bluuebunny/crossref_metadata_2025 huggingface dataset:
Partial validation of a socio-economic system dynamics model against a process based hydro-geological model
Authors: Uygur İzel , Yoloğlu Onur Cem , Copty Nadim Kamel , Daloğlu Çetinkaya İrem , Saysel Ali Kerem
Published: February 2023

We develop a high order, multi-loop nonlinear (system dynamics) model for socio-economic sustainability assessment of groundwater resources. Structure and behavior validation of dynamic system models as such pose several challenges. While some of these challenges stem from the ambiguities in theoretical representations of multi-sectorial systems, others stem from the lack of sufficient time varying data sets to calibrate the model reference behavior. In this paper, we focus on partial validation of the groundwater component of this multi-sectorial model. For this purpose, we test the behavioral response of the system dynamics model against a process-based surface/subsurface hydrogeological model. For testing purposes, the hydrogeological model is regarded as the best representation of the reality (a synthetic reality), concerning groundwater flows and accumulations. The system dynamics model is built on Stella Architect and runs on annual time steps for a time horizon of 20 years. The embedded groundwater is a non-spatial, one compartment representation -a box model- of the saturated zone, changing with lateral flows, vertical recharge and anthropogenic extractions. The hydrogeological model is built on the UFZ1-MODFLOW computer program. It simulates evapotranspiration and one-dimensional vertical flow through the vadose zone, and horizontal flow through the underlying aquifer system. The model was developed based on available borehole and pumping tests data and calibrated using observed transient groundwater level data. While the box model and the hydrogeological model are different structural entities, the spatially aggregated behavioral response of the latter under specific experimental conditions help structural validation and calibration of the box model. For this purpose, we apply multiple tests on the lateral and vertical recharge of the hydrogeological model under constant boundary hydraulic head, precipitation, irrigation and evapotranspiration conditions to observe the response in spatially aggregated hydraulic head. We repeat the same experiments on the box model, first to confirm the equations used to simulate the aggregated hydraulic flows, and to estimate the two parameters, “aquifer bottom” and “fractional evaporation” for calibration of the spatially aggregated hydraulic head. The testing process is very useful to arrive at a reliable water budget and hydraulic head response in the system dynamics model, which is going to serve for socio-economic sustainability analysis under stakeholder participation.This work was developed under the scope of the InTheMED project. InTheMED is part of the PRIMA program supported by the European Union’s HORIZON 2020 research and innovation program under grant agreement No 1923.
Origin of regional springtime ozone episodes in the Sichuan Basin, China: role of synoptic forcing and regional transport
Authors: yang xianyu
Published: February 2023

The Sichuan Basin (SCB) located in southwestern China has long been considered the most polluted city cluster with exposure to unhealthy levels of ozone (O3) at times. However, the features of O3 regional transport and source contributions in SCB are poorly understood. In this study, ambient measurements, ERA5 reanalysis dataset, IASI O3 column, and the Weather Research and Forecasting-Community Multiscale Air Quality (WRF-CMAQ) modeling system coupled with the Integrated Source Apportionment Method (ISAM) module were used to investigate the formation mechanism and sources of a severe O3 episode in spring 2020 over the SCB. In the first stage of the O3 episode, a high-pressure system persisted over the western SCB and caused northeasterly wind fields, leading to enhanced regional transport from the northern boundary with the O3 contribution from the boundary exceeding 50% across the SCB. As the synoptic pattern evolved, southeasterly winds dominated the SCB and the stagnant zone over the Chengdu Plain confined O3 originating from the southern SCB and Chongqing city, leading to the accumulation of precursors and elevated O3 levels. During the O3 episode, transportation and industrial sources were major contributors to O3 formation especially for the Chengdu Plain and Chongqing city. In addition, the O3-rich air mass in the nocturnal residual layer that formed over Chongqing city was transported to the Chengdu Plain through southeastern corridor at 400-1600m above ground-level under the prevailing southeasterly winds. With sunrise and the development of the atmospheric boundary layer, the O3-rich air mass in the residual layer (RL) was entrained to the ground-level via vertical mixing, which further enhanced O3 pollution across the Chengdu Plain. Our results revealed the mechanism of regional transport via northeastern and southeastern corridors during an O3 episode and demonstrated the need for joint emission regulation across the SCB to mitigate O3 pollution.
Eddy activity and its role in barrier layer thickness variability in the southeast Indian Ocean
Authors: Azaneu Marina , Matthews Adrian , Heywood Karen , Hall Rob
Published: February 2023

Ocean stratification can modulate the upper ocean response and its feedback to atmospheric forcing. Surface freshwater input by advection and precipitation, for example, can change the upper ocean stratification and produce barrier layers. The existence of a barrier layers can affect SST in several ways, for example by reducing entrainment of cooler water at the base of the mixed layer, and consequently may impact air--sea interactions. In the southeastern Indian Ocean, eddies are abundant and can act on transporting warm and fresh waters westward, thus possibly contributing to the formation of barrier layers. Here we initially evaluate the importance of eddy activity in contributing to barrier layer formation and intraseasonal variability in the southern Indian Ocean. Using 15 years (2005-2019) of ocean reanalysis daily data, we estimate how much of the spatial and time variability of barrier layer thickness is related to eddy activity, which is determined by calculating eddy kinectic energy. With the establishment of a relationship between eddy activity and barrier layer thickness, we then proceed to estimate the relationship between barrier layer thickness and local SST anomalies. This way, we seek to infer the significance of eddy activity in affecting SST through barrier layer formation, and thus its potential impact in air--sea interactions and coupled weather systems such as the MJO.
Climate and health in the UK: Thinking across hazards and timescales
Authors: Mitchell Dann , Barciela Rosa , Griffith Gareth , Gasparrini Antonio , Lo Eunice , Simpson Charles
Published: February 2023

Weather and climate variability and trends impact health in a range of different ways. In this work I will cover five hazards, heat/drought, cold, storms/flooding, wildfire, and ‘other’ (e.g. hazards related to infectious diseases). I will give a summary of an expert judgment regarding how much various health outcomes associated with these hazards currently impact the UK population, and how this might change in the future. I will discuss how long exposure needs to be to the hazard before the health outcome is detectable. I will finish with highlighting where there are significant gaps in the literature, and where research groups and funding agencies should focus more, not just in the UK context, but the world.  This work was done through the Met Office academic partnership “temperature and health” group, and involves a group of 50+ experts in climate and/or health. 
The relative role of the subsurface Southern Ocean in driving negative Antarctic Sea ice extent anomalies in 2016-202
Authors: Zhang Liping , Delworth Thomas L. , Yang Xiaosong , Zeng Fanrong , lu feiyu , Morioka Yushi , Bushuk Mitchell
Published: February 2023

The low Antarctic sea ice extent (SIE) following its dramatic decline in late 2016 has persisted over a multiyear period. However, it remains unclear to what extent this low SIE can be attributed to changing ocean conditions. Here, we investigate the causes of this period of low Antarctic SIE using a coupled climate model partially constrained by observations. We find that the subsurface Southern Ocean (SO) played a smaller role than the atmosphere in the extreme SIE low in 2016, but was critical for the persistence of negative anomalies over 2016-2021. Prior to 2016, the subsurface SO warmed in response to enhanced westerly winds. Decadal hindcasts show that subsurface warming has persisted and gradually destabilized the ocean from below, reducing SIE over several years. The simultaneous variations in the atmosphere and ocean after 2016 have further amplified the decline in Antarctic SIE.
New insight into multi-year La Niña dynamics from the perspective of a near-annual ocean process
Authors: Liu Fangyu , Zhang Wenjun , Jin Fei-Fei , Jiang Feng , Boucharel Julien , Hu Suqiong
Published: February 2023

The El Niño-Southern Oscillation (ENSO) exhibits highly asymmetric temporal evolutions between its warm and cold phases. While El Niño events usually terminate rapidly after their mature phase and show an already established transition into the cold phase by the following summer, many La Niña events tend to persist throughout the second year and even re-intensify in the ensuing winter. While many mechanisms were proposed, no consensus has been reached yet and the essential physical processes responsible for the multi-year behavior of La Niña remain to be illustrated. Observations show that a unique ocean physical process operates during multi-year La Niña events. It is characterized by rapid double reversals of zonal ocean current anomalies in the equatorial Pacific which exhibits a fairly regular near-annual periodicity. Analyses of mixed-layer heat budget reveal comparable contributions of the thermocline and zonal advective feedbacks to the SST anomaly growth for the first year of multi-year La Niña events; however, the zonal advective feedback plays a dominant role in the re-intensification of La Niña events. Furthermore, the unique ocean process is identified to be closely associated with the preconditioning heat content state in the central to eastern equatorial Pacific before the first year of La Niña, which sets the stage for the future re-intensification of La Niña. The above-mentioned oceanic process can be largely reproduced by state-of-the-art climate models despite systematic underestimation, providing a potential predictability source for the multi-year La Niña events.
Reproducing storm-time densities with Kp, Hpo and TIMED/SABER CO2 cooling power
Authors: Bruinsma Sean , Laurens Sophie
Published: February 2023

A major application of semi-empirical thermosphere specification models is in the computation of the atmospheric drag force in the orbit determination and prediction of spacecraft as well as debris. The models provide low spatial and temporal resolution average (climatological) predictions of temperature, total and partial densities of the main constituents as a function of location (altitude, latitude, longitude, local solar time), solar and geomagnetic activity, and season. The research DTM2020 thermosphere model uses a new driver for geomagnetic activity, the hourly Hp60 index (https://doi.org/10.5880/Hpo.0001) instead of the three-hourly Kp. However, thermosphere cooling due to enhanced C02 and NO production in particular during storms is not explicitly taken into account in the semi-empirical models. In this study, we will use density observations of CHAMP, GOCE, GRACE, and Swarm, the Kp and Hpo indices, and the TIMED/SABER measured CO2 and NO cooling power per profile and per day, for selected geomagnetic storms. We will investigate the benefits of Hpo vs Kp, and if it is possible to reproduce storm density more precisely in semi-empirical thermosphere models by adding observed cooling power as model driver.
Paleodust cycle in Europe during the last climate cycle
Authors: Rousseau Denis-Didier , Antoine Pierre , Chauvel Catherine , Saulnier-Copard Ségolène , Lagroix France , Hatté Christine , Hopcroft Peter , Fuchs Markus
Published: February 2023

The Last Climate Cycle (LCC, 130-15kyr) has shown cold, dusty (GS) and warmer, non-dusty (GI) intervals, when the atmosphere was 2-20 times more loaded with dust than today. The alternations between GS and GI occurred on millennial time scales, involving climate forcings other than orbital. The transition between GS and GI lasted on average 50 yrs, resulting from a complete climate reorganization that is not presently understood. A data-model project has acquired and investigated European loess sequences to get high-resolution and well-dated paleodust records of the LCC showing Europe experienced millennial paleodust variations through paleosol-loess unit alternations. These alternations correspond to the millennial climate variability as expressed in the Greenland ice cores, with the paleosol developments occurring during GIs, and loess deposition during GSs. Although evidenced for the last climate cycle along a 50°N transect from Brittany to Ukraine, such system prevailed at least also during the penultimate climate cycle with evidence of similar millennial climate variability during the past 192-130 ka interval, equivalent to marine isotope stage 6. Earth System Models contribute i) to characterize the source regions of the paleodust and ii) to reproduce past variations in dust deposition for key paleoclimate scenarios.A key component of our investigation analyses loess samples dated from the last glacial maximum to detect the origin of the deposited material. A first study on the bulk sediment demonstrates that the paleodust deposited over Europe along a long longitudinal transect (about 2000 km) indicates a short distance transport implying local to regional source. Targeting the <2 microns and 2-20 microns grain size fractions and comparing with the previous results from the bulk samples, preliminary results indicate a local to regional origin for the coarse (2-20 microns and bulk) material and a more distant source for the finer fraction (<2 microns), involving longer transport in relation to general atmospheric circulation, for the finer particles. This is a critical new research question because it implies potentially important order of magnitude regional variations in dust radiative forcing that have never been accounted for in simulations of abrupt events.
Long-distance atmospheric transport of microplastic fibers depends on their shapes
Authors: Li Qi , Xiao Shuolin , Cui Yuanfeng , Brahney Janice , Mahowald Natalie
Published: February 2023

Recent studies have highlighted the importance of the atmosphere in the long-range transport of microplastic fibers (MPFs).  However, both dry deposition processes and sources of MPFs are poorly understood due to their complexity in size and shape, which can be 100s $\mu m$ long, possessing round or flat cross-sections with dimensions of $O(1)\,\mu m$ thickness, and $O(10)\,\mu m$ width. Here, we develop a theory-based settling velocity model for MPFs in the atmosphere, predicting a much smaller aerodynamic size than a volumetrically equivalent spherical particle. Incorrect identification of flat fibers as cylindrical ones due to uncertainty in the thickness of sampled MPFs overestimates their dry deposition rate. Accounting for fiber thickness in sampled MPFs leads to a mean residence-time enhancement above $450\%$ compared to spherical-shaped particles, suggesting a much more efficient long-range transport of flat fibers than previously thought and that the ocean might be a major source of atmospheric plastics.
Rapid assessment of earthquake-induced building damage using remote sensing LiDAR data
Authors: Foroughnia Fatemeh , Macchiarulo Valentina , Berg Luis , DeJong Matthew , Milillo Pietro , Hudnut Kenneth W. , Gavin Kenneth , Giardina Giorgia
Published: February 2023

Earthquakes are natural hazards leading to the greatest human and economic losses, which are mostly due to structural collapses. Rapid identification and assessment of earthquake-induced damage to structures is therefore an essential component of the emergency response, and instrumental to effective reconstruction plans. Typically, structural damage assessment is conducted through building-by-building inspections during post-earthquake field reconnaissance missions. These missions are expensive and time-consuming, especially if large areas need to be investigated. Remote sensing techniques provide a relatively low-cost, wide-area alternative to in-situ monitoring. Classification and change detection based on pre- and post-event optical and synthetic aperture radar (SAR) satellite images are the most used approaches to detect damaged structures after earthquakes. However, these techniques only provide qualitative observations of collapsed or severely damaged structures. In this work, we present a new approach for the quantitative assessment of earthquake-induced structural damage based on displacement measurements acquired by Airborne Light Detection And Ranging (LiDAR). The approach is based on the integration between LiDAR-based observations and structural indicators of damage. The application to the analysis of 684 buildings affected by the 2014 Napa earthquake, in California, demonstrates a good agreement between the LiDAR-based results and independent in-situ observations. This work sets the basis for the innovative exploitation of remote sensing data in disaster management.  
Simple climate emulators - fit for net-zero emission scenarios?
Authors: Folini Doris , Bansal Pratyuksh , Eftekhari Aryan , Kübler Felix , Malova Aleksandra , Scheidegger Simon
Published: February 2023

Simple climate models or climate emulators (CEs) are indispensable in the context of climate economics, where the lion share of compute resources is bound to the economic part of the problem. Associated applications traditionally focused on scenarios with strongly increasing carbon emissions. Here we ask to what degree CEs developed with such applications in mind are fit for purpose when it comes to strong reduction or negative emission scenarios, as in the context of the Paris agreement.To this end, we present and discuss an augmented version of the CE used in the seminal DICE model. Augmentation consists of additional carbon reservoirs, notably a land biosphere and / or a middle ocean reservoir, on top of the three standard carbon reservoirs representing atmosphere, upper ocean, and lower ocean. The different CEs are calibrated and tested against output of large-scale Earth System Models from the Coupled Model Intercomparison Project, run on pre-defined emissions scenarios. For the calibration of the CE, we use the same strategy as in our previous work, i.e., two highly idealized test cases to separately calibrate the CE's carbon cycle and temperature response. In contrast to previous work, we strongly augment the set of test cases to which we expose the calibrated CE. Additional test cases address, in particular, strong mitigation as well as negative emission scenarios. As in our previous work, we demand that all test cases are well documented in the climate literature and can be easily implemented based on that literature. Based on these test cases, we discuss what added value the additional carbon reservoirs may offer with regard to the CE and associated econ studies.
The role of coastal aquifers in the composition of major elements in the ocean
Authors: Kiro Yael
Published: February 2023

Submarine groundwater discharge (SGD) is important to coastal aquifers' biogeochemistry and ecology. Most SGD is comprised of circulating seawater in the coastal aquifer. The circulating seawater is driven by several mechanisms with different spatial and temporal scales, from short-term/small-scale circulation driven by tides and waves through seasonal exchange driven by the sea- or groundwater-level changes and up to long-term/large-scale circulation driven by density differences. Although short-term circulation has been shown to affect groundwater chemistry and potentially modify the composition of seawater for some elements, long-term processes have the potential to affect elements (e.g., Na, Ca, K, Mg, Sr) that are controlled by long-term geochemical processes. These are not affected by the short-term/small-scale processes, thus allowing differentiation and quantifying the long-term density-driven circulation only. Being able to differentiate the different circulating seawater components is a critical step toward quantifying major elements fluxes from the coast into the ocean.Our study presents a new compilation of worldwide coastal aquifers' data, which allows for determining the major elements' end-member composition of coastal aquifer groundwaters (see figure). Based on these compositions and their uncertainties, we could quantify the SGD flux of the long-term component due to density-driven circulation. Based on the Ca2+, K+, Sr2+, and 87Sr/86Sr ocean budgets, the calculated long-term SGD flux is 1117±487 km3/y (see figure). Although this flux is small compared to the global SGD water fluxes, it yields elemental fluxes of 8.0±3.5 Tmol Ca, -1.9±0.98 Tmol K, and 0.19±0.036 Tmol Sr per year, which are on the same order of magnitude as the fluxes through rivers.End-member enrichment (+) and depletion (-)Ca2+ - 13±8 mMK+ - -1.48±1.11 mMSr2+ - 0.169±0.081 mM87Sr/86Sr - 0.7089±0.00001 Figure 1: A global compilation of major elements enrichment and depletion in coastal aquifers’ groundwaters. The enrichment/depletion is calculated as the addition/deficit of a particular element compared to its expected concentration due to conservative mixing only.Figure 2: Monte-Carlo simulation results of the long-term circulation (LTC) flux based on the different element and isotope budgets (up) and the combined distribution (bottom).Major results:
Tmol/y

LTC

Rivers

Ca2+

8.0±3.5

13.2±1.3

K+

-1.9±0.98

1.9±0.4

Sr2+

0.19±0.036

0.033±0.006
Cretaceous magmatism from the Sava-Vardar Zone of the Balkans
Authors: Sokol Kristijan , Prelević Dejan , Radivojević Ana
Published: February 2023

Кеy words: Upper Cretaceous magmatism, Sava Vardar Zone, Adria, basaltsThe complex geodynamic evolution of the northernmost Neotethys is the subject of a long-living controversy. The most perplexing issues are related to the waning stage(s) of the Tethyan ocean(s) in the Balkans and the timing of the Europe-Adria collision. Some authors consider this collision to have occurred in the Late Jurassic, whereas others envisage that have happened at the end of the Cretaceous along the Sava-Vardar Zone. The second model assumes this zone contains a relic suture between Africa- and Europe-derived units.Late Cretaceous magmatism along the Sava-Vardar Zone includes several centers of small-volume transitional to alkaline Na-basalt (with subordinate rhyolitic rocks) and rare ultrapotassic lavas. This volcanism occurs in both Europe- and Africa- derived units of the collisional zone. The geochemical and isotope compositions of the Late Cretaceous lavas suggest that they are not a part of dismembered ophiolite sequences, but represent intracontinental magmas derived from variably enriched mantle sources. The transitional to alkaline Na-basaltic lavas show a clear “within plate” geochemical signature with typical mantle-like 87Sr/86Sri, 143Nd/144Ndi and 206Pb/204Pbi ratios with relatively high HFSE/LILE ratios, and without orogenic geochemical signatures such as high LILE/HFSE ratios, positive Pb and negative Ti–Nb–Ta anomalies, whereas the ultrapotassic lavas are lamprophyres demonstrating enriched 87Sr/86Sri, 143Nd/144Ndi and 206Pb/204Pbi ratios, LILE enrichment, and orogenic geochemical signatures. A broad range of MREE/HREE ratios in these locations suggests polybaric mantle melting.Our working melting model is that the mafic melts were generated as a continuum with low-degree melting in the asthenospheric mantle within the garnet stability field and high-degree melting of the freshly metasomatized lithospheric mantle in the spinel stability field. The ultimate trigger of the mantle melting along the Sava-Vardar Zone should be localized extension during transtensional tectonics, in a system of pull-apart basins (Köpping et al., 2019).Acknowledgments: This research was financed by the Science Fund of the Republic of Serbia through project RECON TETHYS (7744807).Köopping, J., Peternell, M., Prelevi_c, D., Rutte, D., 2019. Cretaceous tectonic evolution of the Sava-Klepa Massif, Republic of North Macedonia e results from calcite twin based automated paleostress analysis. Tectonophysics 758. https://doi.org/10.1016/j.tecto.2019.03.010.Please insert your abstract HTML here.
Aeolus: ESA’s wind mission. Status and future challenges
Authors: Parrinello Tommaso , Wernham Denny , Fehr Thorsten , Von Bismarck Jonas , Tran Viet Duc , Romanazzo Massimo , Candra Krisna Trismono , Sathe Aditi , Bickerton Peter , Krisch Isabell , Rennie Michael
Published: February 2023

The European Space Agency (ESA)’s wind mission, Aeolus, was launched on 22 August 2018. It is a member of the ESA Earth Explorer family and its main objective is to demonstrate the potential of Doppler wind Lidars in space for improving weather forecast and to understand the role of atmospheric dynamics in climate variability. Aeolus carries a single instrument called ALADIN: a high sophisticated spectral resolution Doppler wind Lidar which operates at 355 which is the first of its kind to be flown in space.Aeolus provides profiles of single horizontal line-of-sight winds (primary product) in near-real-time (NRT), and profiles of atmospheric backscatter and extinction. The instrument samples the atmosphere from about 30 km down to the Earth’s surface, or down to optically thick clouds. The required precision of the wind observations is 1-2.5 m/s in the troposphere and 3-5 m/s in the stratosphere while the systematic error requirement be less than 0.7 m/s. The mission spin-off product includes information about aerosol and cloud layers. The satellite flies in a polar dusk/dawn orbit (6 am/pm local time), providing ~16 orbits per 24 hours with an orbit repeat cycle of 7 days. Global scientific payload data acquisition is guaranteed with the combined usage of Svalbard and Troll X-band receiving stations.After almost five years in orbit and despite some performance issues related to its instrument ALADIN, Aeolus has achieved all its scientific objectives and gone beyond its original designed life-time in space. Positive impact on the weather forecast has been demonstrated by multiple NWP centres world-wide, with four European meteorological centres now are assimilating Aeolus winds operationally, paving the way to its successor: EPS-Aeolus. Aeolus data is being used with success over a number of innovative research streams with growing scientific impact on literature.The status of the Aeolus mission will be presented including the last main challenge to re-enter the satellite from space with an assisted scenario instead of an uncontrolled one, as initially foreseen by design.
Discrepant decadal trends in global land-surface and air temperatures controlled by vegetation biophysical feedbacks
Authors: Kan Fei , Lian Xu , Cui Jiangpeng , Chen Anping , Mao Jiafu , He Mingzhu , Xu Hao , Piao Shilong
Published: February 2023

Satellite-based land surface temperature (Ts) with continuous global coverage is increasingly used as a complementary measure for air temperature (Ta), yet whether they observe similar decadal trends remains unknown. Here, we systematically analyzed the trend of the difference between satellite-based Ts and station-based Ta (Ts–Ta) over 2003–2018. We found the global land warming rate based on Ts was on average 56.7% slower than that on Ta (Ts–Ta trend: -0.0166℃ yr-1, p<0.01) during daytime of boreal summer. This slower Ts-based warming was attributed to recent Earth greening, which effectively cooled canopy surface through higher evapotranspiration and turbulent heat transfer. However, Ts showed faster warming than Ta during boreal summer nighttime (0.0159℃ yr-1, p<0.01) and boreal winter daytime (0.011℃ yr-1, p=0.14), when vegetation activity is limited by temperature and radiation. Our results indicate potential biases when using Ts in assessments of atmospheric warming and the vegetation-air temperature feedbacks.
Variability of summer-time Arctic sea ice: the drivers and the contribution to the sea ice trend and extremes
Authors: Karami Mehdi Pasha , Koenigk Torben , Tremblay Bruno
Published: February 2023

Understanding the variability of summer-time Arctic sea ice at interannual to multidecadal time scales in the midst of anthropogenically forced sea ice decline is crucial for better predictions of sea ice conditions in the future climate and rapid changes in sea ice. Here, we apply time-frequency analysis to study the modes of variability, extreme events and the trend in the September Arctic sea ice in 100–150 year datasets. We extract the non-linear trend for the sea ice area and provide an estimate for the anthropogenic-driven sea ice loss. For the used dataset, the anthropogenic-related sea ice loss is found to have a rate of ~-0.25 million km2 per decade in the 1980’s and accelerating to ~-0.47 million km2 per decade in 2010’s. By assuming the same rate of sea ice loss in the future, and without the contribution of the internal variability and feedbacks, we can approximate the occurrence of summer sea-ice free Arctic to be around 2060. Regarding the dominant modes of variability for the September sea ice, we find that they have periods of around 3, 6, 17, 28 and 55 years, and show what drives these modes and how they contribute to sea ice extreme events. The main atmospheric and oceanic drivers of sea ice modes include the Arctic oscillation and Arctic dipole anomaly for the 3-year mode, variability of sea surface temperature (SST) in Gulf Stream region for the 6-year mode, decadal SST variability in the northern North Atlantic Ocean for the 17-year mode, Pacific decadal oscillation (PDO) for the 28-year mode, and Atlantic multidecadal Oscillation (AMO) for the 55-year mode. Results show that changes in the sea ice due to internal variability can be as large as forced changes thus can slow down or accelerate the background anthropogenic-driven sea ice loss. By applying the same method, we also present modes of variability and trend of sea ice in the large ensemble global model simulations of EC-Earth model (SMHI-LENS) for the future climate projections and different climate scenarios.
Comparing gravity waves sampled from a kilometre-scale IFS run to AIRS satellite observations
Authors: Lear Emily , Wright Corwin , Hindley Neil , Polichtchouk Inna
Published: February 2023

Gravity waves are small-scale atmospheric waves which transport energy and momentum. These waves impact the large scale circulation and increasing our understanding of them is therefore important to support improvements to weather and climate models. This presentation focusses on gravity waves in the stratosphere using data from a high resolution run of the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) operated at a kilometre-scale spatial resolution, the Atmospheric Infrared Sounder (AIRS) on NASA’s Aqua satellite and the ECMWF ERA5 reanalysis. For this comparison, the IFS run and ERA5 are resampled using the AIRS observational filter. Data are examined during the first 2 weeks of November, as the high resolution model was initialised on the 1st of this month. Wave properties were found using the 2D+1 S-Transform, a spectral analysis technique, which has been previously applied to AIRS data. Asia and surrounding regions are investigated, because preliminary studies of AIRS data suggested strong gravity wave activity in this region during this time period. Gravity waves can also be seen in the high resolution model and ERA5 data at similar times and locations as those in the observations. Higher amplitude gravity waves can be seen in nighttime AIRS data compared to the resampled models. The horizontal wavelengths in the data sets are generally similar in areas of peak gravity wave activity for nighttime data. Weather models are advancing rapidly and kilometre scales, such as the experimental IFS run, could become operational in the next decade. At these grid scales, gravity waves must be resolved instead of parameterized so the models need to be tested to see if they do this correctly. This work provides information on how a cutting edge model resolves gravity waves compared to observations.
Cascading Transitions in the Weak and Strong Coupling Limit
Authors: Sinet Sacha , Kuehn Christian , Bastiaansen Robbin , von der Heydt Anna S. , Dijkstra Henk A.
Published: February 2023

Many components of the Earth system are thought to be prone to dangerous transitions, presenting a big challenge for human societies. Known as tipping elements, those form an intricate network of interacting subsystems, creating the possibility of cascading critical transitions. The presence of those interacting tipping events makes it hard to predict the outcome of climate change. In this research, we investigate those phenomena above the usual approach of linearly interacting bistable components.We propose to study generic nonlinear systems under generic nonlinear interaction. As a first step, we focus on unilaterally coupled components, where a leading and a following subsystem are naturally identified. Using singular perturbation methods, we show how the stability landscape can be approached semi-analytically when considering the weak and strong coupling limit. With only limited knowledge about the system's structure, this method applies to a wide class of interacting systems and allows for approaching steady states with a controlled error. This provides information on important structural features of the bifurcation diagram such as the presence of steady branches, their stability, and bifurcations. Finally, we illustrate our results using climate relevant conceptual models.
Assessing the Cooling Potential of Land Restoration in Africa with Google Earth Engine
Authors: Ruijsch Jessica , Teuling Adriaan J. , Hutjes Ronald W.A.
Published: February 2023

The African continent, although having one of the lowest per-capita contribution to greenhouse gas emissions, is already experiencing the effects of global climate change, resulting in biodiversity loss, droughts, reduced food production, reduced economic productivity and loss of lives. Land restoration and greening practices, such as active reforestation, natural regeneration, and water harvesting are seen as one of the major solutions to mitigate climate change through the carbon sequestration potential of trees. However, land restoration practices can also directly affect the local climate through changes in the biophysical properties of the earth surface (e.g. albedo, evapotranspiration and surface roughness) and can therefore be used as adaptation strategy to reduce the impact of climate change in Africa. Yet, it is currently unknown to what extend land restoration can be used to reduce local temperatures in Africa through biophysical processes, because the net cooling or warming effect of vegetation changes depends on latitude, scale and atmospheric conditions.In this study, we aim to bridge this gap by determining the biophysical cooling and warming effects of land restoration in Africa. To this end, we use MODIS satellite imagery in Google Earth Engine to analyse the effects of vegetation changes (NDVI) in the twenty-first century on albedo and land surface temperature, after which we apply the found relations to predict the cooling effect of potential large-scale land restoration in Africa. Preliminary results show that increases in vegetation cause biophysical cooling in large parts of Africa and especially in dryland areas. Using these relations, we predict that large scale land restoration can decrease the land surface temperature in some areas up to 5 degrees Celsius. With these results we hope to provide more insight in the climate change adaptation potentials of land restoration projects in Africa, as well as other parts of the world.
Observations of aeolian activity on the deflation floor of a foredune trough blowout
Authors: Ruessink Gerben
Published: February 2023

Blowouts on coastal foredunes provide efficient pathways for wind-driven sand transport inland. In this way blowouts affect beach-dune sand budgets, facilitate landward dune migration under sea-level rise and stimulate the dunes’ biodiversity by maintaining a heterogeneous landscape.  While our understanding of the dynamics of blowouts on time scales of months to decades is advancing due to the increasing availability of remote sensing data sets, we have limited empirical data and hence understanding of the short-term (hours) aeolian activity in blowouts and how this activity builds up to longer term blowout dynamics.This contribution documents the first results of a study designed to cover multiple scales of aeolian activity (hours to months) in the foredune trough-blowout system of the Dutch National Park Zuid-Kennemerland. The data used here consist of (i) photographs of one of the deflation basins taken by a time-lapse trap camera every two hours during the day, (ii) wind speeds and directions (at 1-m height) measured by 4 continuously operating ultrasonic anemometers positioned from the seaward side of the same basin to the adjoining depositional lobe, and (iii) wind data (at 10-m height) from a nearby offshore meteorological station. The 120-m long instrumented basin has an approximately linearly upward sloping floor with steep lateral walls and is about 100 m wide at its mouth, reducing to about 20 m at the start of the depositional lobe. Good-quality images were manually classified into five categories with increasing aeolian activity from no transport (class 0), isolated streamers on a small portion of the deflation floor (class 2) to intense streamer activity everywhere (class 4). The first results, based on images collected in fall 2022, indicate that streamer activity (class 2 or higher) is restricted to moments when the wind speed at the blowout mouth exceeds about 5 to 6 m/s and the offshore wind approach direction is within 40 to 50 degrees of the blowout axis. For these directions the wind is steered into the blowout and, depending on the approach angle, accelerates over the deflation floor by up to 50%. Aeolian activity on the deflation floor is absent or very small (class 0 or 1) for larger approach angles (even at offshore wind speeds of 10 – 15 m/s) because the wind is no longer steered into the blowout. These first results thus indicate the importance of the wind speed on the deflation floor and the offshore wind approach angle (relative to the blowout axis) for short-term aeolian activity in the blowout.
The Value of Legacy data - securing access and reuse of 25 years of data
Authors: Clark Adrian , Hansen Kurt
Published: February 2023

Researchers need access to infrastructures to make their research data findable, accessible, interoperableand reusable, known as FAIR. The FAIR principles of data sharing transcend disciplines and encapsulatethe aims and ideals of Open Data advocates.As researchers look to make their research data FAIR, in some disciplines this may result in data beingshared in disparate solutions. If we look at the Geosciences for example, a researcher may use GitLab toshare their code, a hosted website for discoverability and separate storage for the preservation oflegacy data. Research groups often possess a rich heritage of data spanningperiods of several decades. However, this legacy almost never gets proper attention due to lackof funding, and thus lack of long-term maintenance plans. As a consequence, the legacy data aretypically unreadable and inaccessible due to obsolete formats and technologies in which they areprovided.This presentation will demonstrate how 25 years of wind data at the Technical University of Denmark(DTU) has been shared in accordance with the FAIR principles in their Figshare powered repository.We’ll demonstrate how the long term availability of the data is secured and how discoverability is ensuredand data reuse is encouraged with robust metadata. This presentation will also touch on the importance ofdata reuse throughout the research lifecycle and showcase this for both an academic and lay audiencethrough the features of the DTU Data repository.
Improved bias-adjustment methods for subdaily precipitation extremes
Authors: Van de Vyver Hans , Van Schaeybroeck Bert , De Cruz Lesley , Hamdi Rafiq , Termonia Piet
Published: February 2023

Extreme precipitation events are responsible for severe damage to various aspects of human society and ecosystems. Short-term extremes especially affect people in urban areas through flash floods. Extremely heavy precipitation is increasing in frequency and intensity due to global warming and Regional Climate Models (RCMs) of high-resolution are needed to estimate associated increased risks. However, even the RCMs that explicitly resolve deep convection are known to significantly underestimate subdaily precipitation extremes. Impact modellers and other users of climate projections therefore often use some form of bias correction. In this study, we propose bias adjustment methods especially designed for the estimation of future subdaily extreme precipitation return levels. These methods take into account the scaling intensity-duration-frequency (IDF) relationship between different levels of accumulation, and jointly estimate extreme rainfall over multiple rainfall durations (i.e. from hourly to multi-day extreme precipitation events). After comparison with established methods, we identify only one method that preserves the scaling IDF relationship, which is a necessary condition to have bias-adjusted return levels consistent among the different durations. A comparative analysis in a multi-model pseudo-reality setting shows that this method is superior to existing bias adjustment methods.Finally, future projections of bias-adjusted subdaily precipitation return levels for Belgium are obtained in the form of an ensemble of 28 EURO-CORDEX simulations at 0.11° spatial resolution, under the RCM8.5 emission scenario.
Leaf acclimation to elevated CO2 is independent of soil nitrogen fertilization and rhizobial inoculation
Authors: Perkowski Evan A. , Smith Nicholas G.
Published: February 2023

Plants acclimate to increasing CO2 by reducing leaf nutrient allocation and photosynthetic capacity at the leaf level, a response that often occurs alongside growth stimulation at the whole plant level. Nutrient limitation has been hypothesized to be the primary mechanism driving leaf and whole plant acclimation responses to CO2, as nutrient availability commonly limits primary productivity and may decrease with increasing CO2 over time. However, recent work leveraging photosynthetic least-cost theory indicates that these acclimation responses may instead be the result of optimal resource investment toward photosynthetic capacity, which maximizes nutrient allocation to whole plant growth. Acclimation responses to CO2 may also vary in species with different nutrient acquisition strategies, but few studies have examined these responses across a soil nitrogen availability gradient and in species with different nutrient acquisition strategies. To test whether nutrient limitation or optimal leaf resource investment controls leaf and whole plant acclimation responses to CO2 and how nutrient acquisition strategy modifies these responses, we grew Glycine max L. (Merr) seedlings under two atmospheric CO2 levels, with and without Bradyrhizobium japonicum inoculation, and across nine soil nitrogen fertilization treatments in a full factorial growth chamber experiment. After seven weeks, G. max demonstrated a strong downregulation in leaf nitrogen content, Vcmax25, and Jmax25 under elevated CO2, patterns that were not causally linked to changes in soil nitrogen fertilization or inoculation treatment. A relatively stronger downregulation in leaf nitrogen content than Vcmax25 increased the proportion of leaf nitrogen content allocated to photosynthesis, while a relatively stronger downregulation in Vcmax25 than Jmax25 stimulated Jmax25:Vcmax25 under elevated CO2. These leaf acclimation responses to elevated CO2 corresponded with strong stimulations in total leaf area and total biomass, a pattern that was generally stronger with increasing fertilization and in inoculated pots. Whole plant acclimation responses to CO2 were driven by reductions in the cost of acquiring nitrogen with increasing fertilization and inoculation. Overall, these results provide strong support for patterns expected from photosynthetic least-cost theory, showing that optimal resource investment is the primary mechanism governing G. max acclimation responses to elevated CO2.
Varying drivers of humid heat extremes over Africa
Authors: Birch Cathryn , Keane Richard , Marsham John
Published: February 2023

Africa is particularly vulnerable to present day and future temperature extremes due to its (sub)tropical location, its growing population and the challenges of adapting to extreme heat in many of its regions. Globally, the vast majority of past research on the drivers of heatwaves is focused on dry bulb temperature extremes. The drivers of humid heat extremes vary by location and there is limited understanding of the drivers in all parts of the world, but particularly over Africa. Previous published research by the authors showed increased humidity, cloud, rainfall and/or evaporation drive events over most of Africa. However, across the central African equatorial belt, where absolute values of wet bulb temperature are highest, humid heat extremes are driven by both increased temperature and humidity, and cloud and rainfall anomalies are less important. Here we use ERA5 reanalysis to identify multi-day, large-scale humid heat events over different regions of Africa and quantify the roles of moisture transport, cloud, rainfall and atmospheric circulation. We compare and contrast the different sub-tropical and tropical climatic regions of Africa and present a detailed case study of coastal East Africa. East Africa is of particular interest due to its high climatological wet bulb temperatures, its high population, and its coastal location where the land-sea breeze may be a key control on humid heat extremes. We identify the time of day and locations in coastal East Africa that experience the highest daily maximum wet bulb temperatures and discuss the controlling factors.