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Abstract

The radius of maximum wind (RMW) defines the location of the maximum winds in a tropical cyclone and is critical to understanding intensity change as well as hazard impacts. A comparison between the Hurricane Analysis and Forecast System (HAFS) models and two statistical models based off the National Hurricane Center official forecast is conducted relative to a new baseline climatology to better understand whether models have skill in forecasting the RMW of North Atlantic tropical cyclones. On average, the HAFS models are less skillful than the climatology and persistence baseline and two statistically derived RMW estimates. The performance of the HAFS models is dependent on intensity with better skill for stronger tropical cyclones compared to weaker tropical cyclones. To further improve guidance of tropical cyclone hazards, more work needs to be done to improve forecasts of tropical cyclone structure.

Development and evaluation of the interactive Model for Air Pollution and Land Ecosystems (iMAPLE) version 1.0
Xu Yue, Hao Zhou, Chenguang Tian, Yimian Ma, Yihan Hu, Cheng Gong, Hui Zheng, and Hong Liao
Geosci. Model Dev., 17, 4621–4642, https://doi.org/10.5194/gmd-17-4621-2024, 2024
We develop the interactive Model for Air Pollution and Land Ecosystems (iMAPLE). The model considers the full coupling between carbon and water cycles, dynamic fire emissions, wetland methane emissions, biogenic volatile organic compound emissions, and trait-based ozone vegetation damage. Evaluations show that iMAPLE is a useful tool for the study of the interactions among climate, chemistry, and ecosystems.

StraitFlux – precise computations of water strait fluxes on various modeling grids
Susanna Winkelbauer, Michael Mayer, and Leopold Haimberger
Geosci. Model Dev., 17, 4603–4620, https://doi.org/10.5194/gmd-17-4603-2024, 2024
Oceanic transports shape the global climate, but the evaluation and validation of this key quantity based on reanalysis and model data are complicated by the distortion of the used modelling grids and the large number of different grid types. We present two new methods that allow the calculation of oceanic fluxes of volume, heat, salinity, and ice through almost arbitrary sections for various models and reanalyses that are independent of the used modelling grids.

Abstract

In the Arctic and subarctic oceans, the relatively low supply of silicon (compared to other nutrients) can make it limiting for the growth of diatoms, a fundamental building block of the oceanic food web. Glaciers release large quantities of dissolved silicon and dissolvable solid amorphous silica phases into high-latitude estuaries (fjords), but the role of these glacially-derived silica phases in sustaining diatom growth in the coastal and open-water sectors remains unknown. Here we show how stable and radiogenic silicon isotopes can be used together to address this question, using southwest Greenland as a case study. This study finds enhanced levels of detrital (i.e., mineral) amorphous silica, likely glacially-sourced, sustaining a large portion of diatom growth observed off the coast, revealing how the phytoplankton community can function during high-meltwater periods.

Abstract

The ocean's organic carbon export is a key control on atmospheric pCO2 and stimulating this export could potentially mitigate climate change. We use a data-constrained model to calculate the sensitivity of atmospheric pCO2 to local changes in export using an adjoint approach. A perpetual enhancement of the biological pump's export by 0.1 PgC/yr could achieve a roughly 1% reduction in pCO2 at average sensitivity. The sensitivity varies roughly 5-fold across different ocean regions and is proportional to the difference between the mean sequestration time τ seq of regenerated carbon and the response time τ pre of performed carbon, which is the reduction in the preformed carbon inventory per unit increase in local export production. Air-sea CO2 disequilibrium modulates the geographic pattern of τ pre, causing particularly high sensitivities (2–3 times the global mean) in the Antarctic Divergence region of the Southern Ocean.

Abstract

The Cross-track Infrared Sounder (CrIS) observations (O) contributed greatly to numerical weather prediction. Further contribution depends on the success of all-sky data assimilation, which requires a method to produce realistic cloud/rain band structures from background fields (i.e., 6-hr forecasts), and to remove large biases of all-sky simulation of brightness temperature (TB) in the presence of clouds. In this study, CrIS all-sky simulations of brightness temperatures at an arbitrarily selected window channel within Typhoon Hinnamnor (2022) are investigated. The 3-km Weather Research and Forecasting model with three microphysics schemes were used to produce 6-hr background forecasts (B). The O − B statistic deviate greatly from Gaussian distribution with large biases in either water clouds, or thin ice clouds, or thick ice clouds within Typhoon Hinnamnor. By developing a linear regression function of three all-sky simulations of TB from 6-hr forecasts with three microphysics schemes, the O − B statistics approximate a Gaussian normal distribution in water clouds, thin ice clouds and thick ice clouds. Taking the regression function that is established by a training data set to combine 6-hr background forecasts at later times, the cloud/rain band structures compared much more favorably with CrIS observations than those from an individual microphysic. Furthermore, the regression coefficients derived from Typhoon Hinnamnor (2022) also work for Typhoon Khanun (2023). The work aims to quantify and remove biases in background fields of TB and generating realistic typhoon cloud/rain band structures in background fields will allow a better description of center position, intensity and size to improve typhoon forecasts.

Abstract

The stepwise development of positive lightning leaders is still not well understood. A recent laboratory study indicated, at high absolute humidity, positive leaders can do steps due to the merging of a separate luminous structure and the primary leader channel, similar to the steps of negative leaders. The humidity may play a key role in the formation of positive leader steps, however, the humidity effect on the positive leader steps has never been explored. In this paper, we examine numerous positive long spark discharges at different humidity levels with the synchronized discharge current and high-speed camera frames recording the evolution of leader channel. The positive leader propagation manners at different humidity levels are compared both morphologically and electrically. The effect of humidity on steps is further analyzed statistically. We found that the positive leader steps characterized by steep-rise current pulse and abrupt channel elongation, which may be led by separate luminous structures, only appear under the condition that high absolute humidity is above a certain threshold. As the ambient humidity increases, these positive leader steps occur more frequently.

Abstract

The long-term trends and seasonality of many tropospheric pollutants are not well characterized in the high Arctic due to a dearth of trace-gas measurements in this remote region. In this study, the inter- and intra-annual variabilities of carbon monoxide (CO), acetylene (C2H2), ethane (C2H6), methanol (CH3OH), formaldehyde (H2CO), formic acid (HCOOH), and peroxyacetyl nitrate (PAN) in the high Arctic region were derived from the total column time-series of ground-based Fourier transform infrared (FTIR) measurements at Eureka, Nunavut (80.05°N, 86.42°W, 2006–2020) and Thule, Greenland (76.53°N, 68.74°W, 1999–2022). Consistent seasonal cycles were observed in the FTIR measurements at both sites for all species. Negative trends were observed for CO, C2H2, and CH3OH at both sites, and for HCOOH at Eureka. Positive trends were detected for C2H6 and H2CO at both sites, and for PAN at Eureka. Additionally, a 19-year simulation was performed using the novel GEOS-Chem High Performance model v14.1.1 for the period of 2003–2021. The model was able to reproduce the observed seasonality of all gases, but all species showed negative biases relative to observations, and CH3OH was found to have a particularly large bias of approximately −70% relative to the FTIR measurements. The GEOS-Chem modeled trends broadly agreed with observations for all species except C2H6, H2CO, and PAN, which were found to have opposite trends in the model. For some species, the measurement-model differences are suspected to be the result of errors or underestimations in the emissions inventories used in the simulation.

Abstract

Current models estimate global aviation contributes approximately 5% to the total anthropogenic climate forcing, with aerosol-cloud interactions having the greatest effect. However, radiative forcing estimates from aviation aerosol-cloud interactions remain undetermined. There is an expected significant increase in aircraft emissions with aviation demand expected to rise by over 4% per year. Soot may play an important role in the ice nucleation of aircraft-induced cirrus formation due to a high emission rate, but the ice nucleating properties are poorly constrained. Understanding the microphysical processes leading to atmospheric ice crystal formation is crucial for the reliable parameterization of aerosol-cloud interactions in climate models due to their impact on precipitation and cloud radiative properties. Ice nucleation of aircraft-emitted soot is potentially affected by particle morphology with condensation of supercooled water occurring in pores followed by ice nucleation. However, soot has heterogeneous properties and undergoes atmospheric aging and oxidation that could change surface properties and contribute to complex ice nucleation processes. This review synthesizes current knowledge of ice nucleation catalyzed by aviation in the cirrus regime and its effects on global radiative forcing. Further research is required to determine the ice nucleation and microphysical processes of cirrus cloud formation from aviation emissions in both controlled laboratory and field investigations to inform models for more accurate climate predictions and to provide efficient mitigation strategies.

Abstract

The thermospheric density and its variations are crucial to aerospace activities as well as space weather research and operation. However, due to the difficulties in observing the thermosphere, there has been a lack of effective descriptions for the general characteristics of thermospheric density. In this paper, the Two-Line-Element data sets (TLEs) from multi-target low Earth orbit satellites are used to derive a proxy of the daily average atmospheric density in the thermospheric shell located in the vicinity of LEOs' orbital altitude. It captures the overall characteristics of the thermosphere and exhibits good correlations (∼0.9) with modeled and observed thermospheric density. By applying the spectral whitening method to this proxy, a new index JsT ${J}_{s}^{T}$ is derived to describe non-periodic perturbation of the density where the specific satellite passed by. The fact that the JsT ${J}_{s}^{T}$ obtained from different satellites within the same thermospheric shell presents significant consistency to each other means that the new index is a good indicator for the overall feature of the variations of thermospheric density, and it is possible to define a unified regional index JrT ${J}_{r}^{T}$ to describe density disturbances for the thermospheric shell where these satellites fly through. Moreover, the JrT ${J}_{r}^{T}$ at different altitudes also present good consistency suggesting the possibility of defining a global index JpT ${J}_{p}^{T}$, capable of describing the density variation of the entire thermosphere.

Abstract

Davemaoite, that is, CaSiO3 perovskite (CaPv), is the third most abundant phase in the lower mantle and exhibits a tetragonal-cubic phase transition at high pressures and temperatures. The phase boundary in CaPv has recently been proposed to be close to the cold slab adiabat and cause mid-mantle seismic wave speed anomalies (Thomson et al., 2019, https://doi.org/10.1038/s41586-019-1483-x). This study utilized accurate deep-learning-based simulations and thermodynamic integration techniques to compute free energies at temperatures ranging from 300 to 3,000 K and pressures up to 130 GPa. Our results indicate that CaPv exhibits a single cubic phase throughout lower-mantle conditions. This suggests that the phase diagram proposed by Thomson et al. requires revision, and mid-mantle seismic anomalies are likely attributable to other mechanisms.

A systemic and comprehensive assessment of coastal hazard changes: method and application to France and its overseas territories
Marc Igigabel, Marissa Yates, Michalis Vousdoukas, and Youssef Diab
Nat. Hazards Earth Syst. Sci., 24, 1951–1974, https://doi.org/10.5194/nhess-24-1951-2024, 2024
Changes in sea levels alone do not determine the evolution of coastal hazards. Coastal hazard changes should be assessed using additional factors describing geomorphological configurations, metocean event types (storms, cyclones, long swells, and tsunamis), and the marine environment (e.g., coral reef state and sea ice extent). The assessment completed here, at regional scale including the coasts of mainland and overseas France, highlights significant differences in hazard changes.

Conversion relationships between Modified Mercalli Intensity and Peak Ground Acceleration for historical shallow crustal earthquakes in Mexico
Quetzalcoatl Rodríguez-Pérez and F. Ramón Zúñiga
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-92,2024
Preprint under review for NHESS (discussion: open, 1 comment)
Seismic intensity reflects earthquake damage, although this parameter is often subjective. On the other hand, peak acceleration values are a direct measure of earthquake effects. Seismic intensity was used to describe historical earthquakes, and its use is rare today. For this reason, it is important to have a relationship between these parameters of strong movements in order to predict the acceleration of historical earthquakes.

Abstract

In March and April 2021, buoys were deployed in the Beaufort Sea, Arctic Ocean, to measure sea-ice horizontal deformation over spatial scales that had not been previously achieved. Geodetic-quality position measurements allowed measurements of strain-rate over lengths from about 200 m to 2 km. Conventional ice-drifters extended spatial coverage up to about 100 km. Past studies find there is multi-fractal behavior for horizontal sea-ice deformation from 10 to 1,000 km. Our results demonstrate that such behavior does not hold when including spatial scales below 10 km. We find that sea-ice deformation is not scale invariant between the scale of individual sea-ice floes and aggregates of floes. Therefore, we cannot expect the same physical laws or forcing to describe sea-ice kinematics over these regimes, nor can we assume log-log linear behavior for mean deformation. Using this scaling behavior as a metric to validate models that resolve sea ice floes and their interactions is hence not recommended.

Atmospheric odd nitrogen response to electron forcing from a 6D magnetospheric hybrid-kinetic simulation
Tuomas Häkkilä, Maxime Grandin, Markus Battarbee, Monika E. Szeląg, Markku Alho, Leo Kotipalo, Niilo Kalakoski, Pekka T. Verronen, and Minna Palmroth
Ann. Geophys. Discuss., https//doi.org/10.5194/angeo-2024-7,2024
Preprint under review for ANGEO (discussion: final response, 3 comments)
We study the atmospheric impact of auroral electron precipitation, by the novel combination of both magnetospheric and atmospheric modelling. We first simulate fluxes of auroral electrons, and then use these fluxes to model their atmospheric impact. We find an increase of up to 200 % in thermospheric odd nitrogen, and a corresponding decrease in stratospheric ozone of around 0.7 %. The produced auroral electron precipitation is realistic, and shows the potential for future studies.

Abstract

In the present study, we use broadband seismic data recorded by 190 stations of the EarthScope program's Transportable Array to construct a 3-D shear wave velocity model for the upper 180 km using a non-linear Bayesian Monte-Carlo joint inversion of receiver functions (RFs) and Rayleigh wave dispersion curves. Ambient noise and teleseismic data are used for obtaining Rayleigh wave phase velocity dispersion curves. A resonance removal filtering technique is applied to the RFs contaminated by reverberations from the thick sedimentary layers that cover most of the region. Our observations of the higher crustal shear velocities (∼3.40 km/s) beneath the Sabine Block (SB), along with the estimated relatively thicker crust (∼34.0 km) and lower crustal V p/V s estimates (∼1.80) in comparison with the rest of the Gulf Coastal Plain (GCP) (∼3.10 km/s for crustal shear velocities, ∼29.0 km for crustal thickness, and ∼1.90 for crustal V p/V s estimates), indicating that this crustal block has different crustal properties from the surrounding coastal plain regions. The southern Ouachita Mountains have a thin crust (∼30.0 km) and low mean crustal V p/V s value (∼1.73), suggesting that lower crustal delamination has occurred in this region. Low velocities in the upper mantle beneath most of the GCP are interpreted as a combined result of thin lithosphere, higher-than-normal temperatures, and possibly compositional variations.

Abstract

Dichlorodifluoromethane (CFC-12) is an ozone-depleting substance and potent greenhouse gas, which was required to be phased out after 2010 under the Montreal Protocol. CFC-12 emissions need to be quantitatively traced. However, estimates of CFC-12 emissions in China based on atmospheric inversions are unavailable after 2010. Here, using atmospheric observations at nine sites across China and inversion techniques, we quantify CFC-12 emissions in China during 2011–2020 (on average 11.0 ± 0.6 Gg yr−1). The emissions derived from observations are 8.5 times larger than the previously reported inventories. Apart from emissions from eastern China revealed in previous studies, this study reveals that 71% of national total emissions were from other parts of China. Moreover, this study reconciled the global CFC-12 emissions during 2011–2020: 28% were traced to China by this study, 9% of emissions were traced in previous studies, while 63% remain untraced, indicating the need for more regional emission inversion studies.

Abstract

The subaerial exposure of the modern continental crust through time remains intensely debated, with estimates of the first exposure ranging from the late Archean to the Neoproterozoic. To constrain when and how much of the continental crust was exposed subaerially during Earth's history, we trained a supervised machine learning model on the compositions of modern subaerial and submerged basalts. Then, we applied this well-trained model to a refined worldwide data set of basaltic compositions and calculated the mean proportions of basalts erupted subaerially since 3.8 billion years ago (Ga). Our results suggest that ∼20% of the basalts were exposed subaerially in the early Archean, which may have driven the synthesis of biopolymers crucial to the origins and evolution of life. The proportion of subaerial basalts increased markedly during two stages between the late Archean and the Paleoproterozoic before reaching the present-day level no earlier than ∼1.8 Ga.

Abstract

Ground-level enhancements (GLEs) are sporadic events that signal the arrival of high fluxes of solar energetic particles (SEPs) that have been produced by solar eruptions. Ground-level enhancement events are characterized by a significant increase in the count rate of ground-based neutron monitors (NMs). The arrival of high-energy SEPs in the atmosphere leads to an enhancement of the radiation environment, with the enhancement at aviation altitudes being particularly hazardous to human health as pilots, crew, and airline passengers can be subjected to dangerous levels of radiation during a GLE. Through the use of a currently expanding library of analyzed GLEs and the application of a newly developed atmospheric radiation model, both of which have been created in-house, we found a strong statistically significant relationship between real-time NM data during GLE events and the radiation doses at aviation altitudes. This result provides a strong scientific basis for the use of real-time NM data as a proxy for radiation dose estimates during GLE events and aids in the development of future nowcasting models to help mitigate the dangerous impacts of future GLEs.

Abstract

The adiabatic invariants (M, J, Φ) and the related invariants (M, K, L*) have been established as effective coordinate systems for describing radiation belt dynamics at a theoretical level, and through numerical techniques, can be paired with in situ observations to order phase-space density. To date, methods for numerical techniques to calculate adiabatic invariants have focused on empirical models such the Tsyganenko models TS05, T96, and T89. In this work, we develop methods based on numerical integration and variable step size iteration for the calculation of adiabatic invariants, applying the method to the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) simulation code, with optional coupling to the Rice Convection Model (RCM). By opening the door to adiabatic invariant modeling with MHD magnetic fields, the opportunity for exploratory modeling work of radiation belt dynamics is enabled. Calculations performed using LFM are cross-referenced with the same code applied to the T96 and TS05 Tsyganenko models evaluated on the LFM grid. Important aspects of the adiabatic invariant calculation are reviewed and discussed, including (a) sensitivity to magnetic field model used, (b) differences in the problem between quiet and disturbed geomagnetic states, and (c) the selection of key parameters, such as the magnetic local time step size for drift shell determination. The rigorous development and documentation of this algorithm additionally acts as preliminary step for future thorough reassessment of in situ phase-space density results using alternative magnetic field models.