bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of weather post-processing methods for operational ensemble hydrological forecasting on multiple catchments in Canada
Authors: Aguilar Andrade Freya Saima , Arsenault Richard , Poulin Annie
Published: February 2023

Hydrological forecasts often contain biases or uncertainty that make them less useful to water resources system managers. They can, however, be further improved using post-processing methods. Post-processing has the capability to reduce overall bias and improve the uncertainty quantification (spread), in order to enhance the usefulness of the forecasts in decision-making. In this study, a Quantile Mapping (QM) post-processing method was implemented on meteorological forecasts assessed in three different configurations: A monthly, a seasonal, and an annual quantile mapping schemes. The evaluation was carried out over 22 watersheds with different basin areas in the south of Canada. Post-processing methods were trained on ECMWF operational forecasts from 2015-2019 inclusively, then applied on forecasts from 2020 and fed to 8 assimilated hydrological models on each catchment. The hydrological forecasts for the year 2020 were generated at a lead time of 8 days and a timestep of 6 hours. The methodology and results were evaluated using the Continuous Ranked Probability Score (CRPS) metric. Results show that all three QM combinations improve the performance of the forecasts at the most distant lead times, showing significant improvements from day 4. The annual QM implementation was shown to perform the best, followed by seasonal or monthly, depending on the watershed.
Coping with the complexity of landscape evolution and how high-resolution topography can help
Authors: Lague Dimitri
Published: February 2023

Since the end of the 19th century, geomorphologists have been on a relentless quest to unravel the mysteries of landscape evolution and explain the diversity of the resulting forms. However, a quantitative model of landscape morphodynamics that is relatively universal and applicable at various time scales still eludes us. This raises an important question: are we, geomorphologists, dumber than the average scientist, or is landscape evolution particularly complex to decipher? ChatGPT tells us that, indeed, landscape evolution is complex. As for many natural phenomena, the complexity of landscape evolution results from 3 elementary components: processes, stochasticity, and heterogeneity. Process geomorphology tackles the complex morphodynamics emerging from the diversity and interactions of physical, chemical, and biological processes that shape the Earth. Stochastic geomorphology addresses the role of fluctuations in the drivers of landscape evolution, such as the frequency-magnitude distribution of precipitation events, landslides, earthquakes, or fires. Heterogeneous geomorphology embraces the variable nature of the properties of landscape elements on which geomorphic processes operate or that they create. This includes, for instance, the distribution of grain sizes, the diversity of rock type, the fractal nature of rock fractures, or the spatial variations in vegetation size and type.Accounting for all these sources of complexity, inasmuch as they can be quantified, is an untractable problem resulting in models of little explainability. Therefore, hypotheses had been and must be formulated to simplify the problem of landscape evolution comprehension and modeling. There is, arguably, a long tradition of emphasizing process complexity to explain landscape dynamics, neglecting or simplifying both stochastic fluctuations and heterogeneity. In this lecture, I shall discuss this view, emphasizing the now well-established importance of stochastic fluctuations, and how little we know of the role of heterogeneity.On this latter topic, I shall illustrate with a variety of examples how time series of high-resolution and high-precision topographic data (4D data) offers unprecedented insights into landscape morphodynamics. Beyond quantifying and detecting a variety of processes and their temporal fluctuations, 4D data allow a systematic quantification of the heterogeneity (e.g., vegetation, grain size, ...) of landscape elements, and spatial variability of geomorphic rates, thus bringing us closer to formulating the role of heterogeneity in landscape dynamics. Yet, this goal can only be achieved if tools to harness the complexity and richness of high-resolution topographic data are developed and made available.Keywords: fluvial incision, landslides, floods, salt marshes, topo-(bathymetric) LiDAR, numerical modeling, machine learning.
Jovimagnetic Secular Variation and Jupiter’s rotation Period
Authors: Connerney Jack , timmins Sidey , jorgensen john , Kotsiaros Stavros , Jorgensen Peter , Herceg Matija , Bloxham Jeremy , Bolton scott , Levin Steve
Published: February 2023

The Juno spacecraft, in polar orbit about Jupiter since July 2016, continues to map the gas giant’s complex magnetic field with ever-increasing resolution in space and time. Comparison of spherical harmonic models (JRM33 and JRM09) derived from Juno measurements representative of different epochs revealed secular variation of the field near the isolated and intense patch of negative flux near the equator known as the Great Blue Spot (GBS). The feature drifts eastward relative to the deep interior at a rate of a few cm/s; if carried at depth by zonal winds, they must penetrate to depths of ~3000 km where the electrical conductivity is sufficient to grip the magnetic field. A dedicated magnetic survey above the GBS was conducted during Extended Mission orbits 36-42 to better characterize the GBS and its evolution during the mission; another is under consideration for later in the mission. Jupiter’s planetary rotation period (per IAU) has been determined with greater accuracy than that provided by observations of its radio emissions (System III (1965): 9h 55m 29.711s +/-0.04s) via a new spherical harmonic analysis allowing for time-dependent dipole coefficients. The drift of the dipole during Juno’s prime mission (by 0.12°/yr) determined this way yields an improved planetary rotation period of 9h 55m 29.698s, if the migration of the dipole is attributed to the limited accuracy of the IAU adopted planetary rotation period. A similar result is obtained by comparison of the JRM33 model with models representing earlier epochs (Voyager in 1979 and Ulysses in 1992). If time permits, we will also discuss particle motion in the complex (high degree and order) magnetic field near Jupiter’s surface and its relevance to local particle fluxes.
Ecosystems threatened by intensified drought with varied vulnerability in Europe
Authors: Chen Qi , Timmermans Joris , Wen Wen , van Bodegom Peter
Published: February 2023

With climate change increasing the severity and duration of droughts, ecosystems may not be able to withstand such droughts causing a rapid collapse. However, at present we lack a quantitative understanding of this ‘buffer capacity’ of ecosystems to these deteriorating droughts. Here, we established continental-scale models to quantify the ecosystem vulnerability and associated drought characteristics impacts for different ecosystems in Europe using high spatial and temporal resolution drought and traits data from remote sensing. Specifically, we observed varying vulnerabilities across ecosystems where vegetation damage increases with earlier, longer and more intense droughts. However, we also found that vulnerability of most ecosystems increases disproportionally when drought severity begins to increase. Collectively, the results suggest that the intensified drought under future climate change could threaten a vast range of ecosystem types. The multi-characteristics assessment of ecosystem vulnerability based on traits in our study will help to forecast and quantify vegetation damage to future global climate change challenges and inform drought mitigation policies.
Decadal reorganization of Subantarctic Mode Water
Authors: Cerovecki Ivana , Haumann F. Alexander
Published: February 2023

Subantarctic Mode Water (SAMW) is one of the most important water masses globally in taking up anthropogenic heat and carbon dioxide. However, its long-term changes in response to varying climatic conditions are not well understood. Here we use data from the ”Estimating the Circulation and Climate of the Ocean” (version 4, release 4, ECCOv4r4) state estimate to calculate SAMW volume budgets for the period 1992 to 2017. They reveal a SAMW volume reorganization on decadal timescales in the Indian and on multidecadal timescales in the Pacific Ocean. In the Pacific, this multidecadal variability exceeds the long-term trend and is governed by an accumulation of signals from the Interdecadal Pacific Oscillation. This implies that SAMW volume trends observed during the shorter Argo period largely arise from the multidecadal variability. In both ocean sectors, the SAMW reorganization exhibits a two-layer density structure, with nearly compensating volume changes of lighter and denser SAMW. They are caused by heat flux changes in the Indian Ocean, freshwater flux changes in the southeast Pacific, and both heat and freshwater flux changes in the central Pacific Ocean. Our results indicate that the recently observed SAMW changes have to be interpreted in the context of the strong long-term variability, which imposes challenges to detecting and attributing climate change signals in SAMW.
Spatial patterns of land use & land cover changes surrounding Colombian water reservoirs
Authors: Salomão Caroline , Alsleben Jonas , Rufin Philippe , Hostert Patrick
Published: February 2023

Hydropower dams can induce spatial and temporal changes in land and water systems in terms of resource access and use. Regardless of the main purpose of these dams (that is, to produce energy), analyzing these changes by the lenses of the water-energy-food nexus helps us to identify the synergies and trade-offs between these components in the watershed context. Changes  in land & water systems happen in different times (dam’s construction and operation), spatial scales and, in many cases, are also influenced by national political-economic context. Colombia is moving towards peace agreements in recent years, and this process already showed impact in the patterns of land and water uses, especially by agricultural systems. This new scenario can create or consolidate some local and national socioeconomic characteristics, adding inequalities beyond the dam’s construction. This work focuses on the land cover and land use transitions surrounding two dams in the Magdalena basin, Betania-Quimbo and Hidrosogamosso. This basin is responsible for 70% of the national energy production, it concentrates the production of important food/energy value chains for the local and global market and possess high biodiversity. Both dams were built in 2009 and started operations after 2015, so Landsat satellite images were used to build the land use & cover maps in 2009, 2015 and 2021 for 7 classes (rice, palm oil, pasture, forest, water surface, temporary and permanent crops and others). Due to the intensity of clouds and high altitudes, Colombia is one of the most difficult regions in the world to build these maps, and for this reason global, or even local, mapping available turn out to be unrealistic. A random forest model was chosen, and, as variables, indexes and spatial temporal metrics using 176 bands in total. To extract the pixel information for training and testing the model, a stratified random sample was run using different secondary maps, and after that, we used Google Earth for visual verification (1196 observation for all years). For the accuracy assessment just the sample from the current year was used. The model was run in Google Earth Engine. The model achieved a similar overall accuracy in all years (79%), and for certain agricultural systems a high accuracy, such as the case of palm oil with100% accuracy in 2021 and 2015, despite reaching 70% in 2009. Accuracy for rice was also high: 95%, 84% and 88% in 2021, 2015 and 2009 respectively. Pasture achieved a medium accuracy: 78% (2021): 83% (2015); and 71% (2009). Water surface achieved a high accuracy.For water surface: 100% in 2021 and 2015, and 97% in 2009. The Forest category reached a medium-high accuracy: 81%, 88% and 77% in 2021, 2015 and 2009 respectively. Land use and Land cover maps of areas impacted by dams is of high importance to support decisions that will be implemented via instruments such as Basin Management Plans or compensatory schemes.
Investigating expanding air pollution and climate change on the African continent using TROPOMI data
Authors: Levelt Pieternel , Stein Deborah , Martinez Sara-Eva , Tang Wenfu , Worden Helen , Emmons Louisa , Gaubert Benjamin , Eskes Henk , van der A Ronald , Veefkind Pepijn
Published: February 2023

In the coming decades, a large increase in population is expected to occur on the African continent, leading to a doubling of the current population, which will reach 2.5 billion by 2050. At the same time, the African continent is experiencing substantial economic growth. As a result, air pollution and greenhouse gas emissions will increase considerably with expected health impacts on the African population. The impact of wildfires also needs to be carefully assessed. Will the frequency of fire episodes increase? And how will this perturbation compare with anthropogenic emissions in urban areas? In the decades ahead, Africa’s contribution to climate change and air pollution will become increasingly important.  Time has come to address the changing role of Africa in understanding and quantifying global environmental change.  What can we learn from the new TROPOMI satellite data for Africa, in combination with emerging modelling efforts including the MUSICA development at NCAR and the development of inverse modelling techniques? How can we deal with the lack of surface observations in many areas of Africa?We will show several recent achievements related to Africa, using space observations and modeling approaches as a contribution towards the development of an integrated community effort to better characterize air quality and climate-related processes in this continent.  This presentation will mainly focus on the potential of the use of TROPOMI data for Africa Research.
Application of an Improved Multi-temporal InSAR Method and Forward Geophysical Model to Document Subsidence and Rebound of the Chinese Loess Plateau Following Land Reclamation
Authors: Zhou Chaodong
Published: February 2023

Land reclamation in the Yan’an New District (YND) on the Chinese Loess Plateau is one of the largest earthworks projects in the world, involving the excavation of loess from ridges and the deposition of the material in adjacent valleys, flattening an area of more than 78 km2. It can take multiple years for the landscape to adjust to the new topography after the earthworks are completed, with subsidence in the fill areas and uplift in the excavation areas. Understanding the pattern and extent of this differential vertical movement has great importance for ensuring the structural integrity of any infrastructure built on the site. We, therefore, studied the spatial deformation field of the YND from January 2015 to December 2018 using satellite synthetic aperture radar interferometry (InSAR) technology. Persistent scatterers (PS) and distributed scatterers (DS) were combined in a novel two-tier network to overcome problems with temporal decorrelation of the InSAR phase signals. The derived deformation field was validated with in-situ ground leveling and GNSS measurements and interpreted using a forward geophysical model. The results indicate that our approach provides a more detailed understanding of the deformation than conventional PSI and SBAS methods. Subsidence of up to 87 mm/yr occurred over about 4.4 km2 of the fill region and uplift of up to 26 mm/yr in the excavated areas. There is a strong linear relationship between these displacements and prior topographic elevation change. The primary cause of subsidence in fill areas is compaction of remoulded loess. Instantaneous elastic and gradual poroelastic deformation are the main causes of uplift in excavated areas.
Simulation and reconstruction of global monthly runoff based on hydrological models and machine learning models
Authors: Zhang Jiawen , Liu Jianyu
Published: February 2023

Hydrological models and machine learning models are widely used in streamflow simulation and data reconstruction. However, a global assessment of these models is still lacking and no synthesized catchment-scale streamflow product derived from multiple models is available over the globe. In this study, we comprehensively evaluated four conceptual hydrological models (GR2M, XAJ, SAC, Alpine) and four machine learning models (RF, GBDT, DNN, CNN) based on the selected 16,218 gauging stations worldwide, and then applied multi-model weighting ensemble (MWE) method to merge streamflow simulated from these models. Generally, the average performance of the machine learning model for all stations is better than that of the hydrological model, and with more stations having a quantified simulation accuracy (KGE>0.2); However, the hydrological model achieves a higher percentage of stations with a good simulation accuracy (KGE>0.6). Specifically, for the average accuracy during the validation period, there are 67% (27%) and 74% (21%) of stations showed a “quantified” (“good”) level for the hydrological models and machine learning models, respectively. The XAJ is the best-performing model of the four hydrological models, particularly in tropical and temperate zones. Among the machine learning models, the GBDT model shows better performance on the global scale. The MWE can effectively improve the simulation accuracy and perform much better than the traditional multi-model arithmetic ensemble (MAE), especially for the constrained least squares prediction combination method (CLS) with 82% (28%) of the stations having a “qualified” (“good”) accuracy. Furthermore, by exploring the influencing factors of the streamflow simulation, we found that both machine-learning models and hydrological models perform better in wetter areas.
Mitigate forecast error in surface wind speed using an offline single-column model with optimal ground forcing
Authors: Feng Jin
Published: February 2023

Current numerical weather prediction models contain significant systematic errors, due in part to indeterminate ground forcing (GF). This study considers an optimal virtual GF (GFo) derived by training observed and simulated datasets of 10-m wind speeds (WS10) for summer and winter. The GFo is added to an offline surface multilayer model (SMM) to revise predictions of WS10 in China by the Weather Research and Forecasting model (WRF). This revision is a data-based optimization under physical constraints. It reduces WS10 errors and offers wide applicability. The resulting model outperforms two purely physical forecasts (the original WRF forecast and the SMM with physical GF parameterized using urban, vegetation, and subgrid topography) and two purely data-based revisions (i.e., multilinear regression and multilayer perceptron). Compared with original WRF forecasting, using the GFo scheme reduces the Root Mean Square Error (RMSE) in WS10 across China by 25% in summer and 32% in winter. The frontal area index of GFo indicates that it includes both the effects of indeterminate GF and other possible complex physical processes associated with WS10.
On the impact of leaf-level processes on the water and carbon canopy-turbulent fluxes
Authors: González Armas Raquel , Vilà-Guerau de Arellano Jordi , de Boer Hugo , Hartogensis Oscar , Mangan Mary Rose , Gibert Fabien
Published: February 2023

Representing the diurnal variability of state meteorological variables, including carbon dioxide, is still an open challenge as shown by the large discrepancies with observations and weather and climate models. These discrepancies translate into different diurnal exchanges of heat, water and carbon dioxide between the canopy and atmosphere. These sub-diurnal differences can propagate to larger temporal and spatial scales.With a systematic approach, we investigate the diurnal gas exchange of both water and carbon dioxide for an irrigated crop. Our investigation is based on a comprehensive observational dataset that ranges from scales covering from the leaf level to the canopy level  to the atmospheric boundary layer gathered at the LIAISE campaign. This campaign took place over two weeks in summer of 2021 in a region of the Ebro basin located in Catalonia, Spain. We focus specially on one of the “supersites” of the campaign: La Cendrosa, which is an irrigated alfalfa field surrounded by a very dry region.Our observational approach is bottom-up in which we first analyze the leaf, second the canopy and third the interactions with the atmosphere at a local field scale. Among the observations, we analyzed leaf gas exchange measurements, turbulent surface fluxes and vertical profiles of driving environmental variables such as radiation, wind, temperature, and specific humidity. To support the observational analysis, we use a land-atmospheric interactive model (CLASS model). This model allows the representation at each of the three levels mentioned: (1) leaf, (2) canopy and (3) field.Our observations show an asymmetry in the diurnal variability of the stomatal conductance, which indicates a larger opening of the stomata during the morning than during the afternoon. To attribute processes to the causality in the stomatal opening, we derive new expressions of the tendency of the stomatal aperture as a function of the mean meteorological drivers including radiation, temperature, atmospheric CO2 concentration, and water vapor deficit. The asymmetry is only simulated by models once specific characteristics of the crop are considered. It is also observed that dynamics at the leaf level such as a closure of the stomata during the midday can cause a dip in the evapotranspiration and enhance the sensible heat flux. Our results open the debate on the circumstances under which it is important to constrain the leaf gas exchange.
The Mars 2020 Three Forks Sample Depot
Authors: Maki Justin , Farley Ken , Stack Katie , Calef Fred , Williams Nathan , Bell James F. III , Herd Chris , Wadhwa Meenakshi , Brown Adrian
Published: February 2023

The Perseverance rover continues to make progress on the task of collecting and documenting a set of Martian samples for future return to Earth by the Mars Sample Return program [1].  Near the end of 2022 the rover had acquired, sealed, and stored onboard a total of 15 rock cores, 2 regolith samples, 1 ambient atmosphere sample, and 3 witness tubes [2]. Of these 21 sealed tubes, 10 have been selected for inclusion in a first depot located in the Three Forks region on the floor of Jezero crater near an outflow basin [3].  In December of 2022 the rover began the construction of this depot.  The Three Forks region was chosen for the depot location because it is an area with flat terrain, no large rocks, and enough area for the Perseverance rover and potential future robotic vehicles to maneuver around the depot without disturbing the sample tubes [4].  The individual sample core tips are imaged by the Mastcam-Z [5] and Cachecam [6] cameras prior to tube sealing and subsequent storage.  These images document the texture and color of the samples and form an important component of the overall sample documentation data set [7].  After the sample tubes are dropped in the depot at pre-designated zones, images of the tubes are acquired with the Front Hazcam, Navcam cameras, and optionally the WATSON camera [8].  These images serve two purposes:  a) to provide confirmation of the tube state to the operations team during sample depot construction and b) formally record the location of the tubes within the Three Forks region for the potential retrieval of the tubes by later missions.  At the time of this writing, construction of the Three Forks sample depot by the rover operations team was underway, with depot completion expected by February 2023.

 

References: 

[1] Farley, K.A., Space Sci Rev 216, 142 (2020).

[2] Herd, C.D.K, et al., LPSC 2023.

[3] September 2022 - MSR/M2020 Sample Depot Science Community Workshop.

[4] N. Williams, Golombek, LPSC 2023.

[5] Bell, J.F. III, Maki, J.N., et al. Space Sci Rev 217, 24 (2021).

[6] Maki, J.N.. et al. Space Sci Rev 216, 137 (2020).

[7] Maki et al., LPSC 2022.

[8] Bhartia, R., et al., Space Sci Rev 217, 58 (2021).
Daily variation of PM2.5 and covarying meteorological conditions during wintertime using long-term observation in Seoul
Authors: Jang Wooseok , Yoon Jin-Ho
Published: February 2023

Understanding co-variability between particulate matter (PM) concentration and meteorological conditions could provide insight into how the former varies under given weather conditions and eventually improve its prediction skill. However, relatively short data length of observed PM2.5 is a challenging issue not limited to Korea. Therefore, in such an analysis PM10, which has reliable observation for more than 30 years, has been widely used as a proxy of fine particles. Also, there are two stations in Seoul, Korea have relatively long-term observed PM2.5 in the period of 2000-current. As a result, more reliable analysis on the daily variation of PM2.5 in comparison with PM10 and meteorological conditions is feasible. First, the winter-mean of both PM10 and PM2.5 showed significant decreasing trends in the period of 2000-2020. Interestingly, decreasing trends of these weakened in the last 10 years with a different rate, resulting in a nearly flat trend of PM2.5 yet a relatively consistent decreasing trend of PM10 in the period of 2010-2020, suggesting a potential discrepancy in the variability of PM2.5 and that of PM10. Second, unlike the previously noted difference in long-term trends of seasonal mean values, PM2.5 and PM10 shared significantly similar daily variabilities if Asian dust cases were removed. In other words, the aforementioned discrepancy in the long-term trend of seasonal mean values of PM2.5 and PM10 does not affect their daily variation. The covarying patterns of PM2.5 and meteorological conditions were denoted as a migratory synoptic system. In particular, a migratory anticyclone from northwest China had significant positive correlation patterns with PM2.5 from two days before and remained stagnant over Korea after two days due to blocking by low pressure over the Northern Pacific. Along with this system, warm temperature anomalies and weak northerlies in the low troposphere were present over Korea, which is a conducive condition for high PM2.5. On the contrary, Asian dust cases were accompanied by cyclone that extended from arid regions of northern China with corresponding negative temperature anomalies and strengthened northerlies. In short, a migratory synoptic system over Korea is tightly correlated with PM2.5 daily variations as well as PM10. But once again, Asian dust events could be an important mechanism to differentiate daily variations of PM2.5 and PM10.
Development of a snowdrift model with the lattice Boltzmann method and comparison with the observation results
Authors: Tanji Seika , Inatsu Masaru , Okaze Tsubasa
Published: February 2023

We developed a snowdrift model to evaluate the snowdrift height around snow fences, which are often installed along roads in snowy, windy locations. The model consisted of the conventional computational fluid dynamics solver that used the lattice Boltzmann method and a module for calculating the snow particles’ motion and accumulation. The calculation domain was a half channel with a flat free-slip boundary on the top and a non-slip boundary on the bottom, and an inflow with artificially generated turbulence from one side to the outlet side was imposed. In addition to the reference experiment with no fence, experiments were set up with a two-dimensional and a three-dimensional fence normal to the dominant wind direction in the channel center. The estimated wind flow over the two-dimensional fence was characterized by a swirling eddy in the cross-section, whereas the wind flow in the three-dimensional fence experiment was horizontally diffluent with a dipole vortex pair on the leeward side of the fence. Almost all the snowdrifts formed on the windward side of the two-dimensional and three-dimensional fences and the outlines were reasonable for the observation results. The snowdrift around the three-dimensional fence also formed along the split streaks on the leeward side. Our results suggested that the fence should be as long as possible to avoid snowdrifts on roads.
When citizen science meets urban climate: The Sydney Schools Weather and Air Quality (SWAQ) monitoring network
Authors: Hart Melissa , Maharaj Angela , Di Virgilio Giovanni , Ulpiani Giulia
Published: February 2023

Sydney’s population is predicted to grow by 30% within twenty years, most of which is slated for the semi-rural fringes. The resulting urbanisation will adversely impact temperature and air quality in these areas of rapid population growth. Currently there are few meteorological and air quality observational sites to adequately monitor the effects of this increased urbanisation on local weather and air quality. This poster will discuss the development of a citizen science project- Schools Weather and Air Quality (SWAQ), which installed meteorology and air quality sensors in schools across Sydney. The sites complement existing networks to target regions lacking monitoring sites e.g., urban growth areas on the rural fringe. Students analyse this research quality data in science, maths, and geography curriculum-aligned classroom activities. The data is freely available online to the public and researchers, enabling everyone to visualize the data and the current weather and air quality at each school's location. SWAQ’s data has been published on TERN- Australia’s Terrestrial Ecosystem Network. The data has been used to assess spatial variability in particulate pollution during Sydney’s black summer wildfires, and the relationship between air pollution and meteorological variables with respect to the built environment and local geography. SWAQ’s success in citizen engagement was recognized as a 2021 Australian Eureka Prize for Innovation in Citizen Science finalist. 
Comparing modern and historical records of cyclone induced extreme sea level events : examples from Australia and the Philippines.
Authors: Switzer Adam D. , Christensen Joseph , Soria Lea
Published: February 2023

To date most natural hazard risk assessments in Australasia do not incorporate long-term and/or prehistoric records of extreme events and coastal development continues to rely on short historical records as a reﬂection of the long-term behaviour of a hazard. In some locations such as southern China or the Philippines historical records may be appropriate as consistent records have been kept for several centuries or even a millennium. However, for much of the Asia-Pacific this is rare as the historical archives rarely stretch beyond World War II. Clearly such short records are inadequate for determining the natural variability of a hazard at multi-decadal timescales and for the extrapolation of extreme events.  While it is well known that the historical record is fragmentary, incomplete and limited in spatial balance, the historical record does provide a key link between instrumental datasets and the prehistoric record that allows for the detailed reconstruction of past events. Here, we compare known historical tropical cyclone events to recent ones in Western Australia (UC1921 and cyclone Herbie) and the central Philippines (Typhoon Haiyan and Ty1897) as examples of integrated studies. The two examples demonstrate the utility of the integrated approach and allow an examination of the similarities and differences between the events. Such efforts must become familiar to those outside of academia, as familiarity breeds awareness and it is through awareness and adoption that the true potential of integrating across disciplines will be recognized.
Reconstruction of Glacier Mass Balance with Surface Energy Balance Modeling across Southwestern Canada
Authors: Draeger Christina , Radic Valentina
Published: February 2023

Current state-of-the-art glacier models for regional and global scales mostly rely on empirical models, such as temperature-index models, which require glacier-specific calibration with in-situ mass balance measurements. In the absence of these measurements, the models suffer from large uncertainties in their projections of glacier mass changes, especially at local scales. One way to address this issue is to transition from the empirical models toward more physics-based models, such as surface energy balance (SEB) models of glacier melt. In this study, we evaluate the performance of a glacier evolution model based on a SEB model with minimal calibration for nearly 15,000 glaciers in Southwestern Canada for the period of 1979–2021. The SEB model is forced with ERA5 reanalysis data with minimal bias corrections or statistical downscaling. The empirical models for accumulation and albedo are, however, calibrated to maximize the match between simulated and observed glaciological mass balance availabe for about 20 glaciers in this region. The simulated regional mass balance and area change are then evaluated against the geodetic mass balance as observed for all glaciers in the region over the last two decades. This study contributes to a better understanding of the applicability of SEB models with minimal calibration in regional glaciation modeling in order to narrow uncertainties in glacier melt projections.
Self-organising maps and surface melt on East Antarctic ice shelves
Authors: Saunderson Dominic , Mackintosh Andrew , McCormack Felicity , Jones Richard Selwyn , Picard Ghislain
Published: February 2023

Surface melt occurs on most ice shelves in Antarctica each summer, with potential impacts on their strength and stability and thus on the ice sheet's contribution to global sea level rise. However, many questions remain regarding the spatiotemporal variability of surface melt and the processes driving it, particularly in East Antarctica where few in situ observations exist. Previous work in this field has largely relied on remote sensing observations to monitor the occurrence and extent of surface melt, often using metrics such as the onset and freeze-up dates of melt each summer, the number of melt days, or the cumulative melting area. Whilst such metrics are often necessary to handle the sheer volume of data produced by satellite observations, much of the information contained within the datasets is lost, hindering attempts to build a more complete picture of melt variability at different spatial and temporal scales, and thus of disentangling the different processes driving melt.To help address this problem, we use the machine learning approach of a Self-Organising Map (SOM) and nearly two decades (2002/03–2020/21) of daily observations from the AMSR-E and AMSR-2 passive microwave sensors, gridded at a spatial resolution of 12.5 km. Here, we present results focused on the Shackleton Ice Shelf in East Antarctica, but our code, implemented in the R programming language, is openly available and can be applied to any Antarctic ice shelf, or adapted for use with other melt datasets.Our results show that the daily distribution of surface melt on the Shackleton Ice Shelf can be described by nine representative spatial patterns of melt. These patterns demonstrate the potential for heterogeneous melt behaviour across the shelf, and thus provide insight into the influence of surface topography, katabatic winds, and surface albedo in driving surface melt. A sensitivity analysis of the SOM algorithm shows that the same general spatial patterns are returned repeatedly regardless of the parameter values used, strengthening confidence in our results and interpretation, and demonstrating the suitability of our approach. We further examine the temporal variability of the nine melt patterns, both within and across melt seasons, finding that there are no significant trends in any of the patterns. Instead, our analysis identifies a number of summers with unusual melt behaviour and also reveals correlations with shelf-wide, summer-averaged surface air temperatures, highlighting that both local and large-scale controls are important for driving surface melt in Antarctica.
Evolution of the groundwater system in the northern continental shelf of South China Sea since Late Pleistocene
Authors: Jiao Jiu Jimmy , Sheng Chong , Yu ShengChao , Luo Xin
Published: February 2023

The South China Sea (SCS) is a marginal sea of the Western Pacific Ocean with a broad continental shelf exposed since the last glacial maximum. Five enormous subaqueous deltas were developed in the then river deltaic estuaries and adjacent continental shelves of the SCS where buried paleochannel systems are widely distributed. Saline groundwater with salinity up to 25 g/L has been observed in the terrestrial aquifer system in the Pearl River Delta but freshened groundwater with salinity <1 g/L observed in the offshore part of the aquifer system in the subaqueous delta. Such a co-existence of both saline groundwater inland and freshened groundwater offshore in the same aquifer system is widely observed in other large-river deltaic estuaries and their adjacent shelves, but the mechanism for such a phenomenon is not much addressed in literature. Using the Pearl River Delta and its adjacent continental shelf in the northern margin of the SCS as an example, a sophisticated paleo-hydrogeologic model considering sea-level change, sedimentation processes, and precipitation variation in the past 50 ka is conducted to simulate the evolution of the groundwater system and is further calibrated with present porewater geochemistry data and stable isotopes. The results indicate that the offshore freshened groundwater was formed during the low-stands since the late Pleistocene, whereas the onshore saline groundwater was generated by paleo-seawater intrusion during the Holocene transgression and that the intrusion disconnected the onshore freshwater and offshore freshened groundwater bodies near coastlines. The response of the groundwater system to the paleoclimatic changes was delayed by about 7-8 ka, thus the paleoclimatic forcings still have a dominant influence on the present-day distribution of the groundwater salinity.
A Deeper Look Into the 2021 Tyrnavos Earthquake Sequence(TES) Reveals Coseismic Breaching of an UnrecognizedLarge-Scale Fault Relay Zone in Continental Greece
Authors: Mouslopoulou Vasiliki , Sudhaus Henriette , konstantinou Kostas , Begg John , Saltogianni Vasso , Männel Benjamin , Antinisari Ratri , Oncken Onno
Published: February 2023

Large magnitude (Mw ∼ ≥6) earthquakes in extensional settings are often associated with simultaneous rupture of multiple normal faults as a result of static and/or dynamic stress transfer. Here, we report details of the coseismic breaching of a previously unrecognized large-scale fault relay zone in central Greece, through three successive normal fault earthquakes of moderate magnitude (Mw 5.7–6.3) that occurred over a period of ∼10 days in March 2021. Specifically, joint analysis of InSAR, GNSS and seismological data, coupled with detailed field and digital fault mapping, reveals that the Tyrnavos Earthquake Sequence (TES) was accommodated at the northern end of a ∼100 km wide transfer structure, by faults largely unbroken during the Holocene. By contrast, the southern section of this relay zone appears to have accrued significant slip during Holocene. InSAR-derived displacements agree with the loci of eight subtle, previously undetected, faults that accommodated coseismic and/or syn-seismic normal fault slip during the TES. Kinematic modeling coupled with fault mapping suggests that all involved faults are interconnected at depth, with their conjugate fault-intersections acting largely as barriers to coseismic rupture propagation. We also find that the TES mainshocks were characterized by unusually high (>6 MPa) stress-drop values that scale inversely with rupture length and earthquake magnitude. These findings, collectively suggest that the TES propagated north-westward to rupture increasingly stronger asperities at fault intersections, transferring slip between the tips of a well-established, but previously unrecognized, relay structure. Fault relay zones may be prone to high stress-drop earthquakes and associated elevated seismic hazard.
Sulfate aerosol formation mechanisms constrained by oxygen and sulfur isotopes at coastal Hong Kong
Authors: Chen Qianjie , Moon Allison , Schauer Andrew , Wang Tao , Alexander Becky
Published: February 2023

Sulfate plays a key role in the formation and growth of aerosol particles and cloud droplets in the troposphere and is thus important for air quality and climate. The formation mechanisms of sulfate vary with oxidant levels and environmental conditions and can be partially revealed by its isotopic signatures. Here we measure oxygen (16O, 17O, 18O) and sulfur isotopes (32S, 34S) of the sulfate aerosol samples collected at coastal Hong Kong, downwind of the highly urbanized Pearl River Delta region. Based on ion measurements, most (95%) of the sulfate collected is non-sea-salt sulfate. The δ34S of sulfate is on average 4.0±2.0 ‰ (range 0.7 – 8.0 ‰), at an average sulfur oxidation ratio of 79±9%. The average oxygen-17 excess (Δ17O) is -0.1±0.3 ‰, suggesting an important role of OH / transition metals / reactive halogens. The δ18O of sulfate is on average 4.9±2.1 ‰. The Markov-Chain Monte Carlo model will be used to further constrain sulfate formation mechanisms.
Climate change, landscapes and human impacts during the 4.2kyr event in Mesopotamia and beyond
Authors: Hill Daniel , de Gruchy Michelle , Deckers Katleen , Lawrence Dan
Published: February 2023

The 4.2kyr event saw major changes in civilizations across the world, often attributed to climate change and widespread drought. Indeed, there are high quality palaeohydrological proxies that seem to document a significant drying at this time in Egypt, the Indus Valley and in the Near East. In Mesopotamia, settlements were abandoned, agricultural practices shifted and the Akkadian Empire ended. Climate model simulations covering 5000-3000 years ago are able to reproduce much of the evidence for Holocene climate change and some of the key reductions in mid-late Holocene precipitation. However, unlike some other regions, the annual mean rainfall in Mesopotamia at 4.2kyr is similar to the adjoining millennia. The climate model simulates significant droughts during this time, but these are within the range seen both before and after.The end of the middle Holocene saw rapid population growth in Mesopotamia, with significant urban centres putting pressure on local resources. Although the models suggest no significant change in climate, the archaeological evidence shows the exploitation of a dryer landscape, both in existing sites and new urban centres in dryer regions. This time also sees changing agricultural practices and the loss of available sources of wood. Vegetation models suggest little impact of climate change on the natural landscape, although drought years bring major losses in net primary productivity. However, human activities in Mesopotamia could have affected the landscape and exacerbated the impacts of existing drought cycles. We suggest that an unexceptional drought, combined with a large population and anthropogenic impacts on the landscape contributed to significant societal change in Mesopotamia at 4.2kyr.
Model Comparisons with Juno Observations of the Io Plasma Torus
Authors: Nerney Edward , Bagenal Fran , Wilson Robert , Phipps Phillip
Published: February 2023

Nasa’s JUNO spacecraft, now in its extended mission, is finally passing through the Io plasma torus (IPT) taking in situ measurements of the plasma environment using the JUNO-JADE instrument. Through September of 2025 we will have almost 40 passes through the IPT of JUNO observations. Further, there is recent evidence from ground based optical telescopes that Io recently had a major eruption increasing neutral emission close to Io around Thanksgiving of 2022 (C. Schmidt, personal communication, 2022). We have been developing a nominal torus model based on in situ plasma measurements from previous missions, emission modeling of UV spectra, and ground based optical emission derived plasma parameters. Physical chemistry modeling informs our model and is another point of comparison. We use Phipps & Bagenal (2021) to define the centrifugal equator, along with the newest JUNO based magnetic field model (Connerney et al. 2022), and using diffusive equilibrium to find the plasma distribution along a magnetic field line. We will compare our IPT model with observations from JUNO before, during, and after the Thanksgiving 2022 eruption. We will compare JUNO observations with a physical chemistry model of the IPT to constrain the source rate, radial transport diffusion coefficient, transport timescale, and how these vary throughout the eruption.
PHIPS-HALO Radiative Measurement Applications to Atmospheric Bullet Rosette Ice Crystals
Authors: Wagner Shawn , Schnaiter Martin , Xu Guanglang , Nehlert Franziska , Järvinen Emma
Published: February 2023

Cirrus clouds provide a substantial amount of coverage in the earth’s atmosphere, resulting in a major impact on the global radiative budget. The extent of the radiative impact is determined by the aspherical ice crystal composition within the cirrus. Thus, a proper understanding of ice crystal single scattering properties is necessary for accurate climatological modeling and forecasting. One of the most relevant cirrus ice crystal habits is a polycrystalline bullet rosette, where individual bullets are radiating from the same nucleation point. Comprehensive studies on the dependencies of ice crystal habit formation have shown that bullet rosettes grow at a range of ice supersaturations with temperatures below -40 °C; environmental conditions frequently found within high altitude cirrus clouds. The Particle Habit Imaging Polar Scattering (PHIPS-HALO) probe is a unique aircraft mounted instrument which simultaneously acquires high-resolution stereo images and single scattering properties of individual cloud ice crystals. The ability to combine observed angular scattering functions with detailed images of their related crystals allows for in-depth analysis of the radiative effects of specific habits in critical atmospheric systems such as cirrus clouds. Here, a detailed explanation of the PHIPS-HALO performance and capabilities is provided with an investigation of single scattering properties of atmospheric bullet rosettes. Bullet rosette stereo-images were taken during a range of flights from the CIRRUS-HL campaign and were analyzed for their maximum dimensions as well as for crystal complexity and visually inspected for number of bullets per rosette, individual bullet aspect ratios and bullet hollowness. These bullet rosette microphysical properties were then associated with environmental conditions and with the simultaneously measured angular light scattering function and resulting asymmetry parameter. Angular scattering functions and asymmetry parameters are discussed for bullet rosettes grouped into subsets by complexity parameter. Results indicate that much lower asymmetry parameters represent real atmospheric bullet rosette crystals than what is expected by theoretical studies assuming smooth surfaces.