Abstract
High-latitudinal mixed-phase clouds significantly affect Earth's radiative balance. Observations of cloud and radiative properties from two field campaigns in the Southern Ocean and Antarctica were compared with two global climate model simulations. A cyclone compositing method was used to quantify “dynamics-cloud-radiation” relationships relative to the extratropical cyclone centers. Observations show larger asymmetry in cloud and radiative properties between western and eastern sectors at McMurdo compared with Macquarie Island. Most observed quantities at McMurdo are higher in the western (i.e., post-frontal) than the eastern (frontal) sector, including cloud fraction, liquid water path (LWP), net surface shortwave and longwave radiation (SW and LW), except for ice water path (IWP) being higher in the eastern sector. The two models were found to overestimate cloud fraction and LWP at Macquarie Island but underestimate them at McMurdo Station. IWP is consistently underestimated at both locations, both sectors, and in all seasons. Biases of cloud fraction, LWP, and IWP are negatively correlated with SW biases and positively correlated with LW biases. The persistent negative IWP biases may have become one of the leading causes of radiative biases over the high southern latitudes, after correcting the underestimation of supercooled liquid water in the older model versions. By examining multi-scale factors from cloud microphysics to synoptic dynamics, this work will help increase the fidelity of climate simulations in this remote region.
Abstract
Deep learning is applied to many complex tasks in the field of wireless communication, such as modulation recognition of spectrum waveforms, because of its convenience and efficiency. This leads to the problem of a malicious third party using a deep learning model to easily recognize the modulation format of the transmitted waveform. Some existing works address this problem directly using the concept of adversarial examples in the computer vision field without fully considering the characteristics of the waveform transmission in the physical world. Therefore, we propose two low-interception waveforms (LIWs) generation methods, the LIW and ULIW algorithms, which can reduce the probability of the modulation being recognized by a third party without affecting the reliable communication of the friendly party. Among them, ULIW improves LIW algorithm by simulating channel noise during training cycle, and substantially reduces the perturbation magnitude while maintaining low interception accuracy. Our LIW and ULIW exhibit significant low-interception performance in both numerical simulations and hardware experiments.
Abstract
While deterministically predicting the time and location of earthquakes remains impossible, earthquake forecasting models can provide estimates of the probabilities of earthquakes occurring within some region over time. To enable informed decision-making of civil protection, governmental agencies, or the public, Operational Earthquake Forecasting (OEF) systems aim to provide authoritative earthquake forecasts based on current earthquake activity in near-real time. Establishing OEF systems involves several nontrivial choices. This review captures the current state of OEF worldwide and analyzes expert recommendations on the development, testing, and communication of earthquake forecasts. An introductory summary of OEF-related research is followed by a description of OEF systems in Italy, New Zealand, and the United States. Combined, these two parts provide an informative and transparent snapshot of today's OEF landscape. In Section 4, we analyze the results of an expert elicitation that was conducted to seek guidance for the establishment of OEF systems. The elicitation identifies consensus and dissent on OEF issues among a non-representative group of 20 international earthquake forecasting experts. While the experts agree that communication products should be developed in collaboration with the forecast user groups, they disagree on whether forecasting models and testing methods should be user-dependent. No recommendations of strict model requirements could be elicited, but benchmark comparisons, prospective testing, reproducibility, and transparency are encouraged. Section 5 gives an outlook on the future of OEF. Besides covering recent research on earthquake forecasting model development and testing, upcoming OEF initiatives are described in the context of the expert elicitation findings.
Earthquake insurance in Iran: solvency of local insurers in light of current market practices
Mohsen Ghafory-Ashtiany and Hooman Motamed
Nat. Hazards Earth Syst. Sci., 24, 2707–2726, https://doi.org/10.5194/nhess-24-2707-2024, 2024
Iranian insurers have been offering earthquake coverage since the 1990s. However, despite international best practices, they still do not use modern methods for risk pricing and management. As such, they seem to be accumulating seismic risk over time. This paper examines the viability of this market in Iran by comparing the local market practices with international best practices in earthquake risk pricing (catastrophe modeling) and insurance risk management (European Solvency II regime).
Shaping shallow landslide susceptibility as a function of rainfall events
Micol Fumagalli, Alberto Previati, Paolo Frattini, and Giovanni B. Crosta
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-140,2024
Preprint under review for NHESS (discussion: open, 0 comments)
Shallow landslides are mass movements of limited thickness, mainly triggered by extreme rainfalls, that can pose a serious risk to the population. This study uses statistical methods to analyse and simulate the relationship between shallow landslides and rainfalls, showing that in the studied area shallow landslides are modulated by rainfall but controlled by lithology. A new classification method considering the costs associated with a misclassification of the susceptibility is also proposed.
An optimal transformation method applied to diagnose the ocean carbon budget
Neill Mackay, Taimoor Sohail, Jan David Zika, Richard G. Williams, Oliver Andrews, and Andrew James Watson
Geosci. Model Dev., 17, 5987–6005, https://doi.org/10.5194/gmd-17-5987-2024, 2024
The ocean absorbs carbon dioxide from the atmosphere, mitigating climate change, but estimates of the uptake do not always agree. There is a need to reconcile these differing estimates and to improve our understanding of ocean carbon uptake. We present a new method for estimating ocean carbon uptake and test it with model data. The method effectively diagnoses the ocean carbon uptake from limited data and therefore shows promise for reconciling different observational estimates.
Improving the Gaussianity of radar reflectivity departures between observations and simulations using symmetric rain rates
Yudong Gao, Lidou Huyan, Zheng Wu, and Bojun Liu
Atmos. Meas. Tech., 17, 4675–4686, https://doi.org/10.5194/amt-17-4675-2024, 2024
A symmetric error model built by symmetric rain rates handles the non-Gaussian error structure of the reflectivity error. The accuracy and linearization of rain rates can further improve the Gaussianity.
A nitrate ion chemical-ionization atmospheric-pressure-interface time-of-flight mass spectrometer (NO3− ToFCIMS) sensitivity study
Stéphanie Alage, Vincent Michoud, Sergio Harb, Bénédicte Picquet-Varrault, Manuela Cirtog, Avinash Kumar, Matti Rissanen, and Christopher Cantrell
Atmos. Meas. Tech., 17, 4709–4724, https://doi.org/10.5194/amt-17-4709-2024, 2024
Calibration exercises are essential for determining the accuracy of instruments. We performed calibrations on a NO3¯ ToFCIMS instrument to determine its sensitivity and linearity for detecting various organic compounds. Our findings revealed significant variability, over several orders of magnitude, in the calibration factors obtained. The results suggest that relying on a single calibration factor from H2SO4 for the quantification of all compounds detected by this technique is not appropriate.
On the temperature stability requirements of free-running Nd:YAG lasers for atmospheric temperature profiling through the rotational Raman technique
José Alex Zenteno-Hernández, Adolfo Comerón, Federico Dios, Alejandro Rodríguez-Gómez, Constantino Muñoz-Porcar, Michaël Sicard, Noemi Franco, Andreas Behrendt, and Paolo Di Girolamo
Atmos. Meas. Tech., 17, 4687–4694, https://doi.org/10.5194/amt-17-4687-2024, 2024
We study how the spectral characteristics of a solid-state laser in an atmospheric temperature profiling lidar using the Raman technique impact the temperature retrieval accuracy. We find that the spectral widening, with respect to a seeded laser, has virtually no impact, while crystal-rod temperature variations in the laser must be kept within a range of 1 K for the uncertainty in the atmospheric temperature below 1 K. The study is carried out through spectroscopy simulations.
Abstract
This paper addresses one of the critical questions of scientific inquiry: How do we know when a given data set is representative of the phenomenon being examined? For paleomagnetists, the question is often whether a particular data set sufficiently averaged paleosecular variation (PSV). To this aim, we updated an existing PSV data set that now comprises 2,441 site mean directions from 94 individual studies (PSV10-24). Minimal filtering for data quality resulted in 1,619 sites from 90 publications. Fitting PSV10-24 with two newly defined parameters as well as two existing ones form the basis of a Giant Gaussian Process field model (THG24) consistent with the data. Drawing directions from THG24 yields directional distributions predicted for a given latitude allowing a comparison between empirical distributions and the cumulative distribution function generated by the model. This tests whether the observed data adequately averaged out PSV according to THG24. We applied these tests to five data sets from Large Igneous Provinces from the last billion years and find that they are consistent with the THG24 model as well. Sedimentary data sets that may have experienced inclination shallowing can be corrected using an (un)flattening factor that yields directions satisfying THG24 in a newly-defined, four-parameter space. This approach builds on the Elongation-Inclination (E/I) method of Tauxe and Kent (2004), https://doi.org/10.1029/145gm08, so the approach introduced here is called SVEI. We show examples of the use of SVEI and explain how to use this newly developed Python code that is publicly available in the PmagPy GitHub repository.
Evaluation of the effects of different lightning protection rods on the data quality of C-band weather radars
Cornelius Hald, Maximilian Schaper, Annette Böhm, Michael Frech, Jan Petersen, Bertram Lange, and Benjamin Rohrdantz
Atmos. Meas. Tech., 17, 4695–4707, https://doi.org/10.5194/amt-17-4695-2024, 2024
Weather radars should use lightning protection to be safe from damage, but the rods can reduce the quality of the radar measurements. This study presents three new solutions for lightning protection for weather radars and evaluates their influence on data quality. The results are compared to the current system. All tested ones have very little effect on data, and a new lightning protection system with four rods is recommended for the German Meteorological Service.
Abstract
Monitoring the generation and movement of equatorial plasma bubbles (EPBs) in a large longitude region is crucial important for better understanding their day-to-day variability. Using the newly developed Low lAtitude long Range Ionospheric raDar (LARID) at Dongfang (19.2°N, 108.8°E, dip lat. 13.8°N), China, an extremely long-range experiment for observing EPB irregularities in a range of ±9,600 km to the radar site was first carried out. The results show that EPB irregularities with ranges up to 7,000 and 9,500 km were observed by the east and west beams of LARID, respectively. By incorporating simultaneous observations from GNSS receiver and ionosonde networks, it is demonstrated that the EPBs generated from post-sunset to sunrise over a very wide longitude of ∼140°, from Pacific to Africa could be observed by LARID. The results, for the first time, demonstrate the possibility for tracing global EPBs in real time using a few low latitude over-the-horizon radars.
Abstract
Different meteor radars at low latitudes observed abnormally strong westward mesospheric winds around the March Equinox of 2023, that is, during the first phase of the Mesospheric Semiannual Oscillation. This event was the strongest of at least the last decade (2014–2023). The westward winds reached −80 m/s at 82 km of altitude in late March, and decreased with increasing altitude and latitude. A considerable increase in the diurnal tide amplitude was also observed. The Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension constrained to meteorological reanalysis up to ∼50 km does not capture the observed low-latitude behavior. Additionally, these strong mesospheric winds developed during the westerly phase of the Quasi-Biennial Oscillation, in accordance with the filtering mechanism of gravity waves in the stratosphere proposed in previous works. Finally, analysis of SABER temperatures strongly suggests that the breaking of the migrating diurnal tide may be the main driver of these strong winds.
Abstract
Anti-dipolarization fronts (ADFs), characterized by the rapid increase of the negative magnetic field Bz component, are typically formed at the leading edge of the tailward reconnection jets in the Earth's magnetotail. To date, the electron-scale current structures, which govern the energy conversion at ADFs, are still barely understood due to the lack of high-resolution measurements. Here, using Magnetospheric Multiscale mission, we for the first time report a tailward ADF associated with strong field-aligned current (FAC). The FAC appears at the leading part of the ADF and its densities can reach about 200 nA/m2, which is significantly larger than those reported before. Such current is primarily contributed by the electron flow, which also forms electron beam distribution in the anti-parallel direction. Significant energy conversion (E⋅ J, E is electric field and J is current density) is also observed at the ADF, which is mainly contributed by the FAC and the fluctuating electric fields. This study makes essential steps toward understanding the current system and the energy conversion at the ADF in the Earth's magnetotail.
Abstract
Silver is a highly toxic element for marine organisms. However, its controlling factor in marine sediments remains largely unknown, limiting our understanding of its biogeochemical cycling. Based on a sediment core from the Vietnam upwelling area in the South China Sea, it is found that Ag is significantly enriched in sediments of this area (as high as 0.39 μg/g), and it shows a very similar geochemical behavior to Ca and Sr. Our study supports the theory that Ag could be a marine paleo-productivity indicator. Burial of Ag over the past 3,200 years shows an abrupt increase at around 1850 CE, in concordance with the global atmospheric CO2 record. It is hypothesized that elevated CO2 and global warming enhance marine productivity in the Vietnam coastal upwelling area, favoring the burial of Ag. Human-induced global warming thus significantly impacts its biogeochemical cycling.
Abstract
Dry lightning is a prevalent episodic natural ignition source for wildfires, particularly in remote regions where such fires can escalate into uncontrollable events, burning extensive areas. In this study, we aimed to understand the interplay of environmental, fuel, and geographical factors in evaluating the probability of fire initiation following dry lightning strikes in Tasmania, Australia. We integrated dry lightning, active fire records, and gridded data on fire weather, fuel, and topography into a binary classification framework for both fire-initiating and non-fire-causing lightning strikes. Employing statistical and machine learning techniques, we quantified the likelihood of fire initiation due to dry lightning, with the resampled Random Forest model exhibiting notable performance with an ROC-AUC value of 0.98. Our findings highlight how fuel characteristics and moisture content associated with particular vegetation types influence fire initiation and provide an objective approach for identifying susceptible regions of dry lightning ignitions, informing associated fire management responses.
Abstract
Lunar polar region has become the focus of future explorations due to the possible ice reservoir in the permanently shadowed craters. However, the space environment near the polar crater is quite complicated, and a plasma mini-wake can be caused by the topographic obstruction. So far, three-dimensional (3D) numerical simulations of the mini-wake around a crater far larger than the Debye length are still limited. Here we present a 3D electrostatic hybrid particle-in-cell model to study the plasma mini-wake of a polar crater on scale of about 1 km. It is found that the mini-wake can begin upstream from the crater with a cone angle of about 8.8°. There is a plasma void with extra electrons near the leeward crater wall, where the electric potential can be as low as −60 V. A part of solar wind ions can be diverted into the crater, and the ratio of the diverted flux is about 4% on the crater bottom and about 18% on the windward crater wall, which provide an important source for the surface sputtering. Further studies show that the mini-wake can change with the solar wind parameters and the crater shapes. Our results are helpful to assess the space environment and the water loss rate of a polar crater, and have general implications in studying the plasma mini-wake caused by a crater on the other airless bodies.
Abstract
The influence of northern polar vortex in the stratosphere (SPV) in December-January on Asia's surface air temperature (SAT) in February has been examined using reanalysis data sets and a barotropic model. An out-of-phase interannual linkage between the SPV in December-January and SAT in February during 1979–2022 has been observed, that is, a strong (weak) SPV corresponds to a cooling (warming) over Asia. Approximately 25% of the SAT over Asia in February can be explained by the SPV in December-January. This relationship between the SPV and SAT is independent of the Arctic Oscillation. The influence of the SPV on SAT over Asia cannot be solely explained by radiative processes, but is instead related to circulation anomalies in the troposphere. A stronger SPV tends to result in negative geopotential height anomalies with cyclonic circulation over Asia. The SPV-related geopotential height over Asia is accompanied by a weakened teleconnection pattern between the North Atlantic and Asia, with three centers from the northeastern Atlantic-eastern Europe-Asia, and fewer stationary waves propagated from North Atlantic into Asia. These anomalous circulation patterns and anomalous northerly wind over Central Asia in February are beneficial to the colder air transportation from the higher latitudes to Asia, facilitating a surface cooling over Asia. Our results shed light on the interannual linkage between SPV and SAT over Asia, suggesting that the SPV in December-January could be considered as a new predicator of SAT in February over Asia.
Abstract
Water-soluble organic carbon (WSOC) deposited in ambient snowpack play key roles in regional carbon cycle and surface energy budget, but the impacts of photo-induced processes on its optical and chemical properties are poorly understood yet. In this study, melted samples of the seasonal snow collected from northern Xinjiang, northwestern China, were exposed to ultraviolet (UV) radiation to investigate the photolytic transformations of WSOC. Molecular characteristics and chemical composition of WSOC and its brown carbon (BrC) constituents were investigated using high-performance liquid chromatography interfaced with a photodiode array detector and a high-resolution mass spectrometer. Upon illumination, formation of nitrogen- and sulfur-containing species with high molecular weight was observed in snow samples influenced by soil- and plant-derived organics. In contrast, the representative sample collected from remote region showed the lowest molecular diversity and photolytic reactivity among all samples, in which no identified BrC chromophores decomposed upon illumination. Approximately 65% of chromophores in urban samples endured UV irradiation. However, most of BrC composed of phenolic/lignin-derived compounds and flavonoids disappeared in the illuminated samples containing WSOC from soil- and plant-related sources. Effects of the photochemical degradation of WSOC on the potential modulation of snow albedo were estimated. Apparent half-lives of WSOC estimated as albedo reduction in 300–400 nm indicated 0.1–0.4 atmospheric equivalent days, which are shorter than typical photolysis half-lives of ambient biomass smoke aerosol. This study provides new insights into the roles of WSOC in snow photochemistry and snow surface energy balance.
Prognostic assumed-probability-density-function (distribution density function) approach: further generalization and demonstrations
Jun-Ichi Yano
Nonlin. Processes Geophys., 31, 359–380, https://doi.org/10.5194/npg-31-359-2024, 2024
A methodology for directly predicting the time evolution of the assumed parameters for the distribution densities based on the Liouville equation, as proposed earlier, is extended to multidimensional cases and to cases in which the systems are constrained by integrals over a part of the variable range. The extended methodology is tested against a convective energy-cycle system as well as the Lorenz strange attractor.
