bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of parametric modeling as the geological description of the surrounding rocks in the workings.
Authors: Shekov Vitali , Ivanov Andrei
Published: March 2020

Abstract.  The use of parametric modeling, similar to BIM (Building Information Model) technology, widely used now in the building construction industry, and very interesting to use this approach in documenting and modeling underground space.

Unlike construction sites, not reinforced tunnels and underground workings have a very large specific associated with the properties of the surrounding rocks, which are described by specific technical and physical parameters, taking into account their resistance over a long period while using them for the purpose of extracting a useful fossil.

Geotechnical modules built into Autodesk products are designed to solve specific problems in the construction of concrete tunnels and other facilities related to the bowels. A geological model in that module is a collection of AutoCAD® Civil 3D® triangulation models (planar surfaces) that display the top and bottom of geological layers, indicating the thickness of the geological layer and tracing the boundaries of the surfaces. Solid-state models are formed only at the locations of geological wells, illustrating their composition using conditional 3D AutoCAD® bodies constructed in accordance with good patterns.

Authors of this presentation propose the primitive families for the description of the geological and structural composition of rocks around the not reinforced tunnels are being developed for the Autodesk Civil 3D and Revit program.

At the same time the use of the FreeCAD program, which supports the exchange of parametric data in the IFC (Industrial Foundation Classes) format, can be also very promising, which means that the primitives developed in this program can be used in the Autodesk software too.

Parametric models of rock in the workings can play the role of the information model while calculating the stress, deformations, heat distribution and other physical fields for different technical applications. As an Open Source software with sufficiently developed tools for modeling and parametric description of models based on information modeling, with a certain adaptation, FreeCAD program can be used for this tasks, it can also be used as the basis for creating a unified information system for underground laboratories at different scale of accuracy needed for any calculations.
Impact of the Quasi-Biennial Oscillation on the boreal winter tropospheric circulation in CMIP5/6 models
Authors: Rao Jian , Garfinkel Chaim , White Ian , Schwartz Chen
Published: March 2020

Using 17 CMIP5/6 models with a spontaneously-generated quasi-biennial oscillation (QBO)-like phenomenon, this study explores and evaluates three dynamical pathways for impacts of the QBO on the troposphere: (i) the Holtan-Tan (HT) effect on the stratospheric polar vortex and the northern annular mode (NAM), (ii) the subtropical zonal wind downward arching over the Pacific, and (iii) changes in local convection over the Maritime Continent and Indo-Pacific Ocean. More than half of the models can reproduce at least one of the three pathways, but few models can reproduce all of the three routes. Firstly, most models are able to simulate a weakened polar vortex during easterly QBO (EQBO) winters, in agreement with the observed HT effect. However, the weakened polar vortex response during EQBO winters is underestimated or not present at all in other models, and hence the QBO → vortex → tropospheric NAM/AO chain is not simulated. For the second pathway associated with the downward arching of the QBO winds, seven models incorrectly or poorly simulate the extratropical easterly anomaly center over 20–40°N in the Pacific sector during EQBO, and hence the negative relative vorticity anomalies poleward of the easterly center is not resolved in those models, leading to an underestimated or incorrectly modelled height response over North Pacific. However the other ten do capture this effect. The third pathway is only observed in the Indo-Pacific Ocean, where the strong climatological deep convection and the warm pool are situated. Nine models can simulate the convection anomalies associated with the QBO over the Maritime Continent, which is likely caused by the near-tropopause low buoyancy frequency anomalies. No robust relationship between the QBO and El Niño–Southern Oscillation (ENSO) events can be established using the ERA-Interim reanalysis, and nine models consistently confirm little modulation of the ocean basin-wide Walker circulation and ENSO events by the QBO.
Data quality in different paleo archives and covering different time scales: a key issue in studying tipping elements.
Authors: Rousseau Denis-Didier , Barbosa Susanna , Bagniewski Witold , Boers Niklas , Cook Eliza , Fohlmeister Jens , Goswami Bedartha , Marwan Norbert , Rasmussen Sune Olander , Sime Louise , Svensson Anders
Published: March 2020

Although the Earth system is described to react relatively abruptly to present anthropogenic forcings, the notion of abruptness remains questionable as it refers to a time scale that is difficult to constrain properly. Recognizing this issue, the tipping elements as listed in Lenton et al. (2008) rely on long-term observations under controlled conditions, which enabled the associated tipping points to be identified. For example, there is evidence nowadays that if the rate of deforestation from forest fires and the climate change does not decrease, the Amazonian forest will reach a tipping point towards savanna (Nobre, 2019), which would impact the regional and global climate systems as well as various other ecosystems, directly or indirectly (Magalhães et al., 2020). However, if the present tipping elements, which are now evidenced, are mostly related to the present climate change and thus directly or indirectly related to anthropogenic forcing, their interpretation must still rely on former cases detected in the past, and especially from studies of abrupt climatic transitions evidenced in paleoclimate proxy records. Moreover, recent studies of past changes have shown that addressing abrupt transitions in the past raises the issue of data quality of individual records, including the precision of the time scale and the quantification of associated uncertainties. Investigating past abrupt transitions and the mechanisms involved requires the best data quality possible. This can be a serious limitation when considering the sparse spatial coverage of high resolution paleo-records where dating is critical and corresponding errors often challenging to control. In theory, this would therefore almost limit our investigations to ice-core records of the last climate cycle, because they offer the best possible time resolution. However, evidence shows that abrupt transitions can also be identified in deeper time with lower resolution records, but still revealing changes or transitions that have impacted the dynamics of the Earth system globally. TiPES Work Package 1 will address these issues and collect paleorecords permitting to evidence the temporal behavior of tipping elements in past climates, including several examples.

Lenton T. et al. (2008). PNAS 105, 1786-1793.

Nobre C. (2019). Nature 574, 455.

Magalhães N.d. et al. (2020). Sci. Rep. 16914 (2019) doi:10.1038/s41598-019-53284-1

This work is performed under the TiPES project funded by the European Union’s Horizon 2020 research and innovation program under grant agreement # 820970
AQSens: An Interoperable Platform Integrating Citizen Science and Authoritative Air Quality Data
Authors: Jirka Simon , Jürrens Eike Hinderk , Gräler Benedikt , Hollmann Carsten , Kotsev Alexander , Gerboles Michel , Borowiak Annette , Schade Sven
Published: March 2020

Over the last few years there have been many activities to evaluate and use air quality measurements gathered by lower cost devices. This is especially intended to complement the coverage of official air quality measurement networks that deliver authoritative air quality data. Examples of such activities include the AirSensEUR project of the Joint Research Centre (JRC), luftdaten.info, or hackAIR. Combining the data from multiple sources remains a challenge for utilising the full potential of those developments.

With this presentation we aim to introduce the development of an interoperable data platform that allows to integrate both authoritative as well as citizen science air quality measurements. Our presentation will cover especially the following aspects:

Interoperability: For sharing the collected data and to avoid the creation of isolated data silos, it is important to use open interfaces and data encodings. In case of the AQSens project, this comprises the provision of INSPIRE-compliant Download Services based on the SensorThings API (STA) and Sensor Observation Service (SOS) standards of the Open Geospatial Consortium.

Data analytics: Besides providing access to the raw data, different types of data analysis are necessary. On the one hand this comprises the validation of incoming citizen science data in conjunction with corresponding authoritative data sources. On the other hand, the aim is to provide a tool for further data analysis on top of the collected data. For this purpose we show, how the R programming language can be linked to the Sensor Web Server via a dedicated R package (sos4R).

Data visualisation: Finally, for enabling the visual exploration of the collected data, a Web-based client application will be provided. This allows users to connect to the published air quality Data Download Services (in this case the OGC SensorThings API) and to request graph-based time series visualisations combining data from potentially different sources.

In summary, our presentation will show how existing interoperability standards as well as Web technologies can be used for building a Cloud-ready data platform (i.e. relying on Docker) that enables the collection, management, analysis, and visualisation of both Citizen Science and authoritative air quality data.
A Framework for Using Economic Cost-Benefit Analysis in Watershed Conservation, an Experience in Taiwan
Authors: Liang Chung-Yuan , You Jiing-Yun
Published: March 2020

Cost-benefit analysis (CBA) is often applied at different levels of decision supports. CBA is a systematic approach to estimate the strengths and weaknesses of alternatives for decision makings. In many countries, CBA is required by law and regulation in different fields, including policy-making and public investment. The benefits of practicing the management of watershed conservation also need to be quantified so that decision-makers can understand engineering projects better. Applying CBA in watershed conservation can provide a comparison of total economic gains and losses resulting from practices and reveal impacts on different aspects with economic principles. Nevertheless, to quantify the benefits derived from watershed conservation, an array of technical relationships in various aspects which is still unclear requires to be developed. For this concern, this study examined several perspectives of watershed conservation to propose the framework of CBA in watershed conservation for Taiwan. In this study, we focused on four main kinds of sediment control facilities including check dam, embankment, slope protection, and groundsill work, and described the effect of sediment conservation based on theoretical sediment processes in spatial as well as temporal. We further analyzed their utilities from the perspective of the water supply. In addition to sediment control estimations, this study also determined some economic factors which were not determined in the past. We yielded a demand curve of raw water from the water supplying data and calculated a social discount rate from government bond rates. Also, we suggested adopting a general extreme value method to investigate the benefit under an extreme turbidity event and adopting an alternative costing method to estimate the water quality improvement benefits. This framework is successfully applied in Taiwan for the evaluation of watershed conservation projects. With this framework, engineers could perform economic CBA for reservoir watershed conservations more efficiently, practically, and precisely.

Keywords: Watershed conservation, Economic cost-benefit analysis, Sediment control, Reservoir management
Venice lagoon salt marsh vulnerability and halophytic vegetation vertical migration in response to sea level rise
Authors: Yang Zhicheng , Silvestri Sonia , Marani Marco , D’Alpaos Andrea
Published: March 2020

Salt marshes are biogeomorphic systems that provide important ecosystem services such as carbon sequestration and prevention of coastal erosion. These ecosystems are, however, threatened by increasing sea levels and human pressure. Improving current knowledge of salt-marsh response to changes in the environmental forcing is a key step to understand and predict salt-marsh evolution, especially under accelerated sea level rise scenarios and increasing human pressure. Towards this goal, we have analyzed field observations of marsh topographic changes and halophytic vegetation distribution with elevation collected over 20 years (between 2000 and 2019) in a representative marsh in the Venice lagoon (Italy).

Our results suggest that: 1) on average, marsh elevation with respect to local mean sea level decreased , (i.e. the surface accretion rate was lower than the rate of sea level rise); 2) elevational frequency distributions are characteristic for different halophytic vegetation species, highlighting different ecological realized niches that change in time; 3) although the preferential elevations at which different species have changed in time, the sequence of vegetation species with increasing soil elevation was preserved and simply shifted upward; 4) we observed different vegetation migration rates for the different species, suggesting that the migration process is species-specific. In particular, vegetation species colonizing marsh edges (Juncus and Inula) migrated faster facing to changes in sea levels than Limonium and Spartina , while Sarcocornia was characterized by delayed migration in response to sea level changes. These results bear significant implications for long-term biogeomorphic evolution of tidal environments.
Cloud, radiation, and surface heat flux simulations using Polar WRF with 3DVAR
Authors: Kim dae hui , Kim Hyun Mee , Hong Jinkyu
Published: March 2020

In the Arctic region, cloud is an important factor affecting surface radiation and heat flux. Despite the development of cloud microphysics schemes in the Polar WRF, clouds in the Arctic region still have uncertainties. In this study, the possibility of improving cloud simulations by using data assimilation (DA) and its effects on the enhancement of the forecast accuracy for surface fluxes and meteorological variables are evaluated. The experimental period is from 1 to 19 September 2017.

Forecasts from both the cold start experiment without DA and the warm start experiment with DA underestimated summer arctic clouds. When satellite radiances (AMSU-A and MHS) were assimilated at the analysis time, the distribution and quantity of water vapor were simulated more realistically, which results in the improvement of cloud simulations at the forecast time. As a result, the 25–30 hour forecast error of the downward shortwave (longwave) radiation flux in the warm start experiment which assimilated both conventional observations and satellite radiance data was reduced by 8.1% (12.7%), compared to that in the cold start experiment. The 25–30 hour forecast error of the upward latent (sensible) heat flux in the warm start experiment was also reduced by 7.8% (3.3%), compared to that in the cold start experiment. For the 2 m temperature and 10 m wind, the forecast error with DA was less than that without DA at almost all observation stations. More detailed results will be presented in the conference.

Acknowledgments

This work was supported by the Korea Polar Research Institute (KOPRI, PN20081) and the Korea Meteorological Administration Research and Development Program under grant KMI2018-03712. The simulations are mostly carried out by utilising the supercomputer system supported by the National Center for Meteorological Supercomputer of Korea Meteorological Administration (KMA).
Estimating snow line elevation using publicly available webcam images and Sentinel-2 snow cover maps
Authors: Portenier Céline , Hasler Martina , Gascoin Simon , Wunderle Stefan
Published: March 2020

Publicly available webcam images offer an enormous potential to study the variability of snow cover on a high spatio-temporal scale. Such cameras allow detailed analyses of snow cover on steep slopes due to their oblique view on the mountains and can provide snow cover information even under cloudy weather conditions. Our webcam-based snow cover monitoring network comprises several hundreds of webcams and enables to gather snow cover information over a large area with a minimum amount of manual user input. This information can serve as a reference for improved validation of satellite-based approaches, as well as complement satellite-based snow cover retrieval, in particular under cloudy weather conditions. Here, we present a framework to estimate the regional snow line elevation in the Swiss Alps. The snow line elevation is an important indicator of snow cover in mountainous regions and can be used, for example, as an input for hydrological modeling or to study the seasonality of river discharge. We compare and combine snow line retrieval from Sentinel-2 snow cover maps and webcam-based snow cover information to analyze regional differences in the spring snowmelt period. Since cloud cover is an important factor that affects the quality of satellite-based snow cover products, the combination with snow information from webcams can improve the accuracy and can fill temporal gaps, especially during recurrent cloud cover. Furthermore, we present a method to detect cloud cover in webcam images and discuss limitations of webcam-based snow cover monitoring.
Long-range air transport in Northern Eurasia: Seasonal ozone variations and implications for regional ozone budget
Authors: Shtabkin Yury , Moiseenko Konstantin , Skorokhod Andrey , Berezina Elena
Published: March 2020

Effect of photochemically active species emissions on near-surface air composition in industrial regions is non-local and in many cases can be traced in transcontinental scale. Largescaled plumes of polluted air defined by observations of tracer species on background stations and calculations with chemical-transport models are examples of this effect. In this work we use GEOS-Chem chemical transport model to make an assessment of influence have anthropogenic and biogenic emissions in Europe, European territory of Russia (ETR) and Siberia on total ozone generation taking into account common non-linear properties of O3–NOx–СО–VOC system. It is shown that increasing of ozone production rate due to regional anthropogenic emissions of NOx leads to substantial (up to 20 ppbv) increase of near-surface ozone concentrations in mid-latitudes traced up to 120E. The predominant role of long-range air transport against regional sources of photochemical ozone production was determined for the most part of European Russia and Siberia.
We also make a numerical assessment of ozone balance in Europe, ETR and Siberia. Annual ozone total mass in lower troposphere (from surface to 800 hPa) for Europe, ETR and Siberia depending on region is 1.5–2.4 Tg in warm period (1 April – 30 September) and 1.3–2.2 Tg in cold period (1 October - 31 March). Ozone production in chemical processes with a high degree of accuracy (about 99%) is balanced by total atmospheric transport, while absolute variations in O3 total mass do not exceed 0.5 Tg/year in Europe and 0.4 Tg/year in Siberia.
This work was supported by the Russian Foundation for Basic Research under grant 18-35-20031.
Surface Meteorology and Air–Sea Fluxes in the Southwestern Tropical Atlantic Ocean
Authors: Dourado Marcelo , Lentini Carlos
Published: March 2020

 Recent studies suggest that the Tropical Atlantic Warm Pool (PQAT) contributes to modulate the variability of the ZCIT in the Atlantic Ocean basin and, consequently, the precipitation regime in Brazilian northeastern. Hourly surface meteorology observations from the PIRATA buoy at 19°S, 34°W from August 2010 to November 2018 was used to characterize and estimate the exchanges of heat, freshwater, and momentum between the ocean and the atmosphere over the Tropical. We focus here on recent efforts to observe the surface meteorology and air-sea fluxes using those data to gain insights into how atmospheric variability may govern the structure and variability of the upper ocean there at diurnal and seasonal time scales. The surface fluxes are calculated using the COARE 3.0 algorithm, positive values are to the ocean. Using the observations collected from the mooring deployments, we developed a good understanding of the annual march of the surface forcing of the ocean by the atmosphere. During spring (March, April) mean SST and air temperature are the hottest of the year, 28oC and 26.7oC, respectively; SST is greater than air temperature all over the year, 1oC on average. Wind speed is minimum, the air is drier and there is a peak of precipitation in April. During the autumn (August, September), mean SST and air temperature are the coldest of the year, 24.5oC and 23.6oC. Wind speed increases form 4.4m/s in March to 5.9 m/s in December. The monthly averaged incoming shortwave radiation in July was the lowest of the whole year and maximum in December. Net longwave radiation shows an inverse variability, i.e., maximum in the winter, minimum in the summer. This occurs because the winter air is drier than in the summer. Sensible heat flux is maximum in August due to the increase of the wind speed and an increase of the air-sea temperature difference. Latent flux is higher between April and August due to an increase in wind speed and a drier atmosphere. In the summer the humidity increases and, consequently, the latent heat flux diminishes. Finally, the net heat flux, positive between January and March, is negative between April and August (maximum -36W/m2 in July ) and, again, positive between September and December, maximum +116 W/m2 in December.
Estimation of hail occurrence from satellite, lightning and radar data in Croatia
Authors: Jelic Damjan , Mikus Jurkovic Petra , Malecic Barbara , Vodaric Surija Barbara , Telisman Prtenjak Maja , Strelec Mahovic Natasa
Published: March 2020

In western and central regions of Croatia, as well as Istria peninsula, hail activity is monitored by hail pads and hail observations, the analyses of which shows that these regions have a significant frequency of high-intensity hail events. On 25 June 2017 weather conditions were favorable for development of several MSC in the region, some of which organized into a squall lines, causing severe weather effects over larger portion of Croatia. Hail pad networks reported 46 records of hail all over the region introducing one of the largest number of records in one day. Hail size varied between 1 and 2 cm with exception of 2 stations recording 2.5 and 3.1 cm diameters. Since the episode covers large area and offers high number of hail pad data it is suited for testing other indirect methods for assessment of hail. We are investigating capabilities of satellite products based on HRV and colored enhanced IR 10.8 µm channels (overshooting tops, plume, cold ring...), lightning activity and lightning jump activity to estimate hail occurrence and for the first time for Croatia, inspect radar products in assessing hail intensity.
Which method should we use to draw empirical rainfall thresholds for landslide early warning?
Authors: Peres David Johnny , Cancelliere Antonino
Published: March 2020

Landslide thresholds determined empirically through the combined analysis of rainfall and landslide data are at the core of early warning systems. Given a set of rainfall and landslide data, several methods do exist to determine the threshold: methods based on triggering events only, methods based on the non-triggering events only, and methods based on both type of rainfall events. The first are the most commonly encountered in literature. Early work determined the threshold by drawing the lower envelope curve of the triggering events “by eye”. More recent work used more sophisticated statistical approaches in order to reduce the subjectivity. Among these methods, the so-called frequentist method has become prominent in the literature. These methods have been criticized because they do not account uncertainty, i.e. the fact that there is not a clear separation between rainfall characteristics of triggering and non-triggering events. Hence, methods based on the optimization of Receiver operating characteristic indices – count of true and false positives/negatives – have been proposed. One of the first methods proposed in this sense referred to the use of Bayesian a-posteriori probability, which is the same of using the so-called ROC Precision index. Others have used the True Skill Statistic. On the other hand, use of non-triggering events only has been discussed just by a few researchers, and the potentialities of this way to proceed have been scarcely explored.

The choice of the method is usually dictated by external factors, such as the availability of data and their reliability, but it should also take into account of the theoretical statistical properties of each method.

Given this context, in the present work we compare, through Monte Carlo simulations, the statistical properties of each of the above-mentioned methods. In particular, we attempt to provide the answer to the following questions: What is the minimum number of landslides that is needed to perform a reliable determination of thresholds? How robust is the method for drawing the threshold – i.e. their sensitivity to artifacts in the data, such as exchanges of triggering events with non-triggering events due to incompleteness of landslide archives? What are the performances of the methods in terms of the whole ROC confusion matrix?

The analysis is performed for various levels of uncertainty in the data, i.e. noise in the separation by triggering and non-triggering events. Results show that methods based on non-triggering events only may be convenient when few landslide data are available. Also, in the case of high uncertainty in the data, the performances of methods based on triggering events may be poor compared to those based on non-triggering events. Finally, the methods based on both triggering and non-triggering events are the most robust.
Strongly structured radio emission observed by LOFAR on August 25, 2014
Authors: Magdalenic Jasmina , Marque Christophe , Fallows Richard , Mann Gottfried , Vocks Christian , Zucca Pietro
Published: March 2020

On August 25, 2014, NOAA AR 2146 produced the M2.0 class flare (peaked at 15:11 UT). The flare was associated with a halo CME and a radio event observed by LOFAR (the LOw-Frequency Array). The radio event consisted of a type II, type III and type IV radio emissions. In this study, we present LOFAR observations of the type II (radio signatures of shock waves) and type III bursts (radio signatures of fast electron beams propagating along open or quasi open field lines).  Both, the type II burst and type III bursts show strong fragmentation of the radio emission. Although fine structures of type II bursts were already reported, the richness of the fine structures observed in the studied event is unprecedented. We found type II fine structures morphologically very similar to the ones sometimes seen superposed on type IV continuum emission, and similar to simple narrowband super short structures (Magdalenic et al., 2006). The group of type III bursts was as usually, observed during the impulsive phase of the flare. The high frequency/time resolution LOFAR observations reveal that only few of the observed type III bursts have a smooth emission profile, and the majority of bursts is strongly fragmented. Surprisingly, fine structures of some type III bursts show similarities to the fine structures observed in the type II burst, but on a smaller frequency scale. Some of the type III bursts show a non-organized patchy structure which gives an indication on the possibly related turbulence processes. We show that these LOFAR observations bring completely new insight and pose a new challenge for the physics of the acceleration of electron beams and associated emission processes.
Long-term variability of central Andes precipitation in the IPSL-CM6A-LR model: origin and causes.
Authors: Villamayor Julián , Khodri Myriam , Jebri Beyrem , Rivera Juan A. , Naranjo Elizabeth B. , Daux Valérie
Published: March 2020

The central Andes have undergone a drying trend over the last decades with adverse socioeconomic effects throughout the south of Argentina and Chile. The long-term precipitation variability in this region has been associated with modes of sea surface temperature (SST) and atmospheric circulation variability acting at decadal-to-multidecadal timescales, such as the Interdecadal Pacific Oscillation and the Southern Annular Mode. More recently, the drying long-term trend of precipitation in central Andes has also been linked to a poleward expansion of the Hadley Cell (HC) in the Southern Hemisphere over the last decades. In previous works several possible causes of the HC expansion have been proposed, involving both external forcing (e.g., greenhouse gases and ozone depletion effects) and internal climate variability (e.g., SST and atmospheric modes).

In this work the origin and the causes of the central Andes precipitation variability at decadal-to-longer time scales are studied. For this purpose, the main modes of climate variability that modulate the central Andes precipitation are first identified. Then the changes of these modes and their influence on precipitation are attributed to different factors of external forcing or to internal climate variability. For this analysis large ensembles of different climate simulations and detection-and-attribution experiments performed with the IPSL-CM6A-LR model are used.
Tracing the global consumption of carbon at subduction zones over the last 230 million years
Authors: Mather Ben , Müller Dietmar , Keller Tobias
Published: March 2020

Chemical heterogeneities in the mantle are typically introduced by recycling oceanic lithosphere through subduction, which transports volatiles into the mantle. The provenance of volatiles, such as carbon, with the down-going plate is varied; here we show how the spatial distribution of carbon evolves through time with the motion of the tectonic plates. Carbon is sequestered at mid-ocean ridges, as new oceanic crust forms, and is transported similar to a conveyor belt until it is recycled at subduction zones. We budget the amount of carbon that has been recycled at subduction zones over the past 230 million years using a global plate reconstruction. The present-day distribution of in-plate carbon, taking into consideration the last 230 million years of plate influx, is predominantly distributed in the Atlantic. In contrast, most of the carbon that was sequestered in Pacific seafloor from 230 Ma has since been subducted. Therefore, it is likely that the carbon stored in Pacific seafloor has played an important role in stimulating volcanic activity along the Ring of Fire.
UKCP: Understanding uncertainty in future changes in precipitation extremes at convection-permitting scale
Authors: Fosser Giorgia , Kendon Elizabeth , Chan Steven , Stephenson David
Published: March 2020

Convection-permitting models (CPMs) provide a better representation of sub-daily precipitation statistics and convective processes, both on climate and NWP time scales, mainly thanks to the possibility to switch off the parameterisation of convection. The improved realism of these models gives us greater confidence in their ability to project future changes in short-duration precipitation extremes.

The first 12-member ensemble of convection-permitting climate simulations over the UK was completed within the latest updates to the UK Climate Projections (UKCP). The 20-year long CPM simulations for present-day and end of century periods are nested in an ensemble of regional climate model (RCM) simulations over Europe driven by a global climate model ensemble. In the driving ensembles, uncertain parameters in the model physics are varied within plausible bounds to sample uncertainty. Although no perturbations are applied directly to the CPMs, this project allow us to provide a first-ever estimate of uncertainty at convection-permitting scale and thus provide UK risk assessment studies with more reliable climate change projections at local and hourly scales.

Here we will present results looking at the uncertainty in future changes in hourly precipitation extremes across the CPM ensemble, and how this differs from the driving RCM ensemble.
Operational Near-real Time Drought Monitoring Using Global Satellite Precipitation Estimates
Authors: Prat Olivier , Courtright Alec , Leeper Ronald , Nelson Brian , Bilotta Rocky , Adams James , Ansari Steve
Published: March 2020

We present an operational near-real time drought monitoring framework on a global scale that uses satellite quantitative precipitation estimates from the NOAA/CDR program (CMORPH-CDR, PERSIANN-CDR). Monthly and daily Standardized Precipitation Indexes (SPI) are computed for various time scales over the entire period of record of the respective datasets. The near-real time availability of CMORPH-CDR permits for a daily update of the global drought conditions starting in 1998, while the longer period of record of PERSIANN-CDR allows to compute global drought conditions since 1983. The SPI sensitivity to different precipitation datasets and to various lengths of record is quantified. Results indicated that both monthly and daily SPIs computed with both CDRs presented the same timing and area for the major droughts episodes over the continental United States as well as for selected drought events around the globe. Furthermore, the difference resulting from the use of the two-parameter Gamma distribution (McKee et al. 1993) and the three-parameter Pearson III distribution (Guttman 1999) is evaluated. The global mapping of the different distribution parameters (2 and 3 parameters respectively for the Gamma and Pearson III distributions) informs us on how to optimally compute the SPI in areas experiencing too much or too little rainfall. Both CMORPH-CDR and PERSIANN-CDR SPIs are evaluated primarily over CONUS where long-term drought monitoring products based on in-situ data exists such as the United States Drought Monitor (USDM) and the nClimGrid derived SPI. A publicly available interactive visualization tool that provides access to global drought information is also presented. The tools is intended to fill some of the drought monitoring information gaps around the globe. A variety of visualization techniques are used to aid in the interpretation of global drought indices while interactive functionality allows users to focus on a specific region and time-scale of interest. Additional information for region specific drought monitoring resources is also provided to help users access regional drought monitoring information.
Quantifying the contribution of Tibetan Plateau (TP) uplift and CO2 decrease for late Eocene and present day climate with emphasis on Meridional Ocean Circulation.
Authors: Ramstein Gilles , Su Baohuang , Jiang Dabang , Zhang Ran , Sepulchre Pierre
Published: March 2020

Since late Eocene (40 Ma), atmospheric CO2 drastically decreased from 4 to 1 PAL.  During this period, two major geological events occurred over Asia: the India/Asia collision producing the uplift of large mountain ranges and the shrinkage of the Paratethys (G. Ramstein et al., Nature, 1997; F. Fluteau et la., JGR, 1999). Most modeling studies focused first on the sensitivity of AGCMs to the Tibetan plateau elevation through simple experiments; then new simulations accounting for more realistic description of paleogeographic reconstructions have been published. Indeed, progress has been done concerning both: paratethys evolution (Z. Zhang et al., PAL PAL PAL, 2007), chronology of uplifts of different mountain ranges (R. Zhang et al., JGR, 2017) and large TP northern shift (R. Zhang et al., EPSL, 2018), but again these experiments focused mostly on atmosphere circulation and hydrologic pattern (monsoon evolution) not specifically on their impacts on ocean dynamics.

Therefore, this study aims to investigate the role of TP uplift on Northern hemisphere ocean circulation through long runs of coupled ocean atmosphere model to analyze its impact not only on atmosphere but also on ocean dynamics. We provided a series of sensitivity simulations disentangling the two different factors, pCO2 decrease and TP uplift. These simulations allow analyzing the response to TP uplift in a warm high CO2 world as Eocene and in a cold low CO2 world as Quaternary (B. Su et al., CP, 2018).

We describe how the TP uplift through changes of atmosphere (surface winds and planetary waves) and hydrology (runoff and precipitation/evaporation patterns) modified the meridional circulation in the North Atlantic and Pacific basins with emphasize on the causes of the two different basins sensitivity to this major mountain range uplift in both contexts.
Morphological controls on groundwater residence times of shallow aquifers
Authors: Gauvain Alexandre , Leray Sarah , Marçais Jean , Vautier Camille , Aquilina Luc , de Dreuzy Jean-Raynald
Published: March 2020

In shallow aquifers, including weathered zones characteristic of crystalline geologic basements, subsurface flows strongly depend on the geomorphological evolution of landscapes as well as on the geological heterogeneity structures. Yet, it remains largely unknown how geomorphology and geology shape the residence times in the aquifers and the transit times  in the receiving stream water bodies.

We investigate this issue with 3D synthetic models of free aquifers. Aquifer models represent hillslopes from the river to the catchment divide with constant slopes, evolving widths and depths. They are submitted to uniform and constant recharge. All flows end up in the river either through the aquifer or through the surface as return flows and saturation excess overland flows. Steady-state flows and transit times to the river are simulated with Modflow and Modpath (Niswonger et al., 2011; Pollock, 2016). The mean and standard deviation of the transit time distribution are systematically determined as functions of the hillslope shapes (convergent or divergent to the river, thinning or thickening to the river) and the ratio of recharge to hydraulic conductivity.

We show that the mean transit time distribution is a function of the geology through the volume of the aquifer divided by the recharge rate even in the presence of seepage areas. The standard deviation of the transit time distribution is a function of the geomorphology through the bulk organization of the groundwater body from the river to the catchment divide. Without seepage, the organization of the groundwater body is efficiently characterized by its barycenter. When seepage occurs, the standard deviation becomes also sensitive to the extent of the seepage zone.

We conclude that mean of the transit time distribution is primarily determined by geology through the accessible aquifer volume while the ratio of the standard deviation to the mean (coefficient of variation) is rather determined by geomorphology through the profile of the aquifer from the river to the catchment divide. We discuss how geophysical data might help to determine the groundwater body and assess the transit time distribution. We illustrate these findings on natural aquifers in the crystalline basements of Brittany-Normandy (France).

References

Niswonger, R.G., Panday, S., Ibaraki, M., 2011. MODFLOW-NWT, A Newton formulation for MODFLOW-2005.

Pollock, D.W., 2016. User guide for MODPATH Version 7—A particle-tracking model for MODFLOW (Report No. 2016–1086), Open-File Report. Reston, VA. https://doi.org/10.3133/ofr20161086
Contribution of clouds radiative forcing to the local surface temperature variability
Authors: Rojas Oscar , Chiriaco Marjolaine , Bastin Sophie , Ringard Justine
Published: March 2020

The local contribution of clouds to the surface energy balance and temperature variability is an important topic in order to apprehend how this intake affects local climate variability and extreme events, how this contribution varies from one place to another, and how it evolves in a warming climate. The scope of this study is to understand how clouds impact temperature variability, to quantify their contribution, and to compare their effects to other surface processes. To do so, we develop a method to estimate the different terms that control temperature variability at the surface (∂T2m /∂t) by using this equation: ∂T2m /∂t=R+HA+HG+Adv where R is the radiation that is separated into the cloud term (Rcloud) and the clear sky one (RCS), HA the atmospheric heat exchange, HG the ground heat exchange, and Adv the advection. These terms are estimated hourly, almost only using direct measurements from SIRTA-ReOBS dataset (an hourly long-term multi-variables dataset retrieved from SIRTA, an observatory located in a semi-urban area 20-km South-West of Paris; Chiriaco et al., 2019) for a five-years period. The method gives good results for the hourly temperature variability, with a 0.8 correlation coefficient and a weak residual term between left part (directly measured) and right part of the equation.

A bagged decision trees analysis of this equation shows that RCS dominates temperature variability during daytime and is mainly modulated by cloud radiative effect (Rcloud). During nighttime, the bagged decision trees analysis determines that Rcloud is the term controlling temperature changes. When a diurnal cycle analysis (split into seasons) is performed for each term, HA becomes an important negative modulator in the late afternoon, chiefly in spring and summer, when evaporation and thermal conduction are increased. In contrast, HG and Adv terms do not play an essential role on temperature variability at this temporal scale and their contribution is barely considerable in the one-hour variability, but still they remain necessary in order to obtain the best coefficient estimator between the directly measured observations and the method estimated. All terms except advection have a marked monthly-hourly cycle.

Next steps consist in characterize the types of clouds and study their physical properties corresponding to the cases where Rcloud is significant, using the Lidar profiles also available in the SIRTA-ReOBS dataset.
Impact of an Interactive SST on the Convective Aggregation Process
Authors: Shamekh Sara , Muller Caroline , Duvel Jean-Philippe , D'Andrea Fabio
Published: March 2020

The spontaneous aggregation of convective clouds over a moist portion of the domain is ubiquitous in cloud resolving model simulations. This phenomenon significantly reduces the domain mean total water vapor and enhances the outgoing long radiation. In this study we use the system of atmospheric modeling (SAM) in a radiative-convective equilibrium (RCE) setup in order to investigate the impact of an interactive sea surface temperature (SST) on the aggregation progress. We use a slab ocean (with depth of 5, 10 and 50 m) with constant target SST to which the domain mean SST is relaxed. Our results show that, consistent with previous studies, an interactive SST delays the aggregation with a larger impact for a shallower slab. This effect is enhanced for a smaller target SST.

The aggregation proceeds by the expansion of non-convective dry areas. Before aggregation, dry areas are associated with warmer surface due to enhanced short-wave radiation. During and after the aggregation, a single large dry patch develops and is associated with a colder surface. This cooling is due to a reduction in downwelling long-wave radiation and to enhanced latent heat flux due to drier boundary layer. The edge of the dry patch has warm SST anomaly forming a ring of warm water around it that favors divergence of low-level moist air from the dry patch and accelerates dry patch expansion. This is favored by a positive surface pressure anomaly (PSFC) in the dry patch.

Therefore, at first, the warm SST anomaly opposes the divergent flow from dry regions, opposing the aggregation. Then the cold SST anomaly that develops in dry regions increases the divergent flow and favors the dry patch expansion. For a small ocean slab, the warm SST anomaly that develops in the dry areas at early times inhibits the dry patch expansion and can significantly delay the beginning of aggregation.
Combination effects of temperature and pressure on the petrophysical properties of bitumen-bearing carbonate rocks: insight for the Majella reservoir (Italy)
Authors: Ruggieri Roberta , Trippetta Fabio
Published: March 2020

Unconventional oils are emerging as an alternative hydrocarbon reserve since conventional oil is depleting nowadays. A kind of unconventional oil is bitumen, which is characterized by high density, high viscosity and API gravity less than 10° and these physical properties are temperature sensitive. Therefore, an accurate assessment of variation in petrophysical properties of bitumen as a function of temperature and pressure is interesting in oil exploration industry.

In this work we investigated the role of heavy hydrocarbons (HHC) in changing petrophysical properties of carbonate-bearing rocks of the Majella reservoir performing seismic wave velocity measurements at increasing temperature. The investigated lithology belongs to the Bolognano formation that outcrops naturally in saturated and unsaturated conditions in the northwest sector of Majella Mountain (in Central Italy).

We conducted ultrasonic measurements of compressional and shear wave velocities on HHC-bearing carbonate samples showing different bitumen content and porosity between 10% and 19%. Firstly, we characterized bitumen density by HCl dissolution of the hosting rock, that resulted to be included between 1.14 and 1.26 gr/cm3 at ambient temperature. Then, we calculated HHC content of our samples, spanning from 2% (low HHC-bearing sample) to 16% (high HHC-bearing sample). Our acoustic velocities point out an inverse relationship with temperature. P- and S-wave velocities depict a distinct trend with increasing temperature depending on the amount of HHC content. Indeed, samples with the highest HHC content show a larger gradient of velocity changes in the temperature range of about 60°-50° C, suggesting that bitumen can be in a fluid state. Conversely, below about 50° C the velocity gradient is lower because, at this temperature, bitumen can change its phase in a solid state. Currently, we are analysing the coupling effect of temperature and pressure on HHC-bearing carbonate samples to test the acoustic response of the investigated samples simulating the reservoir conditions.

Our preliminary results highlight a strongly temperature dependence for HHC-bearing carbonate properties and bitumen influences the acoustic response of carbonate rocks. Such petrophysical characterization would provide a better link between seismic parameters and the hydrocarbon properties with important implications for reservoir characterization from seismic data and for production monitoring. 

 