bluuebunny/crossref_metadata_2025 huggingface dataset:
Decadal change of spring extreme consecutive dry days in the Yangtze River Valley around the early 2000s: Synergistic effect of mega-El Niño/Southern Oscillation, Atlantic Multidecadal Oscillation, and Arctic sea ice
Authors: Zeng Zixuan
Published: February 2023

The Yangtze River Valley (YRV) is the main rice-growing region in China and agriculture production in YRV plays a vital role in ensuring food security. Spring is the key season of plowing preparation and sowing, and drought during this period could cause serious threats to agricultural activity in YRV. As a basic feature of drought, consecutive dry days (CDDs), especially the extreme-CDDs with long duration, could directly reflect the drying degree and serve as a good indicator of drought. Therefore, knowledge of variations and mechanisms of spring extreme-CDDs has significant implications for a comprehensive view of spring drought in YRV. Based on daily station precipitation data, the variability of spring extreme-CDDs in YRV is investigated. It is found that the extreme-CDDs in YRV experienced a significant decadal increase around the early 2000s. Associated with this decadal change, the Mongolian high (MH) and western North Pacific anticyclone (WNPA) are significantly intensified and weakened, respectively. The intensified MH and weakened WNPA lead to anomalous northerlies and water vapor divergence over YRV, providing favorable atmospheric conditions for more extreme-CDDs over the region. Further mechanism analyses suggest that the transition of mega-El Niño/Southern Oscillation (mega-ENSO) from the negative-phase to positive-phase contributes to the decadal weakening of WNPA. And the phase transition of Atlantic Multidecadal Oscillation (AMO) and decadal decrease of sea ice over the Barents Sea lead to intensified MH through exciting atmospheric wave train. Multiple linear regression shows that there could be a synergistic role of mega-ENSO, AMO, and sea ice over the Barents Sea in the decadal change in YRV extreme-CDDs around the early 2000s. Analysis on the simulation of 14 models in the Atmospheric Model Intercomparison Project (AMIP) experiment from phase 6 of the Coupled Model Intercomparison Project (CMIP6) shows that the models can reproduce the observed decadal intensification of MH and weakening of WNPA around the early 2000s, indicating the contribution of mega-ENSO, AMO, and sea ice over the Barents Sea to the decadal changes in MH, WNPA and extreme-CDDs in YRV.
Compound storm surge and river flood events in the coastal zone: Exploring the influence of data sources and compound approach on extreme recurrence levels
Authors: Dubois Kevin , Andreas Dahl Larsen Morten , Drews Martin , Nilsson Erik , Rutgersson Anna
Published: February 2023

Floods are among the most impactful disasters especially in terms of economy in affecting humans’ activities and damaging infrastructures. This is particularly the case along the coast where coastal floods happen. Such floods can be due to three different factors: meteorological (precipitation), hydrological (river runoff) and oceanographic (storm surge). A single factor but also a combination of two or more of such factors happening at the same time can lead to coastal floods also called compound floods. Flood hazards can then be underestimating when compound effects are not considered. This study focuses on coastal compound floods from oceanographic and hydrological phenomena at the coastal city of Halmstad (Sweden). It aims to quantify the risk of such flood events at Halmstad and to analyse the sensitivity of data sources and copula’ approaches.Here, the copula method is used to analyse compound floods based on annual maxima of river discharge and corresponding sea level and vice-versa. A comparison is carried out with the commonly used Extreme Value theory on a single factor and the compound approach. Effects from different data time-series available from observations and models for both river discharge and sea level are studied.This paper concludes the presence of a higher risk of flooding when compound effects are not considered and that the choices made on input datasets and copulas can have a significant impact.
Characterizing CO2 enhancements at major hotspots in South Korea using OCO-3 XCO2 retrievals
Authors: Park Sung-Bin , Kang Yeri , Oh Young-suk , Song Chang-Keun , Park Sang Seo
Published: February 2023

Consistent and long-term monitoring and understanding spatiotemporal distributions of carbon dioxide (CO2) in the atmosphere and local emission sources are essential to achieve the carbon neutrality by 2050. Quantifying accurate spatiotemporal CO2 enhancements is uneasy task because of its relatively long lifetimes in the atmosphere compared with methane and nitrogen dioxide. If the observatory is situated close to the area affected by transboundary air pollutants and local emission sources (e.g., cities, power plant, industrial areas etc.), estimating CO2 enhancements are even more challenging. Satellite CO2 observations are powerful to examine local to regional CO2 enhancements from the emission hotspot regions with wider spatial coverage compared with ground-based observatory. Especially, NASA's Orbiting Carbon Observatory-3 (OCO-3) has demonstrated its feasibility to quantify local CO2 emissions from the emission hotspots. To better understand source-sink characteristics of CO2 in South Korea, we examined spatiotemporal distributions in local CO2 enhancements of the several hotspots from the OCO-3 Level 2 bias-corrected column-averaged dry-air mole fractions of CO2 (XCO2) v10.4r. We determined CO2 enhancements utilizing monthly climatology statistics from the Fourier Transform Spectrometer (FTS) XCO2, Anmyeon-do (36.5382◦N, 126.3311◦E) in South Korea, subtracted from OCO-3 XCO2 at each pixel. We used FTS-XCO2 measurements from the update Total Carbon Column Observing Network (TCCON) GGG2020 retrieval algorithm. Our preliminary results suggest that CO2 enhancements over the major hotspots in South Korea showed wide ranges from -5 ~ 12 ppm measured from Snapshot Area Maps (SAMs) measurement modes. This large variability may be associated with the definition of enhancement determination, geographical location, and seasonal wind characteristics. We will discuss these potential error sources of uncertainties and how we can enhancement estimates to better quantify CO2 emissions. We anticipate our study provide insights for the robust and reliable quantifications of CO2 enhancements, establish an advanced level of the greenhouse gases and air quality monitoring strategy in South Korea.
The Effect of Nonlinear Viscoelasticity on Planetary Love Numbers
Authors: Maor Ron , Goldsby David
Published: February 2023

The planetary Love number is a dimensionless parameter representing the deformation response of a planetto stress (Love, 1927). In its original formalism, the Love number was defined for pure elastic deformations,but this definition was later extended to linear viscoelastic deformations using the Correspondence Principle(Peltier, 1974). Currently, there are multiple methods for calculating planetary Love numbers that canincorporate advanced rheological models (Henning and Hurford, 2014; Renaud and Henning, 2018; Meliniet al., 2022), yet all of these methods require that the rheology will be limited to linear viscoelasticity.On the other hand, laboratory studies of attenuation on different geological materials suggest a nonlinearviscoelastic behavior due to the movement of dislocations within the lattice (Gueguen et al., 1989; McCarthyand Cooper, 2016). At high enough stresses, dislocations can escape pinning points and interact witheach other (Gremaud, 2009), leading to permanent deformations and attenuation that is dependent onthe amplitude of the oscillations. In this work, we are taking the first step into incorporating nonlinearviscoelasticity in the calculation of planetary Love numbers. Assuming a homogeneous, incompressible,self-gravitating sphere with nonlinear rheology, we are using a numerical scheme to calculate the complexLove number. The results of the numerical model are then compared to the known analytical solutions forthe linear case.
Post-drought root exudation defines soil organic matter stability in a temperate mature forest
Authors: Brunn Melanie , Hafner Benjamin D. , Bölscher Tobias , Hikino Kyohsuke , Jungkunst Hermann F. , Kučerík Jiří , Neff Janina , Pritsch Karin , Sayer Emma J. , Weikl Fabian , Zwetsloot Marie J. , Bauerle Taryn L.
Published: February 2023

Forest soils are crucial for many ecosystem services that rely on soil organic matter (SOM) stability. Carbon allocated to roots and released as exudates to the rhizosphere plays a key role in SOM stabilization. Under periodic drought, elevated root exudation and SOM accumulation have been reported. Yet, whether root exudates control SOM formation and stability in mature forests once the drought ends is largely unknown. We examined whether root exudates from P. abies and F. sylvatica trees relate to SOM formation and stability in soil depth profiles one year following five years of experimental drought (Kroof experiment, Germany). We collected root exudates throughout the rooting zone and combined the data with thermogravimetric analysis of SOM in the rhizosphere and non-rooted soil. We found that the rhizosphere of both species was characterized by stable SOM fractions that did not decrease post-drought, suggesting potential protection of SOM due to rhizodeposition and root exudates. In contrast, stable SOM fractions decreased relative to controls in non-rooted topsoil below P. abies, indicating a loss of stabilized SOM from drought-affected and re-wetted soil. Our measurements provide valuable insights into post-drought SOM formation and mechanisms of SOM stabilization in forest ecosystems under climate change.
Afforestation in water scarce environment under Climate Change: Will trees survive and thrive?
Authors: Eliades Marinos , Theocharidis Christos , Neophytides Stelios , Papoutsa Christiana , Varvaris Ioannis , Pittaki Zampela , Argyriou Athanasios , Djuma Hakan , Bruggeman Adriana , Hadjimitsis Diofantos
Published: February 2023

The EU Forest strategy for 2030 aims in adapting Europe’s forests to the new climatic conditions and weather extremes due to the ongoing Climate Change. Enlarging EU’s forests through afforestation is one of the key objectives of this strategy. However, the success of afforestation in semi-arid regions depends on the capacity of trees to adapt to the drought conditions, which are expected to intensify in the near future. Thus, further research on the long-term forest growth dynamics in these environments is needed. Two different sites, located in Athalassa Forest Park (Nicosia, Cyprus), were selected for monitoring of the NDVI (Landsat, 30 m resolution) between 2000 and 2022.  The park has an average annual rainfall of 315 mm (1980-2010), a mean daily minimum temperature of 5° C (January) and a mean daily maximum temperature of 37° C (July and August). The first site (hereafter referred to as NFO) was converted in 2011 from rainfed agriculture to a mixed species forest by planting seedlings of different, indigenous, drought-tolerant tree and shrub species. The second site (hereafter referred to as EFO) is an established forest. The seasonal understory vegetation (weeds, grass), due to the open character of the forests, had a clear effect on the results as shown by the monthly range of NDVI (0.1 – 0.9). Thus, the minimum value of the annual NDVI was used to examine the forest growth patterns, assuming that this value represents the forest without the effect of understory vegetation. Preliminary results show an average minimum NDVI of 0.32 on EFO with annual changes ranging from 0.23 to 0.42. NFO shows an increasing trend in annual NDVI (r2 = 0.901). More specifically, in 2022 the NDVI of NFO and EFO were similar (0.32). The results indicate that the indigenous trees and bushes in Athalassa manage to survive and grow in this water scarce environment.The authors acknowledge the ‘EXCELSIOR’: ERATOSTHENES: EΧcellence Research Centre for Earth Surveillance and Space-Based Monitoring of the Environment H2020 Widespread Teaming project (www.excelsior2020.eu). The ‘EXCELSIOR’ project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 857510, from the Government of the Republic of Cyprus through the Directorate General for the European Programmes, Coordination and Development and the Cyprus University of Technology.
Multi-variable Pareto optimal calibration of the global hydrological model WaterGAP for 1500 major drainage basins around the globe
Authors: Hasan HM Mehedi , Hosseini-Moghari Seyed-Mohammad , Döll Petra , Güntner Andreas
Published: February 2023

Global hydrological models (GHM) are indispensable tools for understanding hydrological dynamics in natural settings as well as for analysing complex hydrological human-nature systems in critical regions of the globe and for supporting sustainable management policies in current context and future climate change scenarios. However, GHMs suffer from high predictive uncertainties which stem from input data and climate forcing uncertainties, incomplete knowledge about hydrological processes and their imprecise mathematical description, unknown initial and boundary conditions, and uncertain parameters. Reduction of these uncertainty by model calibration has almost never been performed globally for any GHM due to the high number of parameters in these models, the limited availability of observations of critical hydrological variables at a scale suitable for these models, and the high computational complexity and demand of model calibration. To address these issues, we have developed and employed a parallel and scalable multi-criterial Pareto optimal calibration framework to estimate parameters of the state-of-the-art global hydrological model WaterGAP for 1509 drainage basins with available streamflow observations. Model calibration was done against gauge-based observations of streamflow (Q) and terrestrial water storage anomalies of GRACE/GRACE-FO (TWSA). The influential parameters of each basin were identified prior to calibration by a multi-variable sensitivity analysis for the variables Q, TWSA, and percentage snow cover in the case of basins with relevant snow accumulation. We expect that our study will advance methodologies for sensitivity and calibration analyses of GHMs.
Modeling the impacts of climate change on streamflow and nitrate export in a Mediterranean agricultural watershed in Spain
Authors: Oduor Brian Omondi , Campo-Bescós Miguel Ángel , Lana-Renault Noemí , Casalí Javier
Published: February 2023

Nitrate pollution adversely affects water quality, making it unsafe for human consumption and contributing to increased eutrophication. Nitrate exportation in agricultural areas is inevitable; however, climate change introduces great uncertainty into an already very complex problem. Thus estimating the effects of climate change on streamflow and nitrate dynamics would significantly contribute to the management of the affected areas. This research aimed to predict the impacts of climate change on streamflow and nitrate exportation in a Mediterranean rainfed agricultural watershed using the Soil Water Assessment Tool (SWAT). The model was first evaluated for its suitability to simulate streamflow and nitrate loads under rainfed agricultural conditions in the 477 km2 Cidacos River Watershed in Navarre, Spain. The model was then used to analyze the climate change impacts on streamflow and nitrate load in the short-term (2011-2040), medium-term (2041-2070), and long-term (2071-2100) climate projections compared to a historical baseline period (1971-2000) using the RCP4.5 and RCP8.5 CO2 emission scenarios. The model evaluation showed a good model performance during calibration (2000-2011) and validation (2011-2020) for streamflow (NSE = 0.82/0.83) and nitrates load (NSE = 0.71/0.68), indicating its suitability for adoption in the watershed. The climate change projection results showed a steady decline in streamflow and nitrate load for RCP4.5 and RCP8.5 in all the projections, with the long-term projection scenario of RCP8.5 significantly affected. Autumn and winter saw the greatest seasonal declines compared to spring and summer. The decline in streamflow was attributed to the projected decrease in precipitation and increase in actual evapotranspiration due to increasing temperatures, while the nitrate load decline was consistent with the projected streamflow decline. Based on these projections, the long-term projection scenarios of RCP8.5 indicate severe situations requiring urgent policy changes and management interventions to minimize and mitigate the negative consequences. Therefore, better agricultural management practices are needed to ensure sustainable water resource utilization and efficient nitrogen fertilizer application rates in the watershed to reduce pollution.
Hydrodynamic modelling to assess habitat suitability of the Ganga River
Authors: Sonkar Gaurav Kailash , Gaurav Kumar
Published: February 2023

We perform hydrodynamic modelling using a 2D HEC-RAS model to assess the hydraulic habitat suitability in a data-constrained reach (7 km) of the Ganga River. This reach of the Ganga River is located within two structural barriers of the upper Ganga plain, namely the Bijnor barrage in upstream and the Narora barrage in downstream. It is an active river dolphin and gharial habitat. To setup and run the 2D flow simulation in HEC-RAS, we used topographic data from a LiDAR drone survey, channel bathymetry from field campaigns, time-series river stage (to define the boundary conditions of the model domain), and water surface slope from using the real-time kinematic GPS. We use water level time series data from a satellite altimeter (downstream) and discharge measured in the field using an ADCP for model calibration and validation, respectively.We found that the study reach has poor habitat suitability at low flow, which improves at median flow. The use of altimeter datasets for model calibration is quite handy when the in-situ data is not readily available. This study provides a methodological framework to assess the hydraulic habitat suitability in rivers near structural interventions.
Mass balance of the northern Antarctic Peninsula Ice Sheet
Authors: Seehaus Thorsten , Sommer Christian , Malz Philipp , Dethinne Thomas , Navarro Francisco , Shahateet Kaian
Published: February 2023

Some of the highest specific mass change rates in Antarctica are reported for the Antarctic Peninsula. However, the existing estimates for the northern Antarctic Peninsula (<70°S) are either spatially limited or are affected by considerable uncertainties. Within this study, the first assessment of the geodetic mass balance throughout the ice sheet of the northern Antarctic Peninsula is carried out employing bi-static SAR data from the TanDEM-X satellite mission. Repeat coverages from austral-winters 2013 and 2017 are employed. An overall coverage of 96.4% of the study area by surface elevation change measurements is revealed. The spatial distribution of the surface elevation and mass changes points out, that the former ice shelf tributary glaciers of the Prince-Gustav-Channel, Larsen-A&B, and Wordie ice shelves are the hotpots of ice loss in the study area, and highlights the long-lasting dynamic glacier adjustments after the ice shelf break-up events. The highest mass change rate is revealed for the Airy-Seller-Fleming glacier system and the highest average surface elevation change rate is observed at Drygalski Glacier. The comparison of the ice mass budget with anomalies in the climatic mass balance indicates, that for wide parts of the southern section of the study area the mass changes can be partly attributed to changes in the climatic mass balance. The previously reported connection between mid-ocean warming along the southern section of the west coast and increased frontal glacier recession does n
A Numerical Study to Investigate Precipitation Features of Monsoon Deep Depressions over Bay of Bengal: Comparison of Coupled and Control Simulations
Authors: Chakraborty Tapajyoti , Pattnaik Sandeep , Baisya Himadri
Published: February 2023

The present study is aimed to investigate the rainfall characteristics of Monsoon Deep Depressions (MDD) originating over the Bay of Bengal (BoB) basin using a coupled ocean-atmospheric model (COAWST) and a stand-alone atmospheric (WRF) model with a lead time of up to 72h. It is found that though the tracks of the four MDDs considered in the study have been reasonably simulated, the intensity was overestimated in both sets of simulations compared to India Meteorological Department (IMD) best estimates. Upon decomposition of the contributors to the rainrate for the composite of the storms in the deep depression (DD) phase, it was found that the moisture sources/sinks play a more important role than the cloud sources/sinks in modulating the rainfall processes. Further analysis of the moisture sources/sinks showed that the horizontal and vertical advection are the major drivers in modulating the contribution of the moisture sources/sinks. The validation of rainfall using CMORPH datasets suggested that the coupled simulations had a higher skill in rainfall prediction. Furthermore, the composite of different components of moisture sources/sinks (especially vertical advection) was found to be more realistically simulated in COAWST compared to WRF upon validation with MERRA datasets. Analysis of the composite energetics showed that scarcity of bulk kinetic energy in the later hours of the DD phase in COAWST led to the dissipation of the storm core, which led to better prediction of rainfall. On the other hand, a re-intensification of the storm core by means of condensational heating led to an overestimation of rainfall in WRF, which finally resulted in lower skill in rainfall prediction. In spite of the stand-alone atmospheric model capturing the horizontal moisture incursion in the lower levels significantly, the better representation of the vertical structure enabled the coupled model to capture the precipitation features more realistically, increasing skill in rainfall prediction.
Understanding the aerosol-cloud interactions in ship-dominated and cleaner environments in the Celtic Sea.
Authors: Thamban Navaneeth Meena , Wu Huihui , Choularton Thomas , Coe Hugh , Bower Keith , Matthews Emily , Bannan Thomas , Marsden Nicholas , Lee James , Pasternak Dominika , Yang Ming-Xi , Batten Stephanie , Bell Thomas , Temple Loren , Bauguitte Stéphane
Published: February 2023

Aerosol-cloud interaction contributes to one of the highest uncertainties in radiative forcing estimations. Aerosols from ship emissions alter the cloud properties and have become an important source of anthropogenic air pollution in recent decades.  We have measured the size distributions and number concentrations of aerosols in the cloud and outside clouds using various onboard instruments such as cloud droplet probe (CDP; DMT), passive cavity aerosol spectrometer (PCASP, DMT), Scanning Mobility Particle Sizer (SMPS) and Single Particle Soot Photometer (SP2; DMT). The measurements were performed in the ship emission-dominated environments and relatively cleaner regions of the Celtic Sea.  We discuss the difference in the characteristics of in-cloud and out-cloud measurements in these relatively contrasting environments. The measurements were made between 29th September and 12th October 2021 using the Facility for Airborne Atmospheric Measurements (FAAM) research aircraft as a part of the Atmospheric Composition and Radiative forcing changes due to UN International Ship Emissions regulations (ACRUISE) Project.
Challenges, best practices and case examples in muon imaging
Authors: Varga Dezső , Surányi Gergely , Hamar Gergő , Nyitrai Gábor , Balázs László
Published: February 2023

Muography is an inherently multidisciplinary field, and as such presents a wide range of practical and methodological challenges. Regarding instrumentation, the environment drastically differs from the high energy physics laboratory conditions. In addition, the choice of measurement location and the instrument with the most suitable parameters is far from obvious: one needs to balance between improving detection sensitivity (e.g. moving closer to the target) and local possibilities (accessibility, safety). The presentation gives an overview of successful implementations, with detailed case examples with participation of Wigner Research Centre for Physics. Detectors on the surface need to cope with daily thermal cycling and intermittent high humidity periods, as apparent at the Sakurajima Muography Observatory, or imaging a medieval castle in Sicily. Underground detectors on the other hand require fast and efficient installation, since such environments -- particularly mining -- safety concerns limit personal access. Examples include mines from Finland and Bosnia and Herczegovina. From the point of view of methodology, the presentation will discuss the data quality requirement for three dimensional density map reconstruction (tomography). In case of a complicated karst structure, low density zones identified by muon tomography were confirmed by drilling.
Impact of flux type variable exchange method in the atmosphere-ocean coupled version of the Korean Integrated Model (KIM) system for extended medium-range weather forecast
Authors: Yeo Namgu , Chang Eun-Chul , Song Hajoon , Park Junseong , Lee Eunjeong , Koo Myung-Seo
Published: February 2023

Extended medium-range prediction targets a period of up to 30 days, which is a longer period than medium-range (up to 15 days) and shorter than seasonal (up to 3 months) forecast. The atmospheric response to the initial condition significantly impacts predictability in medium-range prediction while ocean response which is a slower change compared to the atmosphere is also an important factor in extended medium-range prediction. Thus, it is important to consider not only initial forcing but also air-sea interaction containing ocean response in extended medium-range prediction. The interactions in the earth system model can be considered among the atmosphere, ocean, sea-ice, and ocean wave by coupling of each components. The Korean Integrated Model (KIM) system, which is a global atmospheric forecast model, was developed by the Korea Institute of Atmospheric Prediction Systems. Recently, the ocean and sea-ice model components have been coupled with the KIM atmosphere system, and continuous efforts are being made to improve its performance. The air-sea interaction in an atmosphere-ocean coupled system can be considered by exchanging the variables that require interaction between components with a coupler. The bulk type exchange method basically transfers state variables such as temperature, pressure, and wind, which are used to get flux variables that contain interacting information among the atmosphere, ocean, and sea-ice. The bulk method is simple but the energy budget at the interface among the model components may become inconsistent due to the use of different formulas during calculation of the flux variables. In this study, exchange variables are changed by replacing atmospheric state variables with flux and momentum variables, which are the final form used in the ocean model. It is found that the corrected flux and momentum of the ocean surface resulting from the flux type exchange method change the ocean structure, particularly over the low latitude region. The atmosphere reacts to the changed ocean state, affecting not only the lower atmosphere but also the upper atmosphere. The results show that the flux type variable exchange method has advantages for considering air-sea interaction, which would improve the performance of extended medium-range weather forecast compared to the bulk type exchange method.Keywords: extended medium-range forecast, coupled model, air-sea interaction, bulk type methodAcknowledgementThis work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2022-01210.  
Modelling of PM formation in cooling tower plumes
Authors: Wolke Ralf , Gatzsche Kathrin , Tilgner Andreas
Published: February 2023

The PM fraction in ambient air due to the formation of secondary inorganic sulphate and nitrate from the emissions of large lignite-fired power plants in Germany is investigated. The power plants are equipped with natural draft cooling towers. The flue gases are fed directly into the cooling towers, giving them an additional lift. The exhausted gas-steam mixture contains the gases CO, CO2, NO, NO2 and SO2, the directly emitted primary particles and additionally an excess of "free" sulphate ions in water solution, which are not neutralized by cations after the desulfurization stages.  The precursor gases NO2 and SO2 are capable of forming nitric and sulfuric acids by various routes. The acids can be neutralized by ammonia and produce secondary particulate matter by heterogeneous condensation on pre-existing particles.The investigations are carried out with the regional chemical transport model COSMO-MUSCAT as well as with the air parcel model SPACCIM, with which multiphase chemical processes can be described in great detail. Possible formation pathways and dependencies, especially on pH and the meteorological situation, will be identified. The aim is also to estimate the maximum PM load in "worst case" scenarios. The metal ions released from the ash and the emitted fraction of "free" sulphate ions remaining in excess after the desulfurization steps play an important role.
Is there an Ozone hole in the Tropics?
Authors: Kuttippurath Jayanarayanan , Gopikrishnan Gopalakrishna Pillai
Published: February 2023

Amount of ozone in the stratosphere is very small as compared to other trace gases in the atmosphere. Yet, significant changes in its concentrations have great consequences in the environment and ecosystems. However, such drastic changes in ozone happens only in the high and middle latitudes, particularly in the polar spring, where chemical ozone loss occurs due to halogen-catalysed chemistry on polar stratospheric clouds. In the tropics, the amount of column ozone is very small and the ozone loss is also very small over the years, as compared to high and mid-latitudes. The ozone analyses in the tropical latitudes show a consistent picture of ozone evolution in the past four decades, as there is no significant loss or increase, although small negative trends are found. Recent studies have demonstrated that these negative trends in the tropical upwelling region are due to the increase in the speed of Brewer-Dobson Circulation, which brings tropospheric ozone to the lower stratosphere. This is clearly pictured in the time series of tropical ozone in recent years. The long-term trend in tropical total column ozone also shows no noticeable difference in recent years from the past decades. No measurements and no analyses show any signature of ozone hole in the tropics and all claims so far made are scientifically not sound and unconvincing. It is very unlikely that we would get an ozone hole outside the polar region.
Trends in health and agriculture-relevant ozone metrics over the United States from WRF-CMAQ reanalysis simulations
Authors: Lacey Forrest , Kumar Rajesh , He Cenlin , Boenhert Jennifer , O'Lenick Cassandra , Wilhelmi Olga , Casali Matthew , Sampson Kevin
Published: February 2023

Ozone concentrations have resulted in significant impacts on both human health and crop production throughout the beginning of the 21st century. Results presented here are from a NASA funded WRF-CMAQ model run at a 12km x 12km gridded horizontal resolution using data assimilation of MODIS AOD and MOPITT CO for a fourteen-year (2005-2018) period to show shifts in atmospheric composition over the continental United States (CONUS). This publicly available data has been aggregated to the maximum daily 8-hour ozone (MDA8) and seasonal ozone (OSDMA8) metrics for each of the EPA regions to show the regional drivers to human health as well as calculation of the accumulated ozone exposure (AOT40 and W126) metrics varying temporally and geographically based on crop data for CONUS available from the United States Department of Agriculture. These aggregation techniques have allowed us to identify both trends and some of the meteorological and atmospheric composition drivers in ozone-related risk for specific outcomes and how they vary geographically. The work presented here will also outline the GIS-based information dissemination platform that can be used by researchers and stakeholders to both access data and assess more detailed collaborative and convergent research questions.
Differences in polar amplifications between present day and Cretaceous with changes in atmospheric CO2 concentration and orbital parameters
Authors: Higuchi Taro , Abe-Ouchi Ayako , Chan Wing-Le , O'ishi Ryota
Published: February 2023

Polar amplification is the phenomenon that external radiative forcing produces a larger change in surface temperature at high latitudes than the global average, which is one of the most robust in climate changes with historical and future increases in atmospheric CO2. Also, it is known that, polar amplifications occurred during past warm periods due to atmospheric CO2 concentrations and orbital parameters different from those in the present day. The Cretaceous is known as one of the warmest periods in the Phanerozoic (Foster et al., 2017). The Cretaceous proxy data indicate remarkable temperature amplifications in the high-latitude and polar region (e.g., Jenkyns et al. 2004), resulting in small equator-to-polar temperature difference. Many previous studies using global climate models have invested the relationship between the polar temperatures and the greenhouse gasses, geography, vegetation, and cloud property in order to elucidate the mechanism (e.g., Otto-Bliesner and Upchurch 1997; Upchurch et al., 2015; Niezgodzki et al., 2017). On the other hand, it is not well understood that differences in polar amplifications between present day and Cretaceous with changes in atmospheric CO2 concentration and orbital parameters. In this study, we systematically investigated the responses of the polar temperatures in the present-day Cretaceous to changes in atmospheric CO2 concentration and the orbital parameters using an atmospheric-ocean-vegetation fully coupled model MIROC4m-LPJ. Our Cretaceous simulations succeeded in reproducing the polar temperature amplification at that time by considering variations in atmospheric CO2 concentration and orbital parameters. Furthermore, it was clarified that, due to the differences in geographical conditions between the modern and the Cretaceous, the temperature of the polar regions responded more sensitively to external radiative forcing such as changes in atmospheric CO2 concentration and orbital parameters in the Cretaceous than in the present-day.
Electron dynamics in guide-field magnetic reconnection
Authors: Tang Binbin , Wang Hanwen , Li Wenya , Zhang Yongcun , Graham Daniel , Khotyaintsev Yuri , Gao Chunhui , Guo Xiaocheng , Wang Chi
Published: February 2023

Magnetic reconnection is a fundamental process that rapidly converts energy from the magnetic field to plasma. Recent studies have shown that a large parallel electric field (E) can appear in guide-field reconnection, and its magnitude can be several times larger than the reconnection electric field. However, the generation of this large E is still not fully understood, and the reaction of electrons to this E has not been fully investigated. In this study, we focus on these issues in a strong guide-field reconnection event (the normalized guide field is ~ 1.5) from Magnetospheric Multiscale (MMS) observations. With the presence of a large E in the electron current sheet, electrons are accelerated when streaming into this E region from one direction, and decelerated from the other direction. Some decelerated electrons can reduce the parallel speed to ~ 0 to form relatively isotropic electron distributions at one side of the electron current sheet, as the estimated acceleration potential (Φ ~ 2 kV) satisfies the relation eΦ ≥ kT, where T is the electron temperature parallel to the magnetic field. Therefore, a large E is generated to balance the parallel electron pressure gradient across the electron current sheet, since electrons at the other side of the current sheet are still anisotropic. Based on these observations, we further show that the electron beta is an important parameter in guide-field reconnection, providing a new perspective to solve the large parallel electric field puzzle in guide-field reconnection.
Effect of roughness length using LULC on the wind intensity of tropical cyclones and its associated inundation
Authors: Tiwari Pawan , Rao Ambarukhana Devendra , Pandey Smita , Pant Vimlesh
Published: February 2023

     India is frequently affected by coastal flooding due to storm surges that significantly effects human lives, coastal infrastructure, and marine ecosystem. Tropical cyclones (TCs) are the most severe storms especially over the Bay of Bengal (BoB) and the Arabian Sea (AS). The vulnerability from the TCs occurs in many ways, which include coastal inundation by extreme water levels, damage of coastal properties caused by strong cyclonic winds, additional flooding caused by cyclone-induced heavy precipitation. The destruction along the coast due to inundation enhances if the cyclone makes landfall near the estuaries, river deltas, or any adjoining rivers in the coastal area. Simulation of inland flooding requires accurate representation of topography and surface roughness over the flood plain. Incorporating Land Use/ Land Cover (LULC) data in numerical simulations help in introducing roughness which alter the cyclonic wind speed over land. This also enhances model capabilities to represent accurate wind during the cyclone period. In the present study, experiments are carried out to simulate extreme water elevations and associated coastal inundation for the recent TC, Yaas (2021) that occurred over the BoB using stand-alone ADCIRC (Advanced circulation) model coupled ADCIRC and SWAN (Simulating Wave Nearshore) model. High-resolution mesh is used to incorporate major river systems and water bodies. Various datasets like Airborne DEM, CARTOSAT-DEM, SRTM-DEM, MIKE-CMAP, and ETOPO-2 are used to prepare the model mesh. The results show that total inundation calculated by the coupled model is higher since the SWAN model gives an extra momentum flux to the ADCIRC model in the form of radiation stress gradient. This results generation of maximum water elevations in the coupled model. As the TC approaches over the land, wind intensity gets reduced due to the presence of different land covers, which have specific roughness lengths. The more the roughness length, higher will be the reduction in the wind speed. To observe modifications in the wind speed over the land and ocean, ERA-5 reanalysis data is used for the 1999 Orissa super cyclone, Hudhud (2014), Amphan (2020), and Nivaar (2020). The results show a reduction of 38.2%, 35.62%, 16.35%, and 29.58% in wind speed at the time of landfall over the land compared to that of over the ocean for the above cyclones respectively. Using standalone ADCIRC and coupled ADCIRC+SWAN model, the simulations are made for TC Vardah (2016) to study the impact of roughness length over the wind intensity based on LULC. The results suggest that there is a significant decrease in the wind intensity over land after modifying the roughness length.
4C-based deconvolution of relationships between carbon pools in Icelandic rivers and streams
Authors: Gallarotti Nora , Bröder Lisa , Lattaud Julie , Haghipour Negar , Eglinton Timothy
Published: February 2023

Rivers are important agents in the lateral transfer of carbon from terrestrial to the marine realm, thus forming a key component of the global carbon cycle. Carbon sources and transformations along the land-ocean aquatic continuum are dynamic with a complex interplay between dissolved and particulate, and inorganic and organic carbon pools. Elucidating interrelationships between these pools is hindered by multiple sources and processes that influence the carbon signatures of these pools in a dissimilar fashion. Icelandic streams and rivers offer an opportunity to directly assess the fluvial carbon pool dynamics due to the virtual absence of sedimentary rocks (e.g., shales, carbonates with a radiocarbon dead signature) that otherwise “muddy the waters” with respect to apparent sources and turnover times. In order to characterize carbon transport patterns of Icelandic rivers and streams, we collected water samples from 43 river systems with watersheds that cover a wide range of catchment properties such as size, water discharge, climate as well as landcover. Here we assess the concentrations as well as the isotopic composition (13C, 14C) of particulate and dissolved organic carbon (POC; DOC, respectively) as well as dissolved inorganic carbon (DIC) alongside stable water isotopes (δ2H, δ18O) and major ion geochemistry. Radiocarbon content (reported as fraction modern; F14C) of POC, DOC and DIC show similar patterns: lower F14C values (i.e., highest radiocarbon ages) are mostly associated with glacial runoff while higher F14C values (younger carbon) correspond to higher soil organic carbon content within the respective catchment. This dataset is but a first glimpse at carbon transport patterns in Icelandic rivers. Biomarker concentrations and isotopic compositions such as leaf waxes (n-alkanes, n-alkanoic acids) and soil derived lipids (branched glycerol dialkyl glycerol tetraether) will be used to further investigate provenance, transport and storage mechanisms in the diverse suite of Icelandic catchments.
Evaluating Environmental Impacts of Flood-Induced Tank Failures: A Risk Chain Model for Soil and Groundwater Contamination in NaTech context
Authors: Giusti Riccardo , Arosio Marcello , Nascimbene Roberto , Martina Mario
Published: February 2023

The European "Floods Directive" requires European River district authorities to create flood damage and risk maps, but the process of assessing flood damage is complex and lacks established methods. Flood risk assessment also requires an understanding of how industrial equipment is vulnerable to flood events and the potential for toxic releases in such scenarios. In this study a practical case is presented regarding multicomponent flood risks in the Secchia River catchment, a tributary of the Po River, and proposes a new risk chain model for evaluating the environmental impact of soil and groundwater contamination in the event of a flood caused by the failure of storage tanks containing hazardous materials. The model is demonstrated using an illustrative case and shown to be a useful tool for managing the risk of such events. Our methodology presents a multi-component model for assessing environmental risk resulting from technological accidents triggered by natural disasters. In particular, we focus on the failure of storage tanks containing hazardous materials due to flooding. The proposed method first evaluates the probability of tank failure under defined flood conditions, including flood height, velocity, and probability of occurrence. To simplify the analysis, we consider all tanks to be unanchored atmospheric storage tanks. The final output of the method for each tank is a monetary estimation of the hypothetical costs for environmental remediation after tank failure, including the contamination of soil and groundwater by the spilled liquid. Our methodology proposed a conservative approach by assuming that all stored liquids are contaminants and by using a fixed value for the density of the stored liquid.To evaluate the probability of tank failure, it has been considered four types of failure dynamics: buckling, displacement, floating and overturning. The tank failure assessment is based on our recent study that developed vulnerability different dynamic models for unanchored steel atmospheric tanks. Our methodology not only evaluates the probability of tank failure during flood events, but also analyses the potential consequences of failure, including direct damages to the tank and costs associated with recovering the spilled product and mitigating contamination in the affected area. The results of this study can be used to develop strategies for minimizing the risks of tank collapse during flood events and to increase awareness of potential NaTech risks. The ultimate goal of this study is to create a comprehensive procedure for evaluating and comparing the dynamics of tank collapse during flood events, including the potential environmental consequences, and providing risk managers with a full understanding of the risks associated with tank failure during flooding, including potential NaTech risks. 
Forecasting extreme geomagnetic storms using different statistical models
Authors: Wang Ting , Parry Matthew , Rodger Craig , Allen Jessica , Petersen Tanja
Published: February 2023

Extreme geomagnetic storm events could cause hazardous damage to the technological infrastructure that increasingly underpins modern society. Being able to forecast the next extreme geomagnetic storm is thus crucial to navigating risks in the 21st century. There have been quite a number of studies on using extreme value theory to forecast future extreme geomagnetic storms. However, to the best of our knowledge, each study selects one model and one estimation method. In this study, we demonstrate that different estimation methods for the same extreme value model and different extreme value models can produce very different estimates of return levels when applied to the same dataset. We propose to use the average of the estimated return levels from different models and different estimation methods to produce more robust and reliable forecasts.We apply this method to the geomagnetic field data measured in every minute in the period between 1994 and 2019 at Eyrewell, Canterbury, New Zealand. We focus on the horizontal components, and estimate the return levels of the ramp change in the horizontal component. The resulting return levels for the ramp change in the horizontal component using different types of models and different estimation methods show the importance of using model-averaged forecasts.In this presentation, we also demonstrate forecasts of future geomagnetic storms using counting processes applied to the wavelet spectrum. 