bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the role of accessory minerals in the Sm-Nd isotopic evolution of ancient rocks: An in-situ LA-(MC)-ICP-MS approach
Authors: Hammerli Johannes
Published: March 2020

The long-lived radiogenic isotope systems Lu-Hf and Sm-Nd have been widely used by geochemists to study magma sources and crustal residential times of (igneous) rocks in order to understand how early crust formed and to model the production rate and volume of continental crust on global and regional-scales during the last ~4.4 Ga. However, while throughout most of Earth’s history Nd and Hf isotope signatures in terrestrial rocks are well correlated due to their very similar geochemical behavior, some of Earth’s oldest rocks show an apparent inconsistency in their Nd and Hf isotope signatures. While Hf isotopes in early Archean rocks are generally (near) chondritic, Nd isotope signatures can be distinctly super- or sub-chondritic. The super-chondritic Nd isotope values in Eoarchean samples would suggest that these rocks are derived from a mantle reservoir depleted by prior crust extraction. The chondritic Hf isotope values, on the other hand, support a mantle source from which no significant volume of crust had been extracted. While a range of different processes, some of them speculative, might explain this Hf-Nd isotope paradox, recent research [1, 2] has shown that relatively simple, post-magmatic, open-system processes can explain decoupling of the typically correlative Hf-Nd isotope signatures. This talk will focus on the importance of identifying Nd-bearing accessory minerals in (Archean) rocks to understand how the Sm-Nd isotope system is controlled and how in situ isotope and trace element analyses by LA-(MC)-ICP-MS in combination with detailed petrographic observations help to understand when and via which processes the two isotope systems become decoupled. Reconstructing the isotopic evolution of the different isotope systems since formation of the protoliths has important implications for our understanding of early crust formation and questions some of the proposed current models for early crust extraction from the mantle.

 

[1] Hammerli et al. (2019) Chem. Geol 2; [2] Fisher et al. (2020) EPSL
Usage of visual and near-infrared spectroscopy to predict soil properties in forest stands
Authors: Thomas Felix , Petzold Rainer , Becker Carina , Werban Ulrike
Published: March 2020

There is a high demand for information about soil conditions in forests stands as it is crucial to ensure sustainable management, to maintain ecosystem services, to preserve timber production and establish proper pest management. Nowadays, the main drivers for changes in soil conditions are element input, forest conversion, subsoil liming and changing climate. These drivers influence nutrients and water availability and are challenging current site mapping methods. However, for impact assessment high-resolution and up-to-date information is needed. As laboratory analysis is time consuming and expensive, alternative approaches are preferred.

The project DIGI-Humus uses methods of reflectance spectroscopy in the visual and near-infrared-region of the electromagnetic spectrum for indirect measurement and prediction of physical and chemical soil properties in forest stands. For this purpose, spectral data were collected under laboratory conditions to build a database of forest soils. We used retained samples from Saxony soil survey, measuring both Oh and Ah horizons. To ensure data quality, we developed our own protocol based on literature review and self-conducted test measurements. The data has been used to successfully calibrate regression models based on different forest types and soil horizons to predict the soil parameters C and N content, C/N ratio and pH-value.

To improve model performance and test its generalization capability, the created library has been extended with new samples from a field campaign conducted in 2019 at an additional local test site. Using this data, the impact of adding new information to the modelling process and the robustness of the models could be evaluated.

The results of this research will be used to assess forest sites regarding nutrients availability, as basis for the development of site specific management strategies and to enhance and improve current methods of periodic site mapping of forest stands.
Coupling of Arctic ozone and stratospheric dynamics and its influence on surface climate: the role of CFC concentrations.
Authors: Friedel Marina , Chiodo Gabriel , Muthers Stefan , Anet Julien , Stenke Andrea , Peter Thomas
Published: March 2020

Arctic stratospheric ozone has been shown to exert a statistically significant influence on Northern Hemispheric surface climate. This suggests that Arctic ozone is not only passively responding to dynamical variability in the stratosphere, but actively feeds back into the circulation through chemical and radiative processes. However, the extent and causality of the chemistry-dynamics coupling is still unknown. Since many state-of-the-art climate models lack a sufficient representation of ozone-dynamic feedbacks, a quantification of this coupling can be used to improve intra-seasonal weather and long-term climate forecasts.

We assess the importance of the ozone-dynamics coupling by performing simulations with and without interactive chemistry in two Chemistry Climate Models. The chemistry-dynamics coupling was examined in two different sets of time-slice simulations: one using pre-industrial, and one using year-2000 boundary conditions. We focus on the impact of sudden stratospheric warmings (SSW) and strong vortex events on stratosphere-troposphere coupling, since these go along with strong ozone anomalies and therefore an intensified ozone feedback.  We compare the runs with and without interactive chemistry.

For pre-industrial conditions, simulations without interactive ozone show a more intense and longer lasting surface signature of SSWs compared to simulations with interactive chemistry. Conversely, for year-2000 conditions, the opposite effect is found: interactive chemistry amplifies the surface signature of SSWs. Following these results, atmospheric CFC concentrations, which differ greatly in the pre-industrial and year-2000 runs, determine the sign of the ozone-circulation feedback, and thus have a strong impact on chemistry-climate coupling. Implications for modeling of stratosphere-troposphere coupling and future projections are discussed.
The neXtSIM-F sea ice forecasting platform
Authors: Williams Timothy , Korosov Anton , Rampal Pierre , Olason Einar
Published: March 2020

The neXtSIM-F forecast system consists of a stand-alone sea ice model, neXtSIM, forced by the TOPAZ ocean forecast and the ECMWF atmospheric forecast, combined with daily data assimilation.

neXtSIM is a novel sea ice model which is able to reproduce sea ice deformation properties and statistics, such as spatial localisation and temporal intermittency,
even at relatively low resolutions. For our forecast we run it at 10km resolution, over a pan-Arctic domain. We assimilate OSISAF SSMI and AMSR2 sea ice concentration products and the SMOS sea ice thickness product by modifying the initial conditions daily and adding a compensating heat flux to prevent removed ice growing back too quickly. 

We present an evaluation of the platform over the period from November 2018 to present, looking at sea ice drift and concentration and extent, and thin ice thickness.

neXtSIM-F is scheduled to become part of the CMEMS Arctic Marine Forecast Center in June 2020.
Continental Hotspots Tracks from Analysis of GOCE Gravity Gradients Data
Authors: Greff-Lefftz Marianne , Panet Isabelle , Besse Jean
Published: March 2020

 Hotspots are thermal instabilities that originate in the mantle and manifest themselves on the surface by volcanism, continental breaks or "traces" observed in the oceans. Theirs effects under the continents are still debated: in addition to a phase of activity associated with surface volcanism, a residual thermal anomaly could persist durably under the lithosphere along the trajectory of the hotspot. For a simple model of thermal anomaly (a parallelogram aligned in a fixed direction), we compute the perturbations of the geoid, of the gravity vector and of the associated gravity gradients, and show that in a coordinate system aligned with the parallelogram, the gravity gradients exhibit a characteristic signal, with an order of magnitude of a few hundred mEotvös, well above the current data detection level. Thus considering four real cases :in North Africa (with Hoggar, Tibesti, Darfur and Cameroon hotspots), in Greenland (Iceland), in Australia (Cosgrove) and in Europe (Eifel), we calculate the paleo-positions of the hotspots for 100 Myr in a reference frame linked to the lithospheric plates, and we build maps of the Bouguer gravity gradients filtered on the spatial scale of a few hundred kilometers (the scale of the hotspot) and oriented along the direction of these trajectories. We clearly detect, in the scale-orientation diagrams, signals aligned in the direction of the movement of the plates on spatial scales of a few hundred kilometers. These preliminary results are very enthusiastic: gradiometric data indeed allow us to follow the tracks of hotspots in the continental lithosphere, for at least 20 Myr.
Turbulent flux estimation in the atmospheric surface layer through flux-gradient similarity during the ALEX17 field campaign
Authors: Martí Belén , Martínez-Villagrasa Daniel , Cuxart Joan
Published: March 2020

Turbulent flux measurements require high frequency sampling in order to characterize appropriately all the variability scales of the atmosphere. A 3D sonic anemometer coupled with a gas detector allows for applying the eddy-covariance method which has become the standard. However, the high cost of this system often implies to look for alternative methods, specially when multiple stations are required. Turbulent fluxes can also be estimated through the flux-gradient similarity theory, requiring observations of mean quantities of (at least) air temperature and humidity at two levels and wind at one height. This approach is more sensitive to the disturbing influence of heterogeneous and complex surfaces and a comparison between methodologies is required under these conditions.

The data used in this study is part of the ALaiz EXperiment 2017-2018 (ALEX17). This campaign was the last within the New European Altas project. It had a duration of over a year with measurements in complex terrain. The location of the experiment is a valley bounded by two mountain ranges that rise 150 m north and over 600 m south. A central site in the centre of the valley was instrumented with a sodar-RASS, an 80-m tower, a surface energy balance (SEB) station with an eddy-covariance system and a surface-layer station (SLS) with the necessary measurements to estimate the turbulent fluxes. In addition, eight supplementary SLS were deployed along the longitudinal and transverse valley axes to characterize the surface layer variability within the valley.

This communication will present a comparison of the friction velocity and sensible heat flux obtained from both the eddy-covariance system and the flux-gradient method at the central site for a time series of 8 months. Friction velocity is highly comparable between methodologies with a correlation of 0.92 and a standard deviation of 0.05. The performance of the sensible heat flux estimation differs between stable and unstable cases, with a correlation of 0.70 and 0.89, respectively, after applying a quality control procedure. The poorer results obtained under stable conditions points out the need for alternative estimations of the sensible heat flux for these cases.
Assessing Sting-Jets in Convection-Permitting Climate Simulations
Authors: Manning Colin , Kendon Elizabeth , Fowler Hayley , Roberts Nigel , Berthou Ségolène
Published: March 2020

This study assesses the added-value offered by a regional convection-permitting climate model (CPM) in its representation of sting-jets (SJs); a mesoscale slanted core of strong winds within a Shapiro-Keyser type of cyclone that can lead to extremely damaging surface wind speeds close to southern side of a cyclone’s centre. Low-resolution climate models cannot resolve SJs, and so estimates of risk posed by extreme winds due to SJs are difficult to determine and will likely be underestimated in coarse-resolution climate simulations.

We analyse three 10-year simulations from the UK Met Office, run at a 2.2km resolution over a European domain. The simulations include a hindcast driven by the ERA-Interim reanalysis dataset (ERAI) for the period 2001-2010, as well as a present day (2001-2010) and future simulation (2100-2109) that follows the RCP8.5 scenario. Both climate simulations are driven by a 25km GCM. To diagnose potential SJ storms in each simulation, we firstly identify cyclone tracks with a cyclone tracking algorithm and apply an objective indicator that identifies the warm seclusion of a Shapiro-Keyser cyclone and the slanted core of strong winds of the sting-jet.

Within this presentation, we will present the objective indicator as well as results of the added value seen in the CPM. In order to identify any added value of the CPM, we analyse differences between the CPM and its respective driving data, in terms of storm severity metrics and their future projections.  An example metric used is the Storm Severity Index that quantifies the overall severity of a storm. In all simulations, the conditional PDF of SSI for sting-jet storms is shifted towards higher values compared to PDF of the SSI from all storms within the studied domain. However, we see little difference in the SSI derived from the CPM and its respective driving model/reanalysis when CPM wind speeds are upscaled to the respective driving reanalysis/GCM grid. In further analysis, we will look to explore the added value at a local scale on the native CPM grid.
Operating an industry-grade quantum differential gravimeter
Authors: Janvier Camille , Ménoret Vincent , Lautier Jean , Desruelle Bruno , Merlet Sebastien , Pereira dos Santos Franck , Landragin Arnaud
Published: March 2020

After three years of development in collaboration with LNE-SYRTE, we report on the development, the integration and the preliminary operation of an industry-grade absolute differential gravimeter. This new generation of instrument goes beyond the possibilities offered by existing gravity gradiometers, as one differential gravimeter measures simultaneously g and the vertical gradient of g [1]. Relying on atom interferometry with cold 87 Rb atoms, a single vertical laser beam simultaneously measures the vertical acceleration experienced by two sets of laser-cooled atoms free-falling from different heights. For each drop, the half-sum of the two vertical accelerations gives access to g and the half-difference to dg / dz. As far as technology is concerned, our differential gravimeter relies on a physical principle and a set of technologies that have already been validated for absolute quantum gravimeters [2].

Our demonstrator is operational since November 2019 and has shown the ability to run continuously for more 18 days without any human attendance.  We will present in detail the experimental results for the measurement of g and dg / dz. Regarding the measurement of the vertical gradient of g, we obtain a short-term sensitivity of 76 E/√t (1E = 10 -9 s -2 = 0.1 µGal/m) and a resolution of a 4 E when data is averaged over 1000 s. Regarding the measurement of g itself, we obtain a short-term sensitivity of 36 µGal/√t and a resolution of a few µGal when data is averaged over 500 s. These are preliminary results and options and future plan to improve the sensitivity and the stability of the measurements will be discussed.

Such quantum differential gravimeter is to our knowledge the only technology that allows for an absolute continuous drift-free monitoring of simultaneously gravity and gravity gradient over timescales from a few minutes to several months.

 

This work has been supported by the DGA, the French Department of Defense.

 

[1] R. Caldani et al., "Simultaneous accurate determination of both gravity and its vertical gradient", Phys. Rev. A 99, 033601 (2019)

[2] V. Ménoret et al., "Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018)
Frontal variability and its impact on chlorophyll in the Arabian Sea
Authors: Wang Yuntao , Ma Wentao , Zhou Feng , Fei Chai
Published: March 2020

Sixteen years satellite observations are used to investigate the frontogenesis, frontal variability and its impact on chlorophyll in the Arabian Sea. Large frontal probability (FP) and high chlorophyll mainly happens near the coast, e.g., near Somalia and Oman, and its value generally decreases with offshore distance. An Empirical Orthogonal Function (EOF) is used to disentangle the spatial and temporal variability of front and chlorophyll. Prominent seasonal cycle of frontal activities is identified, peaking in summer when southwest wind prevails. The seasonality for chlorophyll is same with wind and front near Somalia, which largely impacted by monsoon. During summer, the southwest monsoon drives offshore Ekman transport and induces coastal upwelling. It transports subsurface cold water and nutrients to the surface layer, which generates fronts and enhances chlorophyll, respectively. The frontal activities can be used as an indicator to determine the chlorophyll level that high chlorophyll happens when frontal probability gets higher than 2%. At anomalous field, stronger wind can induce higher frontal activities and chlorophyll. The impact of wind on frontogenesis can extend 1,000km offshore and a simplified linear regression is applied to quantify their relationship. The variability of wind leads chlorophyll by lags increasing with distance, indicating a horizontal offshore transport of coastal water. In winter, the northeast wind is not upwelling favorable, thus the frontal activities and chlorophyll are greatly reduced off Somalia. During this period, large chlorophyll is found in the north off Oman because of mixing, thus its relationship with front is less pronounced. In the upwelling regions, fronts act as an intermedia process that connecting the wind forcing and responses of ecosystem. The frontal activities in Arabian Sea is fundamentally important to improve our understanding of monsoon related ocean dynamics.
The b variability with the Moho depth and the link between aftershocks and afterslip
Authors: Godano Cataldo
Published: March 2020

We have investigated the dependence of the Gutenberg-Richter b parameter on the Moho depth h in many areas of the world. We have found that b increases with h. This observation has be interpreted in terms of aftershocks occurrence. Indeed aftershocks are generated by the stress released by the  afterslip occurred i n the ductile zone beneath the brittle one. The depth of the Moho has been, here, used as an indicator of the coupling between the brittle and the ductile zones. As h increases the coupling increases generating more aftershocks. These are characterized by an higher b value leading to our observation.
Garnet-melt noble gas partitioning and its relevance to the deep isolated reservoir hypothesis
Authors: Flanigan Michaela , Frost Dan , Withers Tony , Keppler Hans
Published: March 2020

Noble gas isotopes have been used to argue that hotspot volcanism taps a deep reservoir in the mantle that has remained largely isolated since the accretion of the Earth.  In order to evaluate the viability of this theory, it is important to understand how noble gases are stored at high pressure, and how processes such as melt separation may influence their transport.  Previous work (eg. Heber et al. 2007) has investigated the partitioning of noble gases in upper mantle minerals (olivine and pyroxenes), but as yet no data are available for other important phases, including garnet and higher-pressure minerals.  This study presents data collected from multi-anvil experiments at 6 GPa and 1700 °C – 1900 °C on artificial basalt compositions similar to those found at ocean island hotspots.  This composition has garnet on the liquidus at these conditions, and we have successfully quenched the melt to a glass.  The partitioning of noble gases between liquidus garnets and co-existing melts has been evaluated using a microprobe and laser ablation mass spectrometry to analyse the gas contents of the two phases.  These results shed light on the behaviour of noble gases in the presence of minerals that have, as yet, not been investigated for their ability to store such volatiles, and on the likelihood of the deep-untapped-reservoir theory.
A synchronous change of mid- to late- Holocene hydroclimate and prehistoric population in coastal East Asia indicated by pollen, XRF and grain size data
Authors: Park Jinheum , Park Jungjae , Yi Sangheon , Kim Jin Cheul , Lee Eunmi , Jin Quihong , Choi Jieun
Published: March 2020

A relationship between climate change and prehistoric civilizations is a topic of growing interest. Here, we present a 6,000-year-long pollen, X-ray fluorescence (XRF), and grain size data of the core STP18-03 from the southern Korean peninsula, spanning the mid- to late- Holocene. The proxies generally show a synchronous change throughout the core. During dry periods, reduced precipitation indicated by lower sand proportion (river discharge) would have hindered tree growth, which then resulted in increased titanium erosion from nearby hills, and vice versa. The drying trend is remarkable during ca. 4.8, 4.3, 4.0, 3.3, 2.7-2.3 ka BP and corresponds with sudden dropping points of a summed probability distribution (SPD) of archaeological records found in the Korean Peninsula. This implies that ancient civilizations of Korea responded highly sensitively to abrupt climate deterioration. As an underlying mechanism of the change, we suggest a role of the equatorial Pacific Ocean. The temporal pattern of our arboreal pollen proportion closely follows that of sea surface temperature (SST) data from the Western Pacific Warm Pool (WPWP) region. Furthermore, the dry periods indicated by our multiple proxies coincide with strong El Niño–Southern Oscillation (ENSO) activity, when the core region of the warm seawater pool deviated eastward than usual. This supports that the equatorial Pacific Ocean has served as an important factor for modulating mid- to late- Holocene hydroclimate of the Korean Peninsula, where the East Asian Summer Monsoon (EASM) accounts for nearly 70 percent of the total annual precipitation amount.
Experimental and Numerical Study on Liquid Sloshing Dynamics with Single Vertical Porous Baffle in a Sway Excited Ship Tank
Authors: k v Sahaj , Thuvanismail Nasar
Published: March 2020

Liquid motion in partially filled tanks may cause large structural loads if the period of tank motion is close to the natural period of fluid inside the tank. This phenomenon is called sloshing. Sloshing means any motion of a free liquid surface inside a container. The effect of severe sloshing motion on global seagoing vessels is an important factor in safety design of such containers. In order to examine the sloshing effects, a shake table experiments were conducted for different water fill depth of aspect ratio 0.163, 0.325 and 0.488. The parametric studies were carried out to show the liquid sloshing effects in terms of slosh frequencies, maximum free surface elevation and hydrodynamic forces acting on the tank wall. Sloshing oscillation for the excitation frequency f1, f2, f3, f4 and f5 are observed and analysed. The excitation frequencies is varied between 0.4566 Hz to 1.9757 Hz and constant amplitudes of 7.5mm was adopted. The movement of fluid in a rectangular tank has been studied using experimental approach and different baffle configurations were adopted for analysing the sloshing oscillation, natural frequencies and variation in wave deflection. The adopted porosities in the present study is 15% – 25 %. Porous screen is placed inside the tank at L/2 location and study is extended for single porous screen for better wave energy absorption. Capacitance wave probes have been placed at tank ends to record the free surface water elevation. Load cells are used to measure the sloshing force inside the tank. Linear variable displacement transducers is used to measure the displacement of shake table. In the present study single porous screen under the action of wave were analysed to understand the wave control performance due to porosity parameters. A boundary element model is developed to calculate problems of wave interaction with a porous screen structure. The numerical results from the present boundary element methods (BEM) are compared with series of experiments conducted in a rectangular tank with various baffle porosities and submerged depths.

 
Observations and simulations of foreshock waves during magnetic clouds
Authors: Turc Lucile , Roberts Owen , Archer Martin , Palmroth Minna , Battarbee Markus , Brito Thiago , Ganse Urs , Grandin Maxime , Pfau-Kempf Yann , Escoubet Philippe , Dandouras Iannis
Published: March 2020

The foreshock is a region of intense wave activity, situated upstream of the quasi-parallel sector of the terrestrial bow shock. The most common type of waves in the Earth's ion foreshock are quasi-monochromatic fast magnetosonic waves with a period of about 30 s. In this study, we investigate how the foreshock wave field is modified when magnetic clouds, a subset of coronal mass ejections driving the most intense geomagnetic storms, interact with near-Earth space. Using observations from the Cluster constellation, we find that the average period of the fast magnetosonic waves is significantly shorter than the typical 30 s during magnetic clouds, due to the high magnetic field strength inside those structures, consistent with previous works. We also show that the quasi-monochromatic waves are replaced by a superposition of waves at different frequencies. Numerical simulations performed with the hybrid-Vlasov model Vlasiator consistently show that an enhanced upstream magnetic field results in less monochromatic wave activity in the foreshock. The global view of the foreshock wave field provided by the simulation further reveals that the waves are significantly smaller during magnetic clouds, both in the direction parallel and perpendicular to the wave vector. We estimate the transverse extent of the waves using a multi-spacecraft analysis technique and find a good agreement between the numerical simulations and the spacecraft measurements. This suggests that the foreshock wave field is structured over smaller scales during magnetic clouds. These modifications of the foreshock wave properties are likely to affect the regions downstream - the bow shock, the magnetosheath and possibly the magnetosphere - as foreshock waves are advected earthward by the solar wind.
Response of the North Atlantic Meridional Overturning Circulation to the Greenland Ice Sheet Freshwater input in the CESM 2.1 model
Authors: Ernani da Silva Carolina , Vizcaino Miren , Katsman Caroline
Published: March 2020

Coupled climate models predict a weakening of the Atlantic Meridional Overturning (AMOC) circulation in the future. However, it is not clear what is the cause of the AMOC weakening. Studies have suggested that the freshwater (FW) is an important factor in the AMOC reduction. There are different sources of FW that may play a role, such as, river discharge, sea ice melt, and precipitation. Currently, due to global warming, the Greenland Ice Sheet (GrIS) melt rate is rising, which increases the amount of freshwater (ice discharge) into the ocean. Thus, it is possible that this input of freshwater would affect the ocean circulation on a regional and global scale. Hence, the GrIS freshwater cannot be neglected. The goal of this study is to understand the impact of the freshwater from GrIS on the North AMOC (NAMOC) strength in the future. We used the Community Earth System Model (CESM) version 2.1, which contains a fully coupled and an active ice sheet, to simulate an idealized greenhouse gas scenario (1% CO2). The CO2 concentration is 1140 ppm at the end of the simulation. The results show that GrIS delivers, on average, about 0.062 Sv/yr of FW to the Subpolar North Atlantic Ocean. The bulk of the total freshwater input comes from the southeastern and southwestern parts of the ice sheet:  the regions where some fast-flowing marine-terminating glaciers are located (e.g. Helheim and Kangerlussuaq). The NAMOC index (maximum barotropic stream function from above 28°N and from 500 m to 5500 m depth) was calculated. It displays a fast weakening, approximately 16.7 Sv (0.11 Sv/yr), during the first 150 yrs. After that, the NAMOC reaches a stable state where the index is around 5.7 Sv (year 350). When the NAMOC index was compared to the FW from GrIS time series, we observed that change in AMOC occurs before the FW starts to increase (from year 200). Our results thus suggest that the FW input from GrIS does not cause significant changes in the AMOC strength. It is necessary to further investigate other possible causes for the strong NAMOC decline in this model.
Land-Use/Land-Cover Changes and Their Influence on Urban Thermal Environment in Zhengzhou City During the Period of 1986 to 2026
Authors: Liu Pei , Han Ruimei , Yang Leiku
Published: March 2020

Rapid urbanization has become a major urban sustainability concern due to environmental impacts, such as development of urban heat island (UHI) and the reduction of urban security states. To date, most research on urban sustainability development has focus on dynamic change monitoring or UHI state characterization. While there is little literature on UHI change analysis. In addition, there has been little research on the impact of land use and land cover changes (LULCCs) on UHI, especially simulates future trend of LULCCs, UHI change, and dynamic relationship of LULCCs and UHI. The purpose of this research is to design a remote sensing based framework that investigates and analysis that how the LULCCs in the process of urbanization affected thermal environment. In order to assesses and predicts impact of LULCCs on urban heat environment, multi-temporal remotely sensed data from 1986 to 2016 were selected as source data, and Geographic Information System (GIS) methods such as CA-Markov model were employed to construct the proposed framework. The results shown that (1) there has been a substantial strength of urban expansion during the 40 years study period; (2) the most far distance urban center of gravity movement from north-northeast (NEE) to west-southwest (WSW) direction; (3) the dominate temperature were middle level, sub-high level and high level in the research area; (4) there was a higher changing frequency and range from east to west; (5) there was significant negative correlation between land surface temperature and vegetation, and significant positive correlation between temperature and human settlement.
A case study of the propagation of precipitation measurement biases into a distributed hydrological model for the Seveso river basin
Authors: Ravazzani Giovanni , Scurati Andrea Roberto , Stagnaro Mattia , Cauteruccio Arianna , Lanza Luca Giovanni , Cislaghi Matteo , Rondanini Chiara , Calabrese Michele
Published: March 2020

Precipitation measurement biases arise from both instrumental and environmental factors. For Tipping Bucket Rain-gauges (TBRs) the underestimation bias due to the employed mechanical principle was largely described in the literature and considered in recent measurement quality standards (e.g. EN 17277:2019), while wind has been recognized as the main environmental factor affecting the measurement. Precipitation Measurements Biases (PMBs) are largely understated and propagate through the modelling of hydrological processes at the catchment scale, affecting the results of hydrological simulation. The present work addresses the propagation of PMBs within a distributed hydrological model applied to the case study of the Seveso river basin, a highly urbanized catchment of about 200 km2 located north of the city of Milan (Italy), which experienced a number of severe floods in the last years. To this aim, four TBRs located within the Seveso catchment area were tested using a field portable calibrator in order to quantify their mechanical bias. The calibrator allows generating constant water flows, which serve as the reference, equivalent to three rainfall rates of 50, 100 and 200 mm/h for a gauge with collecting area of 1000 cm2. Furthermore, the wind-induced error was considered using a numerical Collection Efficiency curve obtained from the computational fluid-dynamic simulation of cylindrical gauges. Flow discharge was simulated using a spatially distributed hydrological model fed by the ARPA Lombardia tipping bucket precipitation network and including PMBs correction techniques. The results are compared to the discharge observations in specific section along the Seveso river and the influence of the PMBs is evaluated. Results show that, for high intensity rainfall events, when TBR measurements are subject to larger underestimation, the bias of peak discharge can be up to about 5 %. Of the same magnitude is the impact of the wind that mostly affects events with low precipitation intensity.

 

References:

EN 17277:2019 - Hydrometry - Measurement requirements and classification of rainfall intensity measuring instruments, European Committee for Standardization, 2019.
Planetary geostrophic Boussinesq dynamics: barotropic flow, baroclinic instability and forced stationary waves
Authors: Dolaptchiev Stamen , Achatz Ulrich , Reitz Thomas
Published: March 2020

Motions on planetary spatial scales in the atmosphere are governed by
the planetary geostrophic equations. However, not much attention has
been paid to the interaction between the baroclinic and barotropic
flow within the planetary geostrophic scaling. This is the focus of
the present study by utilizing planetary geostrophic equations for a
Boussinesq fluid supplemented by an asymptotically derived evolution
equation for the barotropic flow. The latter is effected by meridional
momentum flux due to baroclinic flow and drag by the surface wind. The
barotropic wind on the other hand affects the baroclinic flow through
buoyancy advection. By relaxing towards a prescribed buoyancy profile
the model produces realistic major features of the zonally symmetric
wind and temperature fields. We show that there is considerable
cancelation between the barotropic and the baroclinic surface zonal
mean zonal wind. The linear and nonlinear model response to steady
diabatic zonally asymmetric forcing is investigated. The arising
stationary waves are interpreted in terms of analytical solutions. We
also study the problem of baroclinic instability on the sphere within
the present model.

Reference: Dolaptchiev, S. I., Achatz, U. and Th. Reitz, 2019: Planetary
geostrophic Boussinesq dynamics: barotropic flow, baroclinic
instability and forced stationary waves, Quart. J. Roy. Met. Soc., 145: 3751-3765.
Evaluation of frontal precipitation in CMIP6 models
Authors: Catto Jennifer , Priestley Matthew
Published: March 2020

Process-based evaluation of precipitation is key to understanding climate model biases. It is vital to ensure that precipitation is produced in the model due to the correct mechanisms (or weather system). Atmospheric fronts have been shown to be responsible for a large proportion of total and extreme precipitation in the mid-latitudes. Therefore, representation of precipitation associated with fronts in climate models needs to be tested.

We applied objective front identification to the historical simulations from the CMIP6 archive and linked them with their 6-hourly precipitation accumulations. We compared the model outputs to the results from observationally constrained datasets. The fronts were identified from ERA5 and linked to precipitation estimates from sources including ERA5, and satellite products. This allows the precipitation errors to be decomposed into components associated with the frequency and intensity of frontal and non-frontal precipitation.

The diagnostics from the analysis have been made into metrics which could be used to evaluate model performance and aid in focussing future model development.
Economic loss due to flooding in Europe at 1.5°C global warming
Authors: Sassi Maximiliano , Scudeler Carlotta , Nicotina Ludovico , Assteerawatt Anongnart , Hilberts Arno
Published: March 2020

We study the impact of climate change on European flood economic losses under 1.5°C global warming scenario. Climate scenarios were generated with the Community Atmospheric Model (CAM) version 5 under the protocols of the Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) experiment. Present climate scenario corresponding to the years 2006-2015 includes observed forcing conditions for sea surface temperatures (SSTs) and sea-ice cover. The future 1.5°C scenario was constructed following SST warming according to the response to the RCP2.6 in CMIP5 model simulations. Each scenario comprises five 10-year long simulations that differ in the initial weather state. For each scenario we generated a 1000 years long stochastic set of precipitation based on the main modes of variability of gridded precipitation data through Principal Component Analysis applied to the monthly precipitation fields of the combined 50 simulated years. The other variables were obtained through an analogue month approach. Stochastic monthly fields were subsequently disaggregated in space and time to 3-hourly, 6 km resolution grids, and these were finally fed to a well-calibrated flood-loss model. The flood-loss model comprises a rainfall-runoff component, a flood routing scheme, an inundation component and a financial module that integrates flood hazard, buildings vulnerability, and economic exposure at location level. Prior to model evaluation, the stochastic meteorological forcing was bias-corrected with the stochastic set (based on observations) employed in the construction and calibration of the flood-loss model. The method for bias-correction preserves the ratio of quantiles of the future scenario to the present and preserves the correlation structure of the forcing variables. Average annual loss for Europe with the current-climate scenario generated by CAM is within 10-15% of the current industry estimate (based on observations), which suggests the applicability of the proposed approach. For the future scenario the model suggests a significant increase in loss (> 4 times) with respect to the present, which is in line with other studies for similar future global warming pathways.
Global distribution of persistence of total electron content anomaly
Authors: Sun Yang-Yi , Chen Chieh-Hong , Liu Jann-Yenq , Wu Tsung-Yu
Published: March 2020

Solar activities can disturb the ionosphere globally and induce ionospheric weather phenomena that transit rapidly through a large area. By contrast, sometimes the ionospheric plasma density can remain high or low over a certain location for a few days, which are difficult to be attributed to solar activities. This study shows the location preference of the positive and negative total electron content (TEC) anomalies persisting continuously longer than 24 hours (cross the two terminators) at middle and low latitudes (within ±60ºN geomagnetic latitudes). The TEC is obtained from the global ionospheric map (GIM) of the Center for Orbit Determination in Europe (CODE) (ftp://cddis.gsfc.nasa.gov/pub/gps/products/ionex) under the geomagnetic quiet condition of Kp ≤ 3o during the period of 2005–2018. There are a few (less than 4%) TEC anomalies that can persist over 24 hours. The persistence of the positive TEC anomaly along the ring of fire on the western edge of the Pacific Ocean. The high persistence of the TEC anomalies at midlatitudes suggests that thermospheric neutral wind contributes to the anomaly formation. The temporal and spatial anomalies of the ionospheric electric field, atmospheric electric field (flash), atmospheric gravity wave, and neutral wind over the ring of fire should be further examined for explaining whether the persistence of the TEC anomalies associates with lithospheric activities.
Reduced fraction of young water in Alpine catchments with increased seasonal snow cover
Authors: Ceperley Natalie , Zuecco Giulia , Beria Harsh , Carturan Luca , Michelon Anthony , Penna Daniele , Larsen Joshua , Schaefli Bettina
Published: March 2020

Effective water resource management can benefit from estimations of when water entered the catchment and how long it takes to flow to the outlet. In this context, the so-called young water fraction (Fyw) based on seasonal input and output tracer cycles is becoming increasingly used as robust tool to compare the hydrological function of catchments. In seasonally cold environments, this Fyw estimation is complicated by the fact that a large part of the precipitation will be in the form of snow, will be stored before melting and becoming available as water, resulting in a distinct winter low flow and summer high flow season. Nevertheless, Fyw might enclose extremely interesting information in such environments since they incorporate the relationship between late summer and autumn flow and the previous winter’s snow input.  However, most currently available methods for Fyw estimation do not explicitly account for the seasonal shift of water input from snow. Therefore, we propose a novel framework to explicitly account for this “snowmelt” delay in Fyw and explore related uncertainties using experimental data from three high-elevation Alpine catchments, the Vallon de Nant in Switzerland, and the Noce Bianco at Pian Venezia and the Bridge Creek Catchments in Italy. Experimental data from these environments expose some limitations of existing methods in accounting for unavoidable sampling inconsistencies. Using our method that explicitly accounts for snowmelt, we found extremely low Fyw in these three Alpine catchments: 6%, 13%, and 31%. In this contribution, we will present our method in detail and highlight emerging challenges and implications of the Fyw estimation.
Tropospheric products as a signal of interest – overview of troposphere sensing techniques
Authors: Wilgan Karina , Rohm Witold , Bosy Jaroslaw , Geiger Alain , Siddique M. Adnan , Wickert Jens , Dick Galina
Published: March 2020

Microwave signals passing through the troposphere are delayed by refraction. Its high variations, both in time and space, are caused mainly by water vapor. The tropospheric delay used to be considered only as a source of error that needed to be removed. Nowadays, these delays are also a source of interest, for example, tropospheric delays or integrated water vapor information are being assimilated into nowcasting or numerical weather prediction (NWP) models. Moreover, long time series of tropospheric observations have become an important source of information for climate studies. On the other hand, the meteorological data is supporting the space-geodetic community by providing models that can be used to reduce the troposphere impact on the signal propagation.

There are several ways of observing the troposphere, especially considering water vapor.  First one are the classical meteorological: in-situ measurements, radiosondes or radiometers, from which we can sense directly the amount of water vapor. Another, indirect way of observing the water vapor distribution is by using the Global Navigation Satellite Systems (GNSS). This method is called GNSS meteorology. Other microwave techniques such as Very Long Baseline Interferometry (VLBI), Interferometric Synthetic Aperture Radar (InSAR) or space-based Radio Occultations (RO) can also be used in a similar way to GNSS.

This contribution presents an overview of the troposphere sensing techniques with examples of their applications. We present a multi-comparison of the tropospheric products, i.e. refractivity, tropospheric delays in zenith and slant directions and integrated water vapor. The integration of the different data sources often leads to an improved accuracy of the tropospheric products but requires a careful preparation of data. The combination of the data sources allows for using techniques of complementary properties, for example InSAR with very high spatial resolution with GNSS observations of high temporal resolution. With the emergence of new technologies, some traditional ways of tropospheric measurements can be augmented with the new methods. For example, we have tested meteo-drones as an alternative to radiosondes. The comparisons with GNSS data shows a good agreement of the drone and microwave data, even better than with radiosondes.
Modeling of Southeast Asia biomass burning pollutants to Taiwan during EMeRGe campaigns in Asia
Authors: Lin Chuan-yao , Chen Wan-chin , sheng Yang-fan , Chen Win-Mei , Chien Yi-Yun
Published: March 2020

In springtime happens to be the biomass burning season in Indochina. Under favor weather conditions, the products of biomass burning pollutants could be transported easily to Taiwan and even East Asia. Actually, the complex interactions of these air pollutants and aerosols features in the boundary layer and aloft have resulted in complex characteristics of air pollutants and aerosols distributions in the lower troposphere. The project “Effect of Megacities on the transport and transformation of pollutants on the Regional and Global scales (EMeRGe)” aims to improve our knowledge and prediction of the transport and transformation patterns of European and Asian megacities pollutant outflows. During the EMeRGe campaign in Asia, the composition of the plumes of pollution entering and leaving Asia measured by the new High Altitude and LOng Range (HALO) aircraft research platform. The HALO aircraft performing optimized transects and vertical profiling in Asia during 12 March and 7 April in 2018. To identify the transportation of biomass burning products, a high resolution (9 km) numerical study by Weather Research Forecast coupled with chemistry model (WRF-Chem) was performed during the campaigns. The long-range transport of biomass burning organic aerosol to Taiwan measured by HALO could be more than 2 ug/m3 at the elevation of 2500 m on 20 March, 2018. Model performances and results will discuss in this meeting. Overall, this series of studies significantly fill the gap of our understanding on air pollutants transformation and transport to Taiwan and East Asia, and show the potential directions of future studies.