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Model-based evaluation of cloud geometry and droplet size retrievals from two-dimensional polarized measurements of specMACS

Atmos. Meas. techniques - Mon, 03/25/2024 - 17:35
Model-based evaluation of cloud geometry and droplet size retrievals from two-dimensional polarized measurements of specMACS
Lea Volkmer, Veronika Pörtge, Fabian Jakub, and Bernhard Mayer
Atmos. Meas. Tech., 17, 1703–1719, https://doi.org/10.5194/amt-17-1703-2024, 2024
Three-dimensional radiative transfer simulations are used to evaluate the performance of retrieval algorithms in the derivation of cloud geometry (cloud top heights) and cloud droplet size distributions from two-dimensional polarized radiance measurements of the airborne spectrometer of the Munich Aerosol Cloud Scanner. The cloud droplet size distributions are derived for the effective radius and variance. The simulations are based on cloud data from highly resolved large-eddy simulations.

Deriving the hygroscopicity of ambient particles using low-cost optical particle counters

Atmos. Meas. techniques - Mon, 03/25/2024 - 17:35
Deriving the hygroscopicity of ambient particles using low-cost optical particle counters
Wei-Chieh Huang, Hui-Ming Hung, Ching-Wei Chu, Wei-Chun Hwang, and Shih-Chun Candice Lung
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-39,2024
Preprint under review for AMT (discussion: open, 0 comments)
This study investigates aerosol properties crucial for health, cloud formation, and climate impact. Employing a low-cost sensor system, we assess hygroscopicity of particulate matter (PM), the ability to influence cloud formation to improve the reported PM concentrations from low-cost sensors. The study introduces an alternate methodology for assessing aerosol hygroscopicity, offering insights into atmospheric science, air quality, and cloud dynamics.

MEXPLORER 1.0.0 – a mechanism explorer for analysis and visualization of chemical reaction pathways based on graph theory

Geoscientific Model Development - Mon, 03/25/2024 - 17:31
MEXPLORER 1.0.0 – a mechanism explorer for analysis and visualization of chemical reaction pathways based on graph theory
Rolf Sander
Geosci. Model Dev., 17, 2419–2425, https://doi.org/10.5194/gmd-17-2419-2024, 2024
The open-source software MEXPLORER 1.0.0 is presented here. The program can be used to analyze, reduce, and visualize complex chemical reaction mechanisms. The mathematics behind the tool is based on graph theory: chemical species are represented as vertices, and reactions as edges. MEXPLORER is a community model published under the GNU General Public License.

GTDI: a gaming integrated drought index implying hazard causing and bearing impacts changing

Natural Hazards and Earth System Sciences - Mon, 03/25/2024 - 17:22
GTDI: a gaming integrated drought index implying hazard causing and bearing impacts changing
Xiaowei Zhao, Tianzeng Yang, Hongbo Zhang, Tian Lan, Chaowei Xue, Tongfang Li, Zhaoxia Ye, Zhifang Yang, and Yurou Zhang
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-45,2024
Preprint under review for NHESS (discussion: open, 0 comments)
To effectively track and identify droughts, we developed a novel integrated drought index that combines the effects of precipitation, temperature, and soil moisture on drought. After comparison and verification, the integrated drought index shows superior performance to a single meteorological drought index or agricultural drought index in drought identification. 

Layered Mantle Flow Field Associated With Plate Kinematics and Slab Modulation Underneath the Horseshoe‐Shaped Banda Arc‐Islands

JGR–Solid Earth - Mon, 03/25/2024 - 17:09
Abstract

The Banda arc-continent collision zone signifies one of the most seismically active and tectonically intricate zones. The high convergence rate across the region, coupled with the exceptionally arcuate arc and subducted slab, makes it an ideal locale for investigating interactions between plate (slab) kinematics and plastic flow in the asthenosphere, which can be diagnosed by seismic anisotropy from shear wave splitting analyses. In total, 206 pairs of splitting measurements using teleseismic SKS, SKKS, and PKS, along with 43 pairs using local S phases, are obtained by utilizing broadband seismic data from five permanent seismic stations. To reduce the ambiguity in determining the origin of anisotropy leading to the teleseismic splittings, which lack vertical resolution, crustal anisotropy is constrained according to the sinusoidal moveout of converted S phases at the Moho using receiver functions. A layered anisotropic structure based on joint analyses of the anisotropy measurements characterizing different depth layers suggests the presence of trench-parallel flow both in the mantle wedge and the sub-slab region. The northeastward motion of the slab, entrained by the fast-moving Australian Plate, deflects asthenospheric materials. The modulation results in trench-parallel plastic mantle flows and leads to the steepening of the southern portion of the asymmetric spoon-shaped Banda slab. In the shallower part of the sub-slab region, the northeastward Australian Plate motion produces simple shear in the transitional layer between the rigid lithosphere and the viscous asthenosphere. The shear deformation induces seismic anisotropy with resulting fast orientations in accordance with the plate motion direction.

Scientists discover methods to regulate carbon storage in humus layer of forest in north China

Phys.org: Earth science - Mon, 03/25/2024 - 17:06
It is estimated that 30% of the world's terrestrial carbon stocks are found in the boreal forest, 60% of which is below ground. Organic soil horizons contain about one-third of the soil carbon. Therefore, the stability of boreal soils is critical to understanding global carbon cycle feedbacks to climate change and soil management. However, the regulating factors of humus carbon sequestration in the boreal forests globally are not entirely understood.

New modeling shows the intensity of CO₂ uptake is higher in coastal seas than in the open ocean

Phys.org: Earth science - Mon, 03/25/2024 - 16:50
Coastal seas form a complex transition zone between the two largest CO2 sinks in the global carbon cycle: land and ocean. Ocean researchers have now succeeded for the first time in investigating the role of the coastal ocean in a seamless model representation.

Droughts in Europe could be avoided with faster emissions cuts

Phys.org: Earth science - Mon, 03/25/2024 - 15:21
Rapid climate action could mean devastating dry periods in the Mediterranean become less frequent by the end of the century, a new study shows.

Study documents slowing of Atlantic currents

Phys.org: Earth science - Mon, 03/25/2024 - 14:50
While scientists have observed oceans heating up for decades and theorized that their rising temperatures weaken global currents, a new study led by a University of Maryland researcher documents for the first time a significant slowing of a crucial ocean current system that plays a role in regulating Earth's climate.

Rainforest response to deglaciation impacted by Australian Indigenous populations, study finds

Phys.org: Earth science - Mon, 03/25/2024 - 13:20
Australia's Indigenous populations have played an important role in modifying the continent's landscape over millennia, particularly by using fire to create open spaces for daily activities. This continued until they left the area in approximately 1860 due to British colonization in the preceding decades, beyond which European land management styles and intensive farming practices became a prominent factor.

Reversal of Projected European Summer Precipitation Decline in a Stabilizing Climate

GRL - Mon, 03/25/2024 - 13:00
Abstract

Precipitation projections in transient climate change scenarios have been extensively studied over multiple climate model generations. Although these simulations have also been used to make projections at specific Global Warming Levels (GWLs), dedicated simulations are more appropriate to study changes in a stabilizing climate. Here, we analyze precipitation projections in six multi-century experiments with fixed atmospheric concentrations of greenhouse gases, conducted with the UK Earth System Model and which span a range of GWLs between 1.5 and 5°C of warming. Regions are identified where the sign of precipitation trends in high-emission transient projections is reversed in the stabilization experiments. For example, stabilization reverses a summertime precipitation decline across Europe. This precipitation recovery occurs concurrently with changes in the pattern of Atlantic sea surface temperature trends due to a slow recovery of the Atlantic Meridional Overturning Circulation in the stabilization experiments, along with changes in humidity and atmospheric circulation.

New study reveals unintended consequences of fire suppression

Phys.org: Earth science - Mon, 03/25/2024 - 11:17
The escalation of extreme wildfires globally has prompted a critical examination of wildfire management strategies. A new study from the University of Montana reveals how fire suppression ensures that wildfires will burn under extreme conditions at high severity, exacerbating the impacts of climate change and fuel accumulation.

Machine Learning Analysis of Seismograms Reveals a Continuous Plumbing System Evolution Beneath the Klyuchevskoy Volcano in Kamchatka, Russia

JGR–Solid Earth - Mon, 03/25/2024 - 08:20
Abstract

Volcanoes produce a variety of seismic signals and, therefore, continuous seismograms provide crucial information for monitoring the state of a volcano. According to their source mechanism and signal properties, seismo-volcanic signals can be categorized into distinct classes, which works particularly well for short transients. Applying classification approaches to long-duration continuous signals containing volcanic tremors, characterized by varying signal characteristics, proves challenging due to the complex nature of these signals. That makes it difficult to attribute them to a single volcanic process and questions the feasibility of classification. In the present study, we consider the whole seismic time series as valuable information about the plumbing system (the combination of plumbing structure and activity distribution). The considered data are year-long seismograms recorded at individual stations near the Klyuchevskoy Volcanic Group (Kamchatka, Russia). With a scattering network and a Uniform Manifold Approximation and Projection (UMAP), we transform the continuous data into a two-dimensional representation (a seismogram atlas), which helps us to identify sudden and continuous changes in the signal properties. We observe an ever-changing seismic wavefield that we relate to a continuously evolving plumbing system. Through additional data, we can relate signal variations to various state changes of the volcano including transitions from deep to shallow activity, deep reactivation, weak signals during quiet times, and eruptive activity. The atlases serve as a visual tool for analyzing extensive seismic time series, allowing us to associate specific atlas areas, indicative of similar signal characteristics, with distinct volcanic activities and variations in the volcanic plumbing system.

A Combined Effect of the Earth's Magnetic Dipole Tilt and IMF By in Controlling Auroral Electron Precipitation

JGR:Space physics - Mon, 03/25/2024 - 05:59
Abstract

Auroral particle precipitation is usually assumed to be equally strong for both signs of the B y component of the interplanetary magnetic field (IMF). This is also the case in most currently used precipitation models, which parameterize solar wind driving by empirical coupling functions. However, recent studies have showed that geomagnetic activity is significantly modulated by the signs and amplitudes of IMF B y and the Earth's dipole tilt angle Ψ. This so called explicit B y dependence is not yet included in any current precipitation models. In this paper, we quantify this B y dependence for auroral electron precipitation for the first time. We use precipitation measurements of the Defense Meteorological Satellite Program (DMSP) Special Sensor J instruments from years 1995–2022. We show that the dawnside electron precipitation at energies 13.9–30 keV is greater at auroral latitudes for opposite signs of B y and Ψ in both hemispheres, while the dusk sector is mostly unaffected by B y and Ψ. For energies below 6.5 keV the B y dependence is strong poleward of the auroral oval in the summer hemisphere, also exhibiting a strong dawn-dusk asymmetry. We also show that B y dependence of precipitation modulates ionospheric conductance.

Absence of High Frequency Echoes From Ionosondes During the 23–25 April 2023 Geomagnetic Storm; What Happened?

JGR:Space physics - Mon, 03/25/2024 - 05:49
Abstract

We report an unusual event on absence of high frequency (HF) echoes in ionosonde observations from the ionospheric F2 region during the geomagnetic storm of 23–25 April 2023. This event was observed in both southern and northern hemispheres over two stations, Grahamstown (33.3°S, 26.5°E), South Africa and Pruhonice (50.0°N, 14.6°E), Czech Republic. Significant O/N2 depletion over the stations was observed by TIMED/GUVI, indicating a strong negative ionospheric storm. This is unique since absence of echoes in ionosonde measurements is usually due to strong radio absorption in the ionosphere associated with solar flares. However, there was no flare activity during the periods of “absent” F2 HF echoes. On the other hand, the ionosonde detected echoes from E-layer. TIEGCM simulation reproduced TIMED/GUVI O/N2 depletion and showed that NmE was larger than NmF2 on dayside over Pruhonice. TIMED/GUVI O/N2 also showed a clear spatial gradient in the O/N2 depleted regions, suggesting F-region ionosphere was tilted. By estimating the critical frequency of the F2 layer using GNSS observations, we have shown that it wasn't possible for the ionospheric electron density to reach depletion levels prohibiting reflection of HF echoes from ionosondes. We suggest that this phenomena may have been caused by either (a) maximum electron density of E layer exceeding that of F2 layer and/or (b) ionospheric tilting which made the signals to be reflected far away from the ionosonde locations.

Responses of the Mean Thermosphere Circulation, O/N2 Ratio and Ne to Solar and Magnetospheric Forcing From Above and Tidal Forcing From Below

JGR:Space physics - Mon, 03/25/2024 - 05:39
Abstract

The day-to-day variability (“weather”) associated with the diurnal- and zonal-mean (DZM) circulation, O/N2 ratio and electron density (Ne) of the I-T system due to tidal “forcing from below” and solar flux and magnetosphere (SM) “forcing from above” during 2021 are delineated, diagnosed and quantitatively compared using a series of model simulations designed to separate these responses with respect to their origins. The external forcings are driven by actual tidal, solar wind, and solar flux observations. Both circulation systems occupy the full extent of the I-T, and the SM-forced DZM circulation is 2–3 times more vigorous in terms of vertical and meridional wind magnitudes. Tidal-driven DZM Ne reductions of up to 30%–40% with respect to those of the fully forced I-T system occur, mainly between ±30° latitude, compared to SM-driven increases of up to 15%–20%. In terms of annual variances over this latitude range, tidal-driven DZM Ne variances exceed or equal those of the SM-driven variances. The former is mainly controlled by O/N2 ratio vis-a-vis tidal-forced temperature variations above 150 km. While a similar cause-effect relation exists for the latter, this is superseded by Ne variability associated with solar production. However, DZM I-T system variability forced from below is underestimated in the simulations in two respects: the effects of gravity waves are omitted, and tidal forcing is represented by 45-day running means, as compared with the more realistic actual daily variability of SM forcing. These shortcomings should be ameliorated once multi-satellite missions planned for the future come to fruition.

Fine Structure of Magnetospheric Magnetosonic Waves: 1. Elementary Rising‐Tone Emissions Within Individual Harmonic

JGR:Space physics - Mon, 03/25/2024 - 05:29
Abstract

The present study uncovers the fine structures of magnetosonic waves by investigating the EFW waveforms measured by Van Allen Probes. We show that each harmonic of the magnetosonic wave may consist of a series of elementary rising-tone emissions, implying a nonlinear mechanism for the wave generation. By investigating an elementary rising-tone magnetosonic wave that spans a wide frequency range, we show that the frequency sweep rate is likely proportional to the wave frequency. We studied compound rising-tone magnetosonic waves, and found that they typically consist of multiple harmonics in the source region, and may gradually become continuous in frequency as they propagate away from source. Both elementary and compound rising-tone magnetosonic waves last for ∼1 min which is close to the bounce period of the ring proton distribution, but their relation is not fully understood.

Advancing Permafrost Monitoring With Autonomous Electrical Resistivity Tomography (A‐ERT): Low‐Cost Instrumentation and Open‐Source Data Processing Tool

GRL - Mon, 03/25/2024 - 05:23
Abstract

Permafrost is a widespread phenomenon in the cold regions of the globe and is under-represented in global monitoring networks. This study presents a novel low-cost, low-power, and robust Autonomous Electrical Resistivity Tomography (A-ERT) monitoring system and open-source processing tools for permafrost monitoring. The processing workflow incorporates diagnostic and filtering tools and utilizes open-source software, ResIPy, for data inversion. The workflow facilitates quick and efficient extraction of key information from large data sets. Field experiments conducted in Antarctica demonstrated the system's capability to operate in harsh and remote environments and provided high-temporal-resolution imaging of ground freezing and thawing dynamics. This data set and processing workflow allow for a detailed investigation of how meteorological conditions impact subsurface processes. The A-ERT setup can complement existing monitoring networks on permafrost and is suitable for continuous monitoring in polar and mountainous regions, contributing to cryosphere research and gaining deeper insights into permafrost and active layer dynamics.

Enhancing satellite clock bias prediction in BDS with LSTM-attention model

GPS Solutions - Mon, 03/25/2024 - 00:00
Abstract

Satellite clock bias (SCB) is a critical factor influencing the accuracy of real-time precise point positioning. Nevertheless, the utilization of real-time service products, as supplied by the International GNSS Service, may be vulnerable to interruptions or network failures. In specific situations, users may encounter difficulties in obtaining accurate real-time corrections. Our research presents an enhanced predictive model for SCB using a long short-term memory (LSTM) neural network fused with a Self-Attention mechanism to address this challenge. This fusion enables the model to effectively balance global attention and localized feature capture, ultimately enhancing prediction accuracy and stability. We compared and analyzed our proposed model with convolutional neural network (CNN) and LSTM models. This analysis encompasses an assessment of the model's strengths and suitability for predicting SCB within the BeiDou navigation system, considering diverse satellites, orbits, and atomic clocks. Our results exhibit a substantial improvement in predictive accuracy through the LSTM-Attention model. There has been an improvement of 49.67 and 62.51% compared to the CNN and LSTM models in the 12-h prediction task. In the case of the 24-h prediction task, the improvements escalated to 68.41 and 71.16%, respectively.

A Wasserstein distance-based technique for the evaluation of GNSS error characterization

GPS Solutions - Mon, 03/25/2024 - 00:00
Abstract

The characteristics of residual errors in GNSS positioning are crucial for fault detection and integrity monitoring. Despite the wide use of the zero-mean Gaussian assumption in the navigation community, studies highlight non-Gaussian traits and heavy-tailed patterns in residual errors. The problem will be even more challenging for users in difficult environments where residual errors consist of a combination of multiple modes with high complexity and cannot be fitted with known distributions or empirical models. To address these issues, our work introduces a novel approach leveraging the Wasserstein distance for assessing the performance of error characterization and fault modeling. However, relying solely on the Wasserstein distance value for direct similarity assessment is hindered by its dependency on dimensionality. We propose a second-order Gaussian Wasserstein distance-based precision metric to offer a quantitative evaluation of GNSS error models in terms of both goodness-of-fit and underlying assumptions. We also establish a robust scoring criterion to distinguish between various GNSS error models, ensuring comprehensive evaluation. The proposed method is validated through a known high-dimensional Gaussian model, achieving a score of 99.95 over 100 with a sample size of 10,000. To demonstrate the capability in dealing with complexity, two multivariate complex GNSS models incorporating copula functions to capture intricate inter-dimensional correlations are established and assessed by our approach. Experimental results show that the method can effectively deliver the evaluation of goodness-of-fault models using the establishment of a universal criteria with different dimensions. It provides a quantitative measure on the goodness of fittings and enhances the modeling to reflect the reality, therefore solving the problems raised above. In addition, with this technique, the close-to-reality fault models can be chosen to generate simulated faulty datasets, thus benefiting algorithm testing and improvement. This is also beneficial to more accurate integrity risk assessment to avoid overbounding- or underbounding-resulted false or missed alert.

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