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Unravelling the capacity-action gap in flood risk adaptation
Annika Schubert, Anne von Streit, and Matthias Garschagen
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-121,2024
Preprint under review for NHESS (discussion: open, 0 comments)
Households play a crucial role in climate adaptation efforts. Yet, households require capacities to implement measures. We explore which capacities enable German households to adapt to flooding. Our results indicate that flood-related capacities such as risk perception, responsibility appraisal and motivation are pivotal, whereas financial assets are secondary. Enhancing these specific capacities, e.g. through collaborations between households and municipalities, could promote local adaptation.

Stratospheric aerosol characteristics from SCIAMACHY limb observations: two-parameter retrieval
Christine Pohl, Felix Wrana, Alexei Rozanov, Terry Deshler, Elizaveta Malinina, Christian von Savigny, Landon A. Rieger, Adam E. Bourassa, and John P. Burrows
Atmos. Meas. Tech., 17, 4153–4181, https://doi.org/10.5194/amt-17-4153-2024, 2024
Knowledge of stratospheric aerosol characteristics is important for understanding chemical and climate aerosol feedbacks. Two particle size distribution parameters, the aerosol extinction coefficient and the effective radius, are obtained from SCIAMACHY limb observations. The aerosol characteristics show good agreement with independent data sets from balloon-borne and satellite observations. This data set expands the limited knowledge of stratospheric aerosol characteristics.

Retrieval and analysis of the composition of an aerosol mixture through Mie–Raman–fluorescence lidar observations
Igor Veselovskii, Boris Barchunov, Qiaoyun Hu, Philippe Goloub, Thierry Podvin, Mikhail Korenskii, Gaël Dubois, William Boissiere, and Nikita Kasianik
Atmos. Meas. Tech., 17, 4137–4152, https://doi.org/10.5194/amt-17-4137-2024, 2024
The paper presents a new method that categorizes atmospheric aerosols by analyzing their optical properties with a Mie–Raman–fluorescence lidar. The research specifically looks into understanding the presence of smoke, urban, and dust aerosols in the mixtures identified by this lidar. The reliability of the results is evaluated using the Monte Carlo technique. The effectiveness of this approach is successfully demonstrated through testing in ATOLL, an observatory influenced by diverse aerosols.

The algorithm of microphysical-parameter profiles of aerosol and small cloud droplets based on the dual-wavelength lidar data
Huige Di, Xinhong Wang, Ning Chen, Jing Guo, Wenhui Xin, Shichun Li, Yan Guo, Qing Yan, Yufeng Wang, and Dengxin Hua
Atmos. Meas. Tech., 17, 4183–4196, https://doi.org/10.5194/amt-17-4183-2024, 2024
This study proposes an inversion method for atmospheric-aerosol or cloud microphysical parameters based on dual-wavelength lidar data. It is suitable for the inversion of uniformly mixed and single-property aerosol layers or small cloud droplets. For aerosol particles, the inversion range that this algorithm can achieve is 0.3–1.7 μm. For cloud droplets, it is 1.0–10 μm. This algorithm can quickly obtain the microphysical parameters of atmospheric particles and has better robustness.

Abstract

Over-estimation of summer precipitation over the Tibetan Plateau (TP) is a well-known and persistent problem in most climate models. This study demonstrates the impact of a Gaussian Probability Density Function cloud fraction scheme on rainfall simulations using the Weather Research and Forecasting model. It is found that this scheme in both 0.1° and 0.05° resolutions significantly reduces the wet bias through both local feedbacks and large-scale dynamic process. Specifically, increased cloud water/ice content with this scheme reduces surface shortwave radiation, and consequently surface heat fluxes and evapotranspiration. This, in turn, dampens the large-scale thermal effect of the TP and weakens the exaggerated monsoon circulation and low-level moisture convergence. It is this large-scale dynamic process that contributes the most (∼70%) to the wet bias reduction. Although this paper presents a modeling study, it highlights the cloud radiative feedback to the large-scale dynamics and precipitation over the TP.

Abstract

Natural fault zones are complex, spatially heterogeneous systems. Rock deformation experimental studies simplify the complexity of natural fault zones either as a surface discontinuity between intact rocks (bare-rock surfaces) or as a few mm-thick gouge layer. However, depending on the simplified fault type and its slip history, the response to applied deformation can vary. In this work, we conduct laboratory experiments for investigating the evolution of mechanical parameters of simulated faults made of calcite gouge subjected to multiple (four) identical seismic slip-rate pulses. We observed that, as the number of applied slip-rate pulses increased, (a) initial friction and steady-state friction remained approximatively constant, (b) peak friction and normalized strength excess increased and, (c) the slip distances to achieve peak and steady-state friction, D a and D c , decreased. The greatest changes occurred between the first and the second slip-rate pulse. From this pulse onward, the dissipated energy of the calcite gouge fault was similar to those obtained in bare-rock surfaces experiments. Microstructural analysis showed that, strain is localized in up to two (recrystallized) principal slip zones (PSZ) with sub-micrometric grain size, surrounded by low porosity sintered and non-sintered comminuted gouge domains. We conclude that previous seismic slip episodes impact on both the structure and the strain localization processes within a fault, contributing to its shear fabric evolution. We highlight that the strain localization process identifies the PSZ, dissipating the least amount of energy within the entire experimental fault zone.

Abstract

The quadratic Wasserstein (W2) metric has been proposed as a promising misfit function to mitigate cycle-skipping phenomena in full-waveform inversion. Mathematically, we demonstrate that the smoothness of the W2-based adjoint source is two orders of magnitude higher than that based on L2-norm, which guarantees a larger convergence radius of related inverse problems. However, the oscillatory characteristics of seismic signals and subsequent operations of transforming them into probability densities would decrease the accuracy of the optimal transport map T(t) and exacerbate the nonconvexity of the misfit function. To tackle these challenges, we propose the concept of prescribed direction indicator, which indicates the properly matching direction from predictions to observations, in order to correct inaccurate T(t). 1D synthetic examples suggest that reasonable bijection can be constructed through the proposed method. Numerical experiments demonstrate that it works well during optimization procedures, including enlarging the convergence radius of the inverse problem, improving the computational efficiency and enhancing the reliability of inversion results.

Abstract

The Earth's mantle contains significant amounts of water in the form of hydroxyl in hydrous minerals, nominally anhydrous minerals, and hydrous silicate melts. H2O fluid is thought to be present only in the shallow regions because it will always dissolve tens of weight percent of silicates by forming hydrous silicate melt in the deep mantle. Here I investigated the phase relations in the MgO-SiO2-H2O system by high-pressure experiments at a pressure of 23 GPa and a temperature of 2,000 K, corresponding to the conditions at the bottom of the mantle transition zone and the topmost lower mantle. The experimental results indicate that hydrous melt can contain more than 90 wt.% of H2O, that is, it becomes H2O-rich fluid when coexists only with stishovite. In contrast, silicate-rich hydrous melt is formed when the system is enriched with MgO component. Therefore, H2O-rich fluid may be stabilized in locally SiO2-enriched rocks even at the topmost lower mantle, acting as a water source for the deep lower mantle by slab subduction. The H2O fluid also provide a possible cause for the occurrence of natural ice-VII originated from 660 km depth.

Abstract

This research examines the plasma processes under penetration of the plasma clouds (plasmoids) across the magnetopause which is modeled as a tangential discontinuity (TD). Cases with the parallel magnetic field in both sides out of the TD are under investigation. Plasma parameters and magnetic field were chosen from the MMS mission and other spacecraft observations. The results are important for understanding the following basic space plasma physics problems: (a) plasma cloud deformation and strong phase mixing with magnetospheric plasma; (b) the transfer of mass, momentum and energy of magnetosheath and magnetic cloud plasma into magnetospheric plasmas; (c) necessary conditions for plasma cloud penetration via the magnetopause; (d) wave generation by plasma clouds inside the magnetopause.

Abstract

Basal shear stress on hard-bedded glaciers results from normal stress against bed roughness, which depends on basal water pressure and cavity size. These quantities are related in a steady state but are expected to behave differently under rapid changes in water input, which may lead to a transient frictional response not captured by existing friction laws. Here, we investigate transient friction using Global Positioning System vertical displacement and horizontal velocity observations, basal water pressure measurements, and cavitation model predictions during rain-induced speed-up events at Glacier d'Argentière, French Alps. We observe up to a threefold increase in horizontal surface velocity, spatially migrating at rates consistent with subglacial flow drainage, and associated with surface uplift and increased water pressure. We show that frictional changes are mainly driven by changes in water pressure at nearly constant cavity size. We propose a generalized friction law capable of capturing observations in both the transient and steady-state regimes.

Abstract

This letter reports first simultaneous detection of F-region plasma-depleted structure in O(1D) 630.0 and O(1S) 557.7 nm airglow images on a geomagnetically quiet-night (Ap = 3) of 26 June 2021 from mid-latitude station (Hanle, India) due to enhanced thermospheric 557.7 nm emission. Since nighttime thermospheric 557.7 nm emission over mid-latitudes is predominantly masked by significantly larger mesospheric component, F-region plasma structures are rarely observed in 557.7 nm images. Interestingly, thermospheric 557.7 nm emission was not significant on the following geomagnetically quiet-night as bands of medium-scale traveling ionospheric disturbance were only observed in 630.0 nm images. Poleward wind generated by Equatorial Temperature and Wind Anomaly transported plasma from the boundary of equatorial ionization anomaly, causing significant electron density enhancement around 250 km and descent of F-layer peak over Hanle on 26 June 2021. This amplified the dissociative recombination enabling the simultaneous detection of plasma-depleted structure in 557.7 and 630.0 nm images.

Abstract

How eclogite/pyroxenite-derived melts evolve through the refractory lithosphere above a plume remains poorly understood. Here we conducted layered experiments of reaction between tholeiitic melts and harzburgite at 2–3 GPa, 1,400–1,500°C, with a run duration ranging from 2 to 24 hr. The resulting residual melts exhibit lower SiO2, TiO2, Al2O3, FeO, CaO, and total alkali contents, higher Ni, MgO, and Mg#, and almost constant CaO/Al2O3 compared to the initial tholeiitic melts. The compositions of the residual melts are influenced by factors such as the melt/harzburgite mass ratio, temperature, and run duration. Decreasing the melt/rock ratio or increasing temperature and run duration leads to a greater extent of assimilation. Under disequilibrated conditions (2 hr), the residual melts have higher SiO2, FeO, and MgO, and lower CaO, Al2O3, and total alkali contents compared to those under equilibrated conditions. The results suggest that interface reactions involving olivine dissolution and orthopyroxene precipitation, and chemical diffusion occur simultaneously during the interaction process. The compositions of the residual melts are largely controlled by interface reactions within 2 hr, followed by dominant chemical diffusion between the melts and refertilized harzburgite from 2 to 24 hr. Based on the experimental results, we propose a two-stage model for the origin of Hawaiian shield stage parental magmas. Eclogite/pyroxenite-derived tholeiitic melts first react with harzburgite, with varying melt/rock ratios, to produce residual melts in the deep lithosphere. These residual melts subsequently mix with plume peridotite-derived melts at shallow depths, contributing to the geochemical diversity observed in Hawaiian shield stage lavas.

Abstract

Satellites provide global coverage for monitoring atmospheric greenhouse gases, crucial for understanding global climate dynamics. However, their temporal and spatial resolutions fall short in detecting urban-scale variations. To enhance satellite reliability over urban areas, this study presents the first comprehensive analysis of long-term observations of column-averaged dry air mole fractions of CO2, CH4, and CO (XCO2, XCH4, XCO) using two ground-based fourier transform infrared spectrometers, EM27/SUNs, in a megacity. With over 2 years of observations, our study shows that EM27/SUN measurements can effectively capture the daily and seasonal variability of XCO2, XCH4, and XCO over Seoul, a megacity with complex topography and various emission sources. In addition, we use the advantage of having multiple greenhouse gas satellites targeting Seoul to compare with the EM27/SUNs. Our study highlights the importance of EM27/SUN observations in Seoul to identify the need for improvements in satellites to monitor greenhouse gas behaviors and emissions in urban areas.

Abstract

Recent geophysical studies have highlighted the potential utility of integrating both seismic and infrasound data to improve source characterization and event discrimination efforts. However, the influence of each of these data types within an integrated framework is not yet well-understood by the geophysical community. To help elucidate the role of each data type within a merged structure, we develop a neural network which fuses seismic and infrasound array data via a gated multimodal unit for earthquake-explosion discrimination within the Korean Peninsula. Model performance is compared before and after adding the infrasound branch. We find that the seismoacoustic model outperforms the seismic model, with the majority of the improvements stemming from the explosions class. The influence of infrasound is quantified by analyzing gated multimodal activations. Results indicate that the model relies comparatively more on the infrasound branch to correct seismic predictions.

Abstract

We document the arrival of seismic energy in the core shadow zone up to large distances beyond 150° more than 100 s prior to the core phases. Numerical simulations of the energy transport in an established heterogeneity model show that scattering throughout the entire mantle explains these observations. Diffraction at the core-mantle boundary is unlikely in our 1–2 Hz frequency band and is not required indicating misleading terminology with reference to P diff for the scattered P∗P-energy. Records of the largest deep earthquakes at low-noise stations are key to the observation of the faint precursory signal which changes appearance with increasing distance from a coda-like decay over a constant amplitude level around 130° to an emergent wave train. According to our simulations, different depth layers in the mantle dominate different time-distance windows of the scattered wave train, providing the opportunity to improve the depth resolution of mantle heterogeneity models.

Abstract

Additional ionospheric information is essential for mitigating errors in single-frequency (SF) Global Navigation Satellite Systems (GNSS) positioning. The increasing number of low-cost dual-frequency (DF) receiver users faces limitations in tracking DF observables compared to traditional geodetic receivers. Consequently, ionospheric correction algorithms (ICAs) are also essential for low-cost DF devices in hybrid-frequency positioning. To evaluate the performance of commonly used ICAs during solar cycle 25, our study presents a global statistical investigation of the contribution of five broadcast ionospheric models (BIMs) and the International GNSS Service (IGS) combined real-time global ionospheric maps (IRTG) to the positioning domain, covering both quiet and perturbed ionospheric conditions. The BIMs investigated include the GPS Klobuchar (GPSK), Galileo NequickG (NEQG), NTCM-GlAzpar (NTCMG), BDS-2 Klobuchar (BDSK), and BeiDou Global Ionospheric delay correction Model (BDGIM). Experimental results from standard point positioning indicate that IRTG demonstrates superior overall accuracy compared to all BIMs, with a mean 3D root mean squared (RMS) of 2.76 m during perturbed period. Specifically, GPSK, NTCMG, NEQG, BDGIM, and BDSK exhibit RMS values of 2.03, 1.67, 1.72, 1.62, and 2.36 m during quiet conditions, and 4.02, 3.17, 2.86, 3.14, and 4.44 m during perturbed conditions, respectively. Among the BIMs, NEQG demonstrates superior performance at middle and high latitudes but exhibits lower accuracy than NTCMG and BDGIM at low latitudes during daytime under quiet conditions. BDGIM performs slightly better than NTCMG at low latitudes but slightly worse at high latitudes. BDSK shows notable improvement for high- and mid-latitude regions since 3 June 2020.

Abstract

This paper presents an alternative approach to improve the achievable beam scan angle of a traditional multi-beam waveguide lens antenna. Due to the focusing mechanism by manipulating the geometrical curvatures of the waveguide lens, the angular scan range is limited in the conventional waveguide lens design using dual-focal points of excitations because the geometrical curvatures of the waveguide lens only provide two design freedoms. To overcome this limitation, a solution of treating the waveguide lens as a transmit array consisting of non-identical elements is proposed so that each element of the antenna array can be well calibrated to improve the maximum scan angular range, where a third focus point of excitation can be created by adding another design freedom from the differentiation between non-identical elements. Each element of this new transmitting array can be well calibrated with the help of a mathematical expression to improve the maximum angular scan range. Numerical simulations show that the proposed antenna architecture exhibits better radiation characteristics than the traditional waveguide lens antenna. Radiation characteristics are studied and compared for both types of lens antennas to validate the design concept. The proposed triple-focal point provides a higher gain than the traditional lens antenna with fewer antenna elements. The gains of the beams at ±10°, ±20°, ±30°, and ±40° are found to be 27.78, 26.94, 26.19, and 24.04 dBi, respectively. From the comparison, it is seen that the variation in gain by the proposed triple-focal array design is more stable than the conventional dual-focal point design.

Abstract

We use MHD simulations to study the time sequence of magnetospheric responses to a synthetic event with a southward interplanetary magnetic field (IMF) turning. The onset of dayside magnetopause reconnection launches a weak rarefaction wave and sunward flow in the equatorial magnetosphere simultaneously with a tailward flow through the polar cap. This convection results in the accumulation of magnetic flux in the tail lobes and thinning of the tail current layer which provides favorable conditions for the onset of nightside reconnection. The onset of nightside reconnection about 40 min later closes the Dungey convection cycle, resulting in a second increase in the sunward flow in the equatorial plane. Variations of the magnetopause standoff distance as well as the size of the polar cap (PC) may indicate the onsets of the dayside and nightside reconnections. We compare the results of two MHD models and discuss their differences.

Abstract

Utilizing magnetic field measurements made by the Iridium satellites and by ground magnetometers in North America we calculate the full ionospheric current system and investigate the substorm current wedge. The current estimates are independent of ionospheric conductance, and are based on estimates of the divergence-free (DF) ionospheric current from ground magnetometers and curl-free (CF) ionospheric currents from Iridium. The DF and CF currents are represented using spherical elementary current systems (SECS), derived using a new inversion scheme that ensures the current systems' spatial scales are consistent. We present 18 substorm events and find a typical substorm current wedge (SCW) in 12 events. Our investigation of these substorms shows that during substorm expansion, equivalent field-aligned currents (EFACs) derived with ground magnetometers are a poor proxy of the actual FAC. We also find that the intensification of the westward electrojet can occur without an intensification of the FACs. We present theoretical investigations that show that the observed deviation between FACs estimated with satellite measurements and ground-based EFACs are consistent with the presence of a strong local enhancement of the ionospheric conductance, similar to the substorm bulge. Such enhancements of the auroral conductance can also change the ionospheric closure of pre-existing FACs such that the ground magnetic field, and in particular the westward electrojet, changes significantly. These results demonstrate that attributing intensification of the westward electrojet to SCW current closure can yield false understanding of the ionospheric and magnetospheric state.

Abstract

Given the important role of Atmospheric River precipitation (ARP) in the global hydrological cycle, accurate representation of ARP is significant. However, general circulation models (GCMs) demonstrate bias in simulating ARP. The target of this study is to quantify the performance of ARP intensity/frequency for CMIP6 simulations, and further to improve ARP estimation of CMIP6 using Cycle-Consistent Generative Adversarial Networks (CycleGAN) with highlighting the more accurate ARP features under the global warming background. The findings of this study are as follows: (a) although ARP intensity/frequency in reserved-optimal CMIP6 overall reproduces the observation, it is still underestimated at the stronger Atmospheric river (AR) scales, particularly for the AR highly active mid-latitude regions. (b) The CycleGAN-based bias correction approach markedly diminishes the bias of the CMIP6 simulations within most of the AR scales among both global and the four AR highly active regions. Moreover, the performance of the ARP in AR highly active regions is significant improvement, which is mainly due to the reduction of the bias at the strongest scale. (c) Relative to reference period (1986–2005), ARP intensity/frequency at the strongest scale increase notably under 3°C warming level, with an average value of 373.3% in intensity and 415.9% in frequency for global and the four key regions before correction, and the value is 451.9% and 492.5% after bias correction. The results illustrate that CycleGAN can effectively improve the ARP simulations of GCMs, and an early warning implies that future strong extreme ARP should potentially surpass the current expected.