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Abstract

Efforts to predict long-term changes in continental runoff at both global and basin scales generally remain ambiguous. Here we use a global runoff reconstruction and a Bayesian statistical method to narrow uncertainties in runoff projections from the latest generation of global climate models. Three representative tropical river basins are used to illustrate the application and showcase the potential for substantial reduction in modeling uncertainty. Yet, results are fairly sensitive to the selected reconstruction thus highlighting the need for reliable and homogeneized gridded runoff data sets or river discharge measurements. Moreover, climate models do not account for water withdrawals, whose effect on observed runoff should also be removed in order to detect and attribute the hydrological effect of climate change. Finally, and more importantly, most models fail at capturing the observed recent decrease in runoff ratio, which may highlight either model deficiencies or increasing water derivation over the selected river basins.

Abstract

Contrasting the extensive research on summer atmospheric rivers (ARs) in the Antarctic Peninsula (AP), winter AR impacts are less understood. This study examines a unique warming event from 1 to 3 July 2023, using in situ winter observations and ERA5 reanalysis. On 2 July, Frei station experienced an extreme warm event with a temperature of 2.7°C and a significant rise in the freezing level, coinciding with winter rainfall. A pressure dipole pattern over the AP, with contrasting circulations over Bellingshausen and Weddell Seas, facilitated an AR, carrying warm, humid air initially from South America/Atlantic and then the southeast Pacific. This shift resulted in anomalous water stable isotope composition in precipitation. Trends suggest a strengthening winter pressure dipole, associated with increased AR frequency and higher temperatures in northern AP. These findings highlight the importance of winter observations in exploring AR impacts, bridging knowledge gaps about winter AR behaviors.

Abstract

The Southeast Tropical Indian Ocean (SETIO), dominated by the Indian Ocean monsoon, is an important source region for strong mesoscale eddies. To date, the impacts of the Indian Ocean monsoon on mesoscale eddies have not been clarified. Here we report on the dipole response of mesoscale eddy formation to monsoon transition in the SETIO, using satellite and reanalysis data sets. During the summer monsoon season, anticyclonic eddies are mainly concentrated north of 12°S, while cyclonic eddies are south of 12°S. This situation reverses during the winter monsoon season. We attribute this dipole feature to the oceanic perturbations and current shear during the different monsoon periods. A geographical boundary along 12°S aligns with meridional changes in eddy potential energy, which delineates the generation and direction of the newly-formed eddies. The hot spot region, rich in eddy energy properties, tends to promote eddy formation and endurance during the monsoon periods.

Abstract

Soils are a major source of nitrogen oxides, which in the atmosphere help govern its oxidative capacity. Thus the response of soil nitric oxide (NO) emissions to forcings such as warming or forest loss has a meaningful impact on global atmospheric chemistry. We find that the soil emission rate of NO in Amazonia from a common inventory is biased low by at least an order of magnitude in comparison to tower-based observations. Accounting for this regional bias decreases the modeled global methane lifetime by 1.4%–2.6%. In comparison, a fully deforested Amazonia, representing a 37% decrease in global emissions of isoprene, decreases methane lifetime by at most 4.6%, highlighting the sensitive response of oxidation rates to changes in emissions of NO compared to those of terpenes. Our results demonstrate that improving our understanding of soil NO emissions will yield a more accurate representation of atmospheric oxidative capacity.

Abstract

Reliable pressure determination is crucial for high pressure and temperature experiments and meaningful interpretation of their geophysical implications. However, nearly all commonly-used pressure scales are secondary in nature, meaning their establishments rely on pre-existing primary shock-compression-based pressure scales, which due to their dynamic compression nature, large uncertainty in peak shock temperature estimation and electronic thermal pressure contribution can yield substantial (∼5%) uncertainties at 1 Mbar conditions. To overcome this intrinsic shortcoming, in this study a self-consistent primary pressure scale of KCl B2 phase was experimentally calibrated up to 85 GPa at ambient temperature using an approach through measuring the acoustic wave velocities and molar volume using Brillouin spectroscopy and Synchrotron X-ray diffraction. Best fitting of thermoelastic parameters based on our experimental results yields V 0 = 32.48 (9) cm3 mol−1, K T0 = 21.33 (70) GPa, K0′ ${{K}_{0}}^{\prime }$ = 4.836 (83), G 0 = 16.83 (237) GPa, G′ = 2.147 (115), γ 0 = 1.92 (11) and θ D0 = 251 (22) K. A KCl B2 phase primary pressure scale based on 3rd order Birch-Murnaghan equation of state (EOS) is established without relying on any external (shock compressed-based) pressure scales and further extended also to high temperatures in combination with thermal pressure effect calculated using Mie‒Grüneisen‒Debye model under quasi-harmonic approximation. Our newly established KCl B2 EOS thus enables accurate pressure determinations at simultaneously high pressure and temperature conditions up to Earth's core-mantle boundary and can serve as a benchmark for calibrating other secondary pressure scales.

Abstract

We present a physical mechanism for generating ∼GeV ions in the Jovian radiation belts. The mechanism is called relativistic turning acceleration (RTA) and involves a special form of nonlinear wave trapping by electromagnetic ion cyclotron (EMIC) waves. Necessary conditions for RTA include a near-equatorial source of EMIC waves, strong wave amplitudes (of the order of a few percent of the background magnetic field strength), and a source of ions of sufficiently high energy. RTA occurs when a fraction of equator-ward moving ions encounters pole-ward moving waves, and, in so doing, becomes entrapped and undergoes a turning motion. The trapped ions then move poleward in the same direction as the waves and eventually become detrapped, but during the turning motion the ions undergo significant acceleration. We rigorously verify this process by providing the theory of nonlinear interactions between relativistic protons and coherent EMIC waves. The RTA process has been previously established for the analogous whistler mode wave-electron interaction. We carry out particle simulations for protons at R = 2R J (where R J  = Jovian radius) interacting with EMIC waves of amplitude B w  = 0.02B 0eq (where B 0eq  = background magnetic field strength at the equator). We confirm that a large portion of test protons experience RTA and that some protons of critical energy 240 MeV can be accelerated to 10 GeV in a period of 5 s. The nonlinear acceleration process is crucially controlled by the trapping condition 0 < S < 1 where S is the inhomogeneity factor.

Abstract

The paper presents the effects of the storm-time prompt penetration electric fields (PPEF) and traveling atmospheric disturbances (TADs) on the total electron content (TEC), foF2 and hmF2 in the American sector (north and south) during the geomagnetic storm on 23–24 April 2023. The data show a poleward shift of the Equatorial Ionization Anomaly (EIA) crests to 18°N and 20°S in the evening of 23 April (attributed to eastward PPEF) and the EIA crests remaining almost in the same latitudes after the PPEF reversed westward. The thermospheric neutral wind velocity, foF2, hmF2, and TEC variations show that TADs from the northern and southern high latitudes propagating equatorward and crossing the equator after midnight on 23 April. The meridional keograms of ΔTEC show the TAD structures in the north/south propagated with phase velocity 470/485 m/s, wave length 4,095/4,016 km and period 2.42/2.30 hr, respectively. The interactions of the TADs also appear to modify the wind velocities in low latitudes. The eastward PPEF and equatorward TADs also favored the development of a clear/not so clear F3 layer in northern/southern regions of the equator.

Abstract

The asthenosphere is commonly defined as an upper mantle zone with low velocities and high attenuation of seismic waves, and high electrical conductivity. These observations are usually explained by the presence of partial melt, or by a sharp contrast in the water content of the upper mantle. Low viscosity asthenosphere is an essential ingredient of functioning plate tectonics. We argue that a substantial component of asthenospheric weakening is dynamic, caused by dislocation creep at the base of tectonic plates. Numerical simulations of subduction show that dynamic weakening scales with the surface velocity both below the subducting and the overriding plate, and that the viscosity decrease reaches up to two orders of magnitude. The resulting scaling law is employed in an apriori estimate of the lateral viscosity variations (LVV) below Earth's oceans. The obtained LVV help in explaining some of the long-standing as well as recent problems in mantle viscosity inversions.

Abstract

The study investigates the rapid intensification (RI) of tropical cyclones (TCs) in the Northwestern Pacific. We found that rapid changes in the maximum wind speed (V max ) and the minimum central pressure (P min ) are not always concurrent. RI cases can be categorized into three types: (a) RIv, only V max strengthens rapidly; (b) RIp, only P min decreases rapidly; (c) RIpv, rapid changes in V max and P min occur concurrently. At the onset of RI, RIv-type TCs exhibit the weakest intensity and the smallest size, with deep convection concentrated in the inner-core region; RIp-type TCs are characterized by the strongest cyclone intensity and the largest outer-core size, with strong convection covering the inner- and outer-core regions; RIpv-type TCs show moderate intensity, size, and convection distribution. For RIpv, significant strengthening of wind profile is concentrated in the inner-core region, while for RIp it is more prominent in the outer-core.

Evaluating post-wildfire debris-flow rainfall thresholds and volume models at the 2020 Grizzly Creek Fire in Glenwood Canyon, Colorado, USA
Francis K. Rengers, Samuel Bower, Andrew Knapp, Jason W. Kean, Danielle W. vonLembke, Matthew A. Thomas, Jaime Kostelnik, Katherine R. Barnhart, Matthew Bethel, Joseph E. Gartner, Madeline Hille, Dennis M. Staley, Justin K. Anderson, Elizabeth K. Roberts, Stephen B. DeLong, Belize Lane, Paxton Ridgway, and Brendan P. Murphy
Nat. Hazards Earth Syst. Sci., 24, 2093–2114, https://doi.org/10.5194/nhess-24-2093-2024, 2024
Every year the U.S. Geological Survey produces 50–100 postfire debris-flow hazard assessments using models for debris-flow likelihood and volume. To refine these models they must be tested with datasets that clearly document rainfall, debris-flow response, and debris-flow volume. These datasets are difficult to obtain, but this study developed and analyzed a postfire dataset with more than 100 postfire storm responses over a 2-year period. We also proposed ways to improve these models.

Simulations of the collection of mesospheric dust particles with a rocket instrument
Adrien Pineau, Henriette Trollvik, Herman Greaker, Sveinung Olsen, Yngve Eilertsen, and Ingrid Mann
Atmos. Meas. Tech., 17, 3843–3861, https://doi.org/10.5194/amt-17-3843-2024, 2024
The mesosphere, part of the upper atmosphere, contains small solid dust particles, mostly made up of material from interplanetary space. We are preparing an experiment to collect such particles during a rocket flight. A new instrument has been designed and numerical simulations have been performed to investigate the airflow nearby as well as its dust collection efficiency. The collected dust particles will be further analyzed in the laboratory in order to study their chemical composition.

Abstract

Habitability at the surface of a planet depends on having an atmosphere long enough for life to develop. The loss of atmosphere to space is an important component in assessing planetary surface habitability. Current models of atmospheric escape from exoplanets are not well constrained by observations. Atmospheric escape observations from the terrestrial planets are available in public data archives. We recast oxygen escape rates from Earth derived from an instrument on Dynamics Explorer-1 as function of solar wind and compare them to similar data from Mars. Analysis demonstrates that oxygen escape rates from Mars are not as sensitive to variations in solar power components as those from Earth. Available data from Venus can confirm or refute the assertion that oxygen escape from magnetized planets is more sensitive than that from unmagnetized planets.

Abstract

On New Year's Day 2024, a magnitude 7.6 event struck the Noto Peninsula in central Japan. Prior to this event, an intense earthquake swarm had persisted beneath the northeastern peninsula for more than five years. Geophysical evidence provides insight into the upwelling of deep fluids from the uppermost mantle that triggers the seismic swarm activity. The noble gases and their isotopes have been used as geochemical indicators to determine the origin of the fluids associated with the swarms and their upwelling. Gas samples collected from boreholes around the seismic source region are characterized by anomalously high 3He/4He ratios (∼3.9 RAcor), indicating infiltration of mantle fluids from the subcrustal lithosphere. Using a steady-state advection model, we calculated mantle helium fluxes of 1.1–2.4 × 10−15 mol cm−2 a−1, similar to those estimated for other representative fault zones, such as the San Andreas and North Anatolian faults.

Abstract

Saline lakes contributions to the carbon cycle is crucial to the Qinghai-Tibetan Plateau (QTP) carbon budget. Here, based on the 8-year direct measurement of CO2 flux over the Qinghai Lake (QHL) and 83 collected CO2 flux data estimated by pCO2 sampling from 45 lakes over the QTP, we identified the interannual variations of CO2 flux and its response to the extreme climate events. Results showed: (a) the QHL CO2 absorption weakened in the spring, autumn and winter and turn to CO2 emissions in the summer during 2013–2020; (b) with higher Ts and less precipitation, coupling of positive Pacific Decadal Oscillation (PDO) and El Niño enhanced the summer CO2 emissions; and (c) the PDO and ENSO had obvious superposition effect on the decrease of CO2 absorption in autumn. Our results show the potential mechanism of lake CO2 flux responses to extreme climate and further defines the significance of the QTP carbon budget and cycling.

A modular approach to volatile organic compound samplers for tethered balloon and drone platforms
Meghan Guagenti, Darielle Dexheimer, Alexandra Ulinksi, Paul Walter, James H. Flynn III, and Sascha Usenko
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-96,2024
Preprint under review for AMT (discussion: open, 0 comments)
A robust, automatic VOC collection system was developed for vertical volatile organic compounds (VOCs) sampling associated with the 2022 DOE ARM program-led TRACER in Houston, TX.  This modular sampler has been developed to measure vertical profiles of VOCs to improve near-surface characterization. This article helps fill the current lack of commercially available options for aerial VOC sampling and serves to support and encourage researchers to build and develop custom samplers. 

EMADDC: high quality, quickly available and high volume wind and temperature observations from aircraft using the Mode-S EHS infrastructure
Siebren de Haan, Paul de Jong, Michal Koutek, and Jan Sondij
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-110,2024
Preprint under review for AMT (discussion: open, 0 comments)
This manscript describes the operational method of extracting meteorological information from all airborne aircraft in the European airspace every 20 seconds to 1 minute. The methodology is described and the quality of the wind and temperature observations are evaluated against radiosonde observations.

Abstract

Normal mode analysis is a Laplace-transform method for calculating the surface-loading response of laterally homogeneous spherical Earth models with linear viscoelasticity which delivers modal decay times and amplitudes. It can locally fail owing to numerical singularities arising from the viscoelastic parameters, leading to an incomplete accounting of the surface-loading response. Collocation methods were developed to circumvent this issue. The mixed collocation method includes least-squares fitting to the Laplace-transformed Earth response to determine amplitudes assuming the normal mode decay times are known, while the pure collocation method assumes a series of logarithmically regularly spaced inverse decay times for which amplitudes are determined numerically. Both collocation methods may determine amplitudes that are physically unrealistic and all three methods produce crustal motion predictions that differ significantly. The hybrid normal mode-collocation method presented here applies the normal mode analysis, and then applies the pure collocation to the resulting residuals. This retains the modal structure, while providing an improved fit. Our implementation avoids numerical singularities that may arise from Rayleigh-Taylor instabilities occurring at large times and can be automated. Vertical crustal motions predicted by the hybrid method for North America with the ICE-6G_C loading model and the VM5a viscosity structure have a root mean square (RMS) of 4.49 mm/yr and RMS differences with the normal mode, pure, and mixed collocation method of 0.06, 0.23, and 0.25 mm/yr, respectively. Maximum differences reach 0.20, 0.87, and 0.63 mm/yr. The differences increase for a viscosity profile with a greater viscosity increase with depth that exhibits stronger singularity issues.

Abstract

We present an analysis of Antarctic polar winters from 2005 to 2023 as observed by the Atmospheric Chemistry Experiment (ACE). The unique broad band infrared spectral features in ACE “residual” spectra are used to classify the spectra of polar aerosols by composition into polar stratospheric clouds (PSCs) and sulfate aerosols. The spectra of PSCs are further classified into nitric acid trihydrate, supercooled ternary solutions, supercooled nitric acid, ice-mix, and mixtures of PSCs. A breakdown of PSC composition is presented for each year. Antarctic winter seasons with unusual compositions are: 2011, in which volcanic ash mixed with PSCs was observed from July to August; 2019, which experienced a stratospheric warming event; 2020, the PSC season following the Australian Black Summer pyrocumulonimbus event; and 2023, which had unusually large sulfate aerosols following the Honga-Tonga Honga Ha'apai eruption of 2022.

Abstract

ANCHOR is a novel assimilative model developed at the U.S. Naval Research Laboratory, which was designed for rapid assimilative runs. ANCHOR uses recently developed PyIRI model for the background and for the formation of the background covariance matrix. It only takes a few minutes for ANCHOR to complete the data assimilation (DA) for one day, including data pre-processing and model set up. ANCHOR extracts ionospheric parameters from radio occultation (RO) and ionosonde data using PyIRI formalism and assimilates them as point measurements into maps of the background parameters using a Kalman Filter approach. This paper introduces the ANCHOR algorithm, discusses its coordinate system and background, explains the background covariance formation, discusses the extraction of the ionospheric parameters from the data and the assimilation process, and, finally, shows the results of the observing system simulation experiment with synthetic data simulated using the SAMI3 model. ANCHOR reduces the root mean square errors in the analysis by more than a half for all of the ionospheric parameters in comparison to the background. Finally, this paper discusses advantages and limitations of the parametrized ionospheric DA, highlighting the avenues for its future improvement.

Science, Volume 384, Issue 6703, June 2024.