bluuebunny/crossref_metadata_2025 huggingface dataset:
A network of in situ soil moisture observations operational since 2009
Authors: Vermunt Paul , Van der Velde Rogier , Benninga Harm-Jan , Retsios Bas , Salama Mhd. Suhyb
Published: February 2023

In situ soil moisture measurement networks are essential for developing, improving and validating satellite soil moisture products. In the east of the Netherlands, an area susceptible to droughts, a monitoring network for soil moisture and – temperature has been operational since 2009. Spread across an area of 45 by 40 km, twenty profile monitoring stations observe moisture and temperature in the root zone. Four field campaigns were conducted in order to calibrate the sensors and to assess the spatial representativeness of the measurements.The network has proven to be of great value for validation of satellite products (e.g. for SMAP soil moisture). In addition, continuation of the measurements will increase its value for climate studies. Currently, the network is being redesigned to better suit operational water management in the region, while preserving the value of long time series for climatological research, and taking into account its potential value for future missions. Here, we present an overview of the network and the observations since its establishment, including the adjustments that are being made to the network and research opportunities.Van der Velde, R., Benninga, H.J.F., Retsios, B., Vermunt, P.C., Salama, M.S. (2022) - Twelve years profile soil moisture and temperature measurements in Twente, the Netherlands. Earth System Science Data Discussions, 1-44.Velde, dr. ir. R van der (University of Twente) (2022): Twelve years profile soil moisture and temperature measurements in Twente, the Netherlands. DANS. https://doi.org/10.17026/dans-znj-wyg5
Effect of Major Dust Events on Atmospheric Temperature and Solar Irradiance Components over Saudi Arabia
Authors: Labban Abdulhaleem , Farahat Ashraf
Published: February 2023

In 2021, Saudi Arabia, a leading global oil producer, announced its Middle East Green Initiative with many objectives including reducing carbon emissions by divagating the country away from an oil-based economy and towards renewable. Saudi Arabia has a high potential to become one of the global largest solar energy producers, as it is geographically located on a sunbelt. By 2030, the Saudi government targets building eight solar plants across the country which are expected to produce more than 3,600 MW, enough to power more than 500, 000 homes. However, the vast desert environment in Saudi Arabia increases the dust and aerosol loadings in the atmosphere, which affects the performance of the solar irradiance performance of photovoltaic panels due to the scattering of the solar radiation and the dust deposition on the solar panels. In this work, ground-based data from weather stations located in five Saudi cities: Dammam, Riyadh, Jeddah, Najran, and Arar along with data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate solar irradiance and its correlation with atmospheric and meteorological conditions like air temperature, wind, and aerosol physical parameters. We investigate the effect of three major dust storms that blew over different regions in Saudi Arabia on 20 March 2017, 23 April 2018, and 15 April 2021 on solar irradiance. It is found that there is a strong correlation between aerosol optical parameters like Aerosol Optical Depth (AOD), Ångström exponent, and solar irradiance. Maximum AOD (about 2) is recorded over Jeddah on 19 March 2017, (about 2.3) over Riyadh on 20 March 2017, (about 1.5) over Riyadh on 24 April 2018, and (about 0.9) over Najran on 15 April 2021. Large dust events are found to reduce air temperature by a few degrees in the regions affected by dust loadings. The study found large dust loading decreases the DNI, and GHI components on the solar irradiance, while increasing the DHI component over the cities of Jeddah, Riyadh, and Najran. This could be an indication that scattering from dust particles could play a significant role in the solar irradiance intensity. 
Connecting flood trends to groundwater
Authors: Berghuijs Wouter , Slater Louise
Published: February 2023

Soil moisture is increasingly recognized as shaping fluvial flood trends, but it only represents a fraction of subsurface water storage. In contrast, groundwater in the saturated zone often contributes a significant proportion of river flow, but its effects on large-scale flood trends are poorly understood. We analyzed streamflow and climate records of thousands of catchments to show that baseflow (i.e., groundwater-sustained river flows) affects the magnitude of annual flooding at time scales from days to decades. Annual floods almost always arise through the co-occurrence of high precipitation (rainfall + snowmelt) and elevated baseflow. Consequently, trends and variations of flood magnitudes are often more strongly coupled to antecedent baseflow conditions than antecedent soil moisture and extreme precipitation. This reveals the importance of groundwater in shaping river floods and can decouple flood trends from shifting precipitation extremes and soil moisture.
Water table depth assimilation in integrated terrestrial system models at the larger catchment scale
Authors: Li Fang , Kurtz Wolfgang , Hung Ching Pui , Vereecken Harry , Hendricks Franssen Harrie-Jan
Published: February 2023

As a vital supply of water resources for human society, groundwater plays a significant part in the water cycle, and is closely linked to precipitation, surface water and soil moisture (SM). Groundwater modelling often suffers from a variety of uncertainties, including uncertain forcing data, parameters and initial conditions. To reduce the uncertainties of model predictions, data assimilation (DA) can be used to correct model predictions with observations to improve the estimation of unknown states and parameters. To investigate the effects of assimilation of groundwater data into the integrated model Terrestrial System Modelling Platform (TSMP) on groundwater table depth (WTD) simulations, groundwater assimilation experiments were conducted for the Rur catchment in Germany. 128 ensemble members were generated by perturbing atmospheric forcing variables and saturated hydraulic conductivity, and then the measured daily groundwater data from 2018 were assimilated into the model TSMP by the Localized Ensemble Kalman Filter (LEnKF). The measured data were screened rigorously before assimilation. The spatial autocorrelation analysis of the measured groundwater data and the open loop (OL) simulations showed consistency in the spatial variability of groundwater levels between measurements and simulations. Based on the results of a spatial autocorrelation analysis, three different local radii (10 km, 5 km and 2.5 km) were selected for the assimilation experiments. Comparing the results of the OL and DA experiments, the simulated WTD bias (simulated - measured) and root mean square error (RMSE) were reduced for all DA runs compared to OL. The 10km localization radius gives the smallest RMSE at assimilation locations, with 81% RMSE reduction compared to the OL. Validation with WTD data from independent verification sites shows that localized assimilation improves groundwater simulations only when the distance to assimilated sites is smaller than 2.5km. Independent WTD validation showed a reduction in RMSE of 30% and the best results were from the DA run with 10 km radius. Also soil moisture measurements from the Cosmic Ray Neutron Sensor (CRNS) were used for validation. The simulated SM reproduced the observed temporal fluctuations, with a high correlation between measured and simulated SM (from 0.70 to 0.89, except for the Wuestebach site). However, there was no RMSE reduction of SM for the DA runs compared to the OL.
Statistical study of extreme magnetopause locations
Authors: Grimmich Niklas , Plaschke Ferdinand , Archer Martin , Heyner Daniel , Mieth Johannes , Nakamura Rumi , Sibeck David
Published: February 2023

The magnetopause (MP) is the boundary that separates the solar wind plasma from the Earth’s (inner) magnetosphere. To first order, its equilibrium position is defined by the pressure balance across it. The boundary moves under the influence of varying solar wind conditions and transient foreshock phenomena, thereby sometimes reaching unusually large and small distances from Earth. We investigate the occurrence of such extreme MP distortions. Therefore, we construct a database of magnetopause crossings observed by the THEMIS spacecraft in the years 2007 to mid-2022 using machine learning techniques. Crossing events deviating from the Shue et al. (1998) MP model by more than the reported uncertainties are denoted as extreme distortions. The occurrences of these extreme events in terms of expansion or compression of the magnetosphere are linked to different solar wind parameters. The results should be applied to future magnetopause models and may be validated by MP observations in soft x-ray images by the upcoming SMILE mission.
Neogene synorogenic stratigraphic evolution of southern Apennines
Authors: Ciarcia Sabatino , Vitale Stefano
Published: February 2023

We present a study of the synorogenic deposits associated with the orogenic construction of the southern Apennines. This orogen is a segment of the Alpine chain system bounding the central-western Mediterranean Sea. Southern Apennines form an orogenic belt consisting of the superposition of some successions of the downgoing Adria plate, made of shallow-water to pelagic sedimentary successions. The synorogenic sedimentation was ruled by the migration of the forebulge-foreland basin system, with the flexure of the continental part of the Adria plate since the Oligocene (forebulge stage), mainly due to the slab retreat process. The thrust front-foredeep-forebulge system migrated toward E/NE until the middle Pleistocene. We focussed our attention on the Foreland Basin System synorogenic deposits mainly consist of back-bulge, foredeep, and wedge-top basin sediments.
Seaweed as a resilient food solution in nuclear winter
Authors: Jehn Florian Ulrich , Dingal Farrah Jasmine , Mill Aron , Ilin Ekaterina , Harrison Cheryl , Roleda Michael Y. , Denkenberger David
Published: February 2023

Abrupt sunlight reduction scenarios such as a nuclear winter, an asteroid impact or an eruption of a supervolcano would decimate agriculture as it is practised today. We therefore need resilient food sources for such an event. One promising candidate is seaweed, as it can grow quickly in a wide range of environmental conditions. To explore the feasibility of seaweed in a nuclear winter, we simulate the growth of seaweed on a global scale using an empirical model based on Gracilaria tikvahiae forced by nuclear winter climate simulations. We assess how quickly global seaweed production could be scaled to provide a significant fraction of global food demand. We find seaweed can be grown in tropical oceans, even in nuclear winter. The simulated growth is high enough to allow a scale up to an equivalent of 70 % of the global human caloric demand, while only using a small fraction of the global ocean area. The results also show that the growth of seaweed increases with the severity of the nuclear war, as more nutrients become available due to upwelling. This means that seaweed has the potential to be a viable resilient food source for abrupt sunlight reduction scenarios. 
Contrasting biopore production by deep and shallow rooting rice cultivars in compacted paddy soils and the impacts on subsequent rice growth
Authors: Islam Md Dhin , Price Adam H. , Hallett Paul D.
Published: February 2023

Rice is often grown as multiple crops in one year, with reduced tillage upland cropping following flooded cropping gaining prominence due to water use, soil degradation and labour demands.  This study explored whether a deep rather than shallow rooting rice cultivar grown in a flooded cropping cycle, benefited deeper root growth of follow-on rice in an upland, reduced tillage cropping cycle. In a greenhouse study, a simulated flooded paddy was planted with deep (Black Gora) and shallow (IR64) root cultivars and a plant-free control.  Artificial plough pans were made in between the topsoil and subsoil to form different treatments with no plough pan (0.35 MPa), soft plough pan (1.03 MPa) and hard plough pan (1.70 MPa). After harvest of this ‘first season’ rice, the soil was drained and undisturbed to simulate zero-tillage upland, with a photoperiod insensitive variety (BRRI Dhan 28) planted. Root length, root surface area, root volume, root diameter, number of root tips and branches were measured.  The number of roots penetrating the plough pan was measured from camera images and X-ray CT. The overall root length density (RLD), root surface area, number of root tips and branching of BRRI Dhan 28 did not vary between plough pan and no plough pan treatments.  Compared to the shallow rooting rice genotype,  the deep rooting rice genotype as a ‘first season’ crop promoted 19 % greater RLD, 34 % greater surface area and 29 % more branching of BRRI Dhan 28 in the subsoil. In the topsoil, however, BRRI Dhan 28 had 28 % greater RLD, 35 % greater surface area and 43 % more branching for the shallow rather deep rooting genotype planted in the ‘first season’.  The results suggest that rice cultivar selection for a paddy cycle affects root growth of a follow-on rice crop grown under no-till, with benefits to subsoil access from deep rooting cultivars and topsoil proliferation for shallow rooting cultivars.
Towards area-wide operational tide predictions for the German Bight
Authors: Boesch Andreas
Published: February 2023

The German Federal Maritime and Hydrographic Agency (BSH) operates the Tidal Information Service that is responsible for producing and publishing tidal predictions for German waters. Traditionally, the predictions are produced for tide gauge locations, which are situated almost exclusively at or close to the coastline. Water level observations from the tide gauges are used as input data for the respective tidal analyses. BSH strives to extend these point-wise predictions to an area-wide data set for the German Bight based on simulated water levels. This shall serve the increasing demands in the context of research, shipping and offshore activities. High quality area-wide tidal data might also be usable for the reduction of measurements from satellite altimetry in this region.We present tidal analyses based on simulated water levels using the hydrodynamic-numerical model HBM. This model runs operationally at BSH. Many grid points that cover the Wadden Sea run dry around low water and require special attention in the analyses. Tidal parameters, such has the mean lunitidal intervals and tidal ranges, are compared with data from tide gauges. One challenge is the harmonisation of tidal predictions based on model data with those based on tide gauge observations, in order to produce consistent products. The results from this work could also help to improve the implementation of tides in HBM in the future.
The thermodynamic differences between winter cyclones from midlatitudes and high latitudes
Authors: Tao Dandan , Li Camille , Davy Richard , He Shengping , Michel Clio , Rosendahl Andrea
Published: February 2023

Cyclones carry heat and moisture that impact local conditions along their path. Cyclones with different origins can, however, have different life cycles and cause different impacts. To quantify differences in the thermodynamic evolution of cyclones originating from different latitudes during wintertime, we separate the cyclones according to their origin (cyclogenesis location):  midlatitude (ML) cyclones originating in the North Atlantic and high-latitude (HL) cyclones originating in the Nordic Seas and Barents Seas. It is found that HL cyclones generally carry lower thermodynamic energy as they originate in a cold environment. In contrast, ML cyclones have much higher thermodynamic energy throughout their lifecycle, even though they lose a large amount of heat as they travel long distances from their origin towards the Arctic. For a given region in the high latitudes (e.g., the Barents Sea), the mean vertical profiles of temperature and moisture from the HL group are colder and drier compared to the ones from the ML group, but the maximum values in the HL group can reach those of the ML group. Further analysis for the top 10% warmest profiles in the HL group suggests that these HL cyclones form in a preconditioned warm and moist environment. The precondioning is set up by the large-scale circulation with influences from the upstream North Atlantic. Under special conditions, the formation of high latitude cyclones in a preconditioned warm and moist environment can lead to extreme warming events in the deep Arctic like the one during New Year’s 2015/16.
Combining model results and paleodata using data assimilation
Authors: Goosse Hugues
Published: February 2023

Observations and model results provide two complementary sources of information on past climate variations. The paleo -or proxy - data characterize the changes that occurred at a particular time while models can be used to infer the mechanisms responsible for those changes. Observations and model results are thus ideally used jointly and the first step before applying models to study past and future climate is to evaluate their ability to reproduce the signal recorded in the data. Paleodata and model results can also be combined more profoundly using data assimilation. While classical model-data comparison can only assess the skills of the model, data assimilation can guide the model results to have a better agreement with the real observed changes and thus to reproduce more accurately the processes at their origin.The main challenges in paleo data assimilation will be reviewed here. Issues related to the generation of the model results, the model data comparison and the data assimilation technique itself will be addressed. Some recent achievements and perspectives will then be presented, first for spatial reconstructions based on data assimilation and secondly for the quantification of internal and forced climate variability as well as the role of atmospheric and oceanic circulation in past climate changes.
Stratospheric wave reflection modulates North American cold spells
Authors: Messori Gabriele , Kretschmer Marlene , H. Lee Simon , Wendt Vivien
Published: February 2023

The proposed drivers of wintertime North American cold spells are multifarious, including modes of climate variability, planetary wave patterns and regional-to-continental-scale weather regimes. The Arctic stratospheric polar vortex has also been reported as a potential remote driver. One proposed coupling mechanism between the stratospheric polar vortex and the troposphere is upward-propagating planetary waves being reflected downward by the polar vortex. Here, we present a physically interpretable regional stratospheric wave reflection detection metric and identify the tropospheric circulation anomalies over North America associated with prolonged periods of wave reflection. The stratospheric reflection events show a systematic evolution from a Pacific Trough regime – associated on average with positive temperature anomalies and a near-complete absence of anomalously cold temperatures in North America – to an Alaskan Ridge regime, which favours low temperatures over much of the continent. The most striking feature of the stratospheric reflection events is thus a systematic shift in the tropospheric circulation in North America, associated with a rapid, continental-scale decrease in temperatures. These emerge as continental-scale cold spells by the end of the reflection events. Stratospheric reflection events are thus highly relevant in a tropospheric predictability perspective.
Microbial Risk Assessment for Underground Hydrogen Storage in Porous Rocks
Authors: Thaysen Eike Marie , Armitage Timothy , Slabon Lubica , Hassanpouryouzband Aliakbar , Edlmann Katriona
Published: February 2023

Climate change, triggered by a continuously rising use of carbon based energy sources, is a global concern. Geological hydrogen storage, e.g. in depleted gas fields or saline aquifers, can overcome imbalances between supply and demand in the renewable energy sector and facilitate the transition to a low carbon emissions society, in this way mitigating climate change. However, a range of subsurface microorganisms utilise hydrogen which may have important implications for hydrogen recovery, clogging and corrosion. We created a novel, globally applicable risk categorization tool based on the published environmental growth constraints of all major hydrogen utilizing microbes (hydrogenotrophic methanogens, hydrogenotrophic sulphate reducing bacteria, homoacetogens and hydrogenotrophic dissimilative iron reducing bacteria) and on reports of paleosterile subsurface environments. Application of the tool to 75 depleted or close to depleted gas fields on the UK continental shelf showed that 9 fields fall either within the ´No Risk´ category with temperatures >122 °C, making them the ideal candidates for hydrogen storage from a microbial risk point of view. Hydrogen storage in the 35 ´Low Risk´ fields with temperatures >90 °C or the 22 ´Medium Risk´ fields with temperatures >55 °C and salinities >1.7 M NaCl will require the careful characterization of the microbial community composition to assure that hydrogenotrophic microorganisms are not present. We recommend against utilising depleted gas fields with temperatures <55 °C which are at high risk for adverse microbial effects. Results were mapped and aligned with centres for renewable energy production and out-of-use pipelines suitable for repurposing to transport hydrogen. This showed that No Risk or Low Risk depleted gas fields in the Southern North Sea are the most suitable candidates for hydrogen storage. Our results advise site selection choices in geological hydrogen storage in the UK. Our methodology is applicable to any underground porous rock system globally.
Mapping fish species distributions in River Rhone using environmental DNA and remote sensing
Authors: Zong Shuo , Brantschen Jeanine , Zhang Xiaowei , Albouy Camille , Valentini Alice , Zhang Heng , Altermatt Florian , Pellissier Loïc
Published: February 2023

Biodiversity loss in freshwater river ecosystems is much faster and more severe than in terrestrial systems, and spatial conservation and restoration plans are needed to halt this erosion. Reliable and highly resolved data on the state of and change in biodiversity are critical for effective measures. However, high-resolution biodiversity maps still need to be improved, especially for large riverine systems. Coupling data from the latest global satellite sensors with broad-scale environmental DNA (eDNA) and machine learning could enable fast and precise mapping of the distribution of river organisms. Here, we investigated the potential for combining these methods using a unique fish eDNA data set sampled along the entire length of the Rhone river in Switzerland and France. Using Sentinel 2 and Landsat 8 images, we generated a set of ecological variables describing both the aquatic part (blue) and the surrounding terrestrial landscape of the river (green). We combined these variables with eDNA-based presence and absence data on 29 fish species and used three models to assess environmental suitability for these species. Most models showed good performance, indicating that ecological variables derived from remote sensing can provide valuable information on the ecological determinants of fish species distributions. Variable importance analyses showed that the blue variables (water temperature, water quality, water clarity) had stronger associations than the green variables surrounding the river. The species range mapping indicated a significant transition in the species occupancy along the Rhone, from its source in the Swiss Alps to its outlet into the Mediterranean Sea in southern France. Our study demonstrates the feasibility of combining remote sensing and eDNA to map species distributions in large rivers; this method can be up-scaled to any large river worldwide. Hence, in the future, the approach presented here could be used to predict precise biodiversity distributions in rivers to help design conservation schemes.
Comparative assessment of ozone profile retrievals from OMI, GEMS, and TROPOMI measurements using daily ozonesonde soundings during the ACCLIP summer campaign in 2022
Authors: Bak Juseon , Kim Cheol-Hee , Lee Hyo-Jung , Koo Ja-Ho , Kim Jae-Hwan , Kim Joowan , Baek Kanghyun , Park SangSeo , Jeon Wonbae , Liu Xiong
Published: February 2023

Ozone in the troposphere is an important air pollutant and greenhouse gas, and also acts as a principal oxidant in the lower atmosphere. This ozone is not emitted directly from anthropogenic sources, but formed though the photochemical reaction of nitrogen oxides with hydrocarbons in the presence of heat and sunlight. Ozone and its precursor can be transported across continents and to the oceans. As well, the downward transport from the stratosphere plays an important role in controlling the tropospheric ozone abundance. The spatial distribution and trends of tropospheric ozone should be regularly monitored and described to improve our understanding of the chemical and physical processes controlling tropospheric ozone and hence supplement the emission control suppressing the ozone pollution and climate change. In support of monitoring air quality, climate change, and ozone layer from space, hyperspectral UV measurements have been regularly accumulated from polar orbiting satellites since the late 1990s as well as geostationary service was recently started in 2019, but retrieving ozone profiles are still uncertain, especially over the troposphere. In this study, we present an optimal estimation-based ozone profile algorithm which is matured for processing OMI measurements with the state of art soft calibration. The capability of this research algorithm is also evaluated for retrieving ozone profiles from TROPOMI and GEMS. Each research ozone profile retrieval is inter-compared with the corresponding operational product. As a reference, we use daily ozonesonde soundings launched at Anmyeondo Island in South Korea during August 2022. It is collected as a part of the ACCLIP (Asian Summer Monsoon Chemical & Climate Impact Project) airborne field campaign in July-August, 2022 to investigate the upper troposphere and lower stratosphere composition under the influence of the Asian summer monsoon. In this study, quantitative differences between ozonesonde measurements and satellite data are assessed with the qualitative evaluation of how satellite measurements represent the ozone variability influenced by the atmospheric circulation.
Sesimic Traveltime Tomography Using Deep Learning
Authors: Jo Jun Hyeon , Ha Wansoo
Published: February 2023

Seismic inversion methods performed by a deep neural network trained in a supervised learning manner have shown successful inversion performance in synthetic data examples that target small areas. These deep-learning-based seismic inversions use time-domain wavefields as input data and subsurface velocity models as output data. Since the time-domain wavefields include both traveltimes and amplitudes of seismograms, the size of the input data is considerably large. Therefore, studies that apply deep-learning-based seismic inversions trained on large amounts of field-scale data have not yet been conducted. In this study, to apply the deep-learning-based seismic inversion technique to field-scale data, the velocity models are predicted using only traveltimes of seismic waves as the input data instead of the full time-domain wavefields. If the traveltime information is used as input data, the resolution of the inversion result is diminished, but the data size is significantly decreased, which can reduce GPU memory usage and speed up network training. We call this approach deep-learning traveltime tomography. The results obtained from this method can also be used as initial velocity models for full-waveform inversion. For network training, a large number of field-scale synthetic velocity models and corresponding first-arrival traveltimes with towed-streamer acquisition are created, and then the network is trained with the synthetic dataset. As a result of performing deep-learning traveltime tomography on an example of synthetic velocity models simulating the seafloor strata, inversion results similar to the labels were obtained. Therefore, it was confirmed that the deep-learning traveltime tomography method can immediately predict a field-scale velocity model, unlike the existing deep-learning-based seismic inversion.
A Hydro-Mechanical Analytic Element Model for Seepage Forces
Authors: Toller Erik , Strack Otto
Published: February 2023

Understanding the behavior of hydro-mechanical processes is a challenging task, and groundwater plays an important role in these. We separate the effect of groundwater into two main parts: the pore pressure and the seepage force. Our interest is in the latter part, where we develop a model that incorporates analytically seepage forces in a linear elastic model. This is work in progress; we present our latest developments, focusing on both the theoretical framework and application.The approach is a further development of the Analytic Element Method, which, was recently extended to linear elasticity. We link a groundwater analytic element to a linearly elastic one, including the seepage forces directly in the equation of the linear elastic model. We initially limit the model to one-way coupling and exclude the effect of stresses and strains on the hydraulic conductivity.We present an application where we isolate the impact of the seepage force on the mechanical model focusing on situations where we expect a large pressure gradient.
High-sensitivity detection of HO2 radical by cavity ring-down spectroscopy: prospects for future applications of narrow linewidth lasers
Authors: Zhao Weixiong , Wang Chunhui , Fang Bo , Yang Nana , Cheng Feihu , Hu Xiao , Chen Yang , Zhang Weijun , Fittschen Christa , Chen Weidong
Published: February 2023

The hydroperoxyl radical (HO2) plays a key role in atmospheric chemistry. It reacts with NO to generate hydroxyl radical (OH) and nitrogen dioxide (NO2), resulting in the HOx (= OH + HO2) cycle that governs the atmospheric oxidation capacity and the formation of air pollution, and a net production of ozone that determines the troposphere ozone budget. Quantitative measurement of its absolute concentration is very important. However, due to its short lifetime and low concentration (typically about 108 to 109 molecule/cm3 under atmospheric condition), most of the currently used methods are indirect methods that require chemical conversion; direct measurement remains very challenging.The cavity ring-down spectroscopy (CRDS) technique uses high reflectivity mirrors to increase the effective absorption pathlength to tens of kilometers, enabling very high detection sensitivity; the absolute concentration of the target absorbers can be quantitatively determined by the Beer-Lambert law, providing a powerful tool for direct measurement of free radicals. In this work, we report the development of a portable cavity ring-down spectrometer for direct and absolute measurement of HO2 radical concentration using a distributed feedback (DFB) diode laser operating at 1506 nm. At a pressure of 100 mbar, a detection limit of ~ 7.3×107 molecule/cm3 (1σ, 10s) was achieved with a ring-down time (τ0) of 136 μs. The corresponding detection sensitivity was 1.5×10-11 cm-1, which was close to the state-of-the-art performance.In cavity ring down spectroscopy, the coupling efficiency of the laser beam into the cavity depends on the laser frequency tuning speed and the ratio of the laser linewidth to the cavity mode width. For the DFB laser system, the laser linewidth (~ 2 MHz) was about thousands of times larger than that of the cavity mode (~ 1.2 kHz), which results in the conversion of laser phase noise into amplitude fluctuation, making the cavity injection noisy and limiting the improvement of detection sensitivity. Here, by replacing the DFB diode laser with a narrow linewidth erbium-doped fiber (EDF) laser, the amplitude fluctuation caused by the laser phase noise was reduced and the cavity mode injection efficiency was improved. The sensitivity was improved to 3.9×10-12 cm-1 with a short data-acquisition time of 0.2 s. The one order of magnitude improvement makes further ambient applications look promising.
Increase of injection efficiency in geological CO2 sequestration using SDS and SDBS
Authors: Jung Jongwon , Gang Seokgu , Ryou Jae-Eun
Published: February 2023

Carbon dioxide in the atmosphere causes global warming as a greenhouse gas. Therefore, countries around the world are considering underground storage to reduce carbon dioxide. Carbon dioxide underground storage means injection before waste gas filed, oil field, deep saline aquifer and so on. The temperature and pressure conditions of carbon dioxide for underground storage are supercritical, and a reduction in injection efficiency is expected due to high capillary pressure during injection. In this study, considering the high capillary pressure, utilizing anionic surfactants (SDS, SDBS). Thus, the enhancement of carbon dioxide efficiency with surfactant type and concentration was evaluated. In addition, quantitative injection characteristics according to the injection rate of carbon dioxide were analyzed using a micro model.Experimental results look like follow. Surfactant exhibits higher injection efficiency than water at low carbon dioxide injection rates, and the difference in injection efficiency between water and surfactant decreases as the injection rate increases. However, the differences between the types of surfactants (SDS, SDBS) and concentrations used in this study are relatively modest.To solve the experimental technology limitations in field use, the pore network model is used. The pore network model has the advantage of effective prediction of carbon dioxide injection efficiency in the future. To validate the Pore network model, constructed network is like the micromodel. As a result, the analysis derived the same tendency as the experiment. In the future expected, the pore network model developed in this study will be able to predict carbon dioxide injection.
Coupling hotter and drier extremes under elevating air temperature over eastern monsoon China
Authors: zhang xinxin , Gu Xihui
Published: February 2023

Summer hot and dry extremes (defined as high air temperature and low atmospheric humidity) in monsoon (climatologically high-humidity) region, may cause severe disasters, such as flash droughts. However, it remains unclear whether hot (dry) extremes are amplified on dry (hot) days to warming temperature. Here, taking eastern monsoon China (EMC) as a typical monsoon region, we find a fastest positive (negative) response of air temperature (atmospheric humidity) on driest (hottest) days to per unit warming, indicating amplified warming (drying) of hot (dry) extremes on dry (hot) days (i.e. coupling hotter and drier extremes) especially in southern EMC.  The southern EMC is also a hotspot where the coupling of hot and dry extremes has become significantly stronger during the past six decades. The increasing hot-dry extremes in southern EMC is associated with anomalies in large-scale environmental conditions, such as reduced total cloud cover, abnormal anticyclone in upper atmosphere, intense descending motion, and strong moisture divergence over this region. Land-atmosphere feedbacks play another important role in enhancing the hot-dry coupling via increasing land surface dryness (described as decreasing evaporation fraction). The decreasing evaporation fraction is associated with drying surface soil moisture which is controlled by decreases in pre-summer 1-m soil moisture and summer-mean precipitation. Given hot extremes (atmospheric humidity) are (is) projected to increase (decrease) in the future, it is very likely to witness more hot-dry days in monsoon regions and associated disasters, which should be mitigated by adopting adaptive measures. 
Sensitivity of ocean heat content to atmospheric forcing in the period of global warming hiatus
Authors: Albert Fernández Chavely , Köhl Armin , Stammer Detlef
Published: February 2023

Between 1998 and 2012, there was a smaller rate of global warming, known as the "global warming hiatus". One of the suggested causes is that during this period additional heat sequestration occurs into the deep ocean layers such that deep layers warm at a greater rate than the upper layers. This research is focused on the origins of changes in ocean heat content during the hiatus period, defined in this case as the last 10 years of adjoint model run, where the cost function is defined. Adjoint sensitivities are used to determine the influence of atmospheric forcing (heat and freshwater fluxes and wind stress) on the ocean heat content. The MIT General Circulation Model with a resolution of 2° x 2° is used over the period 1978-2008 to determine adjoint sensitivities of the globally and temporally (over the last 10 years, defined as hiatus period) integrated vertical heat fluxes across various depth levels. The contributions of different forcing components to the vertical heat flux anomalies are obtained from the scalar product between sensitivities and the anomalies of the atmospheric forcing.  For this, the atmospheric forcing anomalies are computed with respect to the climatology calculated over the period 1948-1968 when there was almost no change in the ocean heat content.A more pronounced increase in ocean heat uptake during the hiatus period has been evidenced by the forward run of the model. Wind anomalies represent more than half of the contribution to the increase in heat flux across 300m, suggesting that the excess of heat stored by the ocean is transferred adiabatically to the deeper layers and that the zonal wind is one of the major drivers of ocean heat uptake. In the Southern Ocean, the sensitivities to the wind stress change from positive to negative when the hiatus starts. This indicates that, during the hiatus, the rate of change of ocean heat content is opposite to the one of the wind stress. The Southern Ocean presents smaller values of the computed amplitude weighted mean time, meaning that this region has the fastest response to changes in surface atmospheric forcing.
Showcasing the Potential of Crowd-sourced Observations for Flood Model Calibration
Authors: Dasgupta Antara , Grimaldi Stefania , Ramsankaran Raaj , Pauwels Valentijn , Walker Jeffrey
Published: February 2023

Floods are one the costliest natural disasters, having caused global economic losses worth over USD 51 million and >6000 fatalities just in 2020. Hydrodynamic modelling and forecasting of flood inundation requires distributed observations of flood depth and extent to enable effective evaluation and to minimize uncertainties. Given the decline of in situ hydrological monitoring networks, Earth Observation (EO) has emerged as a valuable tool for model calibration and evaluation in data scarce regions, as it provides synoptic observations of flood variables. However, low temporal frequencies and the (currently) instantaneous nature of EO, still limits the ability to characterize fast moving floods. The concurrent rise of smartphones, social media, and internet access has recently led to the emerging discipline of citizen sensing in hydrology, which has the potential to complement real-time EO and in situ flood observations. Despite this, methods to effectively utilise crowd-sourced flood observations to quantitatively assess model performance are yet to be developed. In this study the potential of crowd-sourced flood observations for hydraulic model evaluation is demonstrated for the first time. The channel roughness for the hydraulic model LISFLOOD-FP was calibrated using just 32 distributed high-water marks and wrack marks collected by the community and provided by the Clarence Valley Council for the 2013 flood event. Since the timings of acquisition of these data points were unknown, it was assumed that these provide information on the peak flow. Maximum model simulated and observed water levels were thus compared at observation locations for each model realization, and errors were quantified through the root mean squared error (RMSE) and the mean percentage difference (MPD), respectively. Peak flow information was also extracted from the 11 available hydrometric gauges along the Clarence River and used to constrain the roughness parameter, to enable the quantification of value addition from the citizen sensed observations. Identical calibrated parameter values were obtained for both data types resulting in a mean RMSE value of ∼50 cm for peak flow simulation across all gauges. Outcomes from this study demonstrate the utility of uncertain crowd-sourced flood observations for hydraulic flood model calibration in ungauged catchments.
Modelling the impact of Biogenic Volatile Organic Compound emissions on Formic Acid concentrations above Central Europe
Authors: Liaskoni Marina , Clerbaux Cathy , Huszar Peter
Published: February 2023

Formic acid (HCOOH) is among the most abundant carboxylic acids in the atmosphere however, its sources are poorly understood. Photochemical production is thought to be the dominant source of atmospheric HCOOH globally, contributing 60–80% of its total budget. Particularly, he OH‐initiated  oxidation of isoprene produces HCOOH via several known pathways. Here we present a study of how BVOC emissions estimated by the MEGAN model contribute to HCOOH concentrations above central Europe for the 2021 year while the CAMx chemistry transport model was used to calculate the species concentrations. The CAMx produced HCOOH column densities are compared with IASI/AERIS columns while the modelled near surface isoprene concentrations are compared with AirBase data. Although, spatially there is a good agreement between the modeled and the observed values, their magnitude is underestimated in most cases indicating some missing source or underestimated production of formic acid.
Physical interpretation of slow earthquake migration process based on a friction law
Authors: Ariyoshi Keisuke
Published: February 2023

Natural faults host various types of migrating slow earthquake phenomena, with migration speeds much lower than seismic wave speeds and different moment-duration scaling from regular earthquakes. To advance the obtained quantitative understanding of the migration process and long duration of slow earthquakes,  I study a chain reaction model in a population of brittle asperities based on a rate- and state-dependent friction on a 3-D subduction plate boundary. Simulation results show that the migration speed is quantitatively related to frictional properties by an analytical relation derived here. By assuming that local pore water in front of the migration drives rapid tremor reversal and is so local as to hold a constant stress drop, the application of the analytical solution to observational results suggests that (i) the temporal changes of observed migration speeds for the rapid tremor reversal could be explained by about 70% reduction of the effective normal stress; (ii) effective normal stress for the deeper extension of seismogenic segment in the western part of Shikoku is about 1.5 times greater than that in the central part. Applying rupture time delay between slow earthquake asperities for a duration longer than the regular earthquake, I also conclude that (iii) the characteristic slip distance of rate-and-state friction for low-frequency earthquakes is roughly between 30 μm and 30 mm; (iv) the stress and strength drops of very low-frequency earthquakes is much smaller than 1 MPa.References:Ariyoshi, K. (2022). Extension of aseismic slip propagation theory to slow earthquake migration. Journal of Geophysical Research: Solid Earth, 127, e2021JB023800. https://doi.org/10.1029/2021JB0238
Evidence of high-pressure metamorphism along the Mahanadi Shear Zone in the Eastern Ghats Province, eastern India: implications on tectonics and continental assembly involving India and East Antarctica.
Authors: Karmakar Shuvankar , Bose Sankar , Ghosh Gautam , Sorcar Nilanjana , Mukherjee Sneha
Published: February 2023

Mafic granulites occur as enclaves within host mylonitized felsic rocks along the WNW-ESE trending, northerly dipping (40°-80°) Mahanadi Shear Zone (MSZ) of the Eastern Ghats Province (EGP), eastern India. Mafic granulite enclaves are characterized by the mineral assemblages Grt+Cpx+Pl+Qtz±Opx±Hbl±Bt (type-1) and Opx+Cpx+Pl+Hbl±Bt (type-2). The type-1 mafic granulite is the focus of the present study and this rock occurs as small enclaves (up to a few tens of meters in maximum size) within mylonitic augen gneiss, finer grained felsic gneiss (Qtz+Kfs+Pl+Bt±Grt), and type-2 mafic granulite. The type-1 mafic granulite is partially to completely recrystallized, massive to crudely foliated rock containing the peak metamorphic assemblage of coarse granoblastic garnet (Grt), clinopyroxene (Cpx), plagioclase (Pl) and quartz (Qtz). Coarse Grt contains inclusion of hornblende (Hbl) which suggests that the peak assemblage was formed by Hbl-dehydration melting. While the peak assemblage is stable in most of the samples, coarse Grt shows partial decomposition to a symplectic intergrowth of Cpx+Pl±Opx (orthopyroxene) in a few samples. Phase chemical data suggest that the rim compositions of coarse Grt show small but significant drop in pyrope content (ΔPrp = 2-3 mole%) from the core, while the coarse Cpx shows more magnesian core (XMg = 0.76) than the rim (XMg=0.68). Plagioclase core is more albitic (XAb = 0.40) compared to the rim composition (XAb=0.16). Geothermobarometric calculations show that the peak pressure of metamorphism was 14-12 kbar at a temperature of ~760-840°C, whereas the rim compositions of Grt in association of coarse Cpx+Pl+Qtz and symplectic Cpx+Pl±Opx yield pressure of 8-9 kbar at ~700-750°C. This suggest a near-isothermal (ΔT=60-90°C) decompression (ΔP=3-6 kbar) of the thickened lower crust indicating exhumation related to thrusting. This regional-scale thrusting was followed by an event of cooling that produced Hbl- and Bt-bearing assemblages. Combining the inferred prograde and retrograde histories, we reconstruct a clockwise P-T path from the studied type-1 mafic granulites. Identification of such clockwise P-T path with characteristic high-temperature decompression from the MSZ is a first of its kind from the interior of the EGP which is otherwise characterized by ca. 1000-900 Ma ultrahigh temperature metamorphism (UHTM; T>900°C) at 7-8 kbar pressure. This study thus shows convincing evidence of a hitherto unrecognized early (> 1000-900 Ma) collisional tectonometamorphic history of the MSZ vis-à-vis the EGP, and hints that the former could represent a fossilized suture zone linked with possible terrane accretion and collision between India and East Antarctica.