We investigate whether and how spatial organisation affects the pathway to precipitation in realistic large-domain large-eddy simulations of the North Atlantic trades. We decompose the formation of surface precipitation (P) into a production phase, where cloud condensate is converted into rain, and a sedimentation phase, where rain falls towards the ground while some of it evaporates. With strengthened organisation, rain forms in weaker updrafts from smaller mean cloud droplets so that cloud condensate is less efficiently converted into rain. At the same time, organisation creates a locally moister environment and modulates the microphysical conversion processes shaping rain properties. This acts to reduce evaporation so that more of the produced rain reaches the ground. Organisation thus affects how the two phases contribute to P. It only weakly affects the total precipitation efficiency. We conclude that the pathway to precipitation differs with spatial organisation and suggest that organisation buffers rain development.
Ensemble forecasting is a promising tool to aid in making informed decisions against risks of coastal storm surges. Although tropical cyclone (TC) ensemble forecasts are commonly used in operational numerical weather prediction systems, their potential for disaster prediction has not been maximized. Here we present a novel, efficient, and practical method to utilize a large ensemble forecast of 1000 members to analyze storm surge scenarios toward effective decision making such as evacuation planning and issuing surge warnings. We perform the simulation of TC Hagibis (2019) using the Japan Meteorological Agency’s (JMA) non-hydrostatic model. The simulated atmospheric predictions were utilized as inputs for a statistical surge model named the Storm Surge Hazard Potential Index (SSHPI) to estimate peak surge heights along the central coast of Japan. We show that Pareto optimized solutions from an ensemble storm surge forecast can describe potential worst (maximum) and optimum (minimum) storm surge scenarios while exemplifying a diversity of trade-off surge outcomes among different coastal places. For example, some of the Pareto optimized solutions that illustrate worst surge scenarios for inner bay locations are not necessarily accountable for bringing severe surge cases in open coasts. We further emphasize that an in-depth evaluation of Pareto optimal solutions can shed light on how meteorological variables such as track, intensity, and size of TCs influence the worst and optimum surge scenarios, which is not clearly quantified in current multi-scenario assessment methods such as those used by JMA/National Hurricane Center in the United States.
The monsoons in Pakistan have been exceptionally harsh in recent decades, resulting in extraordinary drought conditions and record flooding events. The changing frequency of extreme events is widely attributed to climate change. However, given this region's long history of floods and droughts, the role of natural climate variability cannot be rejected without a careful diagnosis. Here, we examine how oceanic and atmospheric variability has contributed to unusual precipitation distributions in West South Asia. Variations in sea surface temperatures in the tropical Pacific and northern Arabian Sea, and internal atmospheric variability related to the circumglobal teleconnection pattern and the subtropical westerly jet stream, explain more than 70% of monthly summer precipitation variability in the 21st century. Several of these forcings have co-occurred with record strength during episodes of extreme monsoons, which have exacerbated the overall effect. Climate change may have contributed to increased variability and the in-phase co-occurrences of the identified mechanisms, but further research is required to confirm any such connection.
The tool of phase-field modeling for the prediction of chemical as well as microstructural evolution during crystallization from a melt in a mineralogical system has been developed in this work. We provide a compact theoretical background and introduce new aspects such as the treatment of anisotropic surface energies that are essential for modeling mineralogical systems. These are then applied to two simple model systems - the binary olivine-melt and plagioclase-melt systems - to illustrate the application of the developed tools. In one case crystallization is modeled at a constant temperature and undercooling while in the other the process of crystallization is tracked for a constant cooling rate. These two examples serve to illustrate the capabilities of the modeling tool. The results are analyzed in terms of crystal size distributions (CSD) and with a view toward applications in diffusion chronometry; future possibilities are discussed. The modeling results demonstrate that growth at constant rates may be expected only for limited extents of crystallization, that breaks in slopes of CSD-plots should be common, and that the lifetime of a given crystal of a phase is different from the lifetime of this phase in a magmatic system. The last aspect imposes an inherent limit to timescales that may be accessed by diffusion chronometry. Most significantly, this tool provides a bridge between CSD analysis and diffusion chronometry - two common tools that are used to study timescales of magmatic processes.
Plasma bubbles are regions of depleted plasma within the upper thermosphere/ionosphere that form during post-sunset hours near the magnetic equator. These structures tend to align with local geomagnetic field lines, extend upwards hundreds of kilometers along geomagnetic longitudes, and thousands of kilometers along geomagnetic latitudes. These large scale plasma density gradients can attenuate lower frequency radio waves, while small scale structures along the walls can interfere with centimeter scale wavelengths via Fresnel and Bragg scattering. Large scale statistical analysis of this phenomenon can further understanding of their occurrence and subsequent behavior. The current study utilizes Global-Scale Observations of the Limb and Disk (GOLD) 135.6 nm nightglow data from October 5, 2018 to September 30, 2022. GOLD has a unique perspective from geostationary orbit, allowing a constant and consistent view of nightglow and structures over the Americas and Atlantic. A plasma bubble detection method is developed and used to generate a database of plasma bubble occurrences. Occurrences are used to calculate plasma bubble drift speeds and separations. Clear seasonality in plasma bubble occurrence rate is evident. Overall occurrences peak during December solstice months and minimize during June solstice for longitudes seen by GOLD. Within GOLD’s field of view, higher occurrences are seen to the west during December solstice and east during June solstice. Plasma bubble drift speeds and separations show consistent distributions regardless of magnetic region, geographic region, season, or local time. This suggests plasma bubbles behave consistently and regularly once formed, at least on spatial scales seen by GOLD.
Diatoms are among the most efficient marine organisms for primary production and carbon sequestration, absorbing at least 10 billion tonnes of carbon dioxide every year. Yet, the spatial distributions of these planktonic organisms remain puzzling and the underlying physical processes poorly known. Here we investigate what dynamical conditions are conductive to episodic diatom blooms in oligotrophic waters based on Lagrangian diagnosis and satellite-derived phytoplankton functional types and ocean currents. The Lagrangian coherence of the flow is diagnosed in space and time simultaneously to identify which structures favor diatom growth. Observations evidence that flow structures with a high degree of coherence (40 days or longer) in high turbulent kinetic energy and vorticity sustain high concentrations of diatoms in the sunlite layers. Our findings show that the integration of Eulerian kinematic variables into a Lagrangian frame allows revealing new dynamical aspects of geophysical turbulence and unveil transport properties having large biological impacts.
Radiation energy balance at the top of the atmosphere (TOA) is a critical boundary condition for the Earth climate. It is essential to validate it in the global climate models (GCM) on both global and regional scales. However, the comparison of overall radiation field is known to conceal compensating errors. Here we use a new set of radiative kernels to diagnose the radiation biases by different geophysical variables in the latest GCMs. We find although clouds remain a primary cause of radiation biases, the radiation biases caused by non-cloud variables are of comparable magnitudes. Many GCMs tend to have a cold bias in the air temperature and a moist bias in the tropospheric humidity, which lead to considerable biases in TOA radiation budget but are compensated by cloud biases. These findings signify the importance of validating the GCM-simulated radiation fields, with respect to both the overall and component radiation biases.
The current increase in temperature over Greenland and other glaciated regions allows for more surface melt, which poses the question of the impact of this extra amount of meltwater on ice dynamics. As subglacial hydrology models evolve they are now easier to apply to realistic scenarios to quantify the effect of an increase in melt on the dynamics of glaciers. However, a number of processes linking the surface melt to the water pressure at the base of glaciers are still overlooked in models due to a lack of knowledge or an excess of complexity. Here, we apply a subglacial hydrology model coupled to an ice dynamics model to a synthetic geometry to investigate the impact of moulins distribution on the dynamics of the glacier. Our results show that a sparser distribution of moulins leads to the faster development of the efficient drainage system and greatly slows down the glacier.
Based on Bohr's model of hydrogen atom, the main purpose of this text is to propose a new hypothesis for the model of hydrogen atom and perform mathematical calculations and verifications using experimental values and physical constants. The new model can not only provide the explanations that the existing theories failed to provide, but also can be used to construct neutrons, atomic nuclei, and individual atoms and molecules by involving only electrons and protons and their interactions. This means we only need to know how single electron and proton interact with each other, then we can establish a full model of hydrogen atom, and then we can establish other atomic nuclei. After all, all matter in the universe is made from hydrogen atoms through nuclear fusion.
Capital works projects, particularly the modification of coastal rivers, are becoming increasingly significant to economic activities worldwide as a response to climate-driven changes and urbanization. The benefits of channel modification projects can be realized quickly, but the altered movement of sediments in the river channel can lead to unintended morphologic changes decades later. An example of this is the closure of the San Bernard River mouth, located on the central coast of Texas, which was clogged by sediments in the 1990s as a result of two major projects in the area: the diversion of the Brazos River channel (1929) and the construction of the Gulf Intracoastal Waterway (GIWW) (1940s). The objective of this study was to document the delayed geomorphic response to the projects using historical aerial imagery and provide a snapshot of flow pathways in the area using measurements collected in situ. Results showed that the GIWW was the main conduit for river flow as it bisects the San Bernard 2 km inland of its river mouth, reducing discharge in the terminal limb of the river. Due to reduced flow, the river mouth became clogged with wave-transported sediment supplied the Brazos River which had been diverted to within 6 km of the San Bernard. With no connection to the sea, altered sediment and flow pathways have led to numerous hazards and costly corrective dredging projects. To optimize the cost-effectiveness of channel modification projects their long-term impact must be considered as managers continue to adapt to ever-changing coastal zones.
The Madden-Julian oscillation (MJO) has remarkable impacts on global weather and climate systems. Understanding its changes under a warming climate provides insights into how MJO-related phenomena may change accordingly. This study examines the future changes in MJO projected by 23 Coupled Model Intercomparison Project Phase 6 (CMIP6) models that produce a realistic MJO propagation in their historical runs. Results from the multi-model mean show a ~17% increase in MJO precipitation amplitude, a ~9% increase in propagation speed, a ~2-day decrease in MJO period, and a ~5° eastward extension. Analysis of the lower tropospheric moisture budget suggests the dominant role of an increased meridional advection of mean moisture caused by the steepening of mean moisture over the Indo-Pacific warm pool in a warming climate. This leads to a stronger positive moisture tendency to the east of MJO convection, and hence a more eastward MJO propagation with strengthened amplitude and faster speed.
The ‘signal-to-noise paradox’ for seasonal forecasts of the winter NAO is often described as an ‘underconfident’ forecast and measured using the ratio-of-predictable components metric (RPC). However, comparison of RPC with other measures of forecast confidence, such as spread-error ratios, can give conflicting impressions, challenging this informal description. We show, using a linear statistical model, that the ‘paradox’ is equivalent to a situation where the reliability diagram of any percentile forecast has a slope exceeding 1. The relationship with spread-error ratios is shown to be far less direct. We furthermore compute reliability diagrams of winter NAO forecasts using seasonal hindcasts from the European Centre for Medium-range Weather Forecasts and the UK Meteorological Office. While these broadly exhibit slopes exceeding 1, there is evidence of asymmetry between upper and lower terciles, indicating a potential violation of linearity/Gaussianity. The limitations and benefits of reliability diagrams as a diagnostic tool are discussed.
Pore fluids are ubiquitous throughout the lithosphere and are commonly cited as the cause of slow-slip and complex modes of tectonic faulting. We investigate the role of fluids for slow-slip and the frictional stability transition and find that the mode of fault slip is mainly unaffected by pore pressures. We shear samples at effective normal stress (σ’n) of 20 MPa and pore pressures Pp from 1 to 4 MPa. The lab fault zones are 3 mm thick and composed of quartz powder with median grain size of 10 µm. Fault permeability evolves from 10-17 to 10-19 m2 over shear strains up to 26. Under these conditions, dilatancy strengthening is minimal. Slow slip may arise from dilatancy strengthening at higher fluid pressures but for the conditions of our experiments slip rate-dependent changes in the critical rate of frictional weakening are sufficient to explain slow-slip and the stability transition to dynamic rupture.
Gamma-ray glows are observational evidence of relativistic electron acceleration due to the electric field in thunderclouds. However, it is yet to be understood whether such relativistic electrons contribute to the initiation of lightning discharges. To tackle this question, we started the citizen science “Thundercloud Project’, where we map radiation measurements of glows from winter thunderclouds along Japan sea coast area. We developed and deployed 58 compact gamma-ray monitors at the end of 2021. On 30 December 2021, five monitors simultaneously detected a glow with its radiation distribution horizontally extending for 2 km. The glow terminated coinciding with a lightning flash at 04:08:34 JST, which was recorded by the two radio-band lightning mapping systems, FALMA and DALMA. The initial discharges during the preliminary breakdown started above the glow, i.e., in vicinity of the electron acceleration site. This result provides one example of possible connections between electron acceleration and lightning initiation.
The origin of the Mediterranean Outflow is investigated by deploying six millions virtual Lagrangian parcels at the Strait of Gibraltar, and tracing them backward in time using velocity estimates from an eddy-permitting reanalysis. The Lagrangian parcels are followed until they intercept one of three sections. The hypothesis is that each section is associated with distinct water masses: the Gulf of Lions, related to Western Mediterranean Deep Water and Western Intermediate Water, carries 86\% of the Outflow’s transport; the Northern Tyrrhenian, related to Tyrrhenian Deep and Intermediate Waters, carries 1\% of the transport; the Strait of Sicily, related to Levantine Intermediate Waters, carries 13\% of the transport. The median transit times from the sections to the Strait of Gibraltar range from 5 years (Gulf of Lions) to 8 years (Strait of Sicily).
Distributed Acoustic Sensing (DAS) is a technology in which a fiber-optic cable is 1 turned into an acoustic sensor by measuring backscatter of light caused by changes in 2 strain from the surrounding acoustic field. In October 2022, 9 days of DAS and co-3 located hydrophone data were collected in Puget Sound near Seattle, WA. Passive data 4 was continuously recorded for the duration and a broadband source was fired from 5 several locations and depths on the first and last days. This dataset provides direct 6 comparisons between DAS and hydrophone measurements, and demonstrates the 7 ability of DAS to measure acoustics signals up to ~500Hz. 8 9
Earthquake ruptures are complex physical processes that may vary with the structure and tectonics of the region in which they occur. Characterizing the factors controlling this variability would provide fundamental constraints on the physics of earthquakes and faults. We investigate this by determining finite source properties from second moments of the stress glut for a global dataset of large strike-slip earthquakes. Our approach uses a Bayesian inverse formulation with teleseismic body and surface waves, which yields a low-dimensional probabilistic description of rupture properties including spatial extent, directivity, and duration. This technique is useful for comparing events because it makes only minor geometric constraints, avoids bias due to rupture velocity parameterization, and yields a full ensemble of possible solutions given the uncertainties of the data. We apply this framework to all great strike-slip earthquakes of the past three decades, and we use the resultant second moments to compare source quantities like directivity ratio, rectilinearity, stress drop, and depth extent. We find that most strike-slip earthquakes have a large component of unilateral directivity, and many of these earthquakes show a mixture of unilateral and bilateral behavior. We also notice that oceanic intraplate earthquakes usually rupture a much larger width of the seismogenic zone than other strike-slip earthquakes, suggesting these earthquakes consistently breach the expected thermal boundary for oceanic ruptures. We also use these second moments to resolve nodal plane ambiguity for the large oceanic intraplate earthquakes and find that the rupture orientation is usually unaligned with encompassing fossil fracture zones.
The overwhelming amount of seismic, geodesic and in-situ observations accumulated over the last 30 years clearly indicate that, from a mechanical point of view, faults should be considered as both damageable elastic solids in which highly localized features emerge as a result of very short-term brittle processes and materials experiencing ductile strains distributed in large volumes and over long time scales. The interplay of both deformation mechanisms, brittle and ductile, give rise to transient phenomena associating slow slip and tremors, known as slow earthquakes, which dissipate a significant amount of stress in the fault system. The physically-based numerical models developed to improve our comprehension of the mechanical and dynamical behaviour of faults must therefore have the capacity to treat simultaneously both deformation mechanisms and to cover a wide range of time scales in a numerically efficient manner. This capability is essential, both for simulating accurately their deformation cycles and for improving our interpretation of the available observations. In this paper, we present a numerically efficient visco-elasto-brittle numerical framework that can simulate transient deformations akin to that observed in the context of subduction zones, over the wide range of time scales relevant for slow earthquakes. We implement the model in idealized simple shear simulations and explore the sensitivity of its behavior to the value of its main mechanical parameters.