bluuebunny/crossref_metadata_2025 huggingface dataset:
Observation-Based Physics in Spectral Wave-Forecast Models
Authors: Babanin Alexander
Published: February 2023

Major update of the physics of the third generation models will be presented. The new source terms for wind input, whitecapping dissipation, interaction of waves with adverse winds (negative input) and swell attenuation have been developed and implemented in WAVEWATCH-III, SWAN and WAM models. Physics and parameterisations for the new source functions are based on observations, which allowed us to reveal features and processes previously unknown and not accounted for. For extreme conditions, physics of the wind input and whitecapping dissipation terms exhibit additional features irrelevant or inactive at moderate weather.In particular, the wave growth term was shown to be a nonlinear function of wave steepness (spectral density). Additionally, the wave breaking was found to enhance the wind input. Relative reduction of the wind input at strong-wind/steep-wave conditions was observed, due to full flow separation found at such circumstances. At strong wind forcing, this causes saturation of the sea drag.Spectral distribution of the whitecapping dissipation is the most elusive function to measure. Breaking of waves, and hence such dissipation exhibits a clear threshold behaviour in terms of wave steepness (or saturation spectrum). Other novel observed features are cumulative effect away from the spectral peak (dissipation is not local in wavenumber space), directional bimodality. It was found that at moderate winds the dissipation is fully determined by the wave spectrum whereas at strong winds it is a function of the wind speed.In absence of breaking (swell or other circumstances when the spectral density is below the threshold), other energy sink has to be invoked. It is based on observations of wave-turbulence interactions, and dependence of such interactions on wave steepness.Interaction of the waves with adverse wind is a necessary additional term if the above-mentioned wind input function is employed, since this function only describes forcing of waves by the following wind. These dependences are calibrated by means of observations in tropical cyclones.In order to test the source functions independently, and control the flux balance in the model, additional observation-based constraints are implemented. At each time step, the total momentum input is verified to match an independently known wind stress.Qualitative and quantitative effects and properties of the observation-based source terms are parameterised, and the parameterisations are presented in forms suitable for spectral wave models. The new versions of the models have undergone extensive testing by means of academic tests, regional and global wave hindcast, modelling extreme conditions ranging from tropical cyclones to the marginal ice zone.
Hydroclimatic change regulated fluvial sediment supply in southern North China during the early Permian deglacial warming
Authors: Ma Rui , Yang Jianghai , Liu Jia , Wang Yuan
Published: February 2023

  The early Permian deglacial warming is the critical period in the last icehouse to greenhouse transition in the Phanerozoic and provides an opportunity to investigate the interactions among terrestrial ecosystem evolution, regional tectonics, and climatic perturbations during climate warming. This climate change has been documented by climate modelling and geological proxies, however, its effect on fluvial sediment dispersal remains unknown. During this period, there were a southwardly diachronous aridification in North China. We here employ detrital provenance data to track the changes in continental-scale drainage system and fluvial sediment supply in southern North China. Combing detrital zircon U-Pb age and sandstone petrographic data from the early Permian sedimentary successions in southern North China defined three major sources in the Qinling orogenic belt (P1) to the south, the uplifted Paleoproterozoic-Archean basement in the northern North China margin (P2) and in the Inner Mongolia Orogen (P3) to the north. In the high-resolution chronostratigraphic framework established for North China, we use DZ mixing modeling method to quantitatively estimate the relative sediment contributions of source regions to the early Permian southern North China basin. Our modeling results suggest that the relative contribution of northly sourced detritus (from P2 and P3) increased from ~4 % in the late Gzhelian to early Asselian (ca 301−297 Ma) to ~95 % in the late Asselian to Sakmarian (ca 297−290 Ma), then declined to ~70 % in the early Artinskian (ca 290−286 Ma), finally returned to ~95% in late Artinskian (ca 286−284 Ma), whereas the estimated relative sediment contribution of the these northerly sources remained in high, stable level (~95 %) for the corresponding successions in northern North China .The increase in northerly derived sediment fraction in southern North China through the Asselian-Sakmarian can be interpreted in terms of the enhanced erosion associated with the tectonic evolution of Central Asian Orogenic Belt which caused uplifting in the northern margin of North China. In contrast, the subsequent reduction in the Artinskian is abnormal considering the persistent tectonic activities in the northern margin of North China. It can be linked instead to the climate aridification in the northern North China and resultant decrease in fluvial sediment supply from the northerly sources to the southern North China. This work highlighted the regulation of hydroclimatic change on low-latitude fluvial sediment supply during the early Permian deglacial warming.  
Characteristics of rapidly intensifying tropical cyclones in the South China Sea, 1980-2
Authors: Yang Lei , luo Xi , Zhou Fenghua , Wang Dongxiao , Wang Weiqiang
Published: February 2023

The differences in the characteristics of the rapid intensification (RI) during the TCs that form in the SCS (referred as local TCs) and thatenter the SCS from the western North Pacific (WNP; referred as entering TCs) have not been well studied, which could contribute the inaccuracyof current TC intensity forecast in the SCS. In this study, we used TC observations, reanalysis data and model experiments to analyze the RIoccurrences during local TCs and entering TCs in 1980e2016. We found that the significant interannual and interdecadal variations in RIoccurrences during local eastward-moving TCs were related to the strong intraseasonal oscillation (ISO) over the SCS and the WNP under LaNina conditions. RI during local westward-moving TCs showed insignificant variations as a result of the complex interactions among themonsoon trough, ISO and the large-scale circulation. RI during entering TCs showed strong interdecadal variations, with increased RI after1997, even though the total number of entering TCs has decreased since 1997, which is a result of a higher number of entering TCs in thenorthwestern quadrant of the WNP, a stronger ISO and weak vertical windshear over the SCS and east of the Philippines under negative phase ofPacific Decadal Oscillation. The different variations and related mechanisms of RI indicates that distinct forecasting factors should be consideredfor intensity prediction during local eastward- and westward-moving TCs and entering TCs.
Seabed substrate mapping using MBES data
Authors: Son Sanghun , Bae Jaegu , Lee Doi , Park So Ryeon , Seo Jeong Min , Kim Jinsoo
Published: February 2023

Seafloor mapping is essential for effective management and sustainable development of marine resources. Various attempts have been made to map the seafloor using single beam echo sounders, multi beam echo sounders, and side scan sonars. The purpose of this study is to map the sea floor using backscatter and bathymetry based on multi-beam echo sounders. For seafloor mapping, seafloor cover was defined as rock, gravel, sand, and mud according to the folk structure, and 135 grab data were collected for seafloor mapping and accuracy evaluation. For seafloor mapping, bathymetry depth and depth-based secondary products (aspect, curvature, slope, roughness, eastness, northness, mean, standard deviation) and backscatter intensity and secondary products that can be produced from intensity (mean, variance, roughness) was established. In addition, the output of the GLCM algorithm (angular second moment, contrast, dissimilarity, energy, entropy, homogeneity, max, mean, standard deviation) was constructed to extract various features of backscatter intensity. For seafloor cover, a random forest model, a machine learning technique that shows high performance in various fields, was selected, and the ratio of training and test datasets was selected as 8:2. To improve the performance of the random forest model, a hyperparameter was selected by applying a 5-fold cross validation and grid-search method, and the overall accuracy was 0.83.
Offshore extension of the Ilan Fault in northeast Taiwan
Authors: Chang Chih-Chia , Hsu Shu-Kun , Lin Lien-Kai , Tsai Ching-Hui , Lin Hsiao-Shan
Published: February 2023

The Philippine Sea Plate (PSP) has subducted northwestward beneath the Eurasian Plate (EP) in the northeast Taiwan and has obliquely collided with the EP creating the mountain building. The offshore area of northeastern Taiwan is subject to post-collisional collapse and under extensional regime, forming a series of normal faults. The NE-SW trending Ilan Fault is situated between the Ilan Plain and the Hseushan Range. The Ilan Fault is also call North Ilan Structure (NIS). According to the Taiwan Earthquake Model published by TEC team in 2020, the probability for a Mw 6.9 earthquake happened in NIS in future fifty years is estimated about 13%. However, if the NIS extends to the offshore area, the risk will become greater. This study aims to understand the possible offshore extension of the Ilan Fault and analyze the structural activity. For that, we have collected 24-channel sparker reflection seismic profiles and sub-bottom profilers across the possible fault trace. Based on sparker seismic profiles and sub-bottom profiles, four major normal faults, Fa, Fb, Fc and Fd, trending NE are observed. Faults Fa and Fb are active and have outcropped to the seafloor. A negative flower structure is observed along Fault Fa, which indicates that the regional stress is under transtension. Furthermore, slope failures, slumps and sliding surfaces are found. Overlying on the Last Glacial Maximum (LGM) unconformity, sedimentary layers are tilted in the hanging wall of Fault Fb, indicating Fault Fb is a growth fault. On the other hand, Faults Fc and Fd dip to the NW and SE, respectively. They bound a graben trending NE and only ruptured to the LGM unconformity. It implies that Faults Fc and Fd are no more active.
The CMIP TT Data Citation for a sustainable continuation of a requested and established service
Authors: Stockhause Martina , Ames Sasha
Published: February 2023

Data citation has become a core service for data infrastructures and data repositories, integrated in author guidelines and project proposals. It provides an essential piece in Open Science supporting reuse and enabling credit by integration into the established scientific credit system of scientific references (Scholix) and the envisioned FAIR Digital Object framework. Humans and machines need to be supported for provision and access of the information.Modern data infrastructures are federated and without central funding, especially that of international collaborations. Providing and maintaining state-of-the-art data services does not fit within current funding structures, even though these infrastructures provide core services to a broad community, like the data infrastructure of the Coupled Model Intercomparison Project (CMIP). For the citation service of CMIP6, currently a single person effort, the newly established CMIP Task Team (TT) Data Citation is exploring a set of options for a sustainable data citation service for CMIP7 and further WCRP activities in a cost-benefit approach. Due to the different experiences of its members, the TT brings infrastructure aspects together with the needs of researchers. A governance structure for sustainability, standard agreements and the coordination of further developments will be framed. The background to the TT and first experiences are shared.
Inferring Long Term Averaged Soil Redistribution Pattern using Meteoric 10Be
Authors: Sarkar Arkaprabha , Singh Vimal , Kumar Pankaj , Kumar Pavitra V. , Sharma Rajveer
Published: February 2023

Soil loss is one of the major environmental threats the world is facing due to horizontal expansion of cities and increasing land abuse. It has been previously shown by workers that the abuse or improper use of land and soil had adversely affected early civilisations. Keeping into consideration the imminent threat, a number of methods have been proposed to estimate soil loss e.g. numerical models, monitoring-based field methods. However, these are either time-consuming or inherently carry a degree of uncertainty.One method involves using environmental fallout nuclides as tracers of soil erosion and mapping areas of soil loss and accumulation. The commonly used nuclides in this technique are 137Cs and 7Be. 137Cs is a nuclear fission product and cannot be used to track soil dynamics older than 1940s, while 7Be has a very short half-life and is used to study soil dynamics in a seasonal scale.In this study, we have proposed a method of using meteoric 10Be to trace long-term soil redistribution in a landscape. This cosmogenic nuclide is produced in the atmosphere and reaches the land surface by dry and wet fallout. Once it reaches the surface, it is adsorbed by the soil particles and it mobilizes along with the soil. Thus, higher concentrations indicate net soil accumulation, whereas, lower concentrations are due to net soil loss. The rate of delivery of 10Be flux estimated from global circulation models (GCMs) has been used to calculate rates of erosion.We tested our method in Pranmati catchment, a small river catchment (~93 km2) in Uttarakhand, India and validated by comparing our findings with previously proposed geomorphic transport laws. Our results show that soil erodes from the high lying divergent (convex) topography and accumulates in the low lying convergent (concave) topography. The rates of erosion are also influenced by land cover – erosion in forests is much slower compared to grassland.
Air pollution in rural India: Analysis of satellite NO2 measurements
Authors: Pathak Mansi , Kuttippurath Jayanarayanan
Published: February 2023

India is a country having more than 67% of its population (947 million) residing in rural areas as of 2020. Therefore, health of the people in rural India becomes important for development plans, economy and growth of the nation. As the sources of NO2 are closely linked to the industrial and economic development of a country, we use satellite measurements of NO2 in rural and urban areas of India to analyse the air quality in these areas. Our findings for rural areas show strong seasonal variations, with winter having the highest NO2 (2.0×1015molec./cm2) whereas monsoon having the lowest (1.5×1015molec./cm2) levels. Around 40% of the total NO2 pollution comes from rural sources with 45% of it attributed to road transport, however urban areas with more than 90% of their NO2 from power sector were focused in the past studies. Our assessment shows that the NO2 exposure in rural regions is as severe as in urban areas; indicating the need for more effective reduction measures of population exposure and protection of public health. Henceforth, this study reveals that rural India is gradually getting polluted from its nearby regions as well as from the new sources within, which is a big concern for the health of the large rural population of India. 
Development of real-time forest fire spread prediction model based on big data
Authors: Suh Inseon , Kim Sungmin , Lee Youngmi , Jun Kyewon , Kim Byungsik
Published: February 2023

Spatiotemporal prediction of wildfire spread is very important to minimize damage and respond urgently to these urban forest fires since forest fire damages caused by strong winds such as the Foehn wind are increasing every year, especially along the eastern coastal cities in Korea. Because forest fires spread under the influence of environmental factors such as fuel, topography, and weather, the values of these factors are known as important variables for accurate forest fire spread prediction models. In this study, we developed a forest fire spread prediction model that considers wind speed, wind direction, fuel information, and slope as main factors by analyzing past forest fire damage data in Gangwon-do such as meteorological factors, fuel and terrain characteristics. The wildfire spread prediction model (hereinafter referred to as WINS, Wind field Network for Fire Spread Simulation) produces meteorological information of a numerical forecasting model calibrated with MOS (Model output statistics) as 1km x 1km grid values, and the slope and fuel information between each grid are configured. Land use information in the Gangwon area is divided into artificial grassland, mixed forest, natural measures, coniferous forest, and broad-leaved forest, and the depth of the surface fuel layer and the amount of water removal surface fuel are layered by grid according to Anderson fuel type. As soon as the ignition point information is obtained, the predicted wind speed and wind direction values of the grid are layered by time and GIS-based predicted spatiotemporal information is produced. The WINS model for forest fire cases in the Gangwon region occurred from 2019 to 2021 was verified, and real-time map-based forest fire spread prediction information was utilized by local governments and related stakeholders in the urban forest fire response task and decision-making stage according to the simulated scenario. "This research was supported by the program of Research Program to Solve Urgent Safety Issues (2022M3E9A1095664), through the National Research Foundation of Korea(NRF), funded by the Korean government. (Ministry of Science and ICT(MSIT), Ministry of the Interior and Safety(MOIS))."
Simulating regional inter-annual crop yield variability over multiple decades with the Community Land Model (CLM5)
Authors: Boas Theresa , Bogena Heye , Ryu Dongryeol , Vereecken Harry , Western Andrew , Hendricks-Franssen Harrie-Jan
Published: February 2023

Global climate change with a predicted increase in weather extremes entails vulnerability and new challenges to regional agriculture. While the general impacts of climate change on global food security are a much studied topic, the implications for regional inter-annual yield variability remain unclear. In this study, we analysed the effects of weather trends on regional crop productivity within two agriculturally managed regions in different climate zones, simulated with the latest version of the Community Land Model (version 5.0) over two decades (1999-2019). We evaluated the models’ potential to represent the inter-annual variability of crop yield in comparison to recorded yield variability and different weather indicators, e.g., drought index and growing season length and evaluated which variables (i.e., temperature, precipitation, initial soil moisture content) dominantly drive changes in CLM5-predicted yield variability. The simulation results were able to reproduce the sign of crop yield anomalies, and thus provide a basis on which to study the effects of different weather patterns on inter-annual yield variability. However, the simulations showed limitations in correctly capturing inter-annual differences of crop yield in terms of total magnitudes (up to 10 times lower than in official records). Our results indicate that these limitation arise mainly from uncertainties in the representation of the subsurface soil moisture regime and a corresponding lack of sensitivity towards drought stress. Insights from this work were used to summarize implications for future analysis of CLM5-BGC simulation results over agriculturally managed land and allowed us to discuss and investigate possible technical model improvements.
Heat-related excess mortality in Brazilian urban areas: regional, demographic and social disparities
Authors: Monteiro dos Santos Djacinto , Libonati Renata , Garcia Beatriz , Geirinhas João , Salvi Barbara , Silva Eliane , Rodrigues Julia , Peres Leonardo , Russo Ana , Gracie Renata , Gurgel Helen , Trigo Ricardo
Published: February 2023

Climate Change has increased population exposure to more frequent, more intense, and longer heat waves (HWs) worldwide. South America and particularly Brazil is highly vulnerable to rising temperatures, with limited adaptation resources and a growing and aging urban population. However still lacks research on the direct and indirect impacts of extreme heat on health in these regions, in particular on the role of social and demographic factors, as well as regional disparities in heat-related mortality. This work presents a comprehensive analysis of the occurrence of HW in the 14 most populous metropolitan regions (MRs) in Brazil, comprising circa 35% of the country's population, based on the Excess Heat Factor index. The impact of HWs on mortality was accessed employing the ratio between observed and expected deaths (O/E), which reveals a burden of 48,075 excess heat-related excess deaths over the 2000–2018 period, in line with the recent and significant increase observed in the annual number of days under extreme heat. Diseases of the circulatory and respiratory systems and neoplasms are the dominant causes of death (COD), although other COD little explored in the literature have also presented large O/E values in some MRs, such as diseases of the skin, nervous and genitourinary system, and mental and behavioral disorders. In addition, the vulnerability population profile was investigated considering the splits in terms of gender, age, race, and educational level subgroups. Overall, females, older, low-educational level, and black/brown are the most sensitive groups in most MRs, with significantly larger O/E values. Nonetheless, significant regional disparities were observed, mainly due to North-South socio-economic inequalities existing in Brazil, and differences in health indicators between these regions, such as life expectancy. Our findings are expected to guide the implementation of public mitigation and adaptation strategies in some of the most populated regions of South America.This work was supported by FIOCRUZ [grant VPPCB-003-FIO-19] and FAPERJ [grant E26/202.714/2019]. D.M.S. was supported by FIOCRUZ [grant VPPCB-003-FIO-19].
A Study on the Monitoring of Complex Disaster Using Crowd Source Data
Authors: Lee Jeongha , Hwang Seokhwan
Published: February 2023

As industrialization and urbanization progress around the world, more complex and large-scale complex disasters are occurring, causing numerous casualties and property damage every year. As climate change gradually accelerates and its impact grows, such as recent cold waves and heavy snow in the United States and abnormal temperatures in Europe, it is difficult to predict with existing physical modeling alone. Recently, disasters are gradually expanding in the form of covering not only natural disasters but also various social disasters. Social disasters cover disasters such as fires, infectious diseases, and fine dust caused by human activities. Unlike natural disasters, it is difficult to measure numerical values and predict occurrence patterns in real time, so it is very important to respond quickly through information sharing. There is a limit to establishing the same response system globally to respond to disasters that may occur worldwide, so it is necessary to develop a platform that can quickly share cases while being economical. With the recent development of communication technology, about 70% of the world's population uses smartphones, and various unstructured data are being generated in real time through various social media channels. Individuals act as a sensor and can share their location or current situation in real time. Therefore, the purpose of this study is to develop crowd sourcing technology using social media, analyze the collected data, and present ways to use it in the event of a disaster. In this study, a platform was established to collect and analyze disaster-related SNS data such as floods, fine dust, and forest fires, and it was designed so that users could receive information through websites and apps. As a result of application to various disaster cases in Korea, the temporal and spatial correlation between disaster occurrence patterns and social media data was high, and the possibility of using initial monitoring methods was proved. This result can be applied to all disaster disasters or crimes, and it is expected to be highly useful as it can quickly verify disaster thoughts and share cases in real time. 
Global Carbon Cycle of Earth System Model FIO-ESM with Surface Waves
Authors: Bao Ying
Published: February 2023

FIO-ESM (First Institute of Oceanography-Earth System Model) developed by the First Institute of Oceanography of the Ministry of Natural Resources, is an earth system model with surface gravity wave models and composed of a physical climate model and a global carbon cycle model. The Earth system model has developed from FIO-ESM v1.0, to FIO-ESM v2.0, which has been improved in both its physical climate model and the global carbon cycle model. The marine carbon cycle model of FIO-ESM v2.0 global carbon cycle model has been upgraded from the nutrient-driven model of v1.0 to the NPZD (Nutrient Phytoplankton Zooplankton Detritus) type ocean ecological carbon cycle model, and the terrestrial carbon cycle model has been upgraded from the simple light energy utilization model of v1.0 to the carbon-nitrogen coupling model considering carbon-nitrogen interaction. The atmospheric carbon cycle model is still the CO2 transport processes, with the anthropogenic carbon emissions from the fossil fuel and land use change. In terms of effects of physical process parameterization schemes on the global carbon cycle, the FIO-ESM v2.0 global carbon cycle considers not only the role of non-breaking wave induced mixing on biogeochemical variables, but also the effects of SST diurnal cycle on air-sea CO2 flux. Primary analysis shows that FIO-ESM v2.0 can simulate the global carbon cycle fairly well after considering more complex carbon cycle processes.
Impacts of wildfire aerosol on carbon uptake and sea-ice in the East Siberian Sea
Authors: Seok Min-Woo , Ko Young Ho , Kim Tae-Wook
Published: February 2023

The frequency of wildfires has increased in the Siberian region. Wildfire plumes carrying black carbon and biologically important elements may have impacts on downwind ocean regions including Arctic seas such as the East Siberian Sea (ESS). However, the responses of marine environments to the wildfire plume introduced to the ESS are not well known. In this study, we tried to identify changes in ocean phytoplankton and sea-ice associated with wildfire activities by utilizing satellite-based and reanalysis data. The amount of carbon produced by wildfires in Boreal Asia coincides with the concentration of black carbon, indicating that wildfires are responsible for the majority of the black carbon in the atmosphere. In addition, we could detect wildfire plume-derived significant increases in ocean carbon uptake from satellite-based bio-optical variables (phytoplankton growth and biomass concentration). Summertime black carbon deposition has more than doubled over the last decade, and black carbon deposition was highly correlated with sea-ice melting rate, implying a contribution of black carbon deposition on sea-ice melting, which may increase ocean productivity by enhancing light availability in the upper ESS.   
Characteristics of Medicanes using ERA-5 reanalysis
Authors: Gutiérrez-Fernández Jesús , Miglietta Mario Marcello , González-Alemán Juan Jesús , Gaertner Miguel Ángel
Published: February 2023

Several Medicanes, which have been previously analyzed in the literature, have been studied using ERA-5 reanalyses to identify the environment in which they develop and possibly distinguish tropical-like cyclones from warm seclusions. Initially, the cyclone phase space was analyzed to identify changes in the environmental characteristics. Subsequently, the temporal evolution of several parameters was considered, including sea surface fluxes, CAPE, coupling index, potential intensity, baroclinicity.Although the results are not consistent for all cyclones, some general characteristics can be identified: cyclones develop in areas of moderate-to-high baroclinicity associated with intense jet streams, while in the mature stage the environment becomes less baroclinic. A general reduction in the horizontal extent of the cyclone can be observed as the cyclones begin to show a shallow warm core. In this phase a progressive reduction of the CAPE can be observed in proximity of the cyclone center. Finally, the wind speed appears strongly underestimated compared to the observations, raising some concerns about the applicability of ERA-5 for the detection of wind features.
Reaction of the Upper Atmosphere to the 27-d Solar Cycle - Comparison of CTIPe and TIE-GCM Simulations to Observations
Authors: Dühnen Hanna , Vaishnav Rajesh , Schmölter Erik , Jacobi Christoph
Published: February 2023

Solar EUV radiation is the dominant driver for upper atmosphere ionization. Ionospheric variations that affect radio signal propagation and thus affect technical systems such as satellite-based positioning systems. One significant time scale for the solar variability is the solar 27-day rotation period that causes a corresponding response in ionospheric observables like the height-dependent electron density (Ne) or the integrated total electron content (TEC). To enhance our understanding of the processes within the ionosphere we investigate a combination of observations and physical models, namely the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model and the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM), are analyzed to identify differences in Ne, TEC data and ionized oxygen (O+ and O2+). Furthermore, the model results are compared to ground-based ionosonde Ne measurements with regard to the spatial and temporal response of the ionosphere to the 27-day solar rotation period. Modeled Ne correlates strongly with the observed Ne at mid-latitudes, but at low-latitudes the modeled TEC distribution follows the geomagnetic coordinates more strictly when compared to the observational data. Local TEC and F2 layer peak Ne are well represented by CTIPe, whereas TIE-GCM represents the global TEC and F2 layer peak height well.
Negative surface chlorophyll concentration anomalies in the southeastern Arabian Sea during 2015 and 2019 summers
Authors: Huang Huaming
Published: February 2023

Two extremely low surface chlorophyll concentration events in the southeast Arabian Sea (SEAS, 6oN-15oN, 72oE-77oE) during summers of 2015 and 2019 have been found since 1998. Although warm sea surface temperature (SST) and low nutrients are the direct cause for the anomalously low surface chlorophyll concentration, the physical processes leading to the warm SST anomalies during 2015 and 2019 summer are different. Satellite observations, model outputs and reanalysis data are used to explore the related mechanisms. In 2019, the combined effects of northward local wind anomaly due to extreme positive IOD and westward-propagating downwelling Kelvin wave driven by the easterly anomaly in eastern Sri Lanka weaken the upwelling in the SEAS, leading to warm SST anomaly and suppressing the upward transport of the subsurface nutrients to the surface. A weaker positive IOD occurred in 2015, leading to stronger upwelling in the SEAS than during 2019. Yet, seawater in the SEAS experienced extreme warming (lowest SST exceeded 28.5oC) due to the development of super El Niño in 2015. The significant seawater warming can shoal mixed layer and prevent the nutrients in the subsurface from reaching surface, which is unfavorable for the chlorophyll growth. The thermal balance analysis suggests that the extreme warming in the SEAS was mainly related to more downward shortwave radiation.
The Timing of Decreasing Coastal Flood Protection Due to Sea-Level Rise
Authors: Hermans Tim , Malagón-Santos Victor , Katsman Caroline , Jane Robert , Rasmussen Dj , Haasnoot Marjolijn , Garner Gregory , Kopp Robert , Oppenheimer Michael , Slangen Aimée
Published: February 2023

Sea-level rise (SLR) amplifies the frequency of extreme sea levels as it raises their baseline height. Projections of the frequency amplification of extremes are often computed for arbitrary future years and relative to the historical centennial event, which is not necessarily meaningful locally. Consequently, such projections may not provide salient information to adaptation planners, as they do not indicate when certain flood risk thresholds will be crossed given the current degree of local coastal flood protection.To better support adaptation planning, we introduce a framework that extends the emerging timing perspective on sea-level rise to the frequency amplification of extreme sea levels. Moreover, by relating amplification factors to local flood protection standards estimated with the FLOPROS modelling approach, we project the timing of decreases in the local degree of protection. The sea-level rise required for such decreases is derived from extreme sea-level distributions inferred from GESLA3 observations and combined with the relative sea-level projections of the Sixth Assessment Report of the IPCC until 2150 to compute the timing of these decreases at tide gauges globally.Our central estimates indicate that the estimated degrees of protection will be exceeded 10 times as frequently within the next 30 years (the lead time that large adaptation measures may take) at 26 & 32% of the tide gauges considered, and annually at 4 & 8%, for respectively a low & high emissions scenario (SSP1-2.6 & SSP3-7.0). Even though our results are based on estimated degrees of protection, they highlight that at several locations substantial decreases in the degree of protection may occur before large adaptation measures can be completed. Furthermore, we find that under SSP3-7.0, the same decreases in the degree of coastal protection will occur substantially faster in the future as sea-level rise accelerates. Our projection framework adds a new perspective on the frequency amplifications of extremes that may help adaptation planners to assess the available lead time and useful lifetime of protective infrastructure, given unacceptable decreases in the degree of coastal protection.
Are ensemble NWP forecasts now so good that calibration is unnecessary?
Authors: Bennett James , Robertson David , Shrestha Durga Lal , Robinson Kim , Schepen Andrew
Published: February 2023

For streamflow forecasting, calibration of ensemble numerical weather prediction (NWP) models has long been considered a necessary evil. Necessary, because NWP forecasts are usually too biased to force calibrated hydrological models, they often produce unreliable ensembles and may produce forecasts that are less accurate than simple climatology at longer lead times. Evil, because calibration adds complexity to any forecasting system and the calibration process destroys spatial, temporal and inter-variable correlations in the ensemble, which then must be reconstructed in various and usually unsatisfying ways. As ensemble NWPs improve, the degree to which calibration is ‘necessary’ declines.Here we investigate recent versions of two ensemble NWP models – the European Centre for Medium-range Weather Forecasts ensemble NWP (ECMWF-ens) and the Bureau of Meteorology’s Australian Community Climate and Earth-System Simulator Global Ensemble (ACCESS-GE) NWP. The models are tested over Tasmania, where CSIRO is working with Hydro Tasmania, Australia’s largest generator of hydropower, to establish new ensemble streamflow forecasting systems. Tasmania is mountainous and temperate and features strong rainfall gradients. We apply an existing calibration method – the Catchment-scale Hydrological Precipitation Processor (CHyPP) – which uses a Bayesian Joint Probability model to calibrate ensemble precipitation forecasts.We show that CHyPP improves reliability in both the ECMWF-ens and ACCESS-GE ensembles, but these improvements come at the cost of a slight reduction in skill at short lead times. Uncalibrated ACCESS-GE forecasts generally produce more biased and less reliable forecasts than ECMWF-ens, and we conclude that calibration is necessary for the ACCESS-GE model, both to reduce biases and improve reliability. However, the improvements in bias from calibrating the ECMWF-ens are negligible in some catchments, with the main benefit being improved reliability at longer lead times. This brings into question the need for calibration of the ECMWF-ens model with CHyPP. We note that these findings may not hold outside the Tasmanian catchments tested, where high resolution ensemble NWP forecasts generally perform well. We discuss the implications of these findings with respect to streamflow forecasts.
Importance of in-situ measurements of both N2O and N2 emissions to calibration of biogeochemical models to simulate N budgets
Authors: Takeda Naoya , Friedl Johannes , Rowlings David , Scheer Clemens , Haas Edwin , Kraus David , Grace Peter
Published: February 2023

Denitrification is a key process in the global nitrogen (N) cycle, causing nitrous oxide (N2O) and dinitrogen (N2) emissions. Even though denitrification is assumed to be a major N loss pathway from agroecosystems, field-scale estimates of both N2O and N2 are scarce, reflecting methodological difficulties in measuring and upscaling N2 emissions. Mechanistic biogeochemical models allow estimates of seasonal denitrification losses at the field scale, extrapolating important yet often limited experimental results. However, such predictions rely mostly on N2O data, meaning that the lack of N2 data hinders the validation of overall denitrification rates, which remain a major uncertainty for N budgets.This study investigated denitrification losses and N budgets in two subtropical sugarcane systems using Agricultural Production Systems sIMulator (APSIM) with unique datasets of both N2O and N2 emissions measured in the field with the 15N gas flux method and upscaled over the growing season. Five key soil N parameters in APSIM were identified as influential on N2O and N2 emissions via global sensitivity analysis, followed by generalised likelihood uncertainty estimation to determine their posterior distributions using (i) both N2O and N2 data and (ii) N2O data only.For both approaches, the calibration of APSIM led to larger denitrification (N2O+N2) losses and a shift towards N2 compared to the use of default parameters. Simulated N2O emissions did not differ between the different calibration approaches. However, simulated N2 emissions were larger and agreed better with the observed values when calibrated with both N2O and N2 consistently across sites. This approach also improved the simulation of fertiliser N losses via denitrification, leaching and runoff, compared to the observed fertiliser 15N loss at harvest.These findings indicate that biogeochemical models commonly used with default soil N parameters or calibration limited to N2O data are likely to underestimate denitrification losses, producing a bias in simulations of N budgets. Our findings also highlight the importance to integrate in-situ measurements of N2O and N2 in simulation exercises, and demonstrate how innovative isotope methods can be used to inform biogeochemical models, ensuring more accurate N budget estimates across scales.
The interdecadal changes in the pattern of summer precipitation over the Tibetan Plateau around the mid-1990s
Authors: Shang Wei , Duan Keqin , Ren Xuejuan
Published: February 2023

The interdecadal changes in the pattern of the summer precipitation over the Tibetan Plateau (TP) are studied around the mid-1990s. During 1961-1996, the dominant mode of the interannual variations of summer precipitation over the central-eastern TP is shown a dipole pattern, with opposite variation between the southeastern and northeastern TP. While during 1997-2019, the dominant mode become a mono-sign pattern. During 1961-1996, the dipole pattern of TP precipitation is essentially driven by the North Atlantic Oscillation (NAO) and the related circulation anomalies. However, the impact of NAO on the TP precipitation has weakened since the mid-1990s. In contrast, more intensified positive height anomalies in the upper troposphere are observed over the whole TP regions during 1997-2019. Meanwhile, the southerly moisture flux from the Bay of Bengal and the Philippine Sea is prevalent significantly with strong moisture convergence. This interdecadal spatial shift is mainly attributed to the significant increasing of the sea surface temperature (SST) in the Atlantic Ocean and Indo-Pacific warming pool. The warming SST could induce Rossby waves and propagate to TP regions. The wave train-related positive height anomalies are in favor for the strengthening of the South Asian high (SAH). Moreover, the SAH-related circulation anomalies are primarily responsible for the intense vertical flow anomalies in the TP. As a result, the summer precipitation anomalies over the entire TP regions are largely increased and formed the mono-sign pattern during 1997-2019. Based on the Coupled Intercomparison Project Phase 6 models projection results, further analysis demonstrates that the dominant pattern of summer precipitation in south and north TP shows robustly consistent variation during the center and end of the 21st century, and would become more pronounced under higher scenario. These findings indicate the significant future transformation of TP precipitation pattern and atmospheric circulations in response to greenhouse warming.
From Trace Elements to Petrogenesis: A Machine Learning Approach to Determine Ore Deposit Type from Trace Elements Analysis of Apatite
Authors: Zhou Tong , Qiu Kunfeng , Wang Yu
Published: February 2023

The diverse suite of trace elements incorporated into apatite in ore-forming systems has important applications in petrogenesis studies of mineral deposits. Trace element variations in apatite can be used to distinguish between different types of rocks as well as discriminating between deposit types, and thus have potential as mineral exploration tools. Such classification approaches commonly employ two-variable scatterplots of apatite trace element compositional data. While such diagrams offer easy and convenient visualization of compositional trends, they often struggle to effectively distinguish deposit types because they do not employ all the high-dimensional (i.e. multi-element) information accessible from high-quality apatite trace element analysis. To address this issue, we employ, for the first time, a supervised machine learning-based approach (eXtreme Gradient Boosting, XGBoost) to correlate apatite compositions with ore deposit type, utilizing high-dimensional information. We evaluated 8629 apatite trace element data from five deposit types (porphyry, skarn, orogenic Au, iron oxide copper gold, and iron oxide-apatite) along with unmineralized apatite to discriminate between apatite in mineralized vs unmineralized systems. We could show that the XGBoost classifier efficiently and accurately classifies high-dimensional apatite trace element data according to the ore deposit type (overall accuracy: 94% and F1 score: 89%). Interpretation of the model using the SHAPley Additive exPlanations tool (SHAP) shows that Th, U, Eu and Nd are the most indicative elements for classifying deposit types using apatite trace element chemistry. Our approach has broad implications for the understanding of the sources, chemistry and evolution of melts and hydrothermal fluids resulting in ore deposit formation.Keywords: Machine learning; apatite; Trace elements; Ore deposit type; XGBoost
Sub-daily Antarctic sea-ice variability estimates using swath-based retrieval methods
Authors: de Jager Wayne , Vichi Marcello
Published: February 2023

Satellite-derived sea-ice concentration measurements have traditionally been used to evaluate the impact of climate change on polar regions. However, concentration-based measurements of sea-ice variability do not allow the discrimination of the relative contributions made by thermodynamic and dynamic processes. This prompts the need to use sea-ice drift and type products and develop new methods to quantify changes in sea-ice properties that would indicate trends in the ice characteristics. A component of the sea-ice variability is driven by local weather events, and in some cases is the dominant driver of variability over larger-scale atmospheric features. Previous work by de Jager & Vichi (2022) has suggested that sea-ice vorticity (derived from low resolution sea-ice displacement vectors) may be a useful metric for quantifying dynamical features in Antarctic sea ice; specifically shorter term changes in the ice-interior driven by atmospheric storms. However, this study hypothesised that much of the rotational drift in the underlying sea-ice field was blurred as a result of the relatively large 48-hr temporal resolution of the drift product, therefore highlighting the necessity of measuring sea-ice properties at higher temporal frequencies. This study will therefore assess the usefulness of an overlapping swath-based method of sea-ice displacement retrieval recently made available by the EUMETSAT OSI-SAF. This swath-based method of retrieval allows for analysis of sea-ice variability at sub-daily timescales, which may be more suitable for measuring the effect of weather events on the sea-ice landscape than using daily averages of merged swaths. In situ data of sea-ice conditions were collected on board the SA Agulhas II research vessel in the Atlantic Sector in July, 2022, which will be compared to swath-based satellite estimates. Furthermore, the newly released 24-hr OSI-SAF drift product will also be compared. To complement these drift estimates, a modified swath-based ice-type retrieval method will be presented to add further context to any potential thermodynamic changes affecting the optical properties of the sea-ice surface.