonal thermal response, it is necessary to integrate non-linear processes, particularly those related to vegetation changes. Read more
Alluvial channel response to environmental perturbations: fill-terrace formation and sediment-signal disruption Earth Surface Dynamics DOI 10.5194/esurf-7-609-2019 1 July 2019 We performed seven physical experiments to explore terrace formation and sediment export from a braided alluvial river system that is perturbed by changes in water discharge, sediment supply, or base level. Each perturbation differently affects (1) the geometry of terraces and channels, (2) the timing of terrace formation, and (3) the transient response of sediment discharge. Our findings provide guidelines for interpreting fill terraces and sediment export from fluvial systems. Read more
Contrail cirrus radiative forcing for future air traffic Atmospheric Chemistry and Physics DOI 10.5194/acp-19-8163-2019 27 June 2019 The climate impact of air traffic is to a large degree caused by changes in cirrus cloudiness resulting from the formation of contrails. We use an atmospheric climate model with a contrail cirrus parameterization to investigate the climate impact of contrail cirrus for the year 2050. The strong increase in contrail cirrus radiative forcing due to the projected increase in air traffic volume cannot be compensated for by the reduction of soot emissions and by improvements in propulsion efficiency. Read more
Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy Atmospheric Measurement Techniques DOI 10.5194/amt-12-3417-2019 27 June 2019 This research project assesses biases in traditional, filter-based, aerosol absorption measurements by comparison to state-of-the-art, non-filter-based, or in situ, measurements. We assess biases in traditional absorption measurements for three main aerosol types, including dust and fresh and aged biomass burning aerosols. The main results of this study are that the traditional and state-of-the-art absorption measurements are well correlated and that biases in the former are up to 45 %. Read more
Detecting layer height of smoke aerosols over vegetated land and water surfaces via oxygen absorption bands: hourly results from EPIC/DSCOVR in deep space Atmospheric Measurement Techniques DOI 10.5194/amt-12-3269-2019 20 June 2019 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. Read more
Technical note: A microcontroller-based automatic rain sampler for stable isotope studies Hydrology and Earth System Sciences DOI 10.5194/hess-23-2637-2019 19 June 2019 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. Read more
Induced seismicity in geologic carbon storage Solid Earth DOI 10.5194/se-10-871-2019 19 June 2019 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. Read more