Air quality policies based on scientific information have proved to be effective for controlling air pollution and protecting public health. Intensive field studies provide knowledge that combined to data from emission inventories and air quality monitoring allows to understand the causes that trigger air pollution and catalyze the design of effective control measures. We review the case of Mexico City, where past international collaborative studies were fundamental to improve air quality, but a null progress and a possible reversal to high air pollution levels in recent years suggest that a new dedicated field measurement campaign is urgently needed.

Existing tidal input reduction approaches applied in accelerated morphodynamic simulations aim to capture the dominant tidal forces in a single or double representative tidal cycle, often referred to as a “morphological tide”. These heavily simplified tidal signals fail to represent the tidal extremes, and hence poorly allow to represent hydrodynamics above the intertidal areas. Here, a generic method is developed to construct a synthetic spring-neap tidal cycle that (1) represents the original signal; (2) is exactly periodic; and (3) is constructed directly from full-complexity boundary information. The starting point is a fortnightly modulation of the semi-diurnal tide to represent spring-neap variation, while conserving periodicity. Diurnal tides and higher harmonics of the semi-diurnal tide are included to represent the asymmetry of the tide. The amplitudes and phases are then adjusted to give a best fit to histograms of water levels and water level gradients. A depth-averaged model of the Ems estuary (The Netherlands) demonstrates the effects of alternative tidal input reduction techniques. Adopting the new approach, the shape of the tidal wave is well-represented over the entire length of the estuary, leading to an improved representation of extreme tidal conditions. In particular, representing intertidal dynamics benefits from the new approach, which is reflected by hydrodynamics and residual sand transport patterns that approach non-schematized tidal dynamics. Future morphodynamic simulations forced with the synthetic signal are expected to show a more realistic exchange of sediment between the channels and tidal flats, likely improving their overall predictive capacity.

Ice shelves regulate the stability of marine ice sheets. We track fractures on Pine Island Glacier , a quickly-accelerating glacier in West Antarctica that contributes more to sea level rise than any other glacier. Using an on-ice seismic network deployed from 2012 to 2014, we catalog icequakes that dominantly consist of flexural gravity waves. Icequakes occur near the rift tip and in two distinct areas of the shear margin, and TerraSAR-X imagery shows significant fracture in each source region. Rift-tip icequakes increase with ice speed, linking rift fracture to glaciological stresses and/or localized thinning. Using a simple flexural gravity wave model, we deconvolve wave propagation effects to estimate icequake source durations of 19.5 to 50.0 s, and transient loads of 3.8 to 14.0 kPa corresponding to 4.3 to 15.9 m of crevasse growth per icequake. These long source durations suggest that water flow may limit the rate of crevasse opening.

We analyzed the scale features of satellite infrared (IR) water vapor (WV) brightness temperature observations of tropical cyclones (TCs). This is to characterize the storm information at dominate scales in all-sky radiance assimilation for TC numerical weather prediction. This paper presents the results from the study of Hurricane Patricia (2015). Our study shows that IR WV brightness temperatures have the ability to observe multiscale structures of TCs, ranging from a size of above 1,000 km that covers the entire storm and its surrounding areas to a scale resolving individual convective clouds embedded in the TC. The atmospheric moisture for TC development is mainly represented by large scales covering the storm and surrounding areas while the storm structures are characterized basically by all scales. The large-scale moisture and small-scale convection demonstrate strong correlation and are closely related to the TC development, suggesting the need for all-sky radiance assimilation at multiple scales.

Volcanic crises are often associated with magmatic intrusions or pressurization of magma chambers of various shapes. These volumetric sources deform the country rocks, changing their density, and cause uplift. Both the net mass of intruding magmatic fluids and these deformation effects contribute to surface gravity changes. Thus, to estimate the intrusion mass from gravity changes the deformation effects must be accounted for. We develop analytical solutions and computer codes for the gravity changes caused by triaxial sources of expansion. This establishes coupled solutions for joint inversions of deformation and gravity changes. Such inversions can constrain both the intrusion mass and the deformation source parameters more accurately.

The behaviour of fluids in the crust is key to understanding earthquake occurrence due to the effect of fluid behaviour on fault strength. The attenuation of seismic waves may be locally high in fault zones as fluids are intensely distributed in these zones. This study uses a novel, simple approach to examine near-source attenuation in the focal region of intense swarm activity in the Yamagata-Fukushima border region, Japan. Near-source attenuation was estimated by determining the decay of amplitude ratios of nearby earthquake pairs with travel time differences precisely quantified using a waveform correlation. In the initial ~50 d, Q^(-1) was high, then it significantly decreased to become almost constant for the subsequent period. This pattern is similar to those independently observed for background seismicity rate, b-value, stress drop, and fault strength. These patterns can be attributed to the hypothesis that the swarm was triggered by fluid movement following the 2011 Tohoku-Oki earthquake, and the source and seismicity characteristics and the seismic attenuation were altogether affected by the temporal change in pore pressure. The method demonstrated in this study may be a useful tool to detect high pore pressure anomaly at depth and understand its relationship with earthquake occurrence.

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.

A new method is presented to estimate urban OH concentrations using the downwind decay of the TROPOMI derived NO2/CO ratio combined with Weather Research Forecast (WRF) simulations. Seasonal OH concentrations, NOx and CO emissions for summer (June to October, 2018) and winter (November, 2018 to March, 2019) are derived for Riyadh. WRF is able to simulate NO2 and CO urban plumes over Riyadh as observed by TROPOMI. However, WRF simulated NO2 plumes close to center of the city are overestimated by 25 % in summer and 40 to 50 % in winter compared to TROPOMI observations. WRF simulated CO plumes differ by 10 % with TROPOMI in both seasons. The differences between model and TROPOMI are used to optimize the OH concentration, NOx and CO emissions iteratively using a least squares method. For summer, both the NO2/CO ratio optimization and the XNO2 optimization imply that the OH prior from the Copernicus Atmospheric Monitoring Service (CAMS) has to be increased by 32.03±4.0% . The OH estimations from the NO2/CO ratio and the XNO2 optimization differ by 10 % indicating that the method is quite robust. Summer Emission Database for Global Atmospheric Research v4.3.2 (EDGAR) NOx and CO emissions over Riyadh need to be increased by 42.1±8.7 % and 100.8±9.5%. For winter, the optimization method increases OH by ~52.0±5.3 %, while reducing NOx emission by 15.4±3.4% and doubling the CO emission.

It has been recently advocated that Mars has excellent conditions for oxygen and fuel production directly from atmospheric CO2 using non-equilibrium plasmas. The Martian conditions would be favorable for vibrational excitation and/or enhanced dissociation by electron impact, two important pathways for CO2 plasma dissociation. Herein we confirm these theoretical predictions by measuring, for the first time, the vibrational temperatures of CO2 and the CO and CO2 concentrations in realistic Martian conditions. In situ Fourier transform infrared spectroscopy (FTIR) measurements are performed in experiments conducted in DC glow discharges operating at pressures p=1-5 Torr, discharge currents I=10-50 mA, initial gas temperatures of 220 K and 300 K, both in pure CO2 and in the synthetic Martian atmosphere 96%CO2-2%Ar-2%N2. To analyse and interpret the experimental results, we develop a detailed self-consistent kinetic model for pure CO2 plasmas, describing the coupled electron and heavy-particle kinetics. The simulation results are in very good agreement with the experimental data. It is shown that the low-temperature conditions may enhance the degree of vibrational non-equilibrium and that the Martian atmospheric composition has a positive effect on CO2 decomposition. Accordingly, the present investigation confirms the potential of plasma technologies for in-situ resource utilization (ISRU) on Mars.

Important progress has been made in recent years in characterizing surface soil moisture (SSM) at regional scales, through remote sensing estimates and the implementation of new in situ networks. Each of these sources of information has intrinsic features, such as the dynamic range of the SSM and the temporal frequency of acquisition. Another relevant factor is the period of data availability. Improving the knowledge of the limitations and biases of these features is crucial to increase the potential and the consistency of data sources validations. As a case of study we considered an agricultural area in the Argentinean Pampas, characterized by a sub-humid climate with a marked seasonal dynamic. It also holds a synchronized cropping rhythm and is subject to flooding and waterlogging that can last from days to months. The features mentioned above and considering that the region is almost devoid of irrigation, offer a natural laboratory that is distinguished by a wide dynamic range of SSM conditions. In this context, we analyze and expose different sources of SSM data gaps over long periods of time, using information from in situ stations and from the SMOS and SMAP satellite systems, during 2015-2019. We found SMAP data gaps resulting from the filtering of high SSM signals that are not spurious but typical for this flood-prone region. Reports from national institutions and comparison with other data sources allowed us to identify that high soil water content in the same period in which the data gaps occurred. In a different way, the SMOS register has a low-frequency range of data due to radio frequency interference over the study area. This data gap occurs during a long-anomalously wet period and it is relevant to take it into account when analyzing SMOS data for the full period. Our study shows the importance of using multiple sources of information and the relevance of examining the availability of data.

Microearthquakes reveal the kinematics of the Bárðarbunga caldera ring fault; both during the 2014-2015 volcanic rifting event and gradual caldera collapse, and its subsequent, ongoing re-inflation. Manual analysis of earthquake phase arrivals has been used to produce reliable hypocenter locations with tightly constrained focal mechanisms for events both during and after the eruption. Phase arrival polarities are reversed between events that occurred during the caldera collapse and those that have occurred since. Both precise relative relocations of the seismicity and focal mechanism solutions confirm that this is due to slip reversal on the same ring fault structure. The fault planes are steeply dipping (averaging 78 ± 6°). Furthermore, the spatial distribution of aftershocks following large-magnitude post-eruptive events provides constraints on the shape and size of the fault plane and the amount of slip that typically occurs in caldera events.

Harmful algal blooms (HABs) caused by the dinoflagellate Karenia brevis on the West Florida Shelf have become a nearly annual occurrence causing widespread ecological and economic harm. Effects range from minor respiratory irritation and localized fish kills to large-scale and long-term events causing massive mortalities to marine organisms. Reports of hypoxia on the shelf have been infrequent; however, there have been some indications that some HABs have been associated with localized hypoxia. We examined oceanographic data from 2004 to 2019 across the West Florida Shelf to determine the frequency of hypoxia and to assess its association with known HABs. Hypoxia was present in 5 of the 16 years examined and was always found shoreward of the 50-meter bathymetry line. There were 2 clusters of recurrent hypoxia: midshelf off the Big Bend coast and near the southwest Florida coast. We identified 3 hypoxic events that were characterized by multiple conductivity, temperature, and depth (CTD) casts and occurred concurrently with extreme HABs in 2005, 2014, and 2018. These HAB-hypoxia events occurred when K. brevis blooms initiated in early summer months and persisted into the fall likely driven by increased biological oxygen demand from decaying algal biomass and reduced water column ventilation due to stratification. There were also four years, 2011, 2013, 2015, and 2017, with low dissolved oxygen located near the shelf break that were likely associated with upwelling of deeper Gulf of Mexico water onto the shelf. We had difficulty in assessing the spatiotemporal extent of these events due to limited data availability and potentially unobserved hypoxia due to the inconsistent difference between the bottom of the CTD cast and the seafloor. While we cannot unequivocally explain the association between extreme HABs and hypoxia on the West Florida Shelf, there is sufficient evidence to suggest a causal linkage between them.

High-resolution computer simulations of earthquake sequences in three or even two dimensions pose great demands on time and energy, making lower-cost simplifications a competitive alternative. We systematically study the advantages and limitations of simplifications that eliminate spatial dimensions, from 3D down to 0/1D in quasi-dynamic earthquake sequence models. We demonstrate that, when 2D or 3D models produce quasi-periodic characteristic earthquakes, their behavior is qualitatively similar to lower-dimension models. Certain coseismic characteristics like stress drop and fracture energy are largely controlled by frictional parameters and are thus largely comparable. However, other observations are quantitatively clearly affected by dimension reduction. We find corresponding increases in recurrence interval, coseismic slip, peak slip velocity, and rupture speed. These changes are to a large extend explained by the elimination of velocity-strengthening patches that transmit tectonic loading onto the velocity-weakening fault patch, thereby reducing the interseismic stress rate and enhancing the slip deficit. This explanation is supported by a concise theoretical framework, which explains some of these findings quantitatively and effectively estimates recurrence interval and slip. Through accounting for an equivalent stressing rate at the nucleation size h* into 2/3D models, 0/1D models can also effectively estimate these earthquake cycle parameters. Given the computational efficiency of lower-dimensional models that run more than a million times faster, this paper aims to provide qualitative and quantitative guidance on economical model design and interpretation of modeling studies.

Barrier islands are especially vulnerable to hurricanes and other large storms, owing to their mobile composition, low elevations, and detachment from the mainland. Conceptual models of barrier-island evolution emphasize ocean-side processes that drive landward migration through overwash, inlet migration, and aeolian transport. In contrast, we found that the impact of Hurricane Dorian (2019) on North Core Banks, a 36-km barrier island on the Outer Banks of North Carolina, was primarily driven by inundation of the island from Pamlico Sound, as evidenced by storm-surge model results and observations of high-water marks and wrack lines. Analysis of photogrammetry products from aerial imagery collected before and after the storm indicate the loss of about 18% of the subaerial volume of the island through the formation of over 80 erosional washout channels extending from the marsh and washover platform, through gaps in the foredunes, to the shoreline. The washout channels were largely co-located with washover fans deposited by earlier events. Net seaward export of sediment resulted in the formation of deltaic bars offshore of the channels, which became part of the post-storm berm recovery by onshore bar migration and partial filling of the washouts with washover deposits within two months. The partially filled features have created new ponds and lowland habitats that will likely persist for years. We conclude that this event represents a setback in the overwash/rollover behavior required for barrier transgression.

The Global-scale Observations of the Limb and Disk (GOLD) Mission images middle thermosphere temperature and the vertical column density ratio of oxygen to molecular nitrogen (ΣO/N2) using its far ultraviolet imaging spectrographs in geostationary orbit. Since GOLD only measures these quantities during daylight, and only over the ~140º of longitude visible from geostationary orbit, previously developed tidal analysis techniques cannot be applied to the GOLD dataset. This paper presents a novel approach that deduces two specified non-migrating diurnal tides using simultaneous measurements of temperature and ΣO/N2. DE3 (diurnal eastward propagating wave 3) and DE2 (diurnal eastward propagating wave 2) during October 2018 and January 2020 are the focus of this paper. Sensitivity analyses using TIE-GCM simulations reveal that our approach reliably retrieves the true phases, whereas residual contributions from tides assumed to be absent, the restriction in longitude, and random uncertainty can lead to ~ 50% error in the retrieved amplitudes. Application of our approach to GOLD data during these time periods provides the first observations of non-migrating diurnal tides in measurements taken from geostationary orbit. We identify discrepancies between GOLD observations and TIE-GCM modeling. Retrieved tidal amplitudes from GOLD observations exceed their respective TIE-GCM amplitudes by a factor of two in some cases.

Recent developments of infrastructures and methods are major driving forces in the advances of solid Earth sciences. The deployment of large and dense sensor networks enables data centres to acquire data of increased volume and quality. The analysis of such data provides scientists with a better understanding about natural phenomena in the subsurface. Nevertheless new challenges arise to exploit the growing information potential. Innovative methods based on Artificial Intelligence offer concrete opportunities to tackle those challenges. In this paper we present an investigation of Convolutional Neural Networks (CNN) for seismo-acoustic event classification in the Netherlands. We designed, trained and evaluated two CNN models. Our results suggest that as CNN inputs spectrograms are more suitable than continuous waveforms. We discuss our findings’ potential and requirements for their operational adoption. We focus on explainability aspects and offer an approach to pave the way for a broader uptake of Artificial Intelligence based methods.

4 Key Points: 5 • The SST contrast increases with warming, primarily because the clear-sky green-6 house effect feedback is stronger in the warm region. 7 • As the climate warms, the integrated cooling rate of the atmosphere increases by 8 moving upward into lower pressures and increasing in strength, giving a more top-9 heavy cooling profile. 10 • The more top-heavy cooling rate profile results in increased cloud ice as the cli-11 mate warms. Abstract 13 Warming experiments with a uniformly insolated, non-rotating climate model with a slab 14 ocean are conducted by increasing the solar irradiance. As the climate warms, the sur-15 face temperature contrast between the warm, rising and cooler, subsiding regions increases, 16 mostly as a result of the stronger greenhouse effect in the warm region. The convective 17 heating rate becomes more top-heavy in warmed climates, producing more cloud ice, prin-18 cipally because the radiative cooling rate moves to lower pressures and increases. To pro-19 duce this more top-heavy convective heating, precipitation shifts from the convective to 20 the stratiform parameterization. The net cloud radiative effect becomes more negative 21 in the warm region as the climate warms. At temperatures above about 310K surface 22 temperature contrast begins to decline, and the climate becomes more sensitive. The re-23 duction in SST contrast above 310K again appears to be initiated by clear-sky radiative 24 processes, although cloud processes in both the rising and subsiding regions contribute. 25 The response of clear-sky outgoing longwave to surface warming begins to accelerate in 26 the region of rising motion and decline in the region of subsidence, driving the SST con-27 trast to smaller values. One-dimensional simulations are used to isolate the most rele-28 vant physics. 29 Plain Language Summary 30 A global model of a non-rotating Earth with an ocean that stores heat but does 31 not transport it is run to equilibrium with different values of globally uniform solar heat-32 ing. Despite the complete uniformity of the system, it still develops regions of warm sea 33 surface temperature where rain and rising motion occur, and regions with downward, 34 subsiding air motion where rainfall does not occur. These contrasts look very similar to 35 what is observed in the present-day tropics. As the climate is warmed from current tem-36 peratures toward warmer temperatures, the warm regions warm faster, mostly because 37 the rising regions contain more water vapor. The clouds rise to higher altitudes in the 38 warmer climates, and produce more cloud ice. These changes are shown to arise from 39 well-understood physical processes that are expected to operate in nature. 40

We present a new computational fluid dynamics approach to simulating two-phase flow in hybrid systems containing solid-free regions and deformable porous matrices. Our approach is based on the derivation of a unique set of volume-averaged partial differential equations that asymptotically approach the Navier-Stokes Volume-of-Fluid equations in solid-free-regions and multiphase Biot Theory in porous regions. The resulting equations extend our recently developed Darcy-Brinkman-Biot framework to multiphase flow. Through careful consideration of interfacial dynamics (relative permeability and capillary effects) and extensive benchmarking, we show that the resulting model accurately captures the strong two-way coupling that is often exhibited between multiple fluids and deformable porous media. Thus, it can be used to represent flow-induced material deformation (swelling, compression) and failure (cracking, fracturing). The model’s open-source numerical implementation, hybridBiotInterFoam, effectively marks the extension of computational fluid mechanics into modeling multiscale multiphase flow in deformable porous systems. The versatility of the solver is illustrated through applications related to material failure in poroelastic coastal barriers and surface deformation due to fluid injection in poroplastic systems.