Inverse problems are ubiquitous in hydrological modelling for parameter estimation, system understanding, sustainable water resources management, and the operation of digital twins. While statistical inversion is especially popular, its sampling-based nature often inhibits its application to computationally costly models, which has compromised the use of the Generalized Likelihood Uncertainty Estimation (GLUE) methodology, e.g., for spatially distributed (partial) differential equation based models. In this study we introduce multilevel GLUE (MLGLUE), which alleviates the computational burden of statistical inversion by utilizing a hierarchy of model resolutions. Inspired by multilevel Monte Carlo, most parameter samples are evaluated on lower levels with computationally cheap low-resolution models and only samples associated with a likelihood above a certain threshold are subsequently passed to higher levels with costly high-resolution models for evaluation. Inferences are made at the level of the highest-resolution model but substantial computational savings are achieved by discarding samples with low likelihood already on levels with low resolution and low computational cost. Two example inverse problems, using a rainfall-runoff model and groundwater flow model, demonstrate the substantially increased computational efficiency of MLGLUE compared to GLUE as well as the similarity of inversion results. Findings are furthermore compared to inversion results from Markov-chain Monte Carlo (MCMC) and multilevel delayed acceptance MCMC, a corresponding multilevel variant, to compare the effects of the multilevel extension. All examples demonstrate the wide-range suitability of the approach and include guidelines for practical applications.

Regions of ECH occurrence in different planetary magnetospheres. Two distinct regions of ECH waves are present in Saturn and Jupiter. ECH waves are seen in the equatorial regions outside the high density plasmasphere / plasma torus and also at intermediate latitude in the magnetospheres, where plasma is confined in a thin disc near centrifugal equator.

To understand the relationships between eclogite-facies mineral assemblages, deformation microstructures, and the seismic properties of subducting oceanic crust, eclogites from the Yuka terrane, North Qaidam ultrahigh-pressure metamorphic belt, NW China were studied. Observations of mineral textures, deformation microstructures, and petrofabrics in the eclogites indicate that garnet, omphacite, and phengite were deformed by intra-crystalline deformation (i.e., dislocation creep) during prograde metamorphism. In contrast, amphibole, which was formed by the topotactic replacement of omphacite at fluid-present conditions, is considered to have been deformed by diffusional flow (dissolution–precipitation creep) during amphibolite-facies retrogression associated with exhumation. Based on the petrofabrics in the samples, the seismic properties of the eclogites were calculated depending on eclogite-facies mineral assemblages such as garnet + omphacite (GO), garnet + omphacite + phengite (GOP), garnet + omphacite + phengite + lawsonite (GOPL), garnet + omphacite + phengite + amphibole (GOPA), and garnet + omphacite + amphibole (GOA). We found that the seismic signatures of each of the eclogite-facies mineral assemblages were different. In particular, phengite-bearing eclogites (the GOP/GOPA assemblages), depending on phengite content, produced the strongest seismic anisotropy (AVp and AVs), with a strong polarization anisotropy, that was at least three times higher than bimineralic (phengite-absent) eclogite (GO assemblage). Our results show that phengite, as a stable phase at high pressure and temperature conditions, can play an important role in the creation of trench-parallel seismic anisotropy in the eclogite-facies mineral assemblages found in subduction zones.

Monsoons emerge over a range of land surface conditions and exhibit varying physical characteristics over the seasonal cycle, from onset to withdrawal. Systematically varying the moisture and albedo parameters over land in an idealized modeling framework allows one to analyze the physics underlying the successive stages of monsoon development. To this end we implement an isolated South American continent with reduced heat capacity but no topography in an idealized moist general circulation model. Irrespective of the local moisture availability, the seasonal cycles of precipitation and circulation over the South American monsoon sector are distinctly monsoonal with the default surface albedo. The dry land case (zero evaporation) is characterized by a shallow overturning circulation with vigorous lower-tropospheric ascent, transporting water vapor from the ocean. By contrast, with bucket hydrology or unlimited land moisture the monsoon features deep moist convection that penetrates the upper troposphere. A series of land albedo perturbation experiments indicates that the monsoon strengthens with the net column energy flux and the near-surface moist static energy with all land moisture conditions. When the land-ocean thermal contrast is strong enough, inertial instability alone is sufficient for producing a shallow but vigorous circulation and converging a large amount of moisture from the ocean even in the absence of land moisture. Once the land is sufficiently moist, convective instability takes hold and the shallow circulation deepens. These results have implications for monsoon onset and intensification, and may elucidate the seasonal variations in how surface warming impacts tropical precipitation over land.

Key Points: • We use EISCAT UHF ISR data to study the 1-100 keV electron precipitation at 6 66.7° MLAT observed during 21 years. • The auroral electron precipitation occurrence rate as observed by the radar reaches70% in the 05–06 MLT sector of the main auroral oval.• Electron precipitation with 50–100 keV peak energies is more common than with 30–50 keV peak energies after 06 MLT

Stratospheric aerosol geoengineering focused on the Arctic could substantially reduce local and worldwide impacts of anthropogenic global warming. Because the Arctic receives little sunlight during the winter, stratospheric aerosols present in the winter at high latitudes have little impact on the climate, whereas stratospheric aerosols present during the summer achieve larger changes in radiative forcing. Injecting SO2 in the spring leads to peak aerosol optical depth (AOD) in the summer. We demonstrate that spring injection produces approximately twice as much summer AOD as year-round injection and restores approximately twice as much September sea ice, resulting in less increase in stratospheric sulfur burden, stratospheric heating, and stratospheric ozone depletion per unit of sea ice restored. We also find that differences in AOD between different seasonal injection strategies are small compared to the difference between annual and spring injection.

Pore-pressure depletion in sandstone reservoirs is well known to cause both elastic and inelastic compaction, often resulting in notable surface subsidence and induced seismicity. Recent studies indicate that in such cases inelastic strain, which is often neglected in geomechanical models, represents a significant proportion of the total strain throughout reservoir production. While there has been considerable effort to quantify the proportion of continuous inelastic deformation from the mechanical response of laboratory samples, there has been little focus to date on the associated acoustic response throughout compaction. With this in mind, we employ three coda-wave based processing methods for the active source monitoring of ultrasonic velocity, scattering power, and intrinsic/scattering attenuation during the pore-pressure depletion of core samples from the Slochteren sandstone reservoir in the Groningen gas field (the Netherlands). Our results corroborate previous studies suggesting that initially, inelastic deformation occurs primarily along intergranular boundaries, with intergranular cracking developing towards the end of depletion and particularly for the highest porosity samples. Furthermore, analysis of Biot type intrinsic attenuation indicates that this compaction occurs in several stages of predominately intergranular closure, transitioning into predominantly intergranular slip/cracking, and eventually porosity-dependent intragranular cracking. We demonstrate how this segmentation of pore-pressure driven compaction can be used to characterise differences in sample properties, and monitor the evolution of microstructural inelastic deformation throughout depletion. We further discuss the feasibility of in/cross-borehole monitoring of reservoir compaction, for both improved geo-mechanical modelling and early warning detection of induced seismicity.

The volume, extent and age of Arctic sea ice is in decline, yet winter sea ice production appears to have been increasing, despite Arctic warming being most intense during winter months. Several negative feedback processes help to restore Arctic sea ice volume during the winter, though previous work suggests that these mechanisms will be overwhelmed by warming in the future, leading to a fall in ice production. Here, we analyse winter ice production in the Kara and Laptev seas–sometimes referred to as Arctic “ice factories”, for their outsized role in supplying the Arctic Ocean with young sea ice. Using the Community Earth System Model’s Large Ensemble (CESM-LE), we develop a simple linear model that can explain both the forced rise and forced fall of ice production, in terms of consistent physics. We apply our linear model to observation-based estimates of the same climate variables; our reconstruction of ice production suggests that–just as in CESM-LE–we are currently passing the peak of ice production in the Kara and Laptev seas.

The prevalence of mixing vs. precipitation processes in biomass burning aerosol (BBA) laden air over the southeast Atlantic is assessed during three intensive observation periods during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign. Air in the lower free troposphere (FT) and marine boundary layer (MBL) are treated as separate analyses, although connections are made where relevant. The study, centering on aircraft in-situ measurements of total water heavy isotope ratios, has two main objectives. The first is to gauge whether the atmospheric hydrology, and in particular precipitation, can be constrained primarily through visual assessment of the aircraft isotope ratio data plotted against total water concentration, similarly to several previous studies. However, regression of the data onto a simple model of convective detrainment is also used and alludes to the possibility of a precipitation data product derived from isotope ratios. The second objective is to connect variations in aerosol concentrations to the hydrology as diagnosed by the isotope ratio measurements, and determine whether aerosol variations are attributable to wet scavenging. First, joint water concentration (q) and H2O/HDO isotope measurements (δD) in the lower FT are combined with satellite and MERRA-2 data into simple analytical models to constrain hydrologic histories of BBA-laden air originating over Africa and flowing over the southeast Atlantic. We find that even simple models are capable of detecting and constraining the primary processes at play. Further, a strong correlation between isotopic evidence of precipitation in lower FT air masses and an in-situ indicator of wet scavenging of black carbon – the ratio of black carbon to carbon monoxide (BC/CO) – is shown. In comparison, the correlation between BC/CO and the water concentration itself is low. Since wet scavenging is the primary removal mechanism of black carbon, these findings suggest that isotope measurements could support studies constraining the lifetime of black carbon in the FT. Next, the ability of measurements interpreted with simple analytical models in (q, δD) space to distinguish cloud-top entrainment vs. precipitation signals in the MBL is tested. This proves more difficult than the lower FT analysis since signals are smaller. We find that the largest obstacle to this goal is the (q, δD) values of the entrained airmass at cloud-top. We also compare cloud condensation nuclei (CCN) concentrations in the sub-cloud layer to the isotopic measurements. In 2016 and 2018 IOPs, lower CCN concentrations coincide with isotope ratio evidence of precipitation, indicating aerosol scavenging. However, a more complex model simulating water, isotope ratios, and aerosols would be necessary to achieve more definitive conclusions. For the 2017 IOP, with the highest sub-cloud CCN concentrations, there is no connection between precipitation signals and CCN concentrations.

Basin structures in the northern Los Angeles area have been identified from a nodal seismic array along 10 lines across three basins. The dense array of 758 geophones spaced at 250-300 m apart along the lines and recorded seismic response for 30-35 days. For basin structure investigation, the teleseismic receiver functions technique was used. The primary basin concerted phases were identified from the receiver functions. A shear wave velocity model produced in a separate study using the same dataset was incorporated to convert the basin time arrivals into depth. The deepest part of the San Bernardino basin was identified near Loma Linda fault at 2.8 km. San Gabriel basin exhibit larger basin depths and Ps arrival times of all with a maximum depth of 4 km. The high lateral resolution from the dense array helped revealing more continuous structures and reducing uncertainties in the RFs. We discovered a more complex basin structure than previously identified. Our findings show the basins' core areas are not the deepest. Significant changes in basin depth were observed near some faults i.e. Rialto-Colton fault, Fontana fault, Red Hill fault and Raymond fault. Plain Language Summary Sedimentary basins can contribute to the damage caused by any earthquake. The seismic waves from an earthquake can get trapped and amplified within the basin which may result in a stronger ground shaking with longer duration. The three basins of our study area, San Bernardino, Chino and San Gabriel, are located in a seismically active region. The BASIN (Basin Amplification Seismic INvestigation) project aims to image the subsurface so that the seismic wave response within the basins for any earthquake can be assessed. As part of this project, we identified sedimentary basin shape and depth underneath this region. The P wave from an earthquake generates P to S conversions at boundaries. We used receiver functions to determine basin boundaries from those conversions. Arrival times of the P to S conversions were converted to depth using a velocity model.

Agricultural managed aquifer recharge (AgMAR) is a proposed management strategy whereby surface water flows are used to intentionally flood croplands with the purpose of recharging underlying aquifers. However, legacy nitrate (NO3-) contamination in agriculturally-intensive regions poses a threat to groundwater resources under AgMAR. To address these concerns, we use a reactive transport modeling framework to better understand the effects of AgMAR management strategies (i.e., by varying the frequency, duration between flooding events, and amount of water) on N leaching to groundwater under different stratigraphic configurations and antecedent moisture conditions. In particular, we examine the potential of denitrification and nitrogen retention in deep vadose zone sediments using variable AgMAR application rates on two-dimensional representations of differently textured soils, soils with discontinuous bands/channels, and soils with preferential flow paths characteristic of typical agricultural field sites. Our results indicate that finer textured sediments, such as silt loams, alone or embedded within high flow regions, are important reducing zones providing conditions needed for denitrification. Simulation results further suggest that applying recharge water all-at-once, rather than in increments, increases denitrification within the vadose zone, but transports higher concentrations of NO3- deeper into the profile. This transport into deeper depths can be aggravated by wetter antecedent soil moisture conditions. We conclude that ideal AgMAR management strategies can be designed to enhance denitrification in the subsurface and reduce N leaching to groundwater, while specifically accounting for lithologic heterogeneity, antecedent soil moisture conditions, and depth to the water table.

The world has changed, and the role and responsibilities of scientists have changed as a consequence. Not only is there an increasingly urgent need for scientifically informed multi-scale responses to the global problems we face, but there is also a need to address to the obstructive attitudes toward evidence accumulated and presented through scientific activities. What skills will allow future scientists to continue extending the frontiers of knowledge, to cooperate in response to the wicked problems we face, and negotiate the complexities of denialism? These questions go to the very heart of what it means, and is likely to mean in future, to be a scientist. This in turn goes to the heart of the educational process that will deliver graduates able to address these conundrums. The implications of these considerations will be explored from curriculum design, learning outcomes, and pedagogic perspectives. We start by considering the value of longitudinal curricula, problem based learning approaches and authentic assessment strategies. We demonstrate the utility of an enhanced graduate profile framework as a tool for planning educational interventions across the scales at which they occur -- institution, programme, module, session and individual learner. Based on our experiences in formal teaching, informal student support, and research training at both undergraduate and post-graduate levels, we will reflect on the value of such an approach to science education in this brave new post-truth world.

Outdoor workers perform critical societal functions, often despite higher-than-average on-the-job risks and below-average pay. Climate change is expected to increase the frequency of days when it is too hot to safely work outdoors, compounding risks to workers and placing new stressors on the personal, local, state, and federal economies that depend on them. After quantifying the number of outdoor workers in the contiguous United States and their median earnings, we couple heat-based work reduction recommendations from the US Centers for Disease Control and Prevention with an analysis of hourly weather station data to develop novel algorithms for calculating the annual number of unsafe workdays due to extreme heat. We apply these algorithms to projections of the frequency of extreme heat days to quantify the exposure of the outdoor workforce to extreme heat and the associated earnings at risk under different greenhouse gas emissions mitigation scenarios and, for the first time, different adaptation measures. With a trajectory of modest greenhouse gas emissions reductions (RCP4.5), outdoor worker exposure to extreme heat would triple that of the late 20th century baseline by midcentury, and earnings at risk would reach an estimated $39.3 billion annually. By late century with that same trajectory, exposure would increase four-fold compared to the baseline with an estimated $49.2 billion in annual earnings at risk. Losses are considerably higher with a limited-mitigation trajectory (RCP8.5). While universal adoption of two specific adaptation measures in conjunction could reduce future economic risks by roughly 90%, practical limitations to their adoption suggest that emissions mitigation policies will be critical for ensuring the wellbeing and livelihoods of outdoor workers in a warming climate.

This study explored whether the global temperature had any role in the spread and vulnerability to COVID-19 and how that knowledge can be used to arrest the fast spreading disease. It highlighted that for transmitting the virus, global temperature played an important role and a moderately cool environment was the most favourable state. Whereas, the risk from the virus was reduced significantly for warm places and countries. Based on the temperature of March and April, various degree of vulnerability was identified and countries were specified. The maximum reported case, as well as death, was noted when the temperature was in the range of around 275°K(2°C) to 290°K(17°C). Countries like the USA, UK, Italy and Spain belonged to this category. The vulnerability was moderate when the temperature was less than around 275°K(2°C) e.g., Russia, parts of Canada and a few Scandinavian countries. For temperature 300°K(27°C) and above, a significantly lesser degree of vulnerability was noted. Countries from South Asian Association for Regional Cooperation, South East Asia, the African continent and Australia fell in that category. This work discussed that based on the variability of temperature, countries can switch from one vulnerability state to another. That influence of temperature on the virus and results of previous clinical trials with similar viruses provided a useful insight that regulating the level of temperature can offer remarkable results to arrest and stop the outbreak. Based on that knowledge, some urgent and simple solutions are proposed, which are practically without side effects and very cost-effective too.

ESA is building on almost 15 years of continuous Fiducial Reference Measurements (FRM) from UK-funded shipborne radiometers by establishing a service to provide historic and ongoing FRM measurements to the wider SST community through an International SST FRM Radiometer Network (ships4sst). The ships4sst is open for partners around the world, currently compromising of partners from the UK (University of Southampton, Rutherford Appleton Laboratory, Space ConneXions), Denmark (Danish Meteorological Institute) and France (Ifremer) and will not only collect Shipborne radiometer data but also use the data to validate SLSTR and other satellite SST products with the Felyx MDB tool. Included in the service is a long term data archive of the FRM datasets at Ifremer where the data will be stored in the ships4sst netCDF L2R format. We will show examples of the ships4sst data and demonstrate its use with the newest SLSTR validation results from the ships4sst network regions, showing that SLSTR performs at least as well as its predecessor AATSR. We will also show results of the SLSTR A and B units during the Sentinel-3 tandem phase in 2018 by using triple collocations on the ships4sst FRM data and the SLSTR units on Sentinel 3 A and B.

Earth system models currently struggle to account for the complex effects that land surface heterogeneity can have on land-atmosphere interactions. Subgrid land surface heterogeneity is currently not well accounted for in land-atmosphere interactions in earth system models. There have been attempts to include the impact of this heterogeneity on the atmosphere, but they ignore the development of coherent secondary circulations that can be driven by spatial differential surface heating. A wealth of literature, particularly large-eddy simulation (LES) based studies, shows that these circulations have significant impacts on the development and organization of clouds. In this work, we describe a two-column model with a parameterized circulation driven by atmospheric virtual potential temperature profiles, differences in near surface temperature between the two columns, patterns of surface heterogeneity, and the mean background wind. Key aspects of the proposed model structure are compared with LES output, and the model is then implemented between two otherwise independent single column models. While some avenues for improvement exist, when the circulations are parameterized, we see increased cloud development and realistic changes to the mean profiles of temperature and moisture. The proposed model qualitatively matches expectations from the literature and LES, and points to the potential success of its future implementation in coarse grid models.

Recent advances in imaging techniques and related modeling have made it possible to study micron and sub-micron scales in unprecedented detail. Currently, performing direct simulations at a representative scale has proven computationally prohibitive, hence, the ability to simulate flow cannot keep up with the size of images available (e.g. x-ray micro-tomography or large area scanning electron microscopy). To overcome this issue, we propose to train a neural network architecture to understand relationships between pore-scale morphology and the simulation outputs. With this, we improve our portability and prediction time. Convolutional neural networks are attractive for this task because they support flexible input size, they are able to capture local interactions, and they can find places that present similar patterns. Generally, deeper networks have better prediction performance, but they are very difficult to train due to the vanishing gradient problem. Also, information from different scales is commonly lost along the network.

The cloudy zone (CZ), a nm-sized intergrowth of taenite or tetrataenite crystals (or islands), is the most promising phase to preserve palaeomagnetic records in (stony-)iron meteorites. While slowly-cooled meteorites form tetrataenite – an extremely good recorder – fast-cooled meteorites contain fine-grained taenite islands, which were considered unsuitable for palaeomagnetic studies. In this work, however, we show that nm-sized taenite grains are stable over billion-year timescales, indicating that taenite-bearing meteorites are reliable sources of paleomagnetic information. Additionally, we find a range of sizes for which taenite forms stable single-domain structures. Single-domain states might be preserved even through subsequent tetrataenite ordering, implying that tetrataenite might carry magnetization state inherited from its precursor taenite. This remanent magnetization can be up to 10\textsuperscript{5} years older than that of larger tetrataenite islands in the same meteorite, which would have been reset upon ordering. This allow studding to two distinct events of planetesimal formation from a single sample.