ALBERT

Description: Based on observations of Van Allen Probe‐A during the period from 19 September 2012 to 28 February 2016, the relations of the fast magnetosonic (MS) wave amplitude Bw with kp index, the wave normal angle (WNA), and the wave normalized frequency (norF) are presented. Then, we establish an analytical regression model for MS wave amplitude as a function of geomagnetic storm activity (presented by kp index), L‐shell (L), magnetic local time (MLT), magnetic latitude (λ), and the characteristics of MS wave, that is, wave norF and WNA. From the analytical Bw models, we found MS wave amplitude Bw has a positive relation with the intensity of geomagnetic activities both inside and outside the plasmapause, while the Bw can reach higher values inside the plasmapause than it does outside the plasmapause as the kp index increases. The Bw distribution on the norF demonstrates that most of the wave energies are concentrated on the lower harmonics part, which results from the excitation mechanism of MS waves. In addition, the Bw distribution on the WNA shows that the waves with larger normal angles have higher values of wave amplitude. Our analytic MS wave model agrees with the observed distribution in 3‐D space of L, MLT, and λ well with high value of determine coefficient R2. The extended λ dimension will help us to calculate the more accurate bounced averaged diffusion coefficients during particles transit time.

Description: The accuracy of flood forecasting plays a critical role in flood control operations. It is challenging to reduce flood risk and inform decision-making by adjusting reservoir scheduling strategies under forecasting uncertainty. This study developed a many-objective robust optimization methodology for real-time reservoir flood control operation. Three different machine learning (ML) models were adopted to forecast short-term reservoir inflow and a stacking ensemble multi-ML model (SEM) was then applied to integrate the results. Furthermore, this study established a robust optimal operation model (MOROU) to reduce flood risks and assess the impact of forecast uncertainty on reservoir operation. To improve the efficiency of reservoir utilization, a new indicator called reservoir reserved capacity adaptation (RRCA) was defined and used as one of optimization objectives in MOROU. A scenario to point (STP) method was proposed for searching for robust solutions to solve complex many-objective problems. Methodologies were validated through an application to the Lishimen reservoir, China. The main findings are: (1) all three ML models performed well in flood forecasting, and the SEM model was validated to be able to combine the characteristics of multiple models. (2) MOROU model showed a much narrower distribution for both upstream and downstream flood risks and succeeded in reducing the highest water level by about 1.5%. (3) It was proven that the RRCA could reduce the reservoir discharge flow by an average of 4.52% without taking additional flood control capacity. The findings have significance for searching for robust solutions of real-time reservoir flood control under forecast uncertainty.

Description: An earthquake doublet occurred in the offshore region of Fukushima on 13 February 2021 (Mw 7.1) and 16 March 2022 (Mw 7.3). The joint inversions of strong-motion and teleseismic waveforms reveal that both earthquakes belong to intraslab events, and the unilateral ruptures of the 2021 and 2022 events propagate southwestward and northeastward, respectively. Both events are dominated by thrust motions, and major fault slips are mainly localized away from the rupture initiating area. The geometries and locations of the two seismogenic faults suggest that the Fukushima-Oki doublet arises from the reactivations of two preexisting bending-related faults inside the subducting Pacific plate, which is driven by the downdip compressional stress regime caused by plate unbending. Furthermore, the regional tectonic settings indicate a complicated seismogenic environment for the Fukushima-Oki doublet, in which the dehydration embrittlement and seamount subduction are likely to play significant roles. Additionally, the distinctive rupture patterns of both events are also associated with the variation of fluid content and the small-scale structure of a slab slice enclosed by the two seismogenic faults within the subducting plate, which might control the heterogenous distributions of fault slips and aftershocks. The analysis of Coulomb failure stress changes suggests that the 2021 event and the 2022 foreshock collectively increase the stress loading, which may facilitate the occurrence of the 2022 mainshock, and the seismicity of the seismic belt consisting of the three intraslab sequences following the great 2011 Tohoku-Oki earthquake is also likely to retain active in the future.

Description: This article investigates the second-order consensus issue for multiagent systems subject to both limited communication resources and replay attacks. First, an asynchronous dynamic edge event-triggered (DEET) communication scheme is developed to reduce the utilization of network resources in the absence of attacks. Then, we further consider the case of replay attacks launched by multiple adversaries, under which the transmitted information is maliciously replaced by a previous unnecessary message. To overcome the impact caused by replay attacks, a modified DEET scheme and an effective attack-resilient consensus protocol are well constructed, both of which successfully guarantee second-order consensus in the presence of replay attacks. In addition, internal dynamic variables are utilized in the proposed DEET schemes such that the triggering time sequence does not exhibit Zeno behavior. Finally, one numerical example is provided to illustrate our theoretical analysis.

Description: A new resilient distributed secondary control for AC microgrids is studied based on event-triggered mechanisms and trust-reputation evaluation methods. When distributed generators (DGs) in a microgrid are subject to attacks, their transmitted state information would be tampered and thus affect the dynamics of normal generators. In order to isolate possible attacks, two types of trust evaluation metrics with different attack indices and time scales are designed, by which the performance of neighboring DGs can be assessed for specific practical demands. Based on the trust values of each neighbor, a reputation-propagation method is introduced at triggered time instants to determine whether a DG is under attack by comprehensively incorporating the opinion of mutual neighbors. The dynamic updating law of the communication edge weights is utilized with the derived reputation values. Based on this, a distributed Zeno-free event-triggered control protocols for voltage/frequency restoration and active power sharing are proposed. Sufficient conditions for picking proper control parameters are given in the main theorem. Lastly, the simulations are conducted in MATLAB/SimPowerSystems for several scenarios to validate the effectiveness of the proposed algorithms.

Description: Aerosol optical properties were studied over Chisinau in Moldova, one of the longest running AERONET sites in Eastern Europe. During two decades (September 1999–November 2018), the mean aerosol optical depth (AOD) and Angstrom exponent (AE) were observed as 0.21 ± 0.13 and 1.49 ± 0.29, respectively. The highest AOD (0.24 ± 0.13) and AE (1.60 ± 0.26) were observed during the summer. More than half (∼55%) of the share was occupied by clean continental aerosols with seasonal order of winter (74.8%) 〉 autumn (62%) 〉 spring (48.9%) 〉 summer (44.8%) followed by mixed aerosols with a respective contribution of 30.7% (summer), 28.4% (spring), 22.5 (autumn) and 16.4% (winter). A clear dominance of volume size distribution in the fine mode indicated the stronger influence of anthropogenic activities resulting in fine aerosol load in the atmosphere. The peak in the fine mode was centered at 0.15 μm, whereas that of the coarse mode was centered either at 3.86 μm (summer and autumn) or 5.06 μm (spring and winter). ‘Extreme’ aerosol events were observed during 21 days with a mean AOD (AE) of 0.99 ± 0.32 (1.43 ± 0.43), whereas ‘strong’ events were observed during 123 days with a mean AOD (AE) of 0.57 ± 0.07 (1.44 ± 0.40), mainly influenced by anthropogenic aerosols (during 19 and 101 days of each event type) from urban/industrial and biomass burning indicated by high AE and fine mode fraction. During the whole period (excluding events days), the fine and coarse mode peaks were observed at the radius of 0.15 and 5.06 μm, which in the case of extreme (strong) events were at 0.19 (0.15) and 3.86 (2.24) μm respectively. The fine mode volume concentration was 4.78 and 3.32 times higher, whereas the coarse mode volume concentration was higher by a factor of 1.98 and 2.27 during extreme and strong events compared to the whole period.

Description: Ground-based observational characterization of atmosphere aerosols over Central Asia is very limited. This study investigated the columnar aerosol characteristics over Issyk-Kul, Kyrgyzstan, a background site in Central Asia using the long-term (∼14 years: August 2007–November 2021) data acquired with the Cimel sunphotometer. The mean aerosol optical depth (AOD) and Ångström exponent (AE) during the observation period were 0.14 ± 0.10 and 1.19 ± 0.41, respectively. Both AOD and AE varied across seasons, with highest AOD in spring (0.17 ± 0.17). Regarding the aerosol types, clean continental aerosols were dominant type (65%), followed by mixed aerosols (∼19%), clean marine aerosols (∼14%), dust (0.8%), and urban/industrial and biomass burning aerosol (0.7%). The aerosol volume size distribution was bimodal indicating the influence of both anthropogenic and natural aerosols with clear dominance of coarse mode during the spring season. Mainly dust and mixed aerosols were present during high aerosol episodes while the coarse mode aerosol volume concentration was 7.5 (strong episodes) and ∼19 (extreme episodes) times higher than the whole period average. Aerosol over this background sites were from local and regional sources with some contribution of long-range transport.