Rapid radiation belt recovery following storm time depletion involves local acceleration of multi-MeV electrons in nonlinear interactions with VLF chorus waves. Previous studies of an apparent impenetrable barrier at L ~ 2.8 focused on precipitation loss mechanisms for an explanation of the sharp reduction of multi-MeV electron fluxes earthward of L ~3. Van Allen Probes observations for cases when the plasmasphere is contracted earthward of L ~ 3 indicate that strong coherent signals from VLF transmitters play significant roles in the suppression of nonlinear chorus wave growth earthward of L ~ 3. As a result, local acceleration of 100s keV electrons to MeV energies does not occur in this region. During the recovery of the outer radiation belt when the plasmasphere is significantly contracted, it is the suppression of chorus wave growth and local acceleration by the action of the transmitter waves at the outer edge of the VLF bubble that is responsible for the sharp inner edge of the new MeV electron population and the formation of the impenetrable barrier.

Tidally averaged transport of salt in estuaries is controlled by various subtidal and tidal processes. In this study we show the relative importance of various subtidal and tidal transport processes in a width-averaged sense. This is done for a large range of forcing and geometric parameters, which describe well-mixed to salt wedge estuaries. To this end we develop a width-averaged process-based model aimed at conducting and analysing a large number of experiments (~40,000). We find that the salt transport is dominated by one of seven salt transport balances, or regimes. Four of these regimes are dominated by subtidal processes, while the other three are dominated by tidal processes. Which regime occurs in a part of an estuary depends on four dimensionless parameters, representing local geometry and forcing conditions. One of the regimes features salt import by correlations between the depth-averaged tidal velocity and salinity. While this mechanism was previously only associated with along-channel geometric variations, we find it can also be a dominant mechanism in a significant part of the parameter space due to river-induced tidal asymmetry, independent of river geometry. We apply our classification to a case study of part of the Dutch Rhine delta and compare to decomposition results of a fully realistic three-dimensional model. We find the estuary features two regimes, with import dominated by subtidal shear transport in the seaward part of the estuary and by depth-averaged tidal correlations in the landward part of the estuary.

Quantifying the multiscale feedback between hydrodynamics and biogeochemistry is key to reliable modeling of river corridor systems. However, accurate and efficient hydrodynamics models over large spatiotemporal scales have not yet been established due to limited surveys of riverbed roughness and high computational costs. This work presents a semi-automated workflow that combines topographic and water stage surveys, computational fluid dynamics modeling, distributed wall resistance modeling, and high-performance computing to simulate flow in a 30-kilometer-long reach at the Columbia River during 2011-2019. The results show that this workflow enables a high accuracy in modeling water stage at all seven survey locations during calibration (1 month) and validation (65 months) periods. It also enables a high computational efficiency to model the streamflow during a 58-month solution-time within less than a 6-day wall-clock-time with mesh number, time step, and CPU hours of about 1.2 million, 3 seconds, and 1.1 million hours, respectively. Using the well-validated results, we show that riverbed dynamic pressure is randomly distributed over all spatiotemporal scales with its cross-sectional average values approximately quantified by a normal distribution with a mean and standard deviation of -0.353 m and 0.0352 m; bed shear stress is affected by flowrate and large- and small-scale topographic features with cross-sectional maximum values following a smooth but asymmetric distribution with 90% of its value falling between 5 Pa and 35 Pa; and hydrostatic pressure is influenced by flowrate and large-scale topographic features with cross-sectional maximum values quantified by a discontinuous and skewed distribution determined by streamwise topographic variations.

Here, we develop and test an artificial intelligence (AI)-based approach to monitor major Brazilian aquifers. The approach combines Gravity Recovery and Climate Experiment (GRACE) data and ground-based hydrogeological measurements from Brazil’s Integrated Groundwater Monitoring Network at hundreds of wells distributed in twelve aquifers across the country. We use a model ensemble composed of four different AI models: Extreme Gradient Boost, Light Gradient Boosting Model, CatBoost and Multilayer Perceptron. The approach is further boosted with wavelet and seasonal decomposition processes applied to GRACE data. To determine the sensitivity of the AI approach to data availability, we propose four experiments combining hydrogeological measurements from different aquifers. Groundwater storage estimates from the Global Land Data Assimilation System (GLDAS) are used as the benchmark. The AI approach successfully reproduces groundwater storage estimates ​​at all Brazilian aquifers. Results show that the proposed approach outperforms GLDAS in all experiments, with an average Nash-Sutcliff efficiency of 0.91 and an average RMSE of 0.43cm for the experiment that covers all monitored wells in Brazil. GLDAS resulted in -1.311 and 5.84cm, respectively. This study demonstrates that combining satellite data and AI can be a cost-effective alternative to monitor poorly equipped aquifers at the continental scale.

The highly-explosive eruption of the Hunga-Tonga Hunga Ha’apai volcano (HTHH), that occurred on 15 Jan. in the South Pacific, was associated with a powerful blast that injected gases, steam and aerosols to unprecedentedly high altitudes. Here we present unique observations of the young volcanic aerosol plumes by ground-based lidars at La Reunion island (21°S, 55°E), located directly downwind of the eruption. Two lidars, operating at 355 nm and 532 nm, sampled the overflying plume every nights from 19 Jan. until 28 Jan. We assess both the vertical structure and the optical properties. A wide plume altitude range from 36 km down to 18 km has been highlighted along time, with heterogeneous aerosol optical depth that reached 0.84 at 532 nm and Angström exponents from-0.8 to 1.2. Such temporal evolution is related to both the injection heights of the volcanic material and the stratospheric dynamic and chemistry.

Rock fragments (RF) influence soil hydraulic properties (SHP) and knowledge about the SHP of stony soils is important in vadose zone hydrology. However, experimental evidence on effective SHP of stony soils is still scarce and mostly restricted to water-saturated conditions and low volumetric contents of RF. We examined the influence of RF on SHP through a series of measurements. Stony soils were prepared by packing 250 cm3 cylinders with soils of two textures (sandy loam and silt loam) and with different volumes of RF (up to 50 % v/v) with a diameter of 8-16 mm. Samples were prepared in a way that the background soils (diameter smaller than 2 mm) had identical bulk density. The simplified evaporation method was used to determine the effective SHP of stony soils. We used the obtained SHP data to evaluate the performance of models, which predict the effective SHP of stony soils from SHP of the background soil. The results highlight the systematic dependency of SHP on volumetric content of RF. The difference between modeled and measured SHP was substantial for cases in which the soil contained a high amount of RF. Accounting for the moisture content of RF improved the prediction of the effective WRC of stony soils compared with a simple scaling that used only the content of RF. Among the evaluated models for the effective HCC, the model based on the general effective medium theory (GEM) showed the best performance, particularly for low RF contents.

Although lagged correlations have suggested influences of solar wind velocity (V) and number density (N), IMF Bz, ULF wave power, and substorms (as measured by AE) on MeV electron flux at geosynchronous orbit over an impressive number of hours and days, a satellite’s diurnal cycle can inflate correlations, associations between drivers may produce spurious effects, and correlations between all previous time steps may create an appearance of additive influence over many hours. Autoregressive-moving average transfer function (ARMAX) multiple regressions incorporating previous hours simultaneously can eliminate cycles and assess the impact of parameters, at each hour, while others are controlled. ARMAX influences are an order of magnitude lower than correlations. Most influence occurs within a few hours, not the many hours suggested by correlation. Over all hours, V and N show an initial negative impact, with longer term positive influences over the 9 (V) or 27 (N) h. Bz is initially a positive influence, longer term (6 h) negative effect. ULF waves impact flux in the first (positive) and second (negative) hour before the flux measurement, with further negative influences in the 12- 24 h before. AE (representing electron injection by substorms) shows only a short term (1 h) positive influence. However, when only recovery and after-recovery storm periods are considered (using stepwise regression), there are positive influences of ULF waves and V, negative influences of N and Bz, while AE shows no influence.

A set of 44 sonic velocity well logs from the southern San Joaquin Valley are combined with soil textural data to derive a three-dimensional compressional velocity model. The compaction of a granular medium containing fines provides a conceptual framework for constructing a forward model and defining governing parameters. An iterative quasi-Newton algorithm that allows for bounds on the variables is used to estimate the 18 model parameters. The inversion reduces the misfit to the well log velocities by over an order of magnitude. The resulting velocity model contains a 30% increase in velocity from the surface to a depth of 700 meters. Lateral variations of around 10% occur within the layers of the model, reflecting the textural heterogeneity in the subsurface.

In the text “The Cause of Motion”, I argue the following 6 flaws in the definition of inertia and the law of inertia and propose a solution to correct these problems and mechanism for inertial motion. 1. The definition of inertia does not answer the cause why the object has inertia. 2. The law of inertia does not answer what is the cause of motion. 3. Stationariness and rectilinear motion at constant velocity are two effects that need two causes to explain. 4. We have not found the elementary particles or properties responsible for inertia in matter. 5. The inertial motion of the same matter in gaseous, liquid, solid or other states is completely different. 6. No experiment has proved the existence of inertia or the law of inertia.

The intermediate-depth earthquakes (~200 km) in Hindu Kush, Afghanistan were investigated to prove their origin by tides. An untraditional astronomical method has been used to prove how astronomical parameters influence triggering of earthquakes. In contrast to previous issues, where Moon hour angles were used, Moons declinations were used successfully to prove tidal origin of earthquakes. Maximum earthquakes have been recognized during minor lunar standstills, i.e.

We evaluate the effects of rapidly changing Arctic sea ice conditions on sea salt aerosol (SSA) produced by oceanic wave-breaking and the sublimation of wind-lofted salty blowing snow on sea ice. We use the GEOS-Chem chemical transport model to assess the influence of changing extent of the open ocean, multi-year sea ice, first-year sea ice (FYI), and snow depths on SSA emissions for 1980-2017. We combine snow depths from the Lagrangian snow-evolution model (SnowModel-LG) together with an empirically-derived snow salinity function of snow depth to derive spatially and temporally varying snow surface salinity over Arctic FYI. We find that snow surface salinity on Arctic sea ice is increasing at a rate of ~30% decade-1 and SSA emissions are increasing at a rate of 7-9% decade-1 during the cold season (November – April). As a result, simulated SSA mass concentrations over the Arctic increased by 8-12% decade-1 in the cold season for 1980-2017. Blowing snow SSA accounts for more than 75% of this increase. During the warm season (May – October), sea ice loss results in a 12-14% decade-1 increase in SSA emissions due to increasing open ocean emissions. Observations of SSA mass concentrations at Alert, Canada display positive trends during the cold season (10-12% decade-1), consistent with our pan-Arctic simulations. During fall, Alert observations show a negative trend (-18% decade-1), due to locally decreasing wind speeds and thus lower open ocean emissions. These significant changes in SSA concentrations could potentially affect past and future bromine explosions and Arctic climate feedbacks.

We present a 1:10M scale geologic map of the Aphrodite Map area (AMA) of Venus (0N-57S /60E-80E). Geologic mapping employed NASA Magellan synthetic aperture radar and altimetry data. The AMA geologic map, with detailed structural elements and geologic units covering over one eighth of Venus’ surface, affords an important and unique perspective to test models of global scale geologic processes through time. Geologic relations record a history inconsistent with global catastrophic resurfacing. The AMA displays a regional coherence of preserved geologic patterns that record three sequential geologic eras: the ancient era, the Artemis superstructure era, and the youngest fracture zone era. The ancient era and Artemis superstructure, with a footprint covering more than 25 percent of the surface, are recorded in the Niobe map area to the north. The latter two eras likely overlap in time. The fracture zone domain, part of a globally extensive province, marks the most spatially focused tectonomagmatic domain within the AMA. Impact craters are both cut by, and overprint, fracture zone structures. Twelve percent of AMA impact craters that occur within the fracture zone domain predate or formed during fracture zone development. This observation indicates the relative youth of the fracture zone era and is consistent with the possibility that this domain remains geologically active. The AMA records a rich geologic history of large tract of the surface of Venus and provides an important framework to formulate new working hypotheses of Venus evolution, and contribute to planning future studies of the surface of planets.

We present a comparison of atmospheric transport model simulations for carbonyl sulfide (COS), within the framework of the ongoing atmospheric tracer transport model intercomparison project “TransCom”. Seven atmospheric transport models participated in the inter-comparison experiment and provided simulations of COS mixing ratios in the troposphere over a 9-year period (2010–2018), using prescribed state-of-the-art surface fluxes for various components of the atmospheric COS budget: biospheric sink, oceanic source, sources from fire and industry. Since the biosphere is the largest sink of COS, we tested sink estimates produced by two different biosphere models. The main goals of TransCom-COS are (a) to investigate the impact of the transport uncertainty and emission distribution in simulating the spatio-temporal variability of COS mixing ratios in the troposphere, and (b) to assess the sensitivity of simulated tropospheric COS mixing ratios to the seasonal and diurnal variability of the COS biosphere fluxes. To this end, a control case with state-of-the-art seasonal fluxes of COS was constructed. Models were run with the same fluxes and without chemistry to isolate transport differences. Further, two COS flux scenarios were compared: one using a biosphere flux with a monthly time resolution and the other using a biosphere flux with a three-hourly time resolution. In addition, we investigated the sensitivity of the simulated concentrations to different biosphere fluxes and to indirect oceanic emissions through dimethylsulfide (DMS) and carbon disulfide (CS2). The modelled COS mixing ratios were assessed against in-situ observations from surface stations and aircraft.

In early 2016 equatorward propagating extratropical Rossby waves caused a disruption of the quasi-biennial oscillation (QBO). In this study we show results from NASA’s Atmospheric Infrared Sounder (AIRS) satellite instrument for our analysis. Variances in the 4.3μm CO2 band brightness temperature are analysed. Spatial and temporal variations of gravity waves (GW) activity in the middle atmosphere are analysed for different regions in the tropics. Additionally, we use 8µm brightness temperature data from AIRS to control our findings for deep convective activity. Our results show an increase in GW variances during the QBO westerly phase prior the disruption with highest variances found in the pacific region. However, the Latin America region shows more prominent GW activity in January and February 2016. The temporal correlation of this increased GW activity with zonal winds were highest at the 30hPa level.

This letter compares the predictions of the two expressions that have been proposed for the porosity evolution in the context of rate and state friction. One depends only on the sliding velocity; the other depends only on the state variable. The predictions of the two expressions are similar for simulations of velocity stepping and slide-hold-slide experiments but differ significantly for normal effective stress jumps at constant sliding velocity. The formulation that depends only on the velocity predicts no change in the porosity; the other does. A simulation with a spring-block model indicates that the magnitude of rapid slip events is essentially the same for the two models. Variations of porosity and induced pore pressure near rapid slip events are similar and consistent with experimental observations. Predicted porosity variations during slow slip intervals and the time at which rapid slip events occur are significantly different.

The chemical composition of the deep continental crust is key to understanding the formation and evolution of the continental crust. However, constraining the chemical composition of deep continental crust is limited by indirect accessibility. Here we present a modeling method to constrain deep crustal chemical structures from observed crustal seismic structures. We first compile a set of published composition models for the continental crust. Phase equilibria and compressional wave speeds (VP) are calculated for each composition model at a range of pressure and temperature (278–2223 MPa, 50–1200°C). Functional relationships are obtained between calculated wave speeds and crustal compositions at pressure and temperature conditions within the alpha(α)-quartz stability field. These relationships can invert observed seismic wave speeds of the deep crust to chemical compositions in regions with given geotherms (MATLAB code is provided). We apply these relationships to wave speed constraints of typical tectonic settings of the global continental crust and the North China Craton. Our method predicts that the lower crust in regions with thin- (e.g., rifted margins, rifts, extensional settings, and forearcs) or thick-crust (e.g., contractional orogens) is more mafic than previously estimated. The difference is largest in extensional settings (52.47 ± 1.18 and 51.11 ± 1.61 vs. 59.37 wt. % SiO2). The obtained 2-D chemical structure of the North China Craton further shows features consistent with the regional tectonic evolution history and xenoliths. The obtained chemical structure can serve as a reference model from which chemical features in the deep crust can be recognized.

Physical processes determining the dynamic and thermodynamic structure of a tropical cyclone boundary layer (TCBL) are quite different from anywhere else in the atmospheric boundary layer due to the substantial contribution of latent heating and frictional convergence. These processes regulate the radial and vertical distributions of momentum and enthalpy fluxes that are closely related to storm development and intensification. Our current understanding of TCBL is limited by the number of observations in this region, and a majority of the observational studies assume an axisymmetric structure. Three-dimensional observations and numerical studies show that substantial asymmetric structure exists in the TCBL. This study investigates the link between the asymmetric structure and small-scale processes using a Moist Potential Vorticity (MPV) framework. The simulated TCBL is uniquely characterized as a region of negative MPV with a robust and coherent layer of high-magnitude negative MPV embedded within, referred to as the Potential Vorticity Minimum Layer (PVML). The PVML can interact with the local flow anomalies such as those associated with roll vortices provided they are vertically collocated. The small-scale dynamical processes set the thermodynamic structure inside the TCBL and this interplay modulates the height of the PVML. Since the height of the PVML combines information about the local wind and thermal structures using a materially conserved variable, it is a valuable proxy to study the evolving ‘topography’ of a simulated TCBL.

Long-range U.S. summer rainfall prediction skill is low. Monsoon variability, especially over the West North Pacific Monsoon (WNPM) and/or East Asian Monsoon (EAM) region, can influence U.S. Great Plains hydroclimate variability via a forced Rossby wave response. Here we explored subseasonal monsoon variability as a source of predictability for Great Plains rainfall. The boreal summer intraseasonal oscillation is related to Great Plains convection and Great Plains low-level jet (LLJ) anomalies as well as a cross-Pacific wave train. Using a causal effect network, we found that the time between BSISO-related geopotential height anomalies and Great Plains rainfall anomalies is about 2 weeks; therefore, BSISO convection may be a valuable forecast of opportunity for subseasonal prediction of Great Plains convection anomalies. More specifically, causal link patterns/maps revealed that the above-normal weekly EAM rainfall, rather than WNPM rainfall or general geopotential height activity over the East Asia, was causally linked to Great Plains LLJ strengthening and active Great Plains convection the following week.