bluuebunny/crossref_metadata_2025 huggingface dataset:
Ocean acidification may be increasing the intensity of lightning over the oceans
Authors: Asfur Mustafa , Silverman Jacob , Price Colin
Published: March 2020

The anthropogenic increase in atmospheric CO2 is not only considered to drive global warming, but also ocean acidification. Previous studies have shown that acidification will affect many aspects of carbon uptake and release in the surface water of the ocean through increased primary productivity and decreased biogenic calcification and CaCO3 dissolution. In this report we present a potential novel impact of acidification on the flash intensity of lightning discharged into the oceans. Our experimental results show that a decrease in ocean pH corresponding to the predicted increase in atmospheric CO2 according to the IPCC RCP 8.5 worst case emission scenario will increase the Lightning Flash Intensity (LFI) by ca. 30% by the end of the 21st century relative to 2000. This increase in LFI may have broader implications for the atmospheric NOx production and precipitation as well as the atmospheric ozone budget (O3 and N2O production). In turn, these feedback processes may impact both marine and terrestrial biological uptake of carbon that should be considered in global carbon and climate models.
Evidence for solar-flare and other cosmic-ray events in the 14C record in tree rings: New information and a cautionary tale.
Authors: Jull Anthony , Panyushkina Irina , Miyake Fusa , Salzer Matthew , Baisan Chris , Molnar Mihaly , Varga Tamas , Wacker Lukas , Brehm Nicholas , Tegel Willy
Published: March 2020

Excursions in the radiocarbon (14C) record, which are rapid changes on a scale of a few years are presumed to be caused by an increase of incoming cosmic rays. The excursions at AD 774-775AD and 993-994AD have generated widespread interest and have been reproduced in many different tree-ring records (Miyake et al. 2012, 2013, 2017; Büntgen et al. 2018).  Similar structures have also been detailed, such as at 660BC (Park et al. 2017; O’Hare et al. 2019). Other types of change in 14C production may be due to a mix of SPE and different phenomena, such as around 5480BC (Miyake et al. 2017) and 815BC (Jull et al. 2018). We note that a proposed SPE event about 3371BC (Wang et al. 2018) is currently unconfirmed and this emphasizes the need for an anchored dendro-record to determine possible events. Timing of these events is important to understand the underlying recurrence intervals. A considerable number of processes can affect the cosmic-ray flux, including solar events, gamma-ray bursts, geomagnetic shifts and relatively close supernovae. Such studies are providing a wealth of new information through which to characterize new ‘events’ in 14C structure and to begin to understand the processes behind them. These effects also have introduced more complexity to the international radiocarbon calibration curve.

This research was supported in part by the European Union and the State of Hungary, co-financed by the European Regional Development Fund in the project of GINOP-2.3.2-15-2016-00009 ‘ICER’.

References: Büntgen et al. 2018. Nature Communications 9: 3605; A. J. T. Jull et al. 2014. Geophysics Research Letters 41: 3004-3010; F. Miyake et al. 2012. Nature 486: 282-284; F. Miyake et al. 2013. Nature Communications 4: 1748; F. Miyake et al. 2017. PNAS 114: 881-884; P. O’Hare et al. 2019. PNAS 116: 5961-5966; J. Park et al. 2017. Radiocarbon 59: 1147-1156; F. Y. Wang et al. Nature Communications 18: 1487.
The recession of the Laurentide Ice Sheet in southeast Northwest Territories during the Pleistocene-Holocene transition
Authors: Kelley Samuel E. , Ward Brent , Briner Jason , Ross Martin , Normandeau Philippe , Elliott Barrett
Published: March 2020

The Laurentide Ice Sheet (LIS) during the Pleistocene-Holocene transition provides a useful natural laboratory for examining the behavior of a mid- to high-latitude ice sheet during a period of climatically driven ice sheet thinning and retreat. While the timing and pattern of Pleistocene recession of the LIS are well-constrained along the southern and eastern margins, there is limited chronology constraining the ice margin retreat along the northwestern margin. Here we present new cosmogenic 10Be exposure ages retreat of the western margin of the LIS during the Pleistocene-Holocene transition. Sampling was performed along three transects located between the northern shore of Great Slave Lake and Lac de Gras. Each of the transects is oriented parallel to the inferred ice retreat direction in an attempt to capture a regional rate of retreat. Our new 10Be cosmogenic exposure ages from the southeastern Northwest Territories demonstrate that regional deglaciation occurred around 11,000 years ago. The population of ages broadly overlaps, indicating that either the retreat occurred within the resolution of our chronology or that the ice sheet experienced widespread stagnation and rapid down-wasting. These ages, not corrected for changes in atmospheric depth due to isostatic rebound, are older than minimum limiting radiocarbon constraints by ~1000 years, indicating that existing LIS reconstructions may underestimate the timing and pace of ice margin recession for this sector. Constraining the timing of the recession of the northwest sector of the LIS has the potential to inform our understanding about the damming of large proglacial lakes, such as Glacial Lake McConnell. The ages from our southern transect, collected from elevated bedrock hills, indicate LIS retreat from through the McConnell basin occurred after 12,000 years ago, and thus constitute maximum limiting constraints on the expansion of Glacial Lake McConnell southeastward into the present-day Great Slave Lake basin. Our chronology, combined with other emerging cosmogenic exposure ages constraining LIS deglaciation indicates retreat of the ice margin over 100s of kilometres during the Pleistocene-Holocene transition, exhibiting no evidence of a significant readvance during the Younger Dryas stadial.
Cumulant lattice Boltzmann approach: an application to hydraulic risk
Authors: Di Francesco Silvia , Venturi Sara , Geier Martin
Published: March 2020

The purpose of this work is the implementation and the application of a semi-automatic procedure for modelling flood events, based on the coupled use of a GIS subroutine and a two-dimensional (2D) lattice Boltzmann hydraulic model solving shallow water equations. The lattice Boltzmann method (LBM) with cumulant collision operator is chosen as a numerical technique for the solution of the hydrodynamic problem. The cumulant LBM is based on the use of cumulants as basis and relaxes, in the collision step, quantities (cumulants) that are Galilean invariant by construction. It overcomes the defects in Galilean invariance of the original multi relaxation times methods and it has been shown to further improve stability. An adaptation of the original formulation for a single-phase fluid is therefore proposed and developed to reproduce shallow free surface flows. Special attention is due to the wet-dry front in shallow flows; in fact, a correct simulation of such processes plays a crucial role in practical engineering studies.

The chosen mesoscopic model, thanks to the peculiar characteristic of LBM codes of being easily parallelized, could allow accurate and realistic wave prediction in a low computation time, introducing the possible application for the assessment of the hydraulic risk.

The preparation of the input data (pre-processing) and the analysis of the modelling results (post-processing) are assisted by an interchange routines using an open source GIS platform.

The proposed methodologies are tested and validated through the use of analytical solutions and experimental solutions. Moreover, the suitability of the proposed mathematical model for large scale hydraulic engineering applications is discussed through the modelling of a real flood event, highlighting the good performances of the cumulant model.
Radiative effects of clouds and water vapor on the monsoon
Authors: Byrne Michael , Zanna Laure
Published: March 2020

Monsoons are summertime circulations shaping climates and societies across the tropics and subtropics. Here the radiative effects controlling the climatological monsoon and its response to climate change are investigated using idealized simulations. The influences of clouds, water vapor and CO2 on the monsoon are decomposed using the radiation-locking technique. Seasonal cloud and water vapor radiative effects strongly modulate the climatological monsoon, reducing net monsoon precipitation by approximately half. Warming and moistening of the monsoon by seasonal longwave cloud and water vapor effects are counteracted by a strong shortwave cloud effect. The shortwave cloud effect expedites monsoon onset by approximately 10 days, whereas longwave cloud and water vapor effects delay onset. A simple theory for monsoon onset relates monsoon onset to the efficiency of surface cooling. In climate change simulations the water vapor feedback and CO2 forcing have similar influences on the monsoon, warming the surface and moistening the region. In contrast, clouds have a negligible effect on surface temperature yet dominate the response of the monsoon circulation to climate change. The radiation-locking simulations and analyses advance understanding of how and why radiative processes influence the monsoon, and establish a new framework for interpreting monsoon--radiation coupling in observations, in state-of-the-art models and in different climate states. Moreover, sensitivities of the monsoon to the longwave cloud feedback are found to be similar over the seasonal cycle and under CO2 forcing, suggesting a potential emergent constraint for monsoons in a changing climate.
A new approach to simulating lake-groundwater interactions
Authors: Zhang Bo , Lu Chuiyu , Wang Jianhua , Jarsjö Jerker
Published: March 2020

Lakes have significant hydraulic connections with their surrounding groundwater, thus the coupled simulation of lake and groundwater interactions is an important component of the numerical modelling of groundwater flow. This paper proposes a new approach for simulating lake-groundwater interactions (Sloping Lakebed Method, short for SLM) based on the block-centered finite difference method. In this approach, a discretization of the lakebed elevation in the vertical direction is conducted independently of the spatial discretization of the aquifer system, greatly simplifying the subdivision of the aquifer system. The lakebed is generalized by a slope across each lake cell, and the lake grid cells are classified as fully submerged, partially submerged, and unsubmerged to simulate the interactions between the lake and the aquifer according to the relative elevations of the lake surface and lake bed. Transitions between different states ensure the continuity of the boundary conditions, improving the convergence of the calculation process. The proposed method accounts for all source and sink terms for the lake, establishing a governing equation for lake water balance. The lake stage can then be obtained by solving this equation. A series of tests were run verifying the rationality and superiority of the SLM, suggesting that it provides similar results to those of the well-established MODFLOW LAK3 Package developed by the United States Geological Survey. However, the SLM has significant advantages over LAK3 in its ease of use and calculation stability.
Exploring the nature and timing of glacial climate transitions
Authors: Bauch Henning
Published: March 2020

The causes for major climate transitions in the Upper Pleistocene are based on the assumption that orbital forcing, i.e. the increase in northern hemisphere summer insolation (NHSI), initiates glacial ice sheets to melt away leading to the formation of warm interglacials. Good examples are plentiful available, e.g. major glacial terminations (T) such as T1, 2, or 5. Besides these major climate transitions there are also other glacial terminations across marine substage boundaries that, although seemingly of minor scale, had nevertheless massive climate impacts either globally (MIS4/3, MIS7d/7c) or regionally (MIS5b/5a). While an interglacial decrease in NHSI seems to run in parallel with early glacial inception - as can be noted for the later Holocene and MIS5e - the onset of T2 vs. T1 has long been controversially discussed with respect to its orbitally forced timing. This study therefore explores the involvement of other mechanisms. Primarily, these have to do not so much with internally produced feedback processes but are the consequence of temperature changes to be found in the low-latitudes. Transferred northward through the atmosphere and ocean these changes then feed ice sheet growth and determine its geographical configuration of different magnitudes, also eventually leading to a glacial maximum. During the past, climate transitions from a glacial into an interglacial world therefore did not start with the end of a glacial maximum. It is the time just prior to that particular maximum when the major change occurred.
Global surface air temperatures in CMIP6: Historical performance and future
Authors: Fan Xuewei
Published: March 2020

Surface air temperature outputs from 16 global climate models (GCMs) participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) were used to evaluate agreement with observations over the global land surface for the period 1901–2014. Projections of Bayesian model averaging (BMA) multi-model ensembles under four different Shared Socioeconomic Pathways (SSPs) were also examined. The results reveal that the majority of models reasonably capture the dominant features of the spatial changes in observed temperature with a pattern correlation typically greater than 0.98. However, most models underestimate annual temperature over northeastern North America and overestimate it over central Eurasia. In addition, most CMIP6 models overestimate the warming trend in most regions. The BMA multi-model ensembles show more agreement than individual models do in simulating the spatial patterns of the temperature, but with less spatial variability compared with the observations. In the 21st century, temperature is generally projected to increase over the global land surface under all four SSP scenarios. By the end of the 21st century, temperature is projected to increase by 1.35 °C/100 yr, 3.61 °C/100 yr, 6.39 °C/100 yr and 8.03 °C/100 yr under the SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5 scenarios, respectively, with greater warming projected over the high latitudes of the northern hemisphere and weaker warming over the tropics and the southern hemisphere.
DustIron: Global mineral dust simulations with ECHAM-HAMMOZ for modern and last glacial maximum climate conditions
Authors: Krätschmer Stephan , Werner Martin , Lamy Frank , Völker Christoph , van der Does Michèlle
Published: March 2020

In this study, we present results of new mineral dust simulations performed with the model setup ECHAM-HAMMOZ. The simulations are part of the AWI project DustIron, a coupled data-model approach to investigate past changes of the Southern Hemisphere dust cycle and potential Southern Ocean iron fertilization as a result of atmospheric mineral dust / iron input.

The model setup consists of the latest atmospheric general circulation model release ECHAM6, coupled to the aerosol model HAM2.3 and the atmospheric chemistry model MOZ1.0. Our focus is on dust emission and deposition rates as well as the identification of key source and deposition areas in the Southern Hemisphere by sensitivity experiments for modern (1850 AD) and last glacial maximum (21 ka BP) climate conditions. The spatial patterns of the decadal mean of the simulated annual dust deposition agree well with recent CESM simulation results (Albani et al., 2016) for modern climate conditions. A comparison of the decadal mean of the total global annual dust emissions simulated with ECHAM-HAMMOZ (1361 Tg a-1) to CESM (2785 Tg a-1, Albani et al., 2019) shows that the model performs rather at the lower end concerning global dust emissions. The tendency to a slight underestimation of global annual mineral dust emissions, however, is in agreement with the model’s aerosol evaluation by Tegen et al. (2019).
Spatial Distribution of Chinese Traditional Villages and its Influencing Factors
Authors: Wu Yunong , Zhang Bin , Meyer Burghard C. , Xie Duo , Zeng Yong , Xu Wenjie , Pan Yulian , Liu Guoliang
Published: March 2020

Abstract: Chinese Traditional Villages (TV) were selected from millions of villages based on their important historical and cultural heritage value. The distribution of TV characterized by spatial differentiation is subject to complex and diverse influencing factors. This study takes 6819 TV in China (as of the end of 2019) as research objects to analyse the distribution density of TV in different provinces; the spatial autocorrelation module in ArcGIS' spatial statistical tool was used to analyse the distribution characteristics; a total of 9 factors were selected from the three indicator groups of climate, geography and humanities, and introduced into the clustering and outlier analysis (Anselin Local Moran's I) module to analyse their spatial relationships with TV distribution. The results show that: 1. The spatial distribution of Chinese TV presents an obvious uneven aggregation state. Among them, the highest distribution density was 10.18 per 10,000 km² in Zhejiang province, while less than 0.5 per 10,000 km² in Inner Mongolia, Heilongjiang, Tibet and Xinjiang. The Global Moran's I index of TV distribution is 0.352, and the z-value of normal statistic is 949.76, which has a strong spatial autocorrelation. 2. The distribution of TV is mainly interpreted by humidity index, annual average temperature, elevation, slope, cultural relics, and population. 3. The results of clustering and outlier show that there are significant differences in the effect of the influencing factors on the distribution of TV in different regions. This paper aims to understand the influencing factors that affect the spatial distribution of TV in China and provide more comprehensive research content. This study indicates the importance of further cross-regional analysis of the TV distribution and provides a reference for its environmental management and protective measures and policies.
Deposition of Interior Layer Deposits within East and West Candor as well as Ophir chasms, Valles Marineris, Mars
Authors: Fueten Frank , Burden Amanda , van Patter Ariel , Labrie Josh , Flahaut Jessica , Stesky Robert , Hauber Ernst
Published: March 2020

The Martian Valles Marineris, located on the eastern flank of the Tharsis region, is a 4000 km long linked system of troughs. The formation of the up-to-11 km deep chasmata of Valles Marineris is thought to have taken place during a two-stage process in which ancestral basins collapsed and were later linked by tectonism. Located within most chasmata are enigmatic layered deposits, referred to as interior layered deposits (ILDs), whose origin and mechanism of formation are uncertain. It has been estimated that ILDs cover 17% of the total area, representing 60% by volume of all deposits within Valles Marineris with several deposits nearly reaching the height of the surrounding plateau.

Here we present the results of a detailed study of the ILD mounds located within three of the presumed ancestral basins in the center of Valles Marineris.  In this study HiRISE and CTX images were used to measure layer attitudes of ILDs within East and West Candor and Ophir chasmata. Because only CTX images cover the entire chasms, the ILDs were grouped into distinct varities of bedding based on their appearance in CTX imagery.  In both East and West Candor and Ophir, the stratigraphically lowest unit is a massive unit which displays no layering in any available imagery.  Layered units with dips between 10° and 20° are deposited on top of this massive unit.  The lowest layered units in all three chasms appear to show multiple prominent benches, indicative of significant competency contrasts. These units can be shown in multiple places to be unconformably overlain by thinner layered units.  It is not possible to correlate or determine the number of thinner layered units because the unconformable contacts cannot be correlated. 

The general similarities of types of units and unit relationships between  the ILDs in these three chasms suggests that they share a similar depositional history. We believe that the ILD morphology is most compatible with an environmental setting in which the ancestral basins were lakes which may have been periodically frozen.  We suggest that the unconformities are the result of multiple erosional events indicating that ILD deposition was not continuous.   A general trend of massive units overlain by thinner layered units may reflect a change in the environment and sediment supply.  Associated with this change is a general observation that polyhydrated sulfate is most commonly found on top of the monohydrated material.  Work to correlate more closely units within these chasms, including their mineralogy, is currently ongoing.
Upscaled exact solutions to root water uptake equations for earth system modelling
Authors: Bouda Martin , Javaux Mathieu
Published: March 2020

Earth system models struggle to accurately predict soil-root water flows, especially under drying or heterogeneous soil moisture conditions, resulting in inaccurate description of water limitation of terrestrial fluxes. Recent descriptions of plant hydraulics address this by applying Ohm’s law analogues to the soil-plant-atmosphere hydraulic continuum.

While adequate for stems, this formulation linearises soil-root and within-root resistances by assumption, neglecting the nonlinearity of pressure gradients in absorbing roots. The resulting discretisation error is known to depend strongly on model spatial resolution. At coarse resolution, substantial errors arise in a form depending on the assumed configuration of resistances. In simulations of a drought at the Wind River Crane (WRC) flux site, a parallel Ohm model based on the rooting profile overpredicted hydraulic redistribution, while a series model overpredicted uptake in shallow layers at the expense of deep ones.

A conceptual alternative is to upscale exact solutions to the hyperbolic differential equation that describes root water uptake, by solving for the mean root water potential in each soil subdomain. Upscaled solutions show that multiple soil water potentials affect pressure gradients in each root segment, producing the nonlinearities absent in Ohm models. This upscaled model gave better predictions of WRC drought data and was significantly less prone to over-fitting than the two Ohm models, with more robust predictions beyond calibration conditions.

Analysis reveals classes of root systems of differing architectural complexity that yield a common upscaled model. In numerical experiments, using a simple upscaled model in situations of increasing complexity (e.g., adding individual plants), resulted in bounded errors that decreased asymptotically with increased complexity. The approach is thus a viable candidate for upscaling the effects of heterogenous soil moisture distributions on root water uptake.
Evaluating paleoclimate-paleosoil linkages and soil ecosystem services with a combined soil-climate model
Authors: Finke Peter , Ranathunga Nirmani , Verdoodt Ann , Yu Yanyan , Yin Qiuzhen
Published: March 2020

Loess deposits often contain paleosols that are documenting phases of soil formation associated with interglacials or interstadials. Linkage of the paleosols to paleoclimates is not straightforward when paleoclimates are represented by dynamic (simulated) variables and paleosols by static (measured) soil parameters. We therefore propose to combine a dynamic soil model with a climate model. We define the required processes in such soil model and the output variables that would allow usage of the soil-climate model combination to be used for (past and future) climate change studies. Issues to be considered are the time- and spatial scale of the soil and the climate model. For predictive (global change) studies, the usage of (soil) model outputs to quantify the evolution of the soil natural capital and of ecosystem services must be considered. We give examples for the Chinese Loess Plateau of the evaluation of paleoclimate-paleosol linkages and of simulated soil natural capital and soil ecosystem services with the LOVECLIM-earth system model linked to the SoilGen soil evolution model and conclude that such model combination is an important step forward.
Analytical long-profile models of coupled glacier-fluvial systems
Authors: Deal Eric , Prasicek Günther
Published: March 2020

Glaciers are an effective agent of erosion and landscape evolution, capable of driving high rates of erosion and sediment production. Glacial erosion is therefore an important process mediating the effect of climate on erosion rates and tectonics. Further, as a source of sediment, glacial erosion also has implications for the carbon and silicate cycles, with the potential for longterm feedbacks.  Understanding the interaction of climate, tectonics, glacial erosion and topography will lead to more insight into how glaciers can impact these processes. Simple, analytical long-profile models of fluvial incision are fundamental in tectonic geomorphology and critical for addressing fluvial analogues of problems such as those posed above. The advantage of these simple long-profile models is that they can be applied when information about forcing and boundary conditions is minimal (e.g. in deep time), and they can aid in the development of intuition about how such systems respond in general to different forcing. While models of glacial erosion have existed for quite some time, they tend to be complicated and computationally expensive. Currently, analytical long-profile models do not exist for glacial systems. At the same time, the patterns of glacial erosion and sediment transport, and how these processes respond to climate is fundamentally different than fluvial systems, and cannot be addressed properly with purely fluvial models.

Building on previous work, we introduce several simplifications to make the equations for coupled glacier-fluvial long-profile models easier to use and show that these simplifications have minimal effect on the steady state solution. We then use these new equations to develop an analytical solution for glacier-fluvial long-profiles at erosional steady state. The solution provides glacier geometry, including length and slope, ice thickness, and overall orogen relief for a given uplift rate, rock erodibility, profile length and climatic conditions. To explore the effect of glaciation on the balance between climate, erosion and orogen geometry, we integrate this solution into a critical wedge orogen theory. We find that the total orogen relief should be closely tied to the equilibrium line altitude (ELA), in line with the glacial buzzsaw theory. In addition, our theory predicts that the geometry and average uplift rate of glaciated critical wedge orogens respond more sensitively to changes in climate than those dominated by fluvial erosion. We suggest that the lowered ELA during glacial maxima over the last few million years could have triggered narrowing of critical orogens, with an associated increase in uplift rates within the active orogen core. 
Temperature increase is accelerating in the past five years in Greenland
Authors: Jiang Saiping , Ye Aizhong
Published: March 2020

Understanding the change of Greenlandic temperature is important for assessing and predicting Greenland ice sheet mass, which plays an important role in sea level rise. In this study, we analyze the annual and seasonal coastal Greenlandic temperature during period 1952 ~ 2017 based on the dataset obtained from Danish Meteorological Institute (DMI), focusing on the last five years. Overall, the annual coastal Greenlandic temperature increases during period 1952 ~ 2017 with a rate of 0.23 ℃ decade-1, especially in the south-eastern (0.70 ℃ decade-1) and northern (0.42 ℃ decade-1) region of the island. From seasonal coastal Greenlandic composite temperature (CT) change, winter has the largest change rate (0.28 ℃ decade-1), and summer increases 0.25 ℃ decade-1, while spring warms 0.17 ℃ decade-1 with a smaller variation. And temperature increase is accelerating during period 2013 ~ 2017 according to Mann-Kendall test, especially in the north-eastern and northern region of the island; And the order of seasonal temperature change of the whole island is as follows: annual > autumn > summer > winter > spring. And pearson correlation analysis was used to determine the teleconnection relationship between coastal temperature and large-scale atmospheric-ocean climate indexes, and we have found that Greenland Blocking Index (GBI), Atlantic Multi-decadal Oscillation (AMO), Tropical Northern Atlantic Index (TNA), North Tropical Atlantic Index (NTA), Caribbean Index (CAR), Atlantic Meridional Mode (AMM), East Atlantic (EA) and Western Hemisphere warm pool (WHWP) have a significant positive correlation relationship with coastal temperature in most months except February and May. But North Atlantic Oscillation (NAO), Arctic Oscillation (AO) and Eastern Asia/Western Russia (EAWR) show a significant negative correlation relationship with temperature. On the whole, there exists time lag effect between climate indexes and temperature except GBI, AO and NAO. And from Randomforest model result, we find that GBI, NAO, CO2, AMO, N2O, SF6, CH4, and Northern Oscillation Index (NOI) are most important variables that influence CT change during period 1979 ~ 2017. Finally, we calculated the contribution rate of important variables to temperature change during period 1979 ~ 2017, showing that contribution rate of GBI, CO2 and NOI to temperature change is 48.85%, 36.85%, and 17.58%, respectively. 
Development of artificial neural networks for the prediction of the consumption of pathogenic microorganisms in water and for the calculation of the risk of individual annual contamination
Authors: Gilver Odilon Mendel Kombo Mpindou , Estela Chorda Ramon , Eva Garcia Ganzalez
Published: March 2020

In developing countries, diseases related to lack of water or inadequate water quality cause the death of approximately 5 million people annually, of whom about 1.8 million die from diarrhoeal diseases, 90% of them being children under five, which is equivalent to 4,500 children per day (WHO, 2004; Rojas, 2006). The WHO reports that improvements in water quality alone reduce morbidity from diarrhoeal diseases by a third or more (WHO, 2007), and drinking water treatment plants  are currently the focus of Protozoan studies on water supply. Giardia and Crytosporidium are two of the protozoa that are currently of greatest interest due to their resistance to conventional disinfection processes (Johnson et al., 2003), and they can exist in the presence of high concentrations of free chlorine (Corbitt, 1999). A reality that confirms this fact is that 98% of the individuals affected by epidemic outbreaks in the United States were supplied by drinking water plants using a conventional treatment system.

The DWTP of the Dam that caters 859885 people, corresponds to a series of municipalities in the northern area of the metropolitan area of Valencia (Spain), and the central-north-western districts of the city of Valencia face this problem. In a study conducted from 2006 to 2010, in the water used for human consumption in the city of Valencia, some positive concentrations of networked oocysts were detected. In conclusion, it is possible that the protozoa entered the network, as the analyses indicate, and that the pathology exists in the environment although no outbreaks have been recorded to date. Given that it is present in raw water, it is very convenient and interesting to develop a tool capable of evaluating the water treatment process, from production to the consumer, a useful tool for operators as a support for decision-making. The campaign was carried out throughout the year, taking a weekly sample, the analyses were made with the EPA1623 method. A survey was also carried out in person on volunteers who indicate their age, sex, postal code o and number of glasses of tap water ingested. The purpose of this study was to show how an artificial neural network  can be useful to predict the consumption of pathogenic microorganisms. More specifically, the aim is to develop a backpropagation type neuronal network capable of discriminating between those who consume and those who do not, based on the answers given by the subjects to a questionnaire, with the main objective of demonstrating the usefulness of the methodology based on neuronal networks for risk stratification, applying it to the calculation of the probability of the annual risk of individual contamination of the population supplied
Numerical modelling of dynamic flood topographies in the Terai region, Nepal.
Authors: Creed Maggie J. , Dingle Elizabeth H. , Sinclair Hugh D. , Gautam Dilip , Gourmelen Noel , Borthwick Alistair G.L. , Attal Mikael
Published: March 2020

Rivers sourced from the Himalayas support ~10% of the global population living on the Indo-Gangetic Plain. These rivers can be a source of devastating floods. Flood hazard maps used to inform early warnings systems in the Terai region in southern Nepal are based on static, outdated DEMs, which may not reflect the current river and floodplain topography. Sediment dynamics can change the river course and the distribution of flow down large bifurcation nodes, affecting flood inundation extent. These processes are rarely considered in flood prediction models for this region. In this study, using a 2D depth-averaged hydrodynamic model, several flood scenarios for the Karnali River are investigated, including different DEMs, variable bed elevations, and a scenario with bed levels modified at an important bifurcation node to reflect field observations. Inundation extent varied by upto 14% between scenarios for a 1-in-20 year flood discharge. Our results suggest that combining regular field measurements of bed elevation, with updated DEMs, could help to improve future flood prediction maps. Updating model input parameters is particularly important following large flood events and/or large landslides in the upstream catchment, which could increase bed aggradation and provoke channel switching in highly mobile, alluvial river systems.
Can we explain the low geo-effectiveness of the fast halo CMEs in 2002 with EUHFORIA?
Authors: Schmieder Brigitte , Poedts Stefaan , Verbeke Christine
Published: March 2020

In 2002 (Cycle 23), a weak impact on the magnetosphere of the Earth has been reported for six halo CMEs related to six X-class flares and with velocities higher than 1000 km/s. The registered Dst minima are all between -17 nT and -50 nT.  A study of the Sun-Earth chain of phenomena related to these CMEs reveals that four of them have a source at the limb and two have a source close to the solar disk center (Schmieder et al., 2020). All of CME magnetic clouds had a low z‑component of the magnetic field, oscillating between positive and negative values.

We performed a set of EUHFORIA simulations in an attempt to explain the low observed Dst and the observed magnetic fields. We study the degree of deviation of these halo CMEs from the Sun-Earth axis and as well as their deformation and erosion due to their interaction with the ambient solar wind (resulting in magnetic reconnections) according to the input of parameters and their chance to hit other planets. The inhomogeneous nature of the solar wind and encounters  are also important parameters influencing the impact of CMEs on planetary magnetospheres.

 
How fast to turn around: preventing tipping after a system has crossed a climate tipping threshold
Authors: Ritchie Paul , Cox Peter , Sieber Jan
Published: March 2020

A classical scenario for tipping is that a dynamical system experiences a slow parameter drift across a fold tipping point, caused by a run-away positive
feedback loop. We study what happens if one turns around after one has crossed the threshold. We derive a simple criterion that relates how far the parameter exceeds the tipping threshold maximally and how long the parameter stays above the threshold to avoid tipping in an inverse-square law to observable properties of the dynamical system near the fold. We demonstrate the inverse-square law relationship using simple models of recognised potential future tipping points in the climate system. 
Tropical sources of predictability for summer precipitation over Nordic European countries
Authors: Fuentes Franco Ramón , Koenigk Torben
Published: March 2020

We show evidence that tropical atmospheric variability over the central tropical Pacific modulates the circulation over the western Arctic and the North Atlantic-European sector, impacting the sea ice concentration over the Arctic and the summer precipitation especially over Nordic European countries (NEC). Our results, based on the ERA5 reanalysis, suggest the occurrence of a teleconnection mechanism (similar to the Pacific North American pattern) between the tropical Pacific in early spring and summer precipitation over NEC, and we propose two indices as predictors for NEC summer precipitation based on geopotential height anomalies at 500hPa over the western tropical Pacific during March. After successfully cross-validate an empirical model with both indices as predictors, we show that these indices allow predicting the observed tercile of summer precipitation over big portions of NEC in most of the summers within the 1979-2018 period, with a Heidke skill score greater than 90%.

Furthermore, we analysed CMIP6 simulations, and we found that models that show strong ENSO variability, reproduce the observed link of tropical variability in early spring with precipitation over NEC and ice concentration over the Arctic. In turn, CMIP6 simulations with weak ENSO variability fail to reproduce this observed connection.
Effect of inaccurate specification of time-correlated model error in an Ensemble Smoother
Authors: Ren Haonan , Van Leeuwen Peter Jan , Amezcua Javier
Published: March 2020

Data assimilation has been often performed under the perfect model assumption known as the strong-constraint setting. There is an increasing number of researches accounting for the model errors, the weak-constrain setting, but often with different degrees of approximation or simplification without knowing their impact on the data assimilation results. We investigate what effect inaccurate model errors, in particular, the an inaccurate time correlation, can have on data assimilation results, with a Kalman Smoother and the Ensemble Kalman Smoother.
We choose a linear auto-regressive model for the experiment. We assume the true state of the system has the correct and fixed correlation time-scale ωr in the model errors, and the prior or the background generated by the model contains the model error with the fixed, guessed time-scale ωg which differs from the correct one and is also used in the data assimilation process. There are 10 variables in the system and we separate the simulation period into multiple time-windows. And we use a fairly large ensemble size (up to 200 ensemble members) to improve the accuracy of the data assimilation results. In order to evaluate the performance of the EnKS with auto-correlated model errors, we calculate the ratio of root-mean-square error over the spread of all ensemble members.
The results with a single observation at the end of the simulation time-window show that, using an underestimated correlation time-scale leads to overestimated spread of the ensemble, and with an overestimated time-scale, the results show underestimation in the ensemble spread. However, with very dense observation frequency, observing every time-step for instance, the results are completely opposite to the results with a single observation. In order to understand the results, we derive the expression for the true posterior state covariance and the posterior covariance using the incorrect decorrelation time-scale. We do this for a Kalman Smoother to avoid the sampling uncertainties. The results are richer than expected and highly dependent on the observation frequency. From the analytical solution of the analysis, we find that the RMSE is a function of both ωr and ωg, and the spread or the variance only depends on ωg. We also find that the analyzed variance is not always a monotonically increasing function of ωg, and it also depends on the observation frequency. In general, the results show the effect of the correlated model error and the incorrect correlation time-scale on data assimilation result, which is also affected by the observation frequency.
Performance Evaluation and Operation Mechanism of Deep Borehole Heat Exchanger with Different Types of Boundary Conditions
Authors: Cai Wanlong , Chen Chaofan , Wang Fenghao , Liu Jun , Kolditz Olaf , Shao Haibing
Published: March 2020

Due to its sustainability, continuity and low carbon emissions, the utilization of geothermal energy is gaining more attention all around the world. Shallow geothermal energy is usually extracted through borehole heat exchangers (BHE) with a maximum length up to 150 m. Such systems typically require large space areas, thus limiting its application in built-up urban areas. This study presents a case where deep borehole heat exchanger (DBHE) with a depth down to 2500 m was constructed to extract geothermal energy for building heating purposes. A double-continuum finite element based numerical model was set up to simulate the heat transport process within and around the DBHE. The model has been validated by the experimental data in a demonstration project located in Fengxi, Xi’an China. The heat extracting performance of DBHE under different types of boundary conditions (including the Dirichlet condition and Neumann condition) are evaluated. The amount of thermal recharges from top, sides and bottom of the domain were differentiated and quantified. It is found that different types of boundary conditions will lead to deviations in the simulated heat fluxes and corresponding thermal recharge. The numerical simulations also suggest that the sustainable heat extract capacity of DBHE is mainly determined by the stored heat from the surrounding subsurface, and thermal recharge takes only a limited contribution. According to the calibrated modelling results, the proper heat extraction rate of DBHE in the long-period operation modes is analyzed.
Fluid-driven anthropogenic micro-seismic activity while drilling towards supercritical conditions in the Larderello-Travale geothermal field
Authors: Montanari Domenico , Minetto Riccardo , Plànes Thomas , Bonini Marco , Del Ventisette Chiara , Antunes Veronica , Lupi Matteo
Published: March 2020

This study investigates the seismic activity occurring at the Larderello-Travale geothermal field (LTGF), central Italy, from June 2017 to January 2018. We deployed a network composed of 9 broadband stations around the Venelle 2 well drilling for supercritical fluids. During the experiment, we recognise a group of events that usually occur in swarms and that show a periodic pattern, a narrow frequency band, and almost identical waveforms. Their source is estimated to be located near the well, and their occurrence ceases after about 3 weeks from the conclusion of the drilling. We propose a causal link with the drilling operations where pressure fronts inside the well may promote phase changes and fluid flow across the drilled formations.

Our study sheds light on the anthropogenic seismic activity at the LTGF. More generally, we show that microseismic activity occurring during drilling in high-pressure and high-temperature conditions can remain at low magnitudes and that geothermal wells targeting geothermal fluids in such systems may be handled safely despite the critical conditions encountered at depth. The drilling of the Venelle 2 well is an encouraging example for the development of geothermal energy in critical conditions.
Power-law behaviour of hourly precipitation intensity and dry spell duration over the United States
Authors: Franzke Christian , Yang Lichao , Fu Zuntao
Published: March 2020

Precipitation is an important meteorological variable which is critical for weather risk assessment. For instance, intense but short precipitation events can lead to flash floods and landslides. Most statistical modelling studies assume that the occurrence of precipitation events is based on a Poisson process with exponentially distributed waiting times while precipitation intensities are typically described by a gamma distribution or a mixture of two exponential distributions. Here, we show by using hourly precipitation data over the United States that the waiting time between precipitation events is non-exponentially distributed and best described by a fractional Poisson process. A systematic model selection procedure reveals that the hourly precipitation intensities are best represented by a two-distribution model for about 90% of all stations. The two-distribution model consists of (a) a generalized Pareto distribution (GPD) model for bulk precipitation event sizes and (b) a power-law distribution for large and extreme events. Finally, we analyse regional climate model output to evaluate how the climate models represent the high-frequency temporal structure of U.S. precipitation. Our results reveal that these regional climate models fail to accurately reproduce the power-law behaviour of intensities and severely underestimate the long durations between events.
Emergence of opposite trends in daytime and night-time urban heat island intensities in England
Authors: Lo Eunice , Mitchell Dann , Bohnenstengel Sylvia , Collins Mat , Hawkins Ed , Hegerl Gabriele , Joshi Manoj , Stott Peter
Published: March 2020

Urban environments are known to be warmer than their sub-urban or rural surroundings, particularly at night. In summer, urban heat islands exacerbate the occurrence of extreme heat events, posing health risks to urban residents. In the UK where 90% of the population is projected to live in urban areas by 2050, projecting changes in urban heat islands in a warming climate is essential to adaptation and urban planning.

With the use of the new UK Climate Projections (UKCP18) in which urban land use is constant, I will show that both summer urban and sub-urban temperatures are projected to increase in the 10 most populous built-up areas in England between 1980 and 2080. However, differential warming rates in urban and sub-urban areas, and during day and at night suggest a trend towards a reduced daytime urban heat island effect but an enhanced night-time urban heat island effect. These changes in urban heat islands have implications on thermal comfort and local atmospheric circulations that impact the dispersion of air pollutants. I will further demonstrate that the opposite trends in daytime and night-time urban heat island effects are projected to emerge from current variability in more than half of the studied cities below a global mean warming of 3°C above pre-industrial levels.