bluuebunny/crossref_metadata_2025 huggingface dataset:
Influences of tropical monsoon climatology on the delivery and dispersal of organic carbon over the Upper Gulf of Thailand, SE Asia
Authors: Wu Bin , Wu Xiaodan , Shi Xuefa , Qiao Shuqing , Liu Shengfa , Hu Limin , Liu Jihua , Bai Yazhi , Zhu Aimei , Kornkanitnan Narumol , Khokiattiwong Somkiat
Published: March 2020

The seasonal reversal of monsoon climatology modulates precipitation, currents, river influx and a variety of biogeochemical processes. In the present study, we evaluated the role of tropical monsoon pertaining to fluvial discharge, sediment load, coastal current and water stratification on seasonal organic carbon dynamics during four sampling campaigns in the Upper Gulf of Thailand (UGoT), SE Asia. This study demonstrates that particulate organic carbon (POC) is closely correlated with the river influx of suspended sediment, which is generally regulated by the local rainfall. Higher POC is found near the large estuarine section (Chao Phraya River, CHAO) during southwest monsoon period and the small estuarine section (Mae Klong River, MK) during the tropical cyclones impacted November 2013. POC in the estuarine sections is influenced more by the seasonal shift than the coastal sections. Land-derived organic matter prevails in the small estuarine and coastal sections, while marine-derived organic matter dominates in the CHAO and MK impacted estuarine sections. Total organic carbon (TOC) however displays less significant seasonal monsoon variations than POC. Further, TOC tends to accumulate in the sub-silt fraction of sediments, which mainly occurs in the small estuarine and eastern coastal sections and is obviously influenced more by marine-derived factors. TOC in surface sediment of the CHAO and MK influenced sections however displays more seasonal variations with prevailing river input as evidenced by coarser sediment and higher C/N ratios. Moreover, the almost year round water stratification across the region acts as the barrier in retaining organic carbon in the estuaries and their vicinities from dispersal into the lower portion of Gulf of Thailand. High sedimentation rate (~1.1 cm·yr-1) further facilitates the organic carbon burial in the study area. The delivery, dispersal and burial of organic carbon are closely associated with the climate controlled precipitation, and thus the tropical monsoon climatology under the global warming in particular is an important factor influencing the organic carbon in the UGoT.

Acknowledgements

This study was supported by National Programme on Global Change and Air-Sea Interaction (GASI-02-IND-CJ05, GASI-GEOGE-03), the Natural Science Foundation of China (U1606401), the Qingdao National Laboratory for Marine Science and Technology (2016ASKJ13), the China-Thailand cooperation project “Research on Vulnerability of Coastal Zones”, and the Taishan Scholar Program of Shandong.
CME Expansion as Revealed by Joint Measurements by STEREO, Wind, MESSENGER and Venus Express
Authors: Lugaz Noé , Salman Tarik , Winslow Réka , Al-Haddad Nada , Farrugia Charles , Zhuang Bin , Galvin Antoinette
Published: March 2020

The radial expansion of magnetic ejecta (ME) has been investigated through the analysis of remote observations, the variation of their properties with radial distance and from local in situ plasma measurements showing a decreasing speed profile, as first discussed almost 40 years ago. However, little is known on how local measurements compare to global measurements of expansion and what causes the different expansion properties of different CMEs. In order to correctly forecast CME properties at Earth from measurements below 0.9 AU CME expansion must be considered, and first, understood.  Here, we take advantage of 42 CMEs being measured by two spacecraft in radial conjunction to determine how the magnetic field decrease with distance, as a measure of their global expansion. As all these CMEs are also measured near 1 AU by STEREO or Wind, we are able to determine their local expansion from the speed decrease. We find that these two measures have little relation with each other, even when looking only at the events with the closest conjunctions (in term of angular separation). We also determine the relation between measures of the CME expansion and the CME properties. Lastly, we also determine the evolution of the ME radial, azimuthal and north-south magnetic field with distance, which allow us to compare their evolution with the expectations from force-free field configurations.
Large eddy simulation of boundary-layer turbulence over different underlying surfaces in the Source Region of the Yellow River, northeastern Tibetan Plateau
Authors: Zhang Yunshuai , Huang Qian , Ma Yaoming
Published: March 2020

In order to study the characteristics of turbulence over the homogeneous and inhomogeneous underlying surfaces and its effects on the transport of material and energy in the Source Region of the Yellow River (SRYR), northeast of the Tibetan Plateau. We use the GPS sounding data and eddy covariance data observed during a field experiment in the Ngoring Lake Basin in summer 2012, and for the first time large eddy simulations are performed to investigate the characteristics of the fine turbulence structure in the convective boundary layer (CBL) of the two different underlying surfaces (grassland and lake) in the SRYR. It shows that the simulated CBLs of grassland and lake in the SRYR is in good agreement with the observations, but the characteristics of the turbulence structure in the CBLs are obviously different. The spatio-temporal distribution of turbulence energy and the structure characteristics of thermal bubbles in the CBL above the grassland are consistent with those of the typical thermally driven CBL above the land. Convective rolls are simulated in the shear dominant CBL above the lake. Turbulence intensity in the surface layer above the grassland is higher, while it is larger at the top of CBL above the lake due to the strong entrainment. We also found that the simulations are sensitive to the horizontal resolution on the two different homogeneous underlying surfaces. The higher horizontal resolution should applied to the CBL above the lake to improve the accuracy in the simulation of turbulence kinetic energy and turbulence flux of the surface layer and the entrainment layer, while avoiding underestimating the turbulence flux due to the small range of the waves simulated at low resolution. For the CBL of the grassland, it is suggested that the grid distance should be between 200 m-300 m, which can save the calculation time, also can give the turbulence flux and the fine turbulence structure. In addition, 3-D simulations are also performed to figure out the differences of turbulence intensity over homogeneous and inhomogeneous underlying surfaces. It is found that lake breeze induced by surface inhomogeneity would enhance the wind shear, decreasing the intensity of vertical turbulence and increasing that of horizontal turbulence.
The pressure-relevance of suprathermal solar wind electrons for the heliosheath
Authors: Fahr Hans-Jörg
Published: March 2020

In this presentation solar wind electrons and protons are studied which, after their passage over the solar wind termination shock, are convected downstream into the heliosheath. Due to the electric nature of this shock, downstream electrons appear highly energized with non-equilibrium,  kappa-like  distributions . When looking upon the moments of these downstream electrons and protons, it turns out as a surprise that the pressure of the electrons, compared to the protons, is larger by a factor of 2. Then it is taken into account that the pressure of kappa-distributed particles contains contributions from particles with super-luminal velocities which need to be removed from the pressure values . Even when these reductions are carried out, it is manifest that the heliosheath pressures of electrons and protons are of equal orders of magnitudes. In conclusion it is found that there is no pressure deficit in the heliosheath with respect to the ambient interstellar medium.
Oceanic warm cloud layers within multilevel cloud systems observed by satellite measurements
Authors: Liu Qi , Ding Yuhao , Lao Ping
Published: March 2020

Low-level warm clouds are a major component in multilayered cloud systems and are generally hidden from the top-down view of satellites with passive measurements. By using spaceborne radar data with fine vertical resolution, this study conducts an investigation on oceanic warm clouds embedded in multilayered structures. The occurrences of warm cloud overlapping and the geometric features of several kinds of warm cloud layers are examined. It is found that there are three main types of cloud systems that involve warm cloud layers, including warm single layer clouds, cold-warm double layer clouds and warm-warm double layer clouds. The two types of double layer clouds account for 23% and in the double layer occurrences warm-warm double layer subsets contribute about 13%. The global distribution patterns of these three types differ from each other. Single-layer warm clouds and the lower warm clouds in the cold-warm double layer system have nearly identical geometric parameters, while the upper and lower layer warm clouds in the warm-warm double layer system are distinct from the previous two forms of warm cloud layers. In contrast to the independence of the two cloud layers in cold-warm double layer system, the two kinds of warm cloud layers in the warm-warm double layer system may be coupled. The distance between the two layers in the warm-warm double layer system is weakly dependent on cloud thickness. Given the upper and lower cloud layer with moderate thickness around 1 km, the cloudless gap reaches its maximum exceeding 600 m. As the two cloud layers become even thinner or thicker, the cloudless gap decreases in thickness. It is believed that such knowledge on cloud overlapping is critical for fully understanding the distribution of warm clouds in three-dimensional space. The results derived in this study could help validating cloud results of numerical models, which are indeed three-dimensional in nature. They could also be used to improve the estimation of cloud radiative forcing, since it is affected by cloud occurrences and especially their vertical structures. It should be pointed out that solid explanations for the above cloud features cannot be presented by only using these satellite data themselves. 
Upper ocean heat content (OHC) changes in the tropical Pacific induced by orbital insolation and greenhouse gases (GHG)
Authors: Wang Yue , Jian Zhimin , Dang Haowen , Liu Zhongfang , Jin Haiyan , Zhang Shuai , Luo Li , Wang Xingxing
Published: March 2020

The ocean is the largest heat capacitor of the earth climate system and a main source of atmospheric moist static energy. Especially, upper ocean heat content changes in the tropics can be taken as the heat engine of global climate. Here we provide an orbital scale perspective on changes in OHC obtained from a transient simulation of the Community Earth System Model under orbital insolation and GHG forcings. Considering the vertical stratification of the upper ocean, we calculate OHC for the mixed layer and the upper thermocline layer according to the isotherm depths of 26℃ and 20℃ respectively. Generally, our simulated OHC are dominated by thickness changes rather than temperature changes of each layer. In details, there are three situations according to different forcings:

(1) Higher GHG induces positive mixed layer OHC anomalies inside the western Pacific warm pool but with neglected anomalies outside it. For the upper thermocline layer, there are negative OHC anomalies inside the warm pool and positive anomalies in the subtropical Pacific of two hemispheres. For the total OHC above 20℃ isotherm depth, positive anomalies mainly come from the mixed layer between 15ºS-15ºN and from the thermocline between 15º-30º. Lower obliquity induces similar spatial patterns of OHC anomalies as those of higher GHG, but total OHC anomalies are more contributed by upper thermocline anomalies.

(2) Lower precession results in positive mixed layer OHC anomalies in the core of warm pool (150ºE-150ºW, 20ºS-10ºN) and the subtropical northeastern Pacific, but with negative anomalies in other regions of the tropical Pacific. Upper thermocline layer OHC anomalies have similar patterns but with opposite signs relative to the mixed layer in regions between 15ºN-30ºS. As a combination, positive total OHC anomalies occupy large areas of 130ºE-120ºW from 30ºS to10ºN, while negative anomalies dominate the subtropical north Pacific, the western and eastern ends of the tropical Pacific.

If confirmed by paleoceanographic proxies, our simulated OHC results can be served as the first guide map of anomalous energetic storage & flows in the earth climate system under orbital forcings.
Identification of interplanetary parameter schemes which drive the variability of the magnetospheric radiation environment
Authors: Katsavrias Christos , Nasi Afroditi , Papadimitriou Constantinos , Aminalragia-Giamini Sigiava , Sandberg Ingmar , Jiggens Piers , Daglis Ioannis A.
Published: March 2020

The energetic particles of the outer radiation belt are highly variable in space, time and energy, due to the complex interplay between various mechanisms that contribute to their energization and/or loss. Previous studies have focused on the influence of solar wind and magnetospheric processes on the electron population dynamics, showing that the eventual effect of the various interplanetary drivers results from different combinations of IMF and solar wind parameters. Yet, all of these studies were limited in temporal, spatial and energy coverage. In this work, we take advantage of a large dataset, which includes multipoint measurements of electron fluxes covering a large energy range and various orbits (e.g. Van Allen Probes, GOES, HIMAWARI, SREM monitors, etc.), as well as approximately the whole solar cycle 24 to deduce specific interplanetary parameter schemes that drive enhancements or depletions of relativistic electrons in the outer radiation belt. Our study also investigates parameters which are correlated to the Solar Energetic Particle (SEP) environment with the long-term goal of connecting the two sets of results for coherent merging of environment models.

This work is supported by ESA’s Science Core Technology Programme (CTP) under contract No. 4000127282/19/IB/gg.
Evaluating ecological vulnerability over Qinghai-Tibetan Plateau based on remote sensing and geographic information systems
Authors: Xia Mu , Jia Kun
Published: March 2020

Qinghai-Tibetan Plateau (QTP), known as “the Third Pole”, has one of the most fragile ecosystems in the world. QTP is suffering from external pressures of climate change, human activities, and natural hazards. This study provides a subjective framework in assessing ecological vulnerability (EV) in QTP from 2000 to 2015 based on remote sensing and geographic information system techniques. An ecological vulnerability index (EVI) was established based on 17 indicators mainly acquired from satellite data. Principle component analysis and entropy method were used in determining indicator weights. Annual EVI were calculated based on the weighted sum of all indicators. Five vulnerability levels of potential, light, moderate, heavy and very heavy were graded to describe the spatial and temporal patterns of EVIs. Mann-Kendall trend analysis was performed over QTP during the 16 years. Results indicates QTP is suffering from an overall increasing EVI from eastern to western areas. About 10.43% of QTP has experienced significant EVI decrease, while 7.38% experienced significant increase in EVI.

 
Spatiotemporal forecasting for groundwater level using a WT-LSTM model
Authors: qin wei , Lu Chengpeng , Sun Long , Lu Jiayun
Published: March 2020

Accurate groundwater level forecasting models is essential to ensure the sustainable utilization and efficient protection of groundwater resources. In this paper, a novel method for groundwater level forecasting is proposed on the basis of coupling discrete wavelet transforms (WT) and long and short term memory neural network (LSTM) . In this model, the wavelet transform is used to decompose the cumulative displacement into the term of trend and term of periodicity . The trend term reflects the long-term tendency of groundwater level variation, which is simulated by a linear regression method. The periodic term driven by external factors such as rainfall, the river stage and the distance from river, is modelled using a LSTM method. The distance from river and the distance from observation wells are used for spatiotemporal model interpretation. Finally, the trend term and periodic term are superposed to achieve the cumulative spatiotemporal prediction of groundwater level. A typical study area located in Haihe basin is taken as an example to validate the performance of the proposed model. The proposed mode (WT-LSTM) is compared with the regular artificial neural network (ANN) model and autoregressive integrated moving average (ARIMA) model. The results show that the prediction accuracy of WT-LSTM model is higher than ANN model and ARIMA model, especially during the flood period. Furthermore, the spatiotemporal groundwater level forecasting is not only included the observation of groundwater and precipitation, but should also take the influence factors of surface water into consideration. The proposed model gives a new sight in the prediction of groundwater level.
Crustal structure across the extinct ridge in South China Sea from OBS receiver functions: insights into the spreading rate and the magma supply prior to the ridge cessation
Authors: Yang Ting , Hung Tran Danh , Le Ba Manh , Xue Mei
Published: March 2020

The characteristics of oceanic crust are dependent on the spreading rate of a Mid-Ocean Ridge (MOR). Crustal structure near an extinct MOR, therefore, provide unique constraints on how the magma supply and the crustal accretion respond to the reduced and ultimately ceased spreading. We present the crustal structure beneath 11 OBS sites near the extinct MOR in the central sub-basin of the South China Sea (SCS). We use the Receiver Function (RF) method to reveal the thickness and the Vp/Vs ratio of the crust based on the passive-source OBS data collected in this sub-basin. The thickness of the crust varies systematically with the distance to the ridge.  The thinned crust near the ridge likely indicates that, in the late stage of spreading, the magma supply has diminished and the spreading rate has dropped to the ultra-slow range. While the Vp/Vs ratios at most sites fall into the normal range, there exist a few anomalously high Vp/Vs ratios (> 2.0) at sites very close to the ridge. These high Vp/Vs values can be explained by the serpentinization of the uppermost mantle beneath the sites. As the spreading rate and magma supply were reduced, fractures and fissures were easily developed at the frank of the crust accretion, allowing water enters the lowermost crust and serpentinizes the uppermost mantle.
Characteristics of neutralized mine drainage sediment depending to the depth in semi-active treatment
Authors: Lee Dong-Kil , Cheong Young-Wook , Yim Gil-Jae , Ji Won hyun , Cho Sanghyun
Published: March 2020

In the semi-active treatment process of mine drainage, neutralized mine drainage flows into settling pond to form sedimentary layer. The sedimentation layer is increased in thickness over time by the continuous inflow of sediment, and the bottom  of the sediment layer is compressed by the load of the upper layer. Thus, the physical characteristics of the sedimentary layers change depending on the depth over time. In this study, the sedimentation layers of four semi-active treatment facilities in South Korea were sampled by depth to measure physical properties and chemical composition. As a result of the analysis, the density and water content of the sludge did not change significantly, while the particle size distribution and viscosity were different according to the depth. As a result of statistical analysis, there was a significant correlation between depth, water content, and viscosity of the sediments. In addition, the content of Mn and Fe contained in the sediments was correlated with the content of Ca and Mg.
Understanding factors influencing the wetland parameters of a monthly rainfall-runoff model in the Upper Congo River basin
Authors: Kabuya Pierre , Hughes Denis , Tshimanga Raphael , Trigg Mark
Published: March 2020

Wetland processes considerably influence the flow regime of the downstream river channel, and are important to consider for a better representation of runoff generation within a basin scale hydrological model. The need to understand these processes lead to the development of a wetland sub-model for the monthly time step Pitman hydrological model. However, previous studies highlighted the need to provide guidance to explicitly estimate the wetland parameters rather than using a trial and error calibration approach. In this study, a 2D hydrodynamic river-wetland model (LISFLOOD-FP) is used to explicitly represent the inundation process exchanges between river channels and wetland systems and thereby inform the choice of Pitman wetland model parameters. The hysteretic patterns of these river-wetland processes are quantified through the use of hysteresis indices. Additionally, the hysteretic patterns are connected with the spill and return flow parameters of the wetland sub-model and eventually with the wetland morphometric characteristics. The results show that there is a consistent connection between the degree of hysteresis found in the channel-wetland exchange processes and the Pitman wetland parameters which are also explicitly linked to the wetland morphometric characteristics. The channel capacity to spill (Qcap) is consistently correlated with the hysteresis found between the channel inflow and the wetland storage volume. This anti-clockwise hysteresis represents the time delay between the inundation and drainage processes. The channel spill factor (QSF), in addition to the inundation processes, is also connected with the drainage processes represented by the wetland storage volume and channel outflow anti-clockwise hysteresis. On the other hand, the parameters of the return flow equation have shown a strong consistent relationship with the channel inflow-wetland storage hysteresis. It has also been observed that the wetland average surface slope and the proportion of the wetland storage below the channel banks are the morphometric characteristics that influence the spill and the return flow parameters of the Pitman wetland sub-model. This understanding has a practical advantage for the estimation of the Pitman wetland parameters in the many areas where it is not possible to run complex hydrodynamic models.
Transition of low clouds in the East China Sea and Kuroshio region in winter: A regional atmospheric model study
Authors: Long Jingchao , Wang Yuqing , Zhang Suping , Liu Jingwu
Published: March 2020

Bias in simulating the stratocumulus-to-cumulus transition remains a main source of uncertainties in regional climate projection and can significantly affect the energy budget in climate models. To gain insights into the transition, this study investigates the cloud transition forced by the sea surface temperature (SST) front and synoptic disturbances in the East China Sea and Kuroshio region in winter based on both observations and regional atmospheric model simulations. The Kuroshio SST front greatly accelerates cloud transition by enhancing surface turbulent heat flux, marine atmospheric boundary layer (MABL) dynamical adjustment and cloud-top entrainment. With the sharp SST increase from the cold flank to the Kuroshio SST warm tongue (KWT), surface wind convergence (SWC) over the KWT induced by the SST front and synoptic disturbances[Office1]  enhances the coupling between the cloud layer and subcloud layer. An underlying positive feedback between the SWC and latent heating in the cloud layer can enhance abrupt change in cloud properties and maintain cloud band over the KWT against the decoupling through the so-called “Deepening-Warming” mechanism induced by latent heating. From the KWT downwind southward, the surface layer turbulent mixing weakens, while latent heating in the cloud layer and cloud-top longwave radiative cooling enhance buoyancy and vertical mixing in the cloud layer. This difference in vertical mixing between the cloud layer and subcloud layer facilitates the MABL decoupling and impedes upward moisture transport. Meanwhile, decreasing lower tropospheric stability is conducive to the entrainment of drier and warmer air from above into the cloud layer, strengthening cloud evaporation.
Discounting Future Climate Change and the Equilibrium Real Interest Rate
Authors: Bauer Michael , Rudebusch Glenn
Published: March 2020

The social discount rate is a crucial element required for valuing future damages from climate change. A consensus has emerged that discount rates should be declining with horizon, i.e., that the term structure of discount rates should have a negative slope. However, much controversy remains about the appropriate the overall level of discount rates.

We contribute to this debate from a macro-finance perspective, based on the insight that the equilibrium real interest rate, commonly known as r*, is the crucial determinant of the level of discount rates. First, we show theoretically how r* anchors the term structure of discount rates, using the modern macro-finance theory of the term structure of interest rates to provide a new perspective on classic results about social discount rates. Second, we show empirically that new macro-finance estimates of r* have fallen substantially over the past quarter century---consistent with a broader literature that documents such a secular decline. Bayesian estimation of a state-space model for Treasury yields, inflation and the real interest rate allows us to quantify both the decline in r* and the resulting downward shift of the term structure of social discount rates. Third, we document that this decline in r* and the social discount rate boosts the social cost of carbon and has quantitatively important implications for assessing the economic consequences of climate change. In essence, we demonstrate that the lower new normal for interest rates implies a higher new normal for the present value of climate change damages.
Simulating preferential flow in a two water worlds framework
Authors: Radolinski Jesse , Pangle Luke , Klaus Julian , Scott Durelle , Stewart Ryan
Published: March 2020

Ecohydrological separation has been observed across climates and biomes, and at a fundamental level suggests that water in mobile versus immobile domains may resist mixing over varying periods of time; however little mechanistic evidence exists to explain this separation at a process scale. Non-equilibrium flow in the vadose zone may partially account for widespread perception of distinct hydrological domains yet no studies have weighed its contribution. Using a simple isotope mixing technique, we sought to determine the amount of preferential flow necessary to maintain a two water worlds scenario (i.e., physical separation between mobile and immobile water pools). We constructed 60 cm soil columns (20 cm-ID PVC) containing low soil structure (sieved soil material), subsoil structure (intact B horizon), and soil structure without matrix exchange (tubing reinforced macropores) to simulate multiple preferential flow scenarios. Columns were subjected to 3 rain storms of varying rainfall intensity (~2.5 cm h -1, ~5 cm h -1, and ~11 cm h -1) whose stable isotope signatures oscillated around known baseline values. Isotopic analysis was performed on collected leachate and matrix water sampled via direct vapor equilibration. Preliminary estimates of matrix water indicate up to 100% mixing with infiltrating rain water under low rainfall intensity (2.5 cm h -1) in subsoil structure columns, whereas high intensity rain (11 cm h-1) produced clear separation between columns with intact or artificial soil structure and those controlled for structure (low structure treatment). This separation was confirmed by preferential flow estimates; however minimizing matrix exchange (via artificial macropores) reduced preferential flow by a factor of 4 compared to soil with intact structure. These data suggest that distinct domain separation may only be possible under extreme precipitation intensity; and that exchange with less mobile storage in the soil matrix produces more preferential flow. We intend to use these estimates of preferential flow as a benchmark to understand the prevalence, persistence, and plausibility of ecohydrological separation. As a next step, we will use this conceptual framework to define how recurrent drought, elevated CO2, and warming may alter the partitioning of mobile and immobile water in mountain grasslands.
Expansion of the eastern North Pacific OMZ and the associated denitrification regime
Authors: Devol Allan , Ruef Wendi
Published: March 2020

 

At this point ocean deoxygenation is well documented, including in oxygen minimum zones (OMZs).  Within the large OMZs of the Arabian Sea and eastern Pacific are imbedded areas where oxygen concentrations are so low that they are undetectable by routine CTD sensors (oxygen deficient zones, ODZs).  How do we determine if these ODZ are losing O2?  Furthermore, denitrification occurs in oxygen minimum zones (OMZs) so one might hypothesize that denitrification is likewise expanding if oxygen is decreasing.  This is important because the ocean's fixed nitrogen inventory limits the productivity over large marine areas.

We have investigated these questions in the largest OMZ, the eastern tropical North Pacific (ETNP) through an analysis of  6 repeats of a 1000 km transect along 110o West in the heart of the ETNP ODZ between 1971-2019.  We use N*, a stoichiometric parameter calculated from nitrate and phosphate, as our indicator of denitrification. The more Negative N* the more denitrification has occurred. After secondary QC the values of O2 concentration between potential density 24.75 and 1000m along with N* were integrated across the transect and over the depth of the ODZ.  

The results show a clear decrease in oxygen inventory along with an increase in N*, suggesting deoxygenation and intensification of denitrification over during the 50 year period. We discuss potential mechanisms for denitrification signal increase including ENSO, Pacific Decadal Oscillation, tropical hurricane intensity, and variations in thermocline depth.
Using Eye-tracking and Deep Learning Approach to Promote Naturalness in Urban Landscape
Authors: Qiu Yeshan , Chen Yugang , Che Shengquan
Published: March 2020

Promoting greenness and naturalness has been the integral goal in nature-based solutions for urban environments. Design and building appreciated landscape for subjective public perception is a key factor in the success of promoting urban greenness and naturalness. The current measures of naturalness are siloed from public appreciation and acceptance of urban landscape designs. Our goal is to use state-of-art methods combining traditional design perception evaluation to embed naturalness with public landscape aesthetic perceptions evaluation system. A deep learning and eye-tracking based approach to understand public aesthetic perceptions of landscape street-view images is developed and applied to a case study of Shanghai. We use machine deep learning techniques to identify and assess landscape composition with landscape images and in-situ captured data to study the influence of naturalness of public perceptions of landscape based on a Bayesian network aesthetic evaluation model. The methodology extend the present landscape aesthetic evaluation framework and has the potential to be implemented to much wider applications. Our results indicate a co-conception of naturalness and public appreciation as a proof-of-concept of nature-based solutions.

Key words：Eye-tracking；Deep Learning；Naturalness；Public aesthetic perceptions；Bayesian network aesthetic evaluation
Climate Risk and Vulnerability Assessment in Azerbaijan’s mountain regions
Authors: Zebisch Marc , Terzi Stefano , Crespi Alice , Sonnenschein Ruth , Steger Stefan
Published: March 2020

Mountain regions are an important hotspot of vulnerability to climate change. These ecosystems are experiencing a higher warming rate than other areas in the world, with severe consequences on the environment, the economy and society. This is particularly relevant for Azerbaijan’s mountain regions, where the climate change impacts on water management could lead to severe consequences on the main local socio-economic activities such as agriculture and livestock farming.

For these reasons, the Impact Chains (ICs) methodology has been applied within two regions of Azerbaijan to understand and investigate cause-effect chains of current and future risk from different type of climate hazards following the approach proposed in the Fifth Assessment Report (AR5) of the International Panel on Climate Change (IPCC). ICs provide a consolidated scheme which helps to better understand, systemize and prioritize the factors driving climate impact related risks in a specific system and to perform climate risk assessments. It includes the underlying root-causes of climate risk, hazard, exposure and vulnerability factors and their interactions coming from quantitative and qualitative information.

Here we present the ICs study for Azerbaijan’s mountain regions accounting for flood, drought, erosion, heat stress and forest fires identified as the most relevant hazards in the country.

Climate conditions and future hazard components were assessed looking at future daily temperature and precipitation data until 2099 from two RCP (Representative Concentration Pathways) scenarios provided by the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP). The spatialized dataset is an ensemble of four global climate model simulations at a resolution of 0.5°x0.5°. In particular, the ISIMIP projections were exploited to extract the future evolution and spatial distribution over the region of relevant indicators for climate and climate hazards, including weather extremes and droughts.

The different levels of exposure and vulnerability were evaluated combining quantitative and qualitative information coming from spatial analysis, workshop discussion and questionnaires with local stakeholders and experts.

To finalize the risk assessment, the hazard, exposure and vulnerability components were combined through aggregation and normalisation techniques and risk indicators and hotspot maps for Azerbaijan’s mountain regions were developed.

The information provided by the ICs will be available to further analyse the risk processes and local dynamics, and to support local stakeholders in decision-making process and future investments on risk reduction and climate adaptation plans.
Evaporation from homogeneous and heterogeneous soil systems: Modeling approaches and experimental data
Authors: Assouline Shmuel , Kamai Tamir
Published: March 2020

Accurate estimates of water losses from the soil by evaporation are important for hydrological, agricultural, and climatic purposes. Different analytical and numerical approaches were developed to provide the capability to simulate and predict the dynamics of the evaporation process in terms of fluxes, and water and thermal distributions in the soil profile. Experimental investigation of the process under different boundary conditions is also possible by means of columns and weighing lysimeters. As part, these experimental setups allow addressing the impact of heterogeneity in the drying soil profile. Experimental data resulting from evaporation experiments under natural and laboratory conditions with homogeneous and heterogeneous soil profiles are presented and analyzed. These data are also compared to results from available analytical and numerical models. This comparison points out fundamental limitations of the approaches that assume hydraulic connectivity up to the surface, as well as those that suppose monotonic drying when unsteady conditions prevail. Differences between experimental data and model prediction emphasize challenging knowledge gaps that are part of ongoing research.
Pressure-to-depth conversion models for (ultra-)high-pressure metamorphic rocks: review and application
Authors: Bauville Arthur , Yamato Philippe
Published: March 2020

Pressure estimated from metamorphic rocks is one of the main tools for geodynamic reconstructions. The pressure-temperature path of UHP metamorphic rocks typically shows a linear increase of P and T followed by a rapid drop of Pressure at near-constant temperature. The geological history can be reconstructed by using the metamorphic pressure as a proxy for depth. Researchers often base their geodynamic reconstruction on a simple linear mapping of pressure to depth, by considering that the pressure is the weight of the overlying column of rock or lithostatic pressure. In recent years, an increasing corpus of evidence demonstrates that rocks can experience pressures that deviate from the lithostatic state on the order of GPa. These deviations can be at the scale of the orogen (Petrelli and Podladchikov, 2002), the outcrop (Jamtveit et al., 2018; Luisier et al., 2019); or even at the grain-scale (Tajcmanova, 2015). Thus, these studies raise the concern that metamorphic pressures may not be reliable proxies for depth, and therefore could not be used for geodynamic reconstructions. The objective of this contribution (1) to review the various models proposed in the literature for metamorphic pressure, (2) to formulate analytical models with simple assumptions that can be used to convert metamorphic pressure to depth even in the case where pressure deviates significantly from the lithostatic pressure. We use our pressure-to-depth conversion models to estimate the depth of ~60 samples from various orogens worldwide. The prediction of the different models varies widely. Some models predict depth as deep as 160km for specific samples, while other models predict depth $<75$ km (i.e. deepest depth of the Moho) for all data points.  We discuss the limits of applicability and the geodynamic implications of each model. 
Recent achievements from the Swarm mission on the low latitude space environment and combinations with other satellite missions
Authors: Stolle Claudia , Rodríguez-Zuluaga Juan , Xiong Chao , Yamazaki Yosuke , Kervalishvili Guram , Schreiter Lucas
Published: March 2020

The Swarm three-satellite constellation mission provides high resolution and high-quality observations of the Earth’s magnetic field and of multiple parameters of the ionosphere, which lead to new knowledge on the Earth’s interior and space environment and help to investigate space weather effects on space technology. Several findings would otherwise not have been possible and demonstrate that missions like Swarm are indispensable for Earth and space exploration. In addition, aspects of longterm variations or enhanced understanding in temporal and spatial resolution on regional scales could be gained in combination with other missions. This presentation  focuses on recent achievements on the low latitude ionosphere. Examples include an empirical model of the occurrence of post-sunset equatorial plasma irregularities derived in combination with ten years of CHAMP geomagnetic data, an enhanced description of the Swarm irregularity observations together with regional maps of the South Atlantic ionosphere from GOLD, and the identification of differing GPS scintillation characteristics evoked by the irregularities in comparison with the lower orbit GOCE data. Equatorial electrojet and plasma data from Swarm also helped to empirically prove that Antarctic sudden stratospheric warming events, such as in September 2019, couple to the low latitude ionosphere through modified planetary waves.
Impacts of Snow Darkening by Light-absorbing aerosols on the Water Cycle over the Western Eurasia and East Asia
Authors: Sang Jeong , Kim Maeng-Ki , Lau William K. M. , Kim Kyu-Myong
Published: March 2020

In this paper, we have investigated the snow darkening effects by light-absorbing aerosols on the regional changes of the water cycle over the Eurasian continent using the NASA GEOS-5 Model with aerosol tracers and a state-of-the-art snow darkening module, the Goddard SnoW Impurity Module (GOSWIM) for the land surface. Two sets of ten-member ensemble experiments for 10-years were carried out forced by prescribed sea surface temperature (2002-2011) with different atmospheric initial conditions, with and without SDE, respectively. Results show that SDE can exert a significant regional influence in partitioning the contributions of evaporative and advective processes on the hydrological cycle, during spring and summer season. Over western Eurasia, SDE-induced rainfall increase during early spring can be largely explained by the increased evaporation from snowmelt. Rainfall, however, decreases in early summer due to the reduced evaporation as well as moisture divergence and atmospheric subsidence associated with the development of an anomalous mid- to upper tropospheric anticyclonic circulation. On the other hand, in the East Asian monsoon region, moisture advection from adjacent ocean is a main contributor to rainfall increase in the melting season. Warmer land-surface caused by earlier snowmelt and subsequent drying further increases moisture transport and convergence significantly enhancing rainfall over the region. This findings suggest that the SDE may play an important role in leading to hotter and drier summer over western Eurasia, through coupled land-atmosphere interaction, while enhancing East Asian summer monsoonal precipitation via enhanced land-ocean thermal contrast and moisture transport due to SDE-induced warmer Eurasian continent.

 

This work was supported by the Korea Meteorological Administration Research and Development Program under grant KMI2018-03410.
An ensemble Kalman filter data assimilation system for the whole neutral atmosphere
Authors: Koshin Dai , Sato Kaoru , Miyazaki Kazuyuki , Watanabe Shingo
Published: March 2020

A data assimilation system with a four-dimensional local ensemble transform Kalman filter (4D-LETKF) is developed to make a new analysis data for the atmosphere up to the lower thermosphere using the Japanese Atmospherics General Circulation model for Upper Atmosphere Research. The time period from 10 January 2017 to 20 February 2017, when an international radar network observation campaign was performed, is focused on. The model resolution is T42L124 which can resolve phenomena at synoptic and larger scales. A conventional observation dataset provided by National Centers for Environmental Prediction, PREPBUFR, and satellite temperature data from the Aura Microwave Limb Sounder (MLS) for the stratosphere and mesosphere are assimilated. First, the performance of the forecast model is improved by modifying the vertical profile of the horizontal diffusion coefficient and modifying the source intensity in the non-orographic gravity wave parameterization, by comparing it with radar wind observations in the mesosphere. Second, the MLS observational bias is estimated as a function of the month and latitude and removed before the data assimilation. Third, data assimilation parameters, such as the degree of gross error check, localization length, inflation factor, and assimilation window are optimized based on a series of sensitivity tests. The effect of increasing the ensemble member size is also examined. The obtained global data are evaluated by comparison with the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) reanalysis data covering pressure levels up to 0.1 hPa and by the radar mesospheric observations which are not assimilated.
Numerical Investigation of the Stability of Toppling Rock Slopes Subjected to Glacier Retreat
Authors: Toshkov Nikola , Aaron Jordan , Loew Simon , Glueer Franziska , Gishig Valentin
Published: March 2020

Glacial retreat is often cited as a cause of rock slope instabilities in mountain regions. Until recently, glacial debuttressing was thought to be the main mechanism by which glaciers influence slope stability, however recent work has questioned the efficacy of this mechanism.  It appears that other mechanisms, including slope kinematics and hydro-mechanical interactions between the glacier and slope are important drivers of paraglacial rock slope instabilities.  In the present work, we use discontinuum numerical models to investigate the interaction between rock slope kinematics, slope/glacial hydrology and glacial retreat. 
We perform both a theoretical analysis using a simplified slope geometry, as well as a back-analysis of the Moosfluh Landslide.  For the theoretical analysis, we investigate the response of both toppling and sliding slopes to two factors: the weight of the ice, assumed to be applied as a ductile load acting normal to slope topography, and the variation of the slope water table, which is linked to the ice level and lowers as the glacier retreats. We then apply the insights from the theoretical analysis to investigate the Moosfluh Landslide.  This landslide, which is located at the left flank of the Great Aletsch Glacier Valley (Valais, Switzerland), at the present-day glacial terminus, underwent a dramatic acceleration in 2016 in response to glacier retreat.  The landslide was extensively monitored during this acceleration, and analysis of this data has revealed that the kinematics of movement changed from toppling to secondary sliding.  We simulate the behaviour of the Moosfluh Landslide by implementing a structural model determined from field mapping, and systematically lowering the ice level and slope water table, to simulate glacial retreat.
We find that the interaction between slope kinematics and glacial retreat leads to a complex slope response.  For sliding slopes, the stability of the slope is relatively insensitive to glacial ice loss.  For toppling slopes, the slope response is highly sensitive to ice loss, and the slope is the most unstable at a critical ice level, before ice has completely retreated.  For the Moosfluh instability, we are able to simulate the initial toppling kinematics of this landslide, as well as the transition to sliding triggered by the ice reaching a critical elevation.  Our analysis has important implications for understanding rock slope response to glacial retreat, and highlights the disparate behaviour of toppling and sliding slopes. 
Urban densification potentials and energy impacts in Switzerland
Authors: Eggimann Sven , Orehounig Kristina
Published: March 2020

Building sustainable cities, as set out in the Sustainable Development Goals by the UN, requires sustainable urbanization as well as reducing per capita environmental impacts of living in cities. As a result of a growing population and constrained availability of building space, countries such as Switzerland are faced with increasing pressure on their land resources. They will need to considerably densify in existing urbanized areas to prevent urban expansion. Even though Swiss regulation promote inward settlement development and the creation of compact settlements, only limited analysis is available on the densification potentials combined with sustainability implications. We develop a geospatial explicit analysis framework which allows to up-scale the assessment and evaluation of densification potentials for the whole of Switzerland. An energy simulation tool is used for exploring impacts of different densification strategies on a district scale with respect to energy consumption.