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Abstract

We numerically solve the acoustic radiative transfer equation for seismic S-waves via Monte Carlo simulation. By assuming a von Kármán-type random medium with anisotropic scattering, we are able to simulate a realistic medium and determine its attenuation properties. In this study, we present an improved method, called QEST, to determine the frequency-dependent intrinsic and scattering attenuation by nonlinear envelope inversion for a 1-D multilayer model. Additionally, the spectral source energy of earthquakes and the energy site amplification of stations are determined. The code was applied to real data from the northern and southern Leipzig-Regensburg fault zone (LRZ), Germany, as well as fluid-induced earthquakes at the Insheim geothermal reservoir, Germany. The attenuation was analyzed in several frequency bands between 4.2 and 33.9 Hz and between 6.0 and 67.9 Hz, respectively. The inversion results reveal that the crystalline crustal subsurface along the LRZ shows little to no depth dependence, but there are differences in attenuation between the north and south. At Insheim, the near-surface sedimentary basin exhibits significantly greater absorption and scattering than the crystalline basement. The inversion also shows that isotropic scattering can be an oversimplification and thus underestimate attenuation.

Abstract

In this study, a wideband circularly polarized (CP) H-plane horn antenna based on Gap Waveguide (GW) technology in K-band is presented. The proposed antenna consists of two unconnected metal planes. To produce broadband CP radiation, two main methods are utilized. First, two antipodal tapered plates (ATPs) are added in front of the horn. The ATPs are carefully designed for dissimilar polarization orientations. By this technique, the orthogonal electric fields can be prepared. Then, by embedding three metal square pins near the center of the aperture in both inner plates, the impedance bandwidth (BW) and BW of CP radiation of the proposed horn is entirely improved. Its BW for target |S11| < −10 dB is 18–28 GHz. Also, the peak gain fluctuates between 11.5 and 13 dB. This antenna can provide a 3 dB polarization axial-ratio BW of about 28.5% (20–26 GHz). Total radiation efficiency is higher than 94%. To verify the design, the proposed structure is manufactured and tested. The proposed horn antenna result has an appropriate agreement between measurement and simulation. Its miniaturized dimensions, easy and cheap fabrication, and broadband CP capability make it a proper volunteer for broadband communication systems.

Modelling chemical advection during magma ascent
Hugo Dominguez, Nicolas Riel, and Pierre Lanari
Geosci. Model Dev., 17, 6105–6122, https://doi.org/10.5194/gmd-17-6105-2024, 2024
Predicting the behaviour of magmatic systems is important for understanding Earth's matter and heat transport. Numerical modelling is a technique that can predict complex systems at different scales of space and time by solving equations using various techniques. This study tests four algorithms to find the best way to transport the melt composition. The "weighted essentially non-oscillatory" algorithm emerges as the best choice, minimising errors and preserving system mass well.

Towards a real-time modeling of global ocean waves by the fully GPU-accelerated spectral wave model WAM6-GPU v1.0
Ye Yuan, Fujiang Yu, Zhi Chen, Xueding Li, Fang Hou, Yuanyong Gao, Zhiyi Gao, and Renbo Pang
Geosci. Model Dev., 17, 6123–6136, https://doi.org/10.5194/gmd-17-6123-2024, 2024
Accurate and timely forecasting of ocean waves is of great importance to the safety of marine transportation and offshore engineering. In this study, GPU-accelerated computing is introduced in WAve Modeling Cycle 6 (WAM6). With this effort, global high-resolution wave simulations can now run on GPUs up to tens of times faster than the currently available models can on a CPU node with results that are just as accurate.

How hard do avalanche practitioners tap during snow stability tests?
Håvard B. Toft, Samuel V. Verplanck, and Markus Landrø
Nat. Hazards Earth Syst. Sci., 24, 2757–2772, https://doi.org/10.5194/nhess-24-2757-2024, 2024
This study investigates inconsistencies in impact force as part of extended column tests (ECTs). We measured force-time curves from 286 practitioners in Scandinavia, Central Europe, and North America. The results show a large variability in peak forces and loading rates across wrist, elbow, and shoulder taps, challenging the ECT's reliability. 

Reconstruction of ancient drought in Northwest China and societal responses: A case study of 1759
Zhixin Hao, Meirun Jiang, Haonan Yang, Danyang Xiong, and Jingyun Zheng
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-111,2024
Preprint under review for NHESS (discussion: open, 0 comments)
At ancient time, social system could successfully responded most extreme climate events, such as droughts. To explore society’s adaptability to extreme climate events, we chosen the 1759 drought as a typical case study, then reconstructed the meteorological distribution of drought spatially and temporally, analyzed the impacts of the drought on society, and summarized the adaptive measures employed at the time.

Abstract

Large bursts of non-volcanic tremor (“major” tremor episodes) correlated with geodetic deformation recur regularly in the Cascadia subduction zone and are often called episodic tremor and slip (ETS). Minor episodes of tremor between ETS are ubiquitous but have been understudied. This paper assesses time-invariant characteristics of tremor episodes of all sizes within northern Cascadia. We derive a catalog of tremor episodes ranging in size from 10 to >13,000 tremor events using the results of 17 years of tremor monitoring. Minor episodes represent ∼96% of all 896 tremor episodes and their occurrence varies on 10-km scales. Using estimates for the depth of the forearc Moho and subducting slab, we observe an association between the location of the forearc mantle corner (FMC) and tremor occurrence that leads to along-dip modality. Bimodality, present in southern Washington and Vancouver Island, represents the segmentation of major and minor episodes up-dip and down-dip of the FMC, respectively. Unimodality, present in Puget Sound, results when the FMC is located near the down-dip edge of the ETS zone and no segmentation occurs. We also use our extensive tremor episode catalog alongside three-dimensional regional tomographic velocity models to reassess the relationship between tremor activity and low Vp/Vs signatures in the forearc. We do not find a correlation between tremor episode recurrence intervals and Vp/Vs, contrary to some previous work, suggesting that controls on silica precipitation in the forearc crust are not dominant controls of tremor episode recurrence, or that the association is not widely observable.

Abstract

After days of intense solar activity, active region AR3664 launched seven CMEs toward Earth producing an extreme G5 geomagnetic storm commencing at 17:05 UT on 10 May 2024. The storm impacted power grids, disrupted precision navigational systems used by farming equipment, and generated aurora seen around the globe. The storm produced remarkable effects on composition, temperature, and dynamics in the Earth's thermosphere that were observed by NASA's Global-scale Observations of the Limb and Disk (GOLD) mission and are reported here for the first time. We use synoptic disk images of ΣO/N2 and neutral temperature (at ∼160 km) measured by GOLD to directly link dynamics resulting from the storm with dramatic changes in thermospheric composition and temperature. We observe a heretofore unseen spatial morphology simultaneously in ΣO/N2, neutral temperature, and total electron content. Equator-to-pole temperature differences reach 400 K with high latitude peak neutral temperatures near 160 km exceeding 1400 K.

Abstract

Colorado River streamflow has decreased 19% since 2000. Spring (March-April-May) weather strongly influences Upper Colorado River streamflow because it controls not only water input but also when snow melts and how much energy is available for evaporation when soils are wettest. Since 2000, spring precipitation decreased by 14% on average across 26 unregulated headwater basins, but this decrease did not fully account for the reduced streamflow. In drier springs, increases in energy from reduced cloud cover, and lowered surface albedo from earlier snow disappearance, coincided with potential evapotranspiration (PET) increases of up to 10%. Combining spring precipitation decreases with PET increases accounted for 67% of the variance in post-2000 streamflow deficits. Streamflow deficits were most substantial in lower elevation basins (<2,950 m), where snowmelt occurred earliest, and precipitation declines were largest. Refining seasonal spring precipitation forecasts is imperative for future water availability predictions in this snow-dominated water resource region.

Abstract

We show that the winter Beaufort High (BH) index defined by sea level pressure (SLP) has a robust negative trend under the scenarios SSP5-8.5 and SSP2-4.5, with a reduction by about 5 hPa and 2 hPa, respectively, by the end of the 21st century. The negative trends in the BH SLP are associated with the changes in the background SLP over the Arctic basin. However, the vorticity of the winter BH tends to intensify under SSP5-8.5, but shows no robust increase under SSP2-4.5. The intensification is associated with the enhanced ridge over the Western Arctic. Therefore, it is necessary to take into account the dynamic aspects of the BH, such as vorticity. Based on this assessment, under the most likely emissions scenario, the winter BH is likely to weaken through the 21st century, in terms of SLP, but shows no robust changes in term of vorticity.

Abstract

We present an innovative approach that combines a unique real-time data set documenting absolute dissolution rates of a calcite crystal with an original reactive transport model tailored to the analysis of the dynamics of nano-scale mineral dissolution processes. Providing robust and physically based fundamental understanding on the kinetics of mineral dissolution is at the core of various geo-engineered strategies to quantify chemical weathering patterns across diverse spatial and temporal scales. Here, we rely on data obtained through Atomic Force Microscopy. We provide a mathematical framework to describe three-dimensional dynamics of the mineral surface topography, and show convergence of the numerical approach for vertical grid spacing down to sub-nm resolution.

Science, Volume 385, Issue 6710, August 2024.

Science, Volume 385, Issue 6710, August 2024.

Science, Volume 385, Issue 6710, August 2024.

Science, Volume 385, Issue 6710, August 2024.

Abstract

The Great Lakes Region (GLR) of North America is at the intersection of multiple extratropical cyclone (ETC) tracks, and the region's cold-season climate is heavily influenced by the large temperature gradients and intense precipitation associated with these cyclones. The goal of this study is to understand how ETCs are changing within a warming climate. Historical GLR cyclone characteristics from 1959 to 2021 are examined using a storm tracking algorithm and the ERA-5 atmospheric reanalysis. Of the 886 cyclones identified, half are the large long-track cyclones that are typically included in ETC studies, and half are smaller short-track cyclones that, while not always considered in ETC studies, still have an important impact on the GLR with significant precipitation trends. While all cyclones exhibit strong interannual variability, storm trajectories appear to be migrating northward and, most notably, the cyclones are becoming warmer and wetter at a rate faster than the background climate.

Abstract

It has been difficult to establish trends in the observed jet streams, despite modeling studies suggesting they will move polewards in a warming world. While this is partly due to biases between the models and observations, we propose that another uncertainty is rooted in the choice of statistic used to determine the ‘jet latitude’ — one measure used to quantify the jet position. We use seven different jet latitude statistics, four climate reanalysis products, and CMIP6 simulations to assess the relative importance of different uncertainties associated with lower-tropospheric North Pacific Jet (NPJ) trends. Our results show a statistically significant poleward trend in the observed winter NPJ across all reanalyzes and using all jet latitude statistics. The magnitude of this trend is most sensitive to the choice of statistic. Furthermore, we find that the NPJ shifts poleward in Autumn under high emission scenarios, which is robust to the choice of jet statistic.

Abstract

Ecosystem-scale photosynthetic efficiency (EPE) is proposed as an effective indicator to quantify gross primary productivity (GPP), but how the coupling between EPE and GPP varies as vegetation resilience decreases has not been evaluated. Here, we quantified forest resilience with optimized Bayesian models. With the use of multisource satellite and modeling data, our study revealed that forests on the Loess Plateau and in the Qinba Mountains in China are experiencing rapid resilience loss and are already facing mortality warnings after 2010. Reductions in resilience also drove the marked decoupling of GPP from EPE. Notably, the decline in resilience was accompanied by a decrease in EPE in about 74% of the forests while GPP increased. The mechanism underlying this decoupling could be attributed to enhanced atmospheric water demand and soil water constraints. The dynamic relationships found here could help to improve forest mortality models and enhance photosynthesis-based GPP evaluation.

Abstract

A crucial factor influencing the mass balance of the West Antarctic Ice Sheet is the Amundsen Sea Low (ASL), a climatological low-pressure region situated off the West Antarctic coast. However, albeit the deepening of the ASL since the 1950s has been attributed to anthropogenic forcing, the multi-decadal variability of the ASL remains poorly understood, because of a lack of long observations. Here, we apply a newly developed data assimilation method to reconstruct the ASL over 1870–2000. We study the forced and internal variability of the ASL using our new reconstruction in concert with existing large ensembles of climate model simulations. Our findings robustly demonstrate that an atmospheric teleconnection originating from the tropical Indo-Pacific is the main driver of ASL variability at the multi-decadal time scale, with resemblance to the Interdecadal Pacific Oscillation. Since the mid-20th century, anthropogenic forcing has emerged as a dominant contributor to the strengthening of the ASL.

Abstract

Current global historical reanalyzes prevent to adequately examine the role of the near-core surface wind structural properties on tropical cyclones climate trends. Here we provide theoretical and observational evidences that they are crucial for the monitoring of integrated kinetic energy. The kinetic energy balance is reduced to a simple rule involving two parameters characterizing the surface wind structure and directly suggested by the governing equations. The theory is uniquely verified with a database of high-resolution ocean surface winds estimated from all-weather spaceborne synthetic aperture radar. Such measurements provide indirect estimates of a multiplicative constant modulating the kinetic energy balance and associated with the system thermodynamics. Consequently, accumulated high-resolution acquisitions of the ocean surface shall allow to better monitor the integrated kinetic energy and provide new means to tackle climatological studies of tropical cyclones destructiveness.