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Abstract

Land management can moderate or intensify the impacts of a warming atmosphere. Since the early 1980s, nearly 116,000 km2 of cropland that was once held in fallow during the summer is now planted in the northern North American Great Plains. To simulate the impacts of this substantial land cover change on regional climate processes, convection-permitting model experiments using the Weather Research and Forecasting model were performed to simulate modern and historical amounts of summer fallow. The control simulation was extensively validated using multiple observational data products as well as eddy covariance tower observations. Results of these simulations show that the transition from summer fallow to modern land cover led to ∼1.5°C cooler temperatures and decreased vapor pressure deficit by ∼0.15 kPa during the growing season across the study region, which is consistent with observed cooling trends. The cooler and wetter land surface with vegetation led to a shallower planetary boundary layer and lower lifted condensation level, creating conditions more conducive to convective cloud formation and precipitation. Our model simulations however show little widespread evidence of land surface changes effects on precipitation. The observed precipitation increase in this region is more likely related to increased moisture transport by way of the Great Plains Low Level Jet as revealed by the ERA5 reanalysis. Our results demonstrate that land cover change is consistent with observed regional cooling in the northern North American Great Plains but changes in precipitation cannot be explained by land management alone.

Abstract

In this study, we have determined the single-crystal elasticity of clinohumite [Mg8.85Ti0.19Si3.93O16(OH1.11F0.89)] using Brillouin measurement up to 21 GPa at 300 K and 1 bar at 750 K, respectively. The elasticity of clinohumite was determined to be K S0 = 126.2(3) GPa, G 0 = 79.7(2) GPa with pressure derivatives K S′ = 4.2(1), G′ = 1.3(1), pressure derivatives ∂K S/∂T = −0.024(1) GPa/K, and ∂G/∂T = −0.011(1) GPa/K). We comprehensively examined the effects of varying H2O, fluorine content and thermal states, on the velocity and density structures of the subducted harzburgite layer. Assuming a typical H2O content of 2 wt.% within harzburgite, our modeling has shown that hydrous harzburgite with clinohumite as the decomposition product of serpentine along a hot slab geotherm even has the V P and V S 0.4–0.8(6)% greater than it dry counterpart at 250–380 km depth. Yet in the top transition zone, the addition of H2O and F can effectively lower the sound velocities and density. The F-bearing hydrous harzburgite has the V P and V S 1.1(5)–1.3(3)% lower than its dry counterpart, and only 0.6(5)% and 2.3(5)% greater than the pyrolitic mantle. Along cold slab geotherm, phase A will replace clinohumite as the dominant hydrous phase in the harzburgite, the V P and V S are 4.8(5)–5.3(3)% and 5.9(5)–6.0(3)% greater than the pyrolitic mantle in the upper mantle. In the top transition zone, the difference is approximately 3% in V P and 5% in V S. Our results provide crucial experimental evidence for future assessments of the seismic signals of subducted slabs with different hydrous minerals and thermal states.

A team of researchers from the University of Exeter have shone fresh light on the causes of Oceanic Anoxic Event 2—which saw severe global warming and ocean acidification across the Earth around 94 million years ago. The study is published in Nature Communications.

In recent weeks, a deadly tornado ripped through North Texas and severe thunderstorms knocked out power for hundreds of thousands of area residents and brought flash flooding and hail.

Abstract

Precipitation changes in northern China are projected to increase in the Coupled Model Inter-comparison Project Phase 6 (CMIP6) multi-model ensemble. However, these projections are accompanied by notable inter-model uncertainty, and the sources of this uncertainty remain largely unexplored. By analyzing 30 CMIP6 models, this research explores the source of inter-model uncertainty in projected precipitation change and reveals the fundamental mechanism driving uncertainty spread. Following the empirical orthogonal function of inter-model projected precipitation change, the leading mode displays a seesaw spatial pattern between northwest and north China. This phenomenon predominantly stems from the inter-model divergence of projected sea surface temperature (SST) warming in the North Atlantic. Further scrutinizing the ocean mixed layer heat budget, we discover that the combined effect of surface sensible heat flux, net surface shortwave radiation flux, and ocean heat transport convergence influences heat flux and SST change of North Atlantic. The multi-model projections indicate that localized increases in solar radiation and heat convergence warm sea surface, raising SST and initiating convective motion. This convective motion subsequently transforms the 200 hPa teleconnection wave train, leading to an anti-phase pattern over northern China. This wave pattern modulates total cloud cover percentage, influences surface upward latent heat flux, and adjusts the top of atmosphere outgoing longwave radiation, collectively resulting in the seesaw pattern. Our study underscores the pivotal role of inter-model disparities in North Atlantic SST warming projection, which is a primary driver of precipitation uncertainty in northern China. These insights offer an essential foundation for refining and diminishing inter-model uncertainty.

Parts of Northern California will see a higher risk for wildfires this weekend as dry, hot and windy weather sweeps the region.

Abstract

This study focuses on the causes for the generation of equatorial plasma bubbles (EPBs) over the Indian subcontinent and their correlation with atmospheric-ionospheric disturbances resulting from the eruption of the Tonga volcano on 15 January 2022. Concurrent ionosonde observations obtained from Tirunelveli (8.67°N, 77.81°E) and Prayagraj (25.41°N, 81.93°E) show the presence of spread-F traces in ionograms. Notably, the EPBs are also accompanied by plasma blobs (PBs), with their pronounced occurrence during midnight at Prayagraj and Tirunelveli. Analysis of in situ electron density observations obtained from the Swarm B and C satellites reveals substantial plasma density depletions associated with EPBs. An intriguing observation is the intensification of Pre-Reversal Enhancement (PRE) immediately preceding the onset of spread-F at Tirunelveli due to enhanced eastward F region zonal winds by Tonga Volcano, as seen in the satellite observations. Furthermore, the isofrequency analysis from Tirunelveli shows the presence of gravity wave-like oscillations in the equatorial F-region over India. The investigation of Total Electron Content (TEC) obtained from a Pseudo Random Number (PRN)-14 over Indian longitudes suggests the presence of two dominant modes of Traveling Ionospheric Disturbances (TIDs) with speeds ∼452 m/s and ∼406 m/s having periods in the range of ∼65–75 min. These observations reaffirm that volcano triggered atmospheric/ionospheric disturbances can propagate long distances for several hours and can provide necessary seeding conditions for the generation of EPBs.

Review article: Research progress on influencing factors, data, and methods for early identification of landslide hazards
Heng Lu, Zhengli Yang, Kai Song, Zhijie Zhang, Chao Liu, Ruihua Nie, Lei Ma, Wanchang Zhang, Gang Fan, Chen Chen, and Min Zhang
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-68,2024
Preprint under review for NHESS (discussion: open, 2 comments)
1. Sort out the characteristics, functions, links, and application scope of various measuring tools. 2. Bibliometric analysis of early identification methods for landslide hazards. 3. Review the influencing factors of landslides and summarize data links and application literature. 4. Focused on analyzing 5 early landslide identification methods. 5. In-depth exploration of the internal connections of literature and future development directions.

How can seismo-volcanic catalogues be improved or created using robust neural networks through weakly supervised approaches?
Manuel Titos, Carmen Benítez, Milad Kowsari, and Jesús M. Ibáñez
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-102,2024
Preprint under review for NHESS (discussion: open, 0 comments)
Developing seismo-volcanic monitoring tools is crucial for Volcanic Observatories. Our study reviews current methods using Transfer Learning techniques and finds that while these systems identify nearly 90 % of seismic events, they miss other important volcanic data due to the catalogue-learning bias. We propose a weakly supervised technique to reduce bias and uncover new volcanic information. This method can improve existing databases and create new ones efficiently using machine learning.

Observations of traveling ionospheric disturbances driven by gravity waves from sources in the upper and lower atmosphere
Paul Prikryl, David R. Themens, Jaroslav Chum, Shibaji Chakraborty, Robert G. Gillies, and James M. Weygand
Ann. Geophys. Discuss., https//doi.org/10.5194/angeo-2024-6,2024
Preprint under review for ANGEO (discussion: open, 3 comments)
Travelling ionospheric disturbances are plasma density fluctuations usually driven by atmospheric gravity waves in the neutral atmosphere. The aim of this study is to attribute multi-instrument observations of travelling ionospheric disturbances to gravity waves generated in the upper atmosphere at high latitudes or gravity waves generated by tropospheric weather systems at mid latitudes.

Author(s): Indranil Nayak, Fernando L. Teixeira, Dong-Yeop Na, Mrinal Kumar, and Yuri A. Omelchenko

We present a data-driven reduced-order modeling of the space-charge dynamics for electromagnetic particle-in-cell (EMPIC) plasma simulations based on dynamic mode decomposition (DMD). The dynamics of the charged particles in kinetic plasma simulations such as EMPIC is manifested through the plasma c…

[Phys. Rev. E 109, 065307] Published Mon Jun 17, 2024

A major earthquake 2,500 years ago caused one of the largest rivers on Earth to abruptly change course, according to a new study. The previously undocumented quake rerouted the main channel of the Ganges River in what is now densely populated Bangladesh, which remains vulnerable to big quakes. The study was published in the journal Nature Communications.

Abstract

The intense electron-scale current structures (ECSs) with the current density J ≥ 30 nA/m2 are often observed in the Plasma Sheet (PS) during high-speed bulk flows. Using MMS observations we have analyzed 41 earthward and 37 tailward flow intervals and found 452 and 754 ECSs distributed over the PS region, respectively. Almost all ECSs are generated by high-speed electron beams. The duration of ECSs is ≤1 s, and many of them have a half-thickness L ≤ a few ρ e (ρ e is the gyroradius of thermal electrons). In such thin ECSs electrons become demagnetized and experience the dynamics like that observed in the electron diffusion region. Strong nonideal electric fields (E’) associated with violation of frozen-in condition for electrons are observed in the ECSs. This results in the intense energy conversion with J·E’ up to hundreds pW/m3. The major part of the dissipating energy is transferred to electron heating and acceleration. We suggest that the ECSs are manifestations of kinetic-scale turbulence driven by the high-speed ion bulk flows. The inductive electric fields generated by the growing magnetic fluctuations accelerate electron beams which, in turn, generate the ECSs. The ECSs thinning during their evolution, probably, stops for L ≤ a few ρ e . Further thinning leads to development of kinetic instability causing the current disruption and strong electric field generation. The last accelerates new electron beams which generate new ECSs in other locations. Thus, the life cycles of the ECSs contribute to energy cascade in turbulent plasma at electron kinetic scales.

Abstract

In the Earth's magnetosheath (MSH), several processes contribute to energy dissipation and plasma heating, one of which is wave-particle interactions between whistler waves and electrons. However, the overall impact of whistlers on electron dynamics in the MSH remains to be quantified. We analyze 18 hr of burst-mode measurements from the Magnetospheric Multiscale (MMS) mission, including data from the unbiased magnetosheath campaign during February-March 2023. We present a statistical study of 34,409 whistler waves found using automatic detection. We compare wave occurrence in the different MSH geometries and find three times higher occurrence in the quasi-perpendicular MSH compared to the quasi-parallel case. We also study the wave properties and find that the waves propagate quasi-parallel to the background magnetic field, have a median frequency of 0.2 times the electron cyclotron frequency, median amplitude of 0.03–0.06 nT (30–60 pT), and median duration of a few tens of wave periods. The whistler waves are preferentially observed in local magnetic dips and density peaks and are not associated with an increased temperature anisotropy. Also, almost no whistlers are observed in regions with parallel electron plasma beta lower than 0.1. Importantly, when estimating pitch-angle diffusion times we find that the whistler waves cause significant pitch-angle scattering of electrons in the MSH.

Abstract

A Southern Auroral Electrojet (SAE) index has been recently constructed using several Antarctica magnetometer stations. It has been compared for case studies with the standard Auroral Electrojet (AE) index, and a near-conjugate to the southern stations Northern Auroral Electrojet (NAE) index. We compare the three indices statistically as a function of the accompanying solar wind (SW) and Interplanetary Magnetic Field (IMF) conditions to further explore conjugacy issues. We use 274 days of common north/south data presence between December 2005 and August 2010. We calculate the cross-correlation coefficients and differences between all three pairs. We estimate the effect of the SW/IMF conditions on the index correlations and differences using three groups of data: (a) the entire data set, (b) two separate sets based on the presence or not of Southern Hemisphere stations within the 21-03 Magnetic Local Time (MLT) sector where substorms occur, and (c) separately for the four different seasons. We find that high north-south correlation coefficients are more common during strong SW/IMF driving, while the index differences are also higher, suggesting that the SAE index follows better the northern indices' trend, but has even lower values during active times. The UT study shows that the number of high AE/SAE correlations is slightly lower at all clock angles and dynamic pressure levels for the periods within 1454–1941 UT (when no southern station is within 21–03 MLT). Finally, the results show that the number of high correlations is greater during the northern spring than the winter period.

Abstract

Jupiter's Great Red Spot (GRS) is the largest and longest-lived known vortex of all solar system planets but its lifetime is debated and its formation mechanism remains hidden. G. D. Cassini discovered in 1665 the presence of a dark oval at the GRS latitude, known as the “Permanent Spot” (PS) that was observed until 1713. We show from historical observations of its size evolution and motions that PS is unlikely to correspond to the current GRS, that was first observed in 1831. Numerical simulations rule out that the GRS formed by the merging of vortices or by a superstorm, but most likely formed from a flow disturbance between the two opposed Jovian zonal jets north and south of it. If so, the early GRS should have had a low tangential velocity so that its rotation velocity has increased over time as it has shrunk.

Abstract

At mesoscale, trade wind clouds organize with various spatial arrangements, shaping their effect on Earth's energy budget. Representing their fine-scale dynamics even at 1 km scale climate simulations remains challenging. However, geostationary satellites (GS) offer high-resolution cloud observation for gaining insights into trade wind cumuli from long-term records. To capture the observed organizational variability, this work proposes an integrated framework using a continuous followed by discrete self-supervised deep learning approach, which exploits cloud optical depth from GS measurements. We aim to simplify the entire mesoscale cloud spectrum by reducing the image complexity in the feature space and meaningfully partitioning it into seven classes whose connection to environmental conditions is illustrated with reanalysis data. Our framework facilitates comparing human-labeled mesoscale classes with machine-identified ones, addressing uncertainties in both methods. It advances previous methods by exploring transitions between regimes, a challenge for physical simulations, and illustrates a case study of sugar-to-flower transitions.

Abstract

The last glacial inception (LGI) marks the transition from the interglacial warm climate to the glacial period with extensive Northern Hemisphere ice sheets and colder climate. This transition is initiated by decreasing boreal summer insolation but requires positive feedbacks to stimulate the appearance of perennial snow. We perform simulations of LGI with climate model AWI-ESM-2.1, forced by the astronomical and greenhouse gas forcing of 115,000 years before present. To compare with the preindustrial (PI) simulation, we use a consistent definition of the seasons during the LGI and the PI and evaluate model output on an angular astronomical calendar. Our study reveals a prominent role of the sea-ice albedo feedback to amplify the delayed climate signal at polar latitudes. Through a radiative budget analysis, we examine that the ice-albedo feedback exceeds the shortwave radiative forcing, contributing to the cooling and high latitude snow built-up during LGI.

Abstract

Late Pleistocene glacial terminations are caused by rising atmospheric CO2 occurring in response to atmospheric and ocean circulation changes induced by increased discharge from Northern Hemisphere ice sheets. While climate records place glacial terminations coincident with decreasing orbital precession, it remains unclear why a specific precession minimum causes a termination. We compare the orbital and ice volume configuration at each precession minima over the last million years to demonstrate that eccentricity, through its control on precession amplitude, period and coherence with obliquity, along with ice sheet size, determine whether a given precession minimum will cause a termination. We also demonstrate how eccentricity controls obliquity maxima and precession minima coherence, varying the duration of glaciations. Glaciations lasting ∼100 thousand years are controlled by Earth's eccentricity cycle of the same period, while the shortest (20–40 ka) and longest (155 ka) occupy the maxima and minimums of the 400 thousand year eccentricity cycle.

Abstract

Obvious biases in simulating tropical cyclone (TC) genesis of the current climate models hamper our understanding of TC changes. In this study, we found a delay of the seasonal cycle of TC genesis frequency over the western North Pacific (WNP) in most Coupled Model Intercomparison Project Phase 6 models. During the active TC season, the simulated south-warming and north-cooling surface temperature bias amplifies the meridional gradient and excites thermal winds. This weakens the western North Pacific Subtropical High and easterly monsoon trough, which further reduces TC genesis frequency over the western WNP in summer. But in autumn, positive TC genesis biases were only observed in coupled models over the eastern WNP. Both seasons contribute to the delayed seasonal cycle of TC frequency in models. Our findings highlight the importance of accurate simulation of surface temperature by climate models to TC simulations and aid in future model improvements.