bluuebunny/crossref_metadata_2025 huggingface dataset:
Deposition of brown carbon onto snow: changes of snow optical and radiative properties
Authors: Beres Nicholas , Sengupta Deep , Samburova Vera , Khlystov Andrey , Moosmüller Hans
Published: March 2020

Light-absorbing organic carbon aerosol – colloquially known as brown carbon (BrC) – is emitted from combustion processes and has a brownish or yellowish visual appearance, caused by enhanced light absorption at shorter visible and ultraviolet wavelengths (0.3 µm ≤ λ ≤ 0.5 µm). Recently, optical properties of atmospheric BrC aerosols have become the topic of intense research, but little is known about how BrC deposition onto snow surfaces affects the spectral snow albedo, which can alter the resulting radiative forcing and in-snow photochemistry. Wildland fires in close proximity to the cryosphere, such as peatland fires that emit large quantities of BrC, are becoming more common at high latitudes, potentially affecting nearby snow and ice surfaces.

In this study, we describe the artificial deposition of BrC aerosol with known optical, chemical, and physical properties onto the snow surface and we monitor its spectral radiative impact and compare it directly to modeled values. First, using small-scale combustion of Alaskan peat, BrC aerosols were artificially deposited onto the snow surface. UV-vis absorbance and total organic carbon (TOC) concentration of snow samples were measured for samples with and without artificial BrC deposition. These measurements were used to estimate the imaginary part of the refractive index of deposited BrC aerosol with a volume mixing rule. Single particle optical properties were calculated using Mie theory, and these values were used to show that the measured spectral snow albedo of snow with deposited BrC was in general agreement with modeled spectral snow albedo using calculated BrC optical properties. The instantaneous radiative forcing per unit mass of BrC deposited to the ambient snowpack was found to be 1.23 (+0.14/-0.11) W m-2 per ppm.
Integrating tropical peatland hydrology into a global land surface model (PEATCLSM)
Authors: Apers Sebastian , Bechtold Michel , Baird Andy J. , Cobb Alexander R. , Dargie Greta , Katimon Ayob , Koster Randal D. , Lampela Maija , Mahanama Sarith P. , Page Susan , Reichle Rolf H. , Vanderborght Jan , De Lannoy Gabriëlle J. M. ,   collaborators
Published: March 2020

Tropical peatlands have a specific hydrology that regulates their internal processes and functioning. External disturbances such as drainage, land cover and land use changes, and climate change could disrupt the peat-specific hydrology and convert the immense peatland carbon stocks into strong greenhouse gas (GHG) emitting sources. The need for (more) accurate monitoring of GHG emissions has led to the development of complex biogeochemical models, which highly depend on proper representation of peat-specific land surface hydrology. However, the latter is often inadequately accounted for in global Earth system modeling frameworks.

In this research, we leverage the PEATCLSM modules recently developed for the Catchment land surface model (CLSM) of the NASA Goddard Earth Observing System framework (Bechtold et al., 2019). These modules were evaluated for northern peatlands, hereafter referred to as PEATCLSMN. Here, we present an extended version of PEATCLSM for tropical peatlands with literature-based parameter sets for natural (PEATCLSMT,Natural) and drained (PEATCLSMT,Drained) tropical peatlands. A suite of modeling experiments was conducted to compare the performance of PEATCLSMT,Natural, PEATCLSMT,Drained, PEATCLSMN, and the currently operational CLSM version that includes peat parameters but no peat-specific model structure (CLSMO). Simulations over major tropical peatland regions in Southeast Asia, the Congo Basin, and South and Central America were evaluated with a comprehensive and self-compiled dataset of groundwater table depth (WTD) and evapotranspiration (ET). Preliminary results show that the simulated WTD from CLSMO exhibits too much temporal variability and large biases, either positive or negative. The temporal correlation coefficient between simulated and observed WTD for both PEATCLSMT,Natural (over undeveloped peatlands only) and PEATCLSMT,Drained (over drained peatlands only) is similar to that of PEATCLSMN. However, both tropical versions reduce the average absolute bias to a few centimeters. Performance differences across the major tropical peatland regions are discussed.

Reference: Bechtold, M., De Lannoy, G. J. M., Koster, R. D., Reichle, R. H., Mahanama, S. P., Bleuten, W., et al. (2019). PEAT‐CLSM: A specific treatment of peatland hydrology in the NASA Catchment Land Surface Model. Journal of Advances in Modeling Earth Systems, 11(7), 2130-2162. doi: 10.1029/2018MS001574
Evaluation of a novel non-parametric approach to identify Time of Emergence (ToE) of climate signals
Authors: Pohl Eric , Grenier Christophe , Vrac Mathieu
Published: March 2020

The time when a climate signal permanently exceeds its natural variability is called time of emergence (ToE). ToE shall serve policy makers as an indication of when to expect the climate and the environment to undergo significant changes. Identifying ToE, however, is challenging, primarily because of the lack of a standard to quantify exceedance, which, in turn, requires a definition of a natural background variability. Existing approaches often rely on a high level of arbitrary parameter values, e.g. selecting a specific number of times the standard deviation of a reference period as natural variability, selecting specific moving window widths to smooth a signal, or the arbitrary choice of a significance level for a statistical test. Such choices of course have a large influence on the final results and would in theory require exhaustive sensitivity analyses and discussion.

In order to minimize the level of parameterization for ToE estimates, we have developed a novel approach. It assesses exceedance of a climate signal by measuring distances between probability density functions (PDF) of the signal at different times (reference vs. target periods), using the Hellinger distance (HD) metric. The HD metric can be understood as the geometrical overlap of the respective PDFs and we adjusted it to describe the emergence as dissimilarity (0%-100%). In order to derive the PDFs, we use a kernel density estimator (KDE). This, however, introduces the KDE-bandwidth hyperparameter, which determines how smoothly the PDF is generated. Together with the choices for the length of the target and reference periods, and the end of the reference period, a set of less numerous but unavoidable hyperparameters are present that affect the outcome of ToE estimates. We present an extensive sensitivity analysis and highlight strengths and shortcomings of our approach with respect to the frequently used Kolmogorov–Smirnov (KS) test, and the used distance metric within it. We consider a set of synthetic datasets that show similar features as climate model temperature time series. In these datasets, we control the onset of change, variability levels, or trends in the data. Results show that our approach can more precisely identify the changes as compared to the KS-based approach. In particular when the changes in the signal are of low amplitude and sample sizes are small, our approach performs superior. The sensitivity of our approach in the considered tests to varying KDE-bandwidths is less than 5%. The approach has so far been applied on time-series of annual temperature and precipitation. Changes in the distribution of various other climate variables are potential fields of application. Associated challenges with non normally-distributed data, for example high temporal resolution precipitation data, are discussed.
Honeycomb structures and other intriguing geomorphological features in the North Falkland Basin
Authors: Gafeira Joana , McCarthy Dave , Dodd Tom , Plenderleith Gayle
Published: March 2020

The North Falkland Basin, a Mesozoic-aged sedimentary basin, located 40 km north of the Falkland Islands, is a rift system comprising a series of offset depocentres. The largest of the depocentres, the Eastern Graben, has a proven petroleum system hosting stratigraphic and combined structural-stratigraphic traps. In the shallow section overlying this significant sedimentary basin, there is a selection of unusual geomorphological features observable on 3D seismic data.

These features are observed at time-depths around 20–150 ms two-way-travel-time below the seabed, and are concentrated in three main geographical areas, covering in total more than 600 km2. These oval to polygonal depressions are typically 350–650 m across and have c. 5–10 ms of relief. The depressions are delineated by an interconnected network of V-shaped cracks, which do not appear to have a preferred orientation, and seem to be limited stratigraphically within two reflectors. The features were initially attributed to polygonal faulting but, after further investigation, they appear to be very similar to honeycomb structures observed in the Great South Basin of New Zealand, that were attributed to diagenetic processes. Immediately above the honeycomb structure, there is a series of pockmarks that may be related to fluid expulsion from below. The shallow depths at which they are found and the evidence of fluid expulsion suggests these features could be due to the opal-A/CT transition.

Other intriguing features include a sequence of mounds that are typically 150–250 m wide and display 2–5 ms of height. In seismic profiles, the first few horizons directly below the mounds show small centres of disturbance of the reflection. The amplitude map of this reflector shows a strong amplitude contrast between the mounds and the surrounding areas. The vast majority of the mounds present acoustic shadow towards NW that can extend for a few hundred meters. The geometry and dimensions of these mounds are consistent with deep-water coral mounds and the observed acoustic shadow could result from the preferential accumulation of coral rubble NW of the mounds, which could be indicative of the predominant currents during that period.

This contribution will provide a detailed discussion of the morphology of these geomorphological features and their relationship to the overlying fluid expulsion structures, sedimentary setting as well as suggesting possible mechanisms for their formation.
Paleoenvironmental changes, climate and human impact in the Western Mediterranean Sea during the 4.2 Kyr event along a North-South Transect
Authors: Combourieu-Nebout Nathalie , Coussin Vincent , Miras Yannick , Penaud Aurélie , Picard Casal Sandra , Peyron Odile , Jalali Bassem , Sicre Marie-Alexandrine , Babonneau Nathalie , Cattaneo Antonio
Published: March 2020

The 4.2 ka event is considered a key-period of the Mediterranean climate because of its potential impact on human societies over the Holocene. Numerous records provide a detailed description on its expression in continental and marine archives (e.g. Bini et al, 2019). They generally indicate cold/dry conditions, although not uniformly expressed across the Mediterranean, and summer dryness reinforced by dry winters. Palynological data from the central Mediterranean basin show a complex response of the vegetation during this climatic event that seems to be more pronounced in the southern sites.

In this study, we developed a multidisciplinary approach on two sequences collected in the Western Mediterranean Sea to insight the response of the W-Mediterranean forest along a North-South transect. The two marine records, KSGC-31 (43°N - 3°17.9’E; 60 m water depth, Gulf of Lion margin at 20 km from the coast) and MD04-2801 (36°30.99’ N - 0°30.03’ W, 2067 m water depth, 12km from the Algerian coast) were used to document regional changes in the basin between 5 and 3 kyr BP at a multi-decadal to centennial scale temporal resolution.

Information derived from palynological (pollen, spores, dinocysts, microalgae and non-pollen palynomorphs) and marine proxy data (alkenone-derived SSTs, isotopes...) are combined to evaluate environmental and hydrological changes and how this relate to human activities. Our findings highlight coherent climatic patterns and time-lags along a South-North transect in the Western Mediterranean during the establishment of droughts. They also reveal the first indications of human impact in the two areas. Overall, our study shows the effectively of our approach based on cross-analysis of continental palynological and marine evidences to decipher the chronology of sequence of events embedded in multiproxy records.

Bini, M., Zanchetta, G., Perşoiu, A., et al. : The 4.2 ka BP Event in the Mediterranean region: an overview, Clim. Past, 15, 555–577, https://doi.org/10.5194/cp-15-555-2019, 2019.
Modeling and forecasting the background solar wind with data-driven physics-based models
Authors: Lavarra Michael , Pinto Rui , Rouillard Alexis , Kouloumvakos Athanasios , Bemporad Alessandro , Arge Charles Nickolos , Alexandre Matthieu , Genot Vincent
Published: March 2020

The quasi-steady solar wind flow is a key component of space weather, being the source of corotating density structures that perturb planetary atmospheres and affect the propagation of impulsive perturbations (such as CME). Fast and slow wind streams develop at different places in the solar atmosphere, reflecting the global distribution of the coronal magnetic field during solar cycle and its consequences for heat and mass transport across the corona. I will present recent advances on global solar wind simulations that provides robust and fully physics-based predictions of the structure and physical parameters of the solar wind based on a multi-1D approach (MULTI-VP, ISAM). Such advances relate to the driving the models with time-dependant magnetogram data, to the inclusion of transient heating phenomena, and to switching from a fluid to a multi-species description of the solar wind. The model was also driven by daily synchronic magnetograms (ADAPT) for a full solar rotation and the simulation results were compared to UVCS plane-of-sky data.The simulations produce a large range of synthetic observables (e.g multi-spacecraft in-situ measurements, white-light and EUV imagery) meant to be compared to data from current and future missions (e.g Solar Orbiter and Parker Solar Probe), and to establish physiccal connections between remote observation of the solar surface and corona and the interplanetary medium.
The Solaris Solar Polar Mission
Authors: Hassler Donald M. , Newmark Jeff , Gibson Sarah , Harra Louise , Appourchaux Thierry , Auchere Frederic , Berghmans David , Colaninno Robin , Fineschi Silvano , Gizon Laurent , Gosain Sanjay , Hoeksema Todd , Kintziger Christian , Linker John , Rochus Pierre , Schou Jesper , Viall Nicholeen , West Matt , Woods Tom , Wuelser Jean-Pierre ,   Solaris Team
Published: March 2020

The solar poles are one of the last unexplored regions of the solar system. Although Ulysses flew over the poles in the 1990s, it did not have remote sensing instruments onboard to probe the Sun’s polar magnetic field or surface/sub-surface flows.

We will discuss Solaris, a proposed Solar Polar MIDEX mission to revolutionize our understanding of the Sun by addressing fundamental questions that can only be answered from a polar vantage point. Solaris uses a Jupiter gravity assist to escape the ecliptic plane and fly over both poles of the Sun to >75 deg. inclination, obtaining the first high-latitude, multi-month-long, continuous remote-sensing solar observations. Solaris will address key outstanding, breakthrough problems in solar physics and fill holes in our scientific understanding that will not be addressed by current missions.

With focused science and a simple, elegant mission design, Solaris will also provide enabling observations for space weather research (e.g. polar view of CMEs), and stimulate future research through new unanticipated discoveries.
The ADAM platform
Authors: Mantovani Simone , Natali Stefano , Folegani Marco , Cavicchi Mario , Barboni Damiano , Ferraresi Sergio
Published: March 2020

Operational Earth Observation (EO) satellite missions are entering their 5th lifetime decade, and the need to access historical data has strongly increased, particularly for long-term science and environmental monitoring applications. This trend that drives users to request long time-series of data will increase even more in the future, in particular regarding the interest on global change assessment and monitoring to support policy makers decisions on atmosphere, ocean, cryosphere, carbon and other biogeochemical cycles safeguard.

The Copernicus initiative (https://www.copernicus.eu) is playing a unique and unprecedented role form the point of view of amount, relevance and quality of provided environmental data. In the frame of the European Commission funded activities, the Data and Information Access Service (DIAS) are operated by five different consortia to acquire, process, archive and distribute data from Copernicus and Third-Party Missions.

With this enormous availability of past, present, and future geospatial environmental data, there is the need to make users able to identify the datasets that best fit with their needs and obtain these data in fastest and easiest-to-use possible way. The Advanced geospatial DAta Management - ADAM platform (https://adamplatform.eu/) provides discovery, access, processing and visualization services for data in the distributed cloud environment, significantly reducing the burden of data usability.

ADAM allows the exploitation of the content of EO data archives extended from a few years to decades and therefore makes their continuously increasing scientific value fully accessible. The advances in satellite sensor characteristics (spatial resolution, temporal frequency, spectral sensors) as well as in all related technical aspects (data and metadata format, storage, infrastructures) underline the strong need to preserve the EO space data without time constraints and to keep them accessible and exploitable, as they constitute a humankind asset. This is a typical big data challenge that ADAM can face.  

This paper describes the ADAM platform and various application domains supported with its data science analytics and visualization capabilities.
A new wave hindcast for the North and Baltic Sea region using COSMO-REA6
Authors: Groll Nikolaus
Published: March 2020

Wave hindcasts are still required as improved knowledge of climate variables representing the present marine climate are needed. Most long regional wave hindcasts are driven by numerically downscaled wind fields from global reanalysis. Whereas this approach gives a good representation of the regional wave climate in general, there are some deficits in the characteristics of extreme events. Using regional atmospheric reanalysis, which assimilates atmospheric observations into the numerical model, a better description of extreme events is expected. The regional atmospheric reanalysis COSMO-REA6 from the German Weather Service (DWD) showed that it is capable of a better representation of atmospheric extreme events. For the new regional wave hindcast, covering the North Sea and the Baltic Sea, we use the COSMO-REA6 to force the wave model WAM. It is shown, that his new wind hindcast leads to an improved representation of extreme wave events compared to other regional wave hindcasts and thus supports an important contribution to the understanding of the wave climate of extremes and for the design phase of offshore activities.
Inferring non-steady-state terrestrial vegetation carbon turnover times from multi-decadal space-borne observations on global scale
Authors: Fan Naixin , Besnard Simon , Santoro Maurizio , Cartus Oliver , Carvalhais Nuno
Published: March 2020

The global biomass is determined by the vegetation turnover times (τ) and carbon fixation through photosynthesis. Vegetation turnover time is a central parameter that not only partially determines the terrestrial carbon sink but also the response of terrestrial vegetation to the future changes in climate. However, the change of magnitude, spatial patterns and uncertainties in τ as well as the sensitivity of these processes to climate change is not well understood due to lack of observations on global scale. In this study, we explore a new dataset of annual above-ground biomass (AGB) change from 1993 to 2018 from spaceborne scatterometer observations. Using the long-term, spatial-explicit global dynamic dataset, we investigated how τ change over almost three decades including the uncertainties. Previous estimations of τ under steady-state assumption can now be challenged acknowledging that terrestrial ecosystems are, for the most of cases, not in balance. In this study, we explore this new dataset to derive global maps of τ in non-steady-state for different periods of time. We used a non-steady-state carbon model in which the change of AGB is a function of Gross Primary Production (GPP) and τ (ΔAGB = α*GPP-AGB/ τ). The parameter α represents the percentage of incorporation of carbon from GPP to biomass. By exploring the AGB change in 5 to 10 years of time step, we were able to infer τ and α from the observations of AGB and GPP change by solving the linear equation. We show how τ changes after potential disturbances in the early 2000s in comparison to the previous decade. We also show the spatial distributions of α from the change of AGB. By accessing the change in biomass, τ and α as well as their associated uncertainties, we provide a comprehensive diagnostic on the vegetation dynamics and the potential response of biomass to disturbance and to climate change.   
Soil macropore-matrix mass exchange tracer experiments that account for sorption at macropore walls
Authors: Gerke Horst H. , Dusek Jaromir , Leue Martin , Beck-Broichsitter Steffen , Sobotkova Martina , Dohnal Michal , Vogel Tomas , Snehota Michal , Cislerova Milena , Ellerbrock Ruth H. , Haas Christoph
Published: March 2020

The transfer of water and solutes between soil matrix and macropores controls preferential flow. Mass transfer depends on soil structural geometry and on properties of biopore walls and crack coatings that can differ from those of the matrix with respect to texture, organic matter, bulk density, and porosity. Agrochemicals and other solutes can react during transport along macropores, which has yet not been well-considered. The objective of this study was to study the specific effects of sorption on the reduction of mass exchange due to the effects of sorption at the macropore-matrix interface. Field and lab percolation experiments under unsaturated flow conditions were carried out with intact soil columns to simulate movement of bromide as a conservative and Brilliant Blue, iodide, and Na-Fluorescein as a reactive tracer. Sorption properties were determined separately for the biopore walls and crack coatings. The results suggest that preferential transport of reactive solutes depends even more strongly on the geometry and properties at flow paths surface than conservative solutes. If these properties can be determined, mass transfer coefficients in two-domain models can be related to soil structure and management.
Triple oxygen isotope constraints on the origin of ocean island basalts
Authors: Cao Xiaobin , Bao Huiming , Peng Yongbo
Published: March 2020

 

Understanding the origin of ocean island basalts (OIB) has important bearings on Earth’s deep mantle. Although it is widely accepted that subducted oceanic crust, as a consequence of plate tectonics, contributes material to OIB’s formation, its exact fraction in OIB’s mantle source remains ambiguous largely due to uncertainties associated with existing geochemical proxies. We have shown, through theoretical calculation and examining published data, that unlike many known proxies, triple oxygen isotope compositions (i.e. Δ17O) in olivine samples are not affected by crystallization and partial melting. This unique feature allows olivine Δ17O values to identify and quantify the fractions of subducted ocean sediments and hydrothermally altered oceanic crusts in OIB’s mantle source. In this work, new Δ17O measurements for OIB will be presented, and the implications will be discussed. 

 
Determination of sulfur isotopic ratio by HR-ICP-MS method
Authors: Gareev Bulat , Batalin Georgii , Chugaev Andrey
Published: March 2020

Sulfur is an important geochemical element that is part of many natural compounds. Sulfur takes part in most natural processes. In this case, a change in the valency of this element can occur. The change in sulfur valency is accompanied by isotope fractionation, which gives rise to noticeable shifts in the isotopic composition of this element. Thus, sulfur is one of the important geochemical indicators that can be used to reconstruct the redox conditions of various geological processes, including sedimentation processes in marine basins. For many decades, the traditional method of analyzing the isotopic composition of sulfur in sulfides remains the method involving the oxidation of sulfur to SO2 and the subsequent measurement of the 34S/32S ratio in gas using a mass spectrometer (Giesemann et al., 1994; Grassineau et al., 2001; Studley et al., 2002, etc.). However, with the advent of the inductively coupled plasma method of multi-collector mass spectrometry, new in isotope geochemistry, the corresponding methodological direction began to develop in which this method is used to analyze the sulfur isotopic composition (Krupp et al., 2004; You and Li, 2005; Clough et al ., 2006; Mason et al., 2006; Craddock et al., 2008 and others). The results presented in these works suggest that the MC-ICP-MS method can be used to solve certain problems of studying the natural variations in the sulfur isotopic composition. Therefore, we created optimized methodic for measuring isotope ratio of sulfur. The experimental work was carried out on the instrument base of the laboratory of SEC "Geothermohronology" of the Institute of Geology and Oil and Gas Technologies at Kazan Federal University (IGiNGT KFU, Kazan) and was aimed at creating a set of analytical procedures for chemical sample preparation and mass spectrometric analysis methods. The chemical preparation of pyrite samples included the stage of their acid decomposition using concentrated inorganic acids, which ensured the quantitative transfer of the sulfur of the sample into solution, as well as the stage of obtaining pure sulfur preparations based on the use of ion exchange chromatography. The optimal methodological scheme of mass spectrometric measurement of the 34S / 32S ratio was determined on a Neptune Plus multi-collector mass spectrometer. It takes into account the influence of factors unfavorable for analysis of the isotopic composition of sulfur, such as interference overlays of ions of oxygen, carbon, and nitrogen compounds, as well as the effect of instrumental mass discrimination. The work was supported by the Ministry of Science and High Education of the Russian Federation contract No. 14.Y26.31.0029 in the framework of the Resolution No.220 of the Government of the Russian Federation.
Reanalysis of ring current electron phase space densities using Van Allen Probe observations, convection model, and log-normal Kalman filter
Authors: Aseev Nikita , Shprits Yuri
Published: March 2020

Nowcast and forecast of ring current electron dynamics are crucial for space weather applications since the elevated fluxes of the ring current electrons may lead to surface charging of satellites that operate in the inner magnetosphere. Physics-based models of ring current electron dynamics contain uncertainties in boundary conditions, electric and magnetic fields, electron scattering rates, and plasmapause and magnetopause locations. The accuracy of the models can be improved by correcting the model predictions given the information obtained from in-situ satellite measurements by means of data assimilation techniques.

 

The scarcity of in-situ measurements may complicate the application of data assimilation methods for ring current electrons. The effect of data assimilation methods can be localized in time in space due to the multidimensionality of the ring current models and spatial and temporal limitations of spacecraft measurements. In this work, we investigate whether the Kalman filter can be used to improve ring current model predictions given only sparse satellite measurements. We blend the convection part of the four-dimensional Versatile Electron Radiation Belt code with the Van Allen Probe data, using the log-normal Kalman filter. By using synthetic data, we show that the Kalman filter is capable of correcting errors in model predictions associated with uncertainties in electron lifetimes, boundary conditions, and convection electric fields. We demonstrate that reanalysis retains features that cannot be fully reproduced by the convection model such as storm-time earthward propagation of the electrons down to 2.5 Earth’s radii. The Kalman filter can adjust model predictions to satellite measurements even in regions where data are not available. Our results demonstrate that data assimilation can improve the performance of ring current models, better quantify model uncertainties, and help us to improve the nowcast and forecast of the dynamics of the particles in the inner magnetosphere.
Exploring the links between hydrological forecast skill and multiple flood hazard drivers in southern Africa
Authors: Ficchi Andrea , Cloke Hannah , Zsoter Ervin , Prudhomme Christel , Stephens Liz
Published: March 2020

Severe flooding in southern Africa is caused by a variety of meteorological hazards including intense tropical cyclones and depressions, mesoscale convective complexes and persistent lows which bring extreme rainfall and flood events with different characteristics. Little is known about the relative predictability of flooding associated to these different drivers, especially in operational forecasting systems. Understanding the limits of predictability for the different drivers of flooding is important to provide evidence of forecast capabilities to end-users and decision-makers and build trust in the use of the forecasting systems.

Here we explore the skill of probabilistic flood forecasts from the operational Copernicus Emergency Management Service Global Flood Awareness System (GloFAS v2) over southern Africa. GloFAS provides real-time hydrological forecasts up to 30 days ahead by coupling ensemble weather forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) with hydrological modelling. The GloFAS flood forecasts are openly available and can support humanitarians and other international organisations to trigger action before a devastating flood occurs.

Using hydrological records of past flood events over the last 20 years, the GloFAS forecast skill is assessed by analysing the probability of detection of the events over different lead-times from 1 to 30 days, as well as the consistency and accuracy of predictions of event-based characteristics such as the flood timing and duration. We stratify the analysis by the multi hazard drivers of flooding with a focus on the distinction between tropical cyclones and other types of meteorological events. We suggest that such a stratified analysis of forecast skill can help modellers better understand the sources of predictability in flood forecasts and can support humanitarians to define specific trigger levels for forecast-based action for different types of flood events.
A new method of PWV retrieval over land with remote sensing data: a case of AMSR2
Authors: Jiang Nan , Xu Yan , Xu Tianhe
Published: March 2020

Precipitable water vapor (PWV) is an important parameter reflecting the amount of solid water in the atmosphere, which is widely utilized in the studies of numerical weather prediction (NWP) and climate change. The microwave radiance measurements made by the space-based remote sensing satellites give us the opportunity to make the climate studies on a global scale. So far, PWV retrieval over the ocean has a long data record and the technology is very mature, but in the case of PWV retrieval over land, it is more challenging to isolate the atmospheric signals from the varied surface signals. In this study, we will apply a new retrieval method over land based on the dual-polarized difference (vertical and horizontal) at 19 GHz and 23 GHz using the brightness temperatures from the Global Change Observation Mission-Water (GCOM-W)/Advanced Microwave Scanning Radiometer 2 (AMSR2). We found polarization difference in brightness temperatures has an exponential relation on the amount of PWV. The validation results of the PWV retrieval from the ground-based GNSS stations show that the proposed method has a mean accuracy of 3.9 mm. Thus, the proposed method can give a possibility to improve the accuracy of data assimilation in the NWP applications and is useful for the studies of global climate change with the long-term data records.
Recent landscape changes assessed by remotely sensed data in Pechora Region
Authors: Ardelean Florina , Chețan Marinela , Dornik Andrei , Onaca Alexandru , Georgievski Goran , Drozdov Dmitry , Romanovsky Vladimir , Hagemann Stefan , Nicolsky Dmitry , Sein Dmitry
Published: March 2020

Pechora Region, located in North-East European Russia, is a unique natural environment with high biodiversity and wilderness areas, such as coastal habitats, the Arctic tundra or the Ural Mountains. The area lies on different permafrost zones and faces considerable challenges such as the over-exploitation of natural resources or climate change related. Our objective is to analyze landscape changes in the last 30 years using free available satellite data and identify possible influences on the degradation of permafrost in the study area. We used Surface Reflectance images from Landsat archive between 1985 and 2019. For each year, normalized indices were derived, illustrating consistency of green vegetation, as Normalized Difference Vegetation Index (NDVI), and vegetation moisture, Normalized Difference Moisture Index (NDMI). From MODIS data archive we used land surface temperature (LST), between 2000 and 2019. Moreover, the Global Surface Water dataset which contains maps with the spatial and temporal distribution of permanent and seasonal surface water from 1984 to 2018 was used. These data were aggregated to yearly mean (i.e. NDVI, NDMI, LST) or yearly sum (surface water), for the entire Pechora region. The results reveal a significant increase in NDVI mean. This "greening" of the tundra landscape, especially the southern tundra, between 1985 and 2019 has also been highlighted in other studies in the Arctic. Similarly, NDMI shows a slight increase of vegetation moisture in this area in the last three decades. Vegetation dynamics in the last 20 years is in accordance with LST evolution, showing an increase especially in the August mean temperature, more significant after 2011. From the analysis of the spatio-temporal changes of the water surfaces, a significant increase in seasonal water can be observed after 1997, and a relatively stable trend of permanent waters, with minimum values in 1999, 2003 and 2012. In the same time, an increase in the active layer thickness in the last 20 years of measurements in a site located in the study area has been documented. We conclude that Pechora Region experienced significant landscape changes in the last 30 years, our results showed mostly positive changes on vegetation consistency and moisture, and a high spatial variability of surface water.

Acknowledgement

This work is funded for WUT by a grant of the Romanian National Authority for Scientific Research and Innovation, CCDI-UEFISCDI, project number ERANET-RUS-PLUS-SODEEP, within PNCD III in the frame of ERA-Net plus Russia, TSU is supported by MOSC RF # 14.587.21.0048(RFMEFI58718X0048), AWI and HZG are supported by BMBF (Grant no. 01DJ18016A and 01DJ18016B).
Impact of the Mertz Glacier Tongue calving on the emergence of polynyas in the d'Urville Trough, East Antarctica
Authors: Ricard Lucile , Houssais Marie-Noelle , Herbaut Christophe , Fraser Alexander , Massom Rob , Blaizot Anne-Cecile
Published: March 2020

 

Passive microwave remote sensing observations and atmospheric data are used to characterize the impact of the Mertz Glacier Tongue (MGT) calving in February 2010 on the sea ice conditions in the D’Urville Trough, East Antarctic shelf (139°E-141°E). The main objective is to determine if conditions for dense shelf water production in this area were possibly influenced by the calving. In particular, we look for the existence of winter polynyas capable of sustaining significant sea ice production, a prerequisite for the formation of dense, saline waters. We show that polynyas in the D'Urville area are part of a complex icescape made of fast ice and drifting pack ice. The seasonal evolution of this icescape has been profoundly modified with the calving of the MGT and opening of new polynyas. Pre-calving and post-calving sea ice concentrations are analyzed to identify major patterns of variability. Examination of the fast ice distribution and atmospheric forcing helps to develop a scenario for the formation of low sea ice concentration regions and their relation to the sea ice fluxes, supporting the conclusion that the role of the Adelie Bank as a barrier to the drift ice may have strengthened after the calving.
Climatological Biomass Burning CO – Where it comes from and where it goes.
Authors: Daskalakis Nikos , Kanakidou Maria , Vrekoussis Mihalis , Gallardo Laura
Published: March 2020

Carbon Monoxide (CO) is an important atmospheric trace gas, and among the key O3 precursors in the troposphere, alongside NOx and VOCs. It is among the most important sinks of OH radical in the atmosphere, which controls lifetime of CH4 — a major greenhouse gas. Biomass burning sources contribute about 25% to the global emissions of CO, with the remaining CO being either emitted from anthropogenic sources, or being chemically formed in the atmosphere. Because of CO tropospheric lifetime is about two months; it can be transported in the atmosphere thus its sources have a hemispheric impact on atmospheric composition.

The extent of the impact of biomass burning to remote areas of the world through long range transport is here investigated using the global 3-dimensional chemistry transport model TM4-ECPL. For this, tagged biomass burning CO tracers from the 13 different HTAP (land) source regions are used in the model in order to evaluate the contribution of each source region to the CO concentrations in the 170 HTAP receptor regions that originate from biomass burning. The global simulations cover the period 1994—2015 in order to derive climatological transport patterns for CO and assess the contribution of each of the source regions to each of the receptor regions in the global troposphere. The CO simulations are evaluated by comparison with satellite observations from MOPITT and ground based observations from WDCGG. We show the significant impact of biomass burning emissions to the most remote regions of the world.
Revealing hidden peat structures along the stream network of a boreal forest catchment
Authors: Grabs Thomas , Ledesma José L.J , Laudon Hjalmar , Seibert Jan , Köhler Stephan , Teutschbein Claudia , Bishop Kevin
Published: March 2020

Peat stored in large wetlands plays an important role in the carbon cycle and strongly influences water quality of terrestrial surface water bodies. At the same time, peat is also stored in the direct vicinity of many boreal forest streams. From this strategic position, peat can receive and chemically reset hillslope water before it reaches the stream network. Yet, in contrast to large wetlands, only little spatial information is available on the lateral extent of near-stream peat and even less about its vertical variation. Here, we present field data on peat depth and lateral extent collected from approximately 200 transects (with 12 soil profiles taken per transect) distributed across the entire stream network of the Krycklan boreal catchment in Northern Sweden. This soil profile data revealed a considerable heterogeneity of peat and organic horizon thicknesses. By combining the field data with morphological and geological maps, we show how parent material, stream order and local topography influence near stream peat structures. Furthermore, we discuss potential consequences on surface water quality by linking the detailed peat data set to estimates of lateral, shallow groundwater inflows derived from hydrometric measurements and digital terrain analysis.
Re-analysis of limb anomaly detections in three HST/STIS transit images of Europa: No evidence for plumes
Authors: Roth Lorenz , Giono Gabriel , Ivchenko Nickolay , Saur Joachim , Retherford Kurt , Strobel Darrell , Schlegel Stephan , Ackland Marcus
Published: March 2020

After evidence for present-day geological activity on Jupiter’s moon Europa remained elusive for decades, several recent studies derived the existence of plumes on various locations. We have re-analyzed the three HST/STIS transit images in which Sparks et al. (2016) identified limb anomalies as evidence for Europa’s plume activity. After reproducing the results of Sparks et al. (2016), we find that positive outliers are similarly present in the images as the negative outliers that were attributed to plume absorption. A physical explanation for the positive outliers is missing. We identify two factors that affect the significance of the measured outliers in the region above Europa’s limb: The exact location of Europa on the detector and the description of the statistical fluctuations in the images. When accounting for these factors, the statistical significance of the plume candidate features is about 3 sigma or lower in the three images. The resulting positive and negative outliers are consistent with random statistical occurrence in a sample size given by the number of pixels in Europa's limb region.
Investigating triggering mechanisms for the large hailstorm event of July 10th, 2019 on the Adriatic Sea
Authors: Ricchi Antonio , mazzarella Vincenzo , Sangelantoni Lorenzo , Redaelli Gianluca , Ferretti Rossella
Published: March 2020

A severe weather events hit Italy on July 9-10, 2019 causing heavy damages by the falling of large-size hail. A trough from Northern Europe affected Italy and the Balkans advecting cold air on the Adriatic Sea. The intrusion of relatively cold and dry air on the Adriatic Sea, in a first stage through the "Bora jets" generated by the Dinaric Alps gave rise to a frontal structure on the ground, which rapidly moved from North to South Adriatic. The large thermal gradient (also with the sea surface), the interaction with the complex orography and the coastal zone, generated several storm structures along the eastern Italian coast.  In particular, on 10 July 2019 between 8UTC and 12UTC a deep convective cell (probably a supercell) developed along the coast North of the city of Pescara, producing intense rainfall (accumulated rainfall reaching 130 mm/3h) and a violent hailstorm with hailstones larger than 10 cm in diameter. The storm quickly moved southward, evolving into a complex multicellular structure clearly visible by observing radar data.  In this work the frontal dynamics and the genesis of the storm cell are investigated using the numerical model WRF (Weather Research and Forecasting system). Numerical experiments are carried out using a 1 km grid on Central Italy, initialized using the ECMWF dataset and the Sea Surface Temperature (SST) taken by MFS-CMEMS Copernicus dataset. The sensitivity study investigated both the impact of the initial conditions, the quality and the anomaly of the SST on the Adriatic basin in those days. Furthermore, in order to quantify the importance of the use of different microphysics, Planetary boundary Layer (PBL) and radiative schemes, several experiments are performed. The role of orography in the development and location of the convective cell is also investigated. Preliminary results show that initialization and SST played a fundamental role. In particular, the initialization several hours before the event, coupled with a detailed SST allows to correctly reproduce the atmospheric fields. The microphysics scheme turned out to play a key role for this event by showing a significant greater impact than the PBL, in terms of frontal genesis on both the synoptic and local scale.
Jupiter polar cap high energy particle acceleration observed from Juno
Authors: Jørgensen Peter S. , Jørgensen John L. , Merayo Jose M. G , Benn Mathias , Herceg Matija , Denver Troelz , Connerney John E. P. , Mauk Barry
Published: March 2020

The Juno mission carries the Advanced Stellar Compass (ASC) as primary attitude reference for the MAG investigation. Since Jupiter Orbit Insertion on July 4, 2016, the ASC has continuously monitored high energy particles fluxes in Jupiter’s magnetosphere. In the attitude determination process, the energetic particles with sufficient energy to penetrate the heavily shielded focal plane CCD are detected and characterized to facilitate their removal in the stellar attitude match. Thus highly energetic particles, >15MeV for electrons, >80MeV for protons, and >~GeV for heavier elements, are detected and reported every 250ms. The ASC’s highly optimized radiation shield design enables directional sensitivity, since shielding encountered by particles entering via the optics aperture is less efficient. The directionality offers preferential detection to electrons with energies between 15 and 25MeV and protons with energies between 80 and 100MeV (i.e operates as a particle telescope), whereas particles with energies above these limits may penetrate from any direction. The Juno spacecraft, rotates at 2 RPM, thus particles with energies in the band mentioned, and velocities pointing to the lens exhibit particle flux variation with the spin phase of Juno. Every periJove, Juno traverses a section of the north and south polar caps, and now, past the midpoint of nominal mission, high energetic particles in the aurora regions have been mapped with a high degree of detail. A significant feature is that very intense beams of particles are regularly measured at field lines reaching well beyond L=50, i.e. on distant closed or open field lines. These features are rapidly varying, signifying either a very limited extent, or, high time variability. In the cases where these beams contain particles with energies in the directional sensitive range of the ASC, the source of the beam is from the aurora region, suggesting a polar cap mechanism, capable of accelerating a particle directly to 20MeV. We present examples of flux profiles on open field lines.
Climate change in the tropical Atlantic
Authors: Keenlyside Noel , Crespo Lander , Koseki Shunya , Svendsen Lea , Richter Ingo
Published: March 2020

The tropical Atlantic SST have warmed by about 1 degree over the historical period, with greatest warming in the east, along the African coast and in the Gulf of Guinea. Experiments performed from the Coupled Model Intercomparison Projects (CMIP) indicate that models fail to reproduce this warming pattern, instead showing a rather uniform warming. Future projections with these models also tend to show rather uniform warming. In constrast. results from anomaly coupled models indicate that model biases impact the ability of climate models to simulate warming patterns in the tropical Atlantic. Here we investigate the role of model biases on climate change in the tropical Atlantic in the CMIP experiments. In addition, we have analyzed impacts of global warming on tropical Atlantic climate variability, and we assess the sensitive of the results are to model biases.