bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison study of aerosol impacts on idealized supercell between two bulk microphysics parameterizations
Authors: Wu Wanchen , Huang Wei , Chen Baode
Published: March 2020

Considering aerosol effects via microphysics parameterization is an imperative work in high-resolution numerical weather prediction. This paper uses two bulk microphysics parameterizations, Aerosol-Aware Thompson and CLR schemes, with the Weather and Research Forecast model to study the impacts of aerosols and microphysics scheme on an idealized supercell storm. Our results show that the implementation of aerosols can successfully modify the cloud droplet size and influence the subsequent warm-rain, mixed-phase, and accumulated precipitation. It implies that aerosols can make numerous differences to cloud microphysics properties and processes but the uncertainty in the magnitude of aerosol effects is huge because the two schemes are different from each other since the warm-rain process including CCN activation and rainwater formation. On the other hand, it is also found that the two schemes make tremendous differences in the rainfall pattern and storm dynamics due to the presence of graupel below the freezing level. The Thompson scheme has hail-like graupel which can fall below the freezing level to chill the air temperature effectively, intensify the downdraft, and enhance the uplifting on the front of cold pools. The mean graupel size represented by the two schemes plays a much more important role than the fall-speed formula for the dynamical feedbacks. Our results suggest that particle size is the core of a myriad of microphysics processes and highly associated with key cloud and dynamical signatures.
A syn-collisional or post-collisional belt? In the view from the middle segment of the Central Tianshan Belt
Authors: Lin Wei , Li Le
Published: March 2020

The Tianshan belt is one of the key regions in understanding the tectonics of the Central Asian Orogenic Belt (CAOB), as it presents a typical example of subduction, accretion and collision. Its tectonic evolution is recently in hot debate and draws more and more attention of the international geological society. As a major tectonic segment, the Middle Chinese Tianshan was considered to witness the most significant tectonic events. On the basis of structural and geochronological works, three zones have been recognized namely: 1) the northern zone, composed of weakly metamorphosed sedimentary rocks of Silurian to Carboniferous ages; 2) the central zone, comprised of well sheared amphibolite, marble, quartzo-schist, quartzite, garnet-biotite schist, and orthogneiss; and 3) the southern zone, which consists of amphibolite facies metamorphic rocks whose protolith is considered to be Silurian to Devonian. The most significant deformation was marked on the various schist or gneiss of the central zone. E-W striking, vertical or sub-vertical foliation with horizontal or sub-horizontal mineral and stretching lineations indicate conspicuous strike-slip shearing. Shear criteria indicate a dextral sense of shearand geochronological results indicates it looks like two phase deformation (~290 Ma and ~250 Ma). South-dipping foliation with northward thrusting in the northern zone and north-dipping foliation with southward thrusting in the southern zone show a large-scale flower structure related to the early stage of the dextral strike-slip tectonics of the central zone. The absolute timing of the dextral strike-slip deformation is also discussed in the light of available radiometric dating. Our structural data emphasizes that the post-collisional dextral wrenching has largely modified the architecture of the Tianshan orogenic belt and played a critical role in the tectonic evolution of Central Asia.
Detecting geological structures in coastal area of Buan, South Korea using unmanned aerial vehicle images
Authors: Lee Hong-Jin , Ko Kyoungtae
Published: March 2020

This study attempted to use unmanned aerial vehicle (UAV) photogrammetry for structural mapping at limited exposure outcrops in the west coast area of Buan, South Korea. The west coast area of Buan has a large tidal range, and there are restrictions for traditional structure mapping. High spatial resolution (about 4.5 cm per pixel) UAV images were obtained at low tide from a selected study site. The UAV survey identified 50 brittle structures (fractures and faults that were divided into three groups) and changes in the bedding trace. The bedding trace demonstrates various directional verging of the fold geometry that indicates slump-fault structures. While more research is still necessary, this study demonstrated that UAV mapping techniques are very useful for geological structural analysis in coastal areas.
Soil respiration and its components respond asymmetrically to throughfall reduction and nitrogen additions in a subtropical Moso bamboo forest in the Southwest China
Authors: Wang Yi , Liu Shirong , Luan Junwei
Published: March 2020

The roles of multiple global change are expected for many terrestrial ecosystems in future. As two main global change factors, the impact of drought and nitrogen deposition and their interaction on soil respiration and its components (R) remains unclear. To explore the responses of soil respiration (Rs), autotrophic respiration (Ra) and heterotrophic respiration (Rh) to multiple global change factors, we established a field experiment of throughfall reduction and nitrogen additions in a subtropical Moso bamboo (Phyllostachys heterocycla) forest in the Southwest China, using a 4 × 4 completely randomized design. Results showed that bivariate exponential equation with soil temperature (T) and soil moisture (SWC) (R=a.ebT.SWCc) was fitted to predict Rs, Ra and Rh. Throughfall reduction, nitrogen additions and their interaction had no effect on annual mean Rs and Ra, but nitrogen additions significantly depressed annual mean Rh. Nitrogen additions significantly decreased contribution of Rh to Rs and increased contribution of Ra to Rs, however, the contributions were non-responsive under throughfall reduction. The more positive effect of nitrogen additions on the contribution of Ra to Rs was appeared compared with that of throughfall reduction, thereby more negative effect on the contribution of Rh to Rs. The fine root biomass, fine root carbon and nitrogen storage regulated Rs, while fine root phosphorus storage determined Ra. The Rh was negatively correlated with vector lengths, thus suggesting that microbial carbon limitation caused the decline of Rh. Our findings demonstrate that the nitrogen additions played overriding role than throughfall reduction in affecting the contribution of Ra and Rh to Rs. Moreover, the negative response of temperature sensitivity of Rs and Rh to nitrogen additions, suggesting that that the nitrogen additions may weaken the positive response of soil CO2 emission to global climate warming. Our study highlights asymmetrical responses of Rs, Ra and Rh to throughfall reduction and nitrogen additions and could enhance accurate predictions of soil carbon dynamics in response to multiple global climate change in future.
A recursive approach to long-term prediction of monthly precipitation using genetic programming: case of the Three-River Headwaters Region
Authors: Shi Haiyun , Liu Suning
Published: March 2020

This study develops a recursive approach to long-term prediction of monthly precipitation using genetic programming (GP), and the study area is the Three-River Headwaters Region (TRHR) in China. The daily precipitation data recorded at 29 meteorological stations during 1961-2014 are collected, among which the data during 1961-2000 are used for calibration and the remaining data are for validation. To develop this approach, first, the preliminary estimations of annual precipitation are computed based on a statistical method. Second, the percentage of the monthly precipitation for each month of a year is calculated as the mean monthly precipitation divided by the mean annual precipitation during the study period, and then the preliminary estimation of monthly precipitation for each month of a year is obtained. Third, GP is adopted to improve the preliminary estimations through establishing the relationship of the observations with the preliminary estimations at the past and current times. The calibration and validation results reveal that the recursive approach involving GP can provide the more accurate predictions of monthly precipitation. Finally, this approach is used to predict the monthly precipitation over the TRHR till 2050.
Uptake of urea by “drunken” trees on permafrost
Authors: Fujii Kazumichi , Matsuura Yojiro , Inagaki Yoshiyuki , Hayakawa Chie
Published: March 2020

Boreal forest productivity on permafrost is limited by availability of soil nitrogen (N) in the active layer. Low soil temperature and summer flooding limit microbial N mineralization on shallow permafrost table. Uptake of amino acids by plant root-mycorrhizal association is known to mitigate N limitation in boreal forest soils. However, amino acid hypothesis can not fully explain advantage of black spruce trees in drunken forests due to competition of amino acids between plants, bryophytes, and microbes. Based on the observation of urea accumulation in deeper soil, we test another hypothesis that black spruce trees take up intact urea in deeper soil. Mixture solutions (glutamic acid, urea, ammonium, nitrate), with only one N form labeled by 13C and/or 15N, was injected into the organic/mineral soil layers. We compared two black spruce forest sites with/without shallow permafrost table in northern Canada. We found that black spruce trees take up intact urea as well as amino acids in the shallow permafrost sites. Urea accumulation is explained by low microbial activities to mineralize 14C-labeled urea. The other plants or bryophyte compete with black spruce for amino acids, but not for urea. Since the other black spruce trees in the deeper soil sites rely on amino acids and inorganic N, urea uptake strategy is specific to black spruce trees on shallow permafrost table. The root expansion on hummocky microrelief provides opportunity for leaning trees to access urea. The uptake of intact urea could be one of strategy of black spruce trees to mitigate N limitation in permafrost-affected hummocky soils.
Relationship between sea surface temperature anomalies over tropical Atlantic in late spring and East Asian summer monsoon
Authors: Ahn Joong-Bae , Choi Yeon-Woo
Published: March 2020

This study investigates the relationship between the preceding late spring Sea Surface Temperature (SST) over the tropical Atlantic and the East Asian Summer Monsoon (EASM) based on the observational data and Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations. The results show that warm (cold) tropical Atlantic SST (TASST) during May tends to be followed by a strong (weak) EASM with positive (negative) precipitation anomalies over the subtropical frontal area. Evidence is also provided that the atmospheric teleconnections propagating in both east and west directions are the key mechanisms linking the EASM with the preceding May TASST. That is, the warm TASST anomaly during late spring can persist through the subsequent summer, which, in turn, induces the Gill-type Rossby wave response in the eastern Pacific, exciting the westward relay of the Atlantic signal, as well as the eastward propagation of the Rossby wave along the jet stream. Furthermore, the westward (eastward) propagating teleconnection signal may induce the anomalous anticyclone in the lower troposphere over the Philippine Sea (anomalous tropospheric anticyclone with barotropic structure over the Okhotsk Sea). The anomalous anticyclonic circulation over the Philippine Sea (Okhotsk Sea) brings warm and humid (cold) air to higher latitudes (lower latitudes). These two different types of air mass merge over the Baiu-Meiyu–Changma region, causing the enhanced subtropical frontal rainfall. To support the observational findings, CMIP5 historical simulations are also utilized. Most state-of-the-art CMIP5 models can simulate this relationship between May TASST and the EASM.

Reference: Choi, Y., Ahn, J. Possible mechanisms for the coupling between late spring sea surface temperature anomalies over tropical Atlantic and East Asian summer monsoon. Clim Dyn 53, 6995–7009 (2019) doi:10.1007/s00382-019-04970-3

Acknowledgment: This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2018-01213.

 
Litter decomposition under drought related with litter and decomposer diversity
Authors: Luan Junwei , Liu Shirong , Li Siyu , Wang Yi , Lu Haibo , Zhang Junhui , Han Shijie , Wang Hui , Chen Lin , Zhou Wenjun , Zhang Yiping
Published: March 2020

Litter decomposition is a crucial ecosystem process that driven carbon and nutrient cycling, which can be determined by the diversity of biota that involved in decomposition process. Forest ecosystems at globally have been or being expected to experience drought stress and cause dieback, consequently may lead losses of tree species and soil biota. However, how projected drought affect litter decomposition and its relationship with biodiversity is less understood. We hypothesize that 1) drought depressed the activity of soil biota and retard litter decomposition, while biodiversity loss at both plant and soil organism levels exacerbated the drought induced retarding of litter decomposition; 2) soil biota interaction or the top down control of ecosystem process can be relieved under drought stress. In our study, throughfall reduction experiments were conducted in five locations representing different forest types (i.e., temperate broadleaf-Korean pine mixed forest, warm-temperate oak forest, subtropical bamboo forest, south subtropical evergreen forest, tropical rainforest) along a climate gradient in China. In each location, leaf litter from 4 common native plants and 11 mixtures of these litter types were enclosed in three types of nylon mesh screens litterbags, and were placed in the field of throughfall reduction and control treatments replicated five times. Different combination of litter types represent diversity of litters, and mesh size of litterbags represent diversity of functional group of soil biota (i.e., microorganism, medium-sized fauna, large-bodied fauna) participate into decomposition. The litterbags were incubated in situ for a period of time and were collected, all litter samples were separated into the constituent species immediately after litter retrieval, mass loss, C and N loss of each sample was determined. Thereby the hypothesizes can be testified.
Deep fluid release beneath arcs from delayed breaching of the slab lower crust
Authors: Smit Matthijs , Pogge von Strandmann Philip
Published: March 2020

Slabs in subduction zones with geotherms of 7 K km-1 or higher are expected to dehydrate effectively in the forearc. Nevertheless, large amounts of water are released from these slabs at and beyond subarc depth, indicating that H2O remains slab-bound to much greater depth than expected. It is possible that this reflects a transient sealing effect exerted by the subducting lower crust—a section of the lithosphere that typically undergoes delayed recation and is effectively impermeable until then. To test this concept, we investigated gabbros that were partially transformed to hydrous eclogite along shear zones during subduction. The rocks were subjected to a textural, petrological and Li-chronometric analysis. The observations characterize the progressive stages of transformation, and provide detailed insight into the governing feedbacks among fluid flow, deformation, and reaction. Lithium chronometry indicates that it took only a few weeks for the shear zone network to develop and for the externally derived fluids to traverse this network and drive eclogitization; the switch in these rocks—going from strong to weak and from impermeable to sustaining long-range fluid flow—thus was essentially instanteneous on subduction time scales. The re-equilibration of the rocks occurred well beyond equilibrium at c. 90 km depth, which is where large fluid-filled channel system typically emanate from warm slabs. Our data suggest that the fluids that are produced in the slab mantle throughout the forearc accumulate beneath the Moho until the lower crust is breached by dynamic fluid vents and commences its delayed transformation. The subducting lower crust may thus be a exert a strong control on H2O and element budgets, and the rheology of slabs in warm subduction zones.
Recent pronounced weakening of Asia summer monsoon over the past 450 years
Authors: Liu Yu , Cai Wenju
Published: March 2020

Affecting a multitude of ecological and agricultural systems, the Asia summer monsoon (ASM) is essential for biodiversity and the food security of billions of people. Understanding past changes of the ASM is important for the detection and attribution of its recent evolution and future projection in the context of global warming. However, proxy-based, high-resolution reconstructions of the ASM prior to the period of instrumental measurements that started in the 1950s in China are still missing. Here, we use an ensemble of ten tree-ring width chronologies from the northern margin of the ASM to estimate ASM strength back to 1566 AD. The reconstruction not only reveals severe large-scale droughts in 1586/87 and 1759, but also negative anomalies during persistent locus plagues in the 1860s. The record also shows an unprecedented decrease in ASM since the mid-20th century. Simulations from a coupled climate model suggest that the recent ASM decline could have been induced by increased anthropogenic aerosol emissions over the Northern Hemisphere.
A thematic review of recent urban overheating impacts research in Asia and its applications to climate resilience
Authors: Kohler Manon , Chow Winston T.L.
Published: March 2020

Urban areas will be subjected to temperature increases from a combination of global-scale climate change and local-scale urban heat island drivers. The resultant combined heat risk – urban overheating – will notably challenge cities in securing the resilience of public health to combined urban overheating. Although global climate change research is ubiquitous, the urban climate and biometeorological research literature of this century reveals a lag of (sub-) tropical Asian regional studies behind Europe and North America. Through a systematic research review of international urban-scale climate and biometeorological literature from 2000-2019, we propose to reflect the state of the art of the urban overheating issue in Asia alongside its penetration in the regional climate resilience discourses.

The review reveals (i.) a rise of the number of urban overheating studies throughout in the region in conjunction with rapid demographic and developmental change, except for the central Asia region; (ii.) a “metropolitisation” of the urban heat and biometeorological knowledge, meaning a spatial organization of the knowledge reinforcing the leading position of the Asian national and regional primate cities; (iii.) distinct themes of more research into: large focus on remote-sensed urban heat mapping of Chinese and Indian urban clusters, evaluation of heat mitigation strategies from modeling experiments in nations having economies in transition, compared to more focus on urban-wide heat mortality epidemiological studies in countries already facing aging issues.

Considering the lack of global climate change considerations in urban overheating and biometeorological studies, the review appeals for a more systematic vision of the urban heat issues where urban overheating consequences (i.e. thermal discomfort, heat morbidity, and mortality) are analyzed and discussed conjunctly with the geographical background of the cities, its urban fabric properties, and its socio-demographic dynamics.
Towards onset: shades of ENSO skill
Authors: Squire Dougal , Risbey James
Published: March 2020

Climate forecast skill for the El Nino-Southern Oscillation (ENSO) is better than chance, but has increased little in recent decades. Further, the relative skill of dynamical and statistical models varies in skill assessments, depending on choices made about how to evaluate the forecasts. Using a suite of models from the North American Multi-Model Ensemble (NMME) archive we outline the consequences for skill of how the bias corrections and forecast anomalies are formed. We show that the method for computing forecast anomalies is such a critical part of the provenance of a skill score that any score for forecast anomalies lacking clarity about the method is open to wide interpretation. Many assessments of hindcast skill are likely to be overestimates of attainable forecast skill because the hindcast anomalies are informed by observations over the period assessed that would not be available to a real forecast. The relative skill rankings of forecast models can change between hindcast and forecast systems because the impact of model bias on skill is sensitive to the ways in which forecast anomalies are formed. Dynamical models are found to be more skillful than simple statistical models for forecasting the onset of El Nino events.
The vertical structure of mid-latitude marine stratocumulus simulated by large eddy simulation
Authors: Ren Yangze , Xue Huiwen
Published: March 2020

Cloud feedback in mid-latitude marine stratocumulus is not clearly understood due to few reliable observations. Stratocumulus cloud is the most frequent and extensive cloud type over mid-latitude marine areas and has strong short-wave radiative effect. In this study, large eddy simulation (LES) is used to resolve the vertical structure of mid-latitude marine stratocumulus. We find that, in the wintertime over North Pacific, stratocumulus cloud often forms in regions of high pressure and large-scale sinking motion, and can remain in steady-state for a couple of days. We then choose two typical cases to do LES simulation: One has a lower cloud top height and a stronger temperature inversion (case l), without mesoscale cellular structure; the other has a higher cloud top height and a weaker temperature inversion (case h), with closed-cell cellular structure. The liquid water content profiles are adiabatic, and the boundary layer is well-mixed for both cases. In case l, the main source of turbulent kinetic energy (TKE) is from cloud top long-wave radiative cooling for the entire boundary layer. In case h, TKE production due to cloud-top longwave cooling is only significant in the cloud layer, and the subcloud layer TKE is mainly from surface processes.
Investigation of aerosol absorption with dual-polarization lidar observations
Authors: Huang Zhongwei , Qi Siqi , Zhou Tian , Dong Qingqing , Ma Xiaojun , Zhang Shuang , Bi Jianrong , Shi Jinsen
Published: March 2020

Polarization lidar has been widely used in recent decades to observe the vertical structures of aerosols and clouds in the atmosphere. To obtain more information from polarization lidar measurements, we developed a dual-polarization lidar system that can detect polarization measurements simultaneously at both 355 nm and 532 nm. The vertical distributions of atmospheric aerosols and clouds over northern China were successfully observed by the developed lidar. Observational data during two typical cases (dust events and haze episodes) were used for the analysis in this study. The results showed that for dust-dominated aerosols, the depolarization ratio (DR) at 532 nm was larger than that at 355 nm, but that for air pollutants was smaller. Our results also show that dual-polarization measurements can be used to largely improve aerosol classification. Moreover, we found that there is a good relationship between the absorption coefficient of aerosols and the ratio of DRs at 532 nm and 355 nm for dust aerosols. These results confirm that the absorption characteristics of dust aerosols cause a difference in DR at the UV and VIS wavelengths, and implying that aerosol absorption may be determined by polarization lidar at the ultraviolet and visible wavelengths.
Propagation and transformation of nonlinear internal waves of tidal origin observed in the northeastern East China Sea
Authors: Lee Seung-Woo , Nam SungHyun
Published: March 2020

Oceanic nonlinear internal waves (NLIWs) play an important role in regional circulation, biogeochemistry, energetics, vertical mixing, and underwater acoustics, causing hazards to marine engineering and submarine navigation. Mainly generated by the interaction of the barotropic tides with the bottom topography, they propagate and transform due to wave-wave interaction process. Here, we present characteristics of first two modes of NLIWs observed using high-resolution spatiotemporal data collected in a relatively flat area in the northeastern East China Sea in May 2015. Six groups of NLIWs were identified from the observations: four groups of mode-1 and two groups of mode-2. The amplitude, propagation speed, and characteristic width of mode-1 NLIWs had ranges of 4–16 m, 0.53–0.56 m s-1, and 310–610 m, respectively. The mode-2 NLIWs propagate eastward slowly with a speed less than 0.37 m s-1 with a comparable amplitude of 4–14 m and longer characteristic width of 540–1920 m. Intermodal interactions may take a role in the evolution of mode-1 NLIWs west of the observational area. Our results characterizing the two modes of NLIWs highlight the significance of propagation and transformation of NLIWs and their modal interactions on a broad and shallow shelf.
Dislocation nucleation at nanoscale fluid inclusions: Direct observation from atom probe tomography data of naturally deformed pyrite
Authors: Dubosq Renelle , Rogowitz Anna , Schweinar Kevin , Gault Baptiste , Schneider David
Published: March 2020

In recent years, increasing developments in microscopy and microanalysis have allowed for the direct observation of nanoscale crystalline defects (i.e. dislocations). These defects are particularly important in naturally deformed materials yet this avenue of research remains understudied within the Earth Sciences. Dislocations can now be documented through the use of new and innovative structural and chemical analytical techniques such as electron channeling contrast imaging (ECCI), transmission electron microscopy, and atom probe tomography (APT). The presence and migration of dislocations in crystalline materials, including their role in trace element mobility, play a vital function in the way these materials respond to an applied stress. However, the mechanisms by which dislocations nucleate in minerals remain poorly understood. Prevailing models for dislocation nucleation include generation by Frank-Read sources, stress localization at crack-tips, atomic segregation, and free surface nucleation by critical stress-gradient criterion. Based on recent APT data from naturally-deformed pyrite, combined with electron backscatter diffraction (EBSD) mapping and ECC imaging, we propose a new nucleation mechanism where dislocations are generated by the local stress field in the vicinity of fluid inclusions. The investigated sample consists of a polycrystalline pyrite aggregate within a black shale host rock that has witnessed a peak temperature of 300°C. The combined EBSD and ECCI results reveal crystal plasticity in the form of lattice misorientation up to 8.5° and low-angle grain boundary development. APT data reveals nanoscale fluid inclusions enriched in As, O (H2O), Na and K as well as As- and Co-rich dislocations linked by fluid inclusions. This new model is the first documentation with APT methods of fluid inclusions (voids) in minerals, nanoscale features that are commonly misinterpreted as element clusters or chemically-enriched crystal-defects. The combined data has significant trans-disciplinary implications to the geosciences (structural geology, geochemistry, economic geology, geochronology), the material sciences (metals, ceramics, polymers), and analytical microscopy. Within geochronology voids and dislocations such as these in dated minerals may host elements or isotopes that negatively affect their age. Within ore deposit geology, voids in precious metal-hosting minerals may act as the necessary traps to structurally prevent the metals (gold, silver, copper) from migrating or diffusing out of the host mineral. In material sciences, the presence of such crystalline features can either limit or enhance the performance of engineering materials. Thus, performing APT analysis on crystalline material can help us better understand and predict their physical properties.
Carbon balance of tropical peat ecosystems in Borneo
Authors: Hirano Takashi
Published: March 2020

Tropical peat swamp forest (PSF) is a unique ecosystem rich in carbon and water, which is widely distributed in Southeast Asia’s coastal lowlands, mainly in Borneo, Sumatra and Malay Peninsular. The ecosystem has accumulated a huge amount of organic carbon in peat soil over millennia under the condition of high groundwater level. However, PSF has been reduced and degraded by logging, drainage and burning mainly because of land conversion to oil palm and pulp wood plantations during the last two decades. Such human disturbances potentially increase carbon dioxide (CO2) emissions to the atmosphere through enhanced oxidative peat decomposition and the increased risk of peat fires. Thus, it is essentail to assess the current carbon status of tropical peatlands and quantify the effects of disturbance on the carbon balance to understand the role of tropical peatlands in the regional and global carbon balances. We have continuously measured ecosystem-scale eddy fluxes and soil fluxes of CO2 and methane (CH4) in different tropical peat ecosystems, including a little drained PSF, a drained PSF, a burned ex-PSF and an oil palm plantation, in Central Kalimantan, Indonesia, and Sarawak, Malaysia, in Borneo. Based on the monitoring data, I’ll talk about the carbon balance of tropical peat ecosystems, such as its seasonal variation and its relationship with groundwwater level, and the effect of disturbance due to human activities and ENSO drought on the carbon flux and balance.
The improved thin cloud detection using BRDF model based background reflectance from GOCI geostationary satellite imagery
Authors: Yeom Jong-Min , Kim Hye-Won , Lee Jeongho , Park Seonyoung , Lee Sangcherl
Published: March 2020

In this study, the improved algorithm of thin cloud detection for geostationary ocean color imager (GOCI) satellite was developed to classify the thin cloud area over land area. The new cloud mask approach of GOCI satellite is required to expand its ocean dedicated application to other applications such for vegetation in land or aerosol optical properties (AOPs) in atmosphere due to its attractive shortwave wavelength bands of ocean color sensors. However, when trying to apply the advantages of the ocean color bands to the land area, only visible spectral bands of GOCI make it difficult to expand the land application the other way due to its limitation of cloud detection for relatively bright land surface. Furthermore, the geostationary of GOCI satellite has highly sensitive to geometry location of sun, meaning that high effective (Bidirectional Reflectance Distribution Function) BRDF effects make it also difficult to detect cloud mask in land surface due to its anisotropically scattered surface reflectance. In this paper, cloud mask algorithm of GOCI is proposed to consider those limitations by mainly using background surface reflectance from BRDF model. Therefore, minimum difference in reflectance between TOA and land as baseline of clear atmosphere and background surface reflectance underneath cloud were estimated from BRDF model. In conclusion, our new thin cloud detection is effectively detect the thin cloud over land surface area under limited ocean color bands of GOCI. The improved thin cloud detection algorithm of GOCI will be not only useful for following on instruments such as GOCI-II of Geo-KOMPSAT-2B and Sentinel 3 Ocean and Land Color Instrument (OLCL), but also applicable for existing geostationary satellites such as Geo-KOMPSAT-2A AMI, Himawari, and GOES-R as alternative cloud masking approach.
Numerical simulation of breather dynamics
Authors: Didenkulov Oleg
Published: March 2020

The numerical simulation of the so-called breather turbulence (dynamics of breather ensembles) is performed within the integrable model of modified Korteweg – de Vries equation. Two-breather interaction is considered as an elementary act of the breather turbulence. The possible modes of breather-breather or breather-soliton interactions have been investigated. The influence of such interactions on multi-breather dynamics and its statistical characteristics has been analyzed. The results of direct numerical simulation of breather focusing with “non-optimal” phases allow finding the probability of a possible collision of more than two breathers. The formation of abnormally large pulses (rogue waves) in random ensembles of breathers has been demonstrated.

 
Analysis on the warning situation of sudden water pollution for typical river under different water regime in the river network area
Authors: Li Dayong
Published: March 2020

In this paper, a comprehensive early-warning method of sudden water pollution is used to systematically evaluate the hazards of sensitive receptors after accidents. A coupling model of the river network hydrodynamic and water quality for conventional pollutants and conservative substance is developed to track and predict the behavior and fate of the accidental pollution mass, the expert questionnaires and other means are used to construct a quantitative and qualitative early warning index system to describe the accidental hazard, the AHP and fuzzy comprehensive evaluation method are used to quantitatively evaluate the consequences of accidental hazards and a sudden water pollution risk early warning method based on the process of "accident occurrence-pollution prediction-consequence evaluation" is finally formed. The method is applied to the Yincungang River in the Yixing River Network, and the response of sensitive receptors to the discharge status of risk sources under different water regime is analyzed. The results show that: (a) the duration of the impact from the accident, the maximum standard-exceeding multiple of water quality and the degradation degree of water quality in the sensitive receptors are positively related to the discharge intensity or discharge time of the accident source, but the response time from the accidental impact is negatively related to them. (b) during the non-flood season, the warning situation in the Yincungang River shows a gradual decrease from upstream to downstream; during the main flood season, the warning situation in the upper and middle reaches of Yincungang River shows a decreasing trend, but in the middle and lower reaches that increases.(c) the transport distance and speed of accidental pollutants in the river and the concentration of accidental pollutants in the background at the sensitive receptors determine the quantitative early warning indexes dynamically, which is the fundamental reason for the spatial change of warning situation in different water regime.
Testing early-warning signals for the transition of ecological network properties in wetland complex
Authors: Kim Bin , Lee Hyojeong , Lee Khawon , Park Jeryang
Published: March 2020

Wetlands, which exist in both natural and man-made landscapes, play a critical role in providing various ecosystem services for both ecology and human-being. These services are affected not only by regional hydro-climatic and geologic conditions but also by human activities. On a landscape scale, wetlands form a complex spatial structure by their spatial distribution in a specific geological setting. Consequently, dispersal of inhabiting species between spatially distributed wetlands organizes ecological networks that are consisted of nodes (wetlands) and links (pathways of movement). In this study, we generated and analyzed the ecological networks by introducing deterministic (e.g., threshold distance) or stochastic (e.g., exponential kernel and heavy-tailed model) dispersal models. From these networks, we evaluated structural or functional characteristics including degree, efficiency, and clustering coefficient, all of which are affected by disturbances such as seasonal hydro-climatic conditions that change wetland surface area, and shocks that may remove nodes from the network (e.g., human activities for land development). Specifically, by using the characteristics of the corresponding ecological networks, we analyzed (1) their network robustness by simulating the removal of nodes selected by their degree or area; and (2) the change of variance as the early-warning signal to predict where critical point may occur in global network characteristics affected by disturbances. The results showed that there was not a clear relationship between network robustness and wetland size for node removal. However, when nodes were removed in the order of degree, the network fragmented rapidly. Also, we observed that the variance of network characteristics in the time-series increased in drier hydro-climatic conditions for all the three network models we tested. This result indicates a possibility of using increasing variance as the early-warning signal for detecting a critical transition in network characteristics as the hydro-climatic condition becomes dry. In sum, the observed characteristics of ecological networks are vulnerable to target attack on hubs (structurally important nodes) or drought. Also, the resilience of a wetlandscape can be low after hubs were destroyed or in a dry season causing the fragmentation of habitats. Implications of these results for modeling ecological networks depending on hydrologic systems and influenced by human activities will provide a new decision-making process, especially for restoring and conservation purposes.
Land degradation in high latitude areas: the role of paraglacial land surface changes driven by global warming
Authors: Knight Jasper , Strzelecki Mateusz
Published: March 2020

Enhanced anthropogenic climate change (global warming) is already leading to significant changes in the properties, processes and dynamics of land surfaces of high latitude and high altitude areas. Rapid surface and subsurface warming, ice mass loss and ice margin retreat are now resulting in increased land surface instability. Evidence for this comes from increased sediment yield by mass movements on exposed slopes, and within river systems and along coasts. In turn, increased sediment yield results in geomorphic change in these areas. The concept of paraglacial response describes the nature of changes in sediment yield and land surface geomorphology during rapidly-warming deglacial periods. This concept is increasingly relevant in a global warming context to describe land surface changes in high latitude and high altitude areas. Hitherto, paraglacial land surface responses have not been considered as part of the wider topic of global land degradation, but increased slope sediment yield and changes in the sediment mass budgets of slopes, rivers and coasts have implications for the morphodynamics and geohazards of high latitude and high altitude areas, and are similar to land degradation processes found in other climatic and physical settings. This study highlights the similarities and differences in (i) processes, (ii) spatial and temporal scale of operation, (iii) geomorphic and sediment system responses, (iv) geomorphic and environmental hazards, both direct and indirect, and (v) societal or community impacts and responses. This comparison is undertaken between paraglacial relaxation in recently deglaciated terrain, and land degradation associated with desertification in Africa. Examples of deglaciating land surfaces in Spitsbergen and in mountain blocks worldwide are used to demonstrate the wide range of contemporary paraglacial (land degradation) processes affecting these high latitude and high altitude environments. It is notable that land degradation caused by paraglaciation in these areas pose significant challenges to the sustainability of communities and to environmental monitoring and management.
Compounding Effects of Riverine and Coastal Floods and Its Implications for Coastal Urban Flood Resilience
Authors: Ganguli Poulomi , Merz Bruno
Published: March 2020

Globally more than 600 million people reside in the low elevation (< 10 meters elevation) coastal zone. The densely populated low-lying deltas are vulnerable to flooding primarily in two ways: (1) Due to extreme coastal water level (ECWL) because of either storm surges or heavy rain-induced river floods generated by a severe storm episode. (2) Co-occurrence or successive occurrence of ECWL and river floods as a result of storm-producing synoptic weather conditions leading to compound floods that causes a severe impact than when each of these extremes occurs in an isolation at different times. Most of the earlier assessments that analyzed compound floods, often do not consider the delay between rainfall and streamflow events. River runoff, which also includes subsurface groundwater recharge component, cannot be adequately described by extreme precipitation alone. While most of the literature is limited to analyzing joint dependence between variables considering only central dependence, challenges to flood hazard assessment include difficulty in delineating the severity of riverine floods, especially due to long upper tails of the variables that influence interdependencies between underlying drivers. Despite uncertainties, utilizing the rich database of northwestern Europe, here we assess compound flood severity and its trend by examining spatial interdependencies between annual maxima coastal water level (as an indicator of ECWL) and d-day lagged peak discharge within ±7 days of the occurrence of the ECWL event. Our analysis reveals a spatially coherent dependence pattern with strong positive dependence for gauges located between 52° and 60°N latitude, whereas a weak positive dependence across gauges in > 60°N latitude. Based on a newly proposed index, Compound Hazard Ratio (CHR) that compares the severity of compound floods with at-site design floods, our proof-of-principal analysis suggests nearly half of the stream gauges show amplifications in fluvial flood hazard during 2013/2014’s catastrophic winter storm Xaver that affected most of northern Europe. Furthermore, a multi-decadal (1889 – 2014) temporal evolution of compound flood reveals the existence of a flood-rich period between 1960s and 1980s, especially for the mid-latitude gauges (located within 47° to 60°N), which might be closely linked to the North Atlantic Oscillation (NAO) teleconnection pattern prevailing in the region. On the other hand, gauges at high-latitude (> 60°N) show decreasing to no trend in compound floods. The approach presented here can serve as a basis for developing coastal urban flood risk management portfolios aiding improved resilience and reduce vulnerability in the affected areas.  
A new modeling framework for air pollution forecasting in South America
Authors: Vela Angel , Alvim Debora , Vendrasco Eder , Herdies Dirceu , Figueroa Nilo , Penharkar Jayant
Published: March 2020

Biomass burning episodes are quite common in the central region of South America and represent the dominant aerosol sources during the dry/burning, between August and October. Large amounts of trace gases and aerosols injected into the atmosphere from these fire events can then be efficiently transported to urban areas in southeastern South America, thus affecting air quality over those areas. Observational data have been of fundamental importance to understand the evolution and interaction of biomass burning products with meteorology and chemistry. However, supplementing this information with the use of a comprehensive air quality modeling system in order to anticipate very acute air pollution episodes, and thus avoiding severe impacts on human health, is also required. Considering this, a new regional air pollution modeling framework for South America is being implemented by the Center for Weather Forecasting and Climate Studies (CPTEC), the National Weather Service of Brazil. This new system, based on the Weather Research and Forecasting with Chemistry model (WRF-Chem; Grell et al., 2005), is being run experimentally and its operational implementation is underway. The forecasts were driven by global forecast data from the GFS-FV3 model for meteorology and from the WACCM model for chemistry, both data sets provided every 6 hours. WACCM forecasts are employed to map gas and aerosol background concentrations to the WRF-Chem initial and boundary conditions, according to the MOZCART chemical mechanism. Two experiments of 48-hour real-time forecast simulations were performed, on a daily basis, during August and September of 2018 and 2019. The experiment for 2019 includes the very strong 3-week forest fire event when the Metropolitan Area of São Paulo, the largest metropolitan area in South America, plunged into darkness on August 19, with day turning into night. Model results are in good domain-wide agreement with satellite data and also with in situ measurements. Besides forecasts of meteorological parameters, this new system provides forecasts of regional distributions of primary chemical species (CO, SO2, NOx, particulate matter including black carbon), of secondary species (ozone, secondary organic aerosols) and air pollution related health indices, all parameters with a resolution of 20 km and for the next 72 hours.
Thermal maturity of the accretionary wedge
Authors: Mannu Utsav , Fernández-Blanco David , Miyakawa Ayumu , Gerya Taras , Kinoshita Masataka
Published: March 2020

Records of thermal maturities in boreholes have led to a better understanding of the formation of geological structures, especially the duration of thrusting during the evolution of accretionary wedges. The temporal extent of thrusting is controlled by a host of factors such as the nature of sedimentation, the topography of the incoming plate and so on. As a result, estimating the peak heating through the thermal maturity of organic material can help elucidate which mechanism has played a prominent role in wedge evolution. However, the thermal maturity value expressed as the distribution of vitrinite reflectance is the combined effect of two factors: the geothermal gradient and the time the sediments were exposed to different temperatures. Thus, the distribution of vitrinite reflectance in accretionary wedges does not necessarily reveal the deformational pathway of individual thrusts. Moreover, since the conductivity of the sediments close to the surface (<10 km) is most accessible in borehole data and predominantly controlled by porosity, models of accretionary wedge simulating thermal maturity ought to incorporate the impact of porosity on thermal conductivity. Additionally, phase transitions of the sediments in the wedge, such as smectite-illite transition and the formation of zeolite facies, that lead to increased thermal conductivity and internal angle of friction for sediments at structurally deeper locations within the wedge, must be accounted for in modeling studies. Therefore, we use a 2D thermomechanical model of subduction with empirical porosity values form the Nankai subduction margin and incorporate the effect of phase transitions to simulate the formation of the accretionary wedge under several sedimentary conditions and track the evolution of the vitrinite reflectance. As a result, we gain a holistic picture of deformation in accretionary wedges exploring different scenarios using geodynamic modeling alongside field data.