ISSN  2096-3955

CN  10-1502/P

2022 Vol.6(3)

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Joint observation of the concentric gravity wave event on the Tibetan Plateau
Chang Lai, PengWei Li, JiYao Xu, Wei Yuan, Jia Yue, Xiao Liu, Kogure Masaru, LiLi Qian
2022, 6(3): 219-227. doi: 10.26464/epp2022029
A concentric gravity wave event was captured by a photographer in Nagarzê County (90.28°N, 28.33°E) between 02:00 and 04:00 (local time) on May 11, 2019. This concentric gravity wave event was also observed by the Suomi National Polar-orbiting Partnership satellite and the all-sky airglow imager at Yangbajing station (90.5°E, 30.1°N). The temporal and spatial information on gravity waves from the photographs provided a rare opportunity to study the propagation of gravity waves over the Tibetan Plateau. According to wind and temperature data from the MERRA-2 reanalysis (Modern-Era Retrospective analysis for Research and Applications, Version 2) and empirical models (NRLMSISE-00 [Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar Exosphere] and HWM [horizontal wind model]), we inversely derived the propagation trajectory from the observed wave pattern to the source region by using the ray-tracing method. The source of the concentric gravity wave was identified as deep convection in Bangladesh (90.6°E, 25.0°N). The maximum background wind speed in the propagation direction (31.05 m/s) was less than the phase speed of 53 m/s, which is consistent with the wind-filtering theory.
Runoff variations in the Yangtze River Basin and sub-basins based on GRACE, hydrological models, and in-situ data
WeiLong Rao, WenKe Sun
2022, 6(3): 228-240. doi: 10.26464/epp2022021
Water budget closure is a method used to study the balance of basin water storage and the dynamics of relevant hydrological components (e.g., precipitation, evapotranspiration, and runoff). When water budget closure is connected with terrestrial water storage change (TWSC) estimated from Gravity Recovery and Climate Experiment (GRACE) data, variations in basin runoff can be understood comprehensively. In this study, total runoff variations in the Yangtze River Basin (YRB) and its sub-basins are examined in detail based on the water budget closure equation. We compare and combine mainstream precipitation and evapotranspiration models to determine the best estimate of precipitation minus evapotranspiration. In addition, we consider human water consumption, which has been neglected in earlier studies, and discuss its impact. To evaluate the effectiveness and accuracy of the combined hydrological models in estimating subsurface runoff, we collect discharge variations derived from in situ observations in the YRB and its sub-basins and compare these data with the models’ final estimated runoff variations. The estimated runoff variations suggest that runoff over the YRB has been increasing, especially in the lower sub-basins and in the post-monsoon season, and is accompanied by apparent terrestrial water loss.
Theoretical calculation of tidal Love numbers of the Moon with a new spectral element method
BinBin Liao, XiaoDong Chen, JianQiao Xu, JiangCun Zhou, HePing Sun
2022, 6(3): 241-247. doi: 10.26464/epp2022025
The tidal Love numbers of the Moon are a set of nondimensional parameters that describe the deformation responses of the Moon to the tidal forces of external celestial bodies. They play an important role in the theoretical calculation of the Moon’s tidal deformation and the inversion of its internal structure. In this study, we introduce the basic theory for the theoretical calculation of the tidal Love numbers and propose a new method of solving the tidal Love numbers: the spectral element method. Moreover, we explain the mathematical theory and advantages of this method. On the basis of this new method, using 10 published lunar internal structure reference models, the lunar surface and lunar internal tidal Love numbers were calculated, and the influence of different lunar models on the calculated Love numbers was analyzed. Results of the calculation showed that the difference in the second-degree lunar surface Love numbers among different lunar models was within 8.5%, the influence on the maximum vertical displacement on the lunar surface could reach ±8.5 mm, and the influence on the maximum gravity change could reach ±6 μGal. Regarding the influence on the Love numbers inside the Moon, different lunar models had a greater impact on the Love numbers h2 and l2 than on k2 in the lower lunar mantle and core.
Neogene faulting and volcanism in the Victoria Land Basin of the Ross Sea, Antarctica
Mei Yue, JinYao Gao, ChunFeng Li, Chao Zhu, XinZhi Fan, Guochao Wu, ZhongYan Shen, Han Shi, XiaoXian Cai, YiDong Guo
2022, 6(3): 248-258. doi: 10.26464/epp2022023
The Neogene Terror Rift in the Antarctic Victoria Land Basin (VLB) of the Ross Sea, Antarctica, is composed of the Discovery Graben and the Lee Arch. Many Neogene volcanoes are aligned in the north-south direction in the southern VLB, belonging to the McMurdo Volcanic Group. However, due to multiple glaciations and limited seismic data, the volcanic processes are still unclear in the northern VLB, especially in the Terror Rift. Multichannel seismic profiles were collected at the VLB from the 32nd Chinese National Antarctic Research Expedition (CHINARE). We utilized four seismic profiles from the CHINARE and additional historical profiles, along with gravity and magnetic anomalies, to analyze faults and stratigraphic characteristics in the northern Terror Rift and volcanism in the VLB. Negative flower structures found in the northern Terror Rift suggest that the Terror Rift was affected by dextral strike-slip faults extending from the northern Victoria Land (NVL). After the initial orthogonal tension, the rift transited into an oblique extension, forming a set of downward concaving normal faults and accommodation zones in the Terror Rift. On the Lee Arch, several imbricated normal faults formed and converged into a detachment fault. Under gravitational forces, the strata bent upward and formed a rollover anticline. Many deep faults and thin strata subjected to erosion facilitated volcanic activity. A brittle volcanic region in the VLB was affected by dextral strike-slip movements and east-west extension, resulting in two Neogene volcanic chains that connect three igneous provinces in the VLB: the Hallett, Melbourne, and Erebus Provinces. These two chains contain mud volcanoes with magnetic nuclei, volcanic intrusions, and late-stage volcanic eruptions. Volcanisms have brought about opposite polarities of magnetic anomalies in Antarctica, indicating the occurrence of multiple volcanic activities.
Seismic attenuation compensation with spectral-shaping regularization
QiZhen Du, WanYu Wang, WenHan Sun, Li-Yun Fu
2022, 6(3): 259-274. doi: 10.26464/epp2022024
Because of the viscoelasticity of the subsurface medium, seismic waves will inherently attenuate during propagation, which lowers the resolution of the acquired seismic records. Inverse-Q filtering, as a typical approach to compensating for seismic attenuation, can efficiently recover high-resolution seismic data from attenuation. Whereas most efforts are focused on compensating for high-frequency energy and improving the stability of amplitude compensation by inverse-Q filtering, low-frequency leakage may occur as the high-frequency component is boosted. In this article, we propose a compensation scheme that promotes the preservation of low-frequency energy in the seismic data. We constructed an adaptive shaping operator based on spectral-shaping regularization by tailoring the frequency spectra of the seismic data. We then performed inverse-Q filtering in an inversion scheme. This data-driven shaping operator can regularize and balance the spectral-energy distribution for the compensated records and can maintain the low-frequency ratio by constraining the overcompensation for high-frequency energy. Synthetic tests and applications on prestack common-reflection-point gathers indicated that the proposed method can preserve the relative energy of low-frequency components while fulfilling stable high-frequency compensation.
On the source of the quasi-Carrington Rotation periodic magnetic variations on the Martian surface: InSight observations and modeling
Hao Luo, AiMin Du, ShaoHua Zhang, YaSong Ge, Ying Zhang, ShuQuan Sun, Lin Zhao, Lin Tian, SongYan Li
2022, 6(3): 275-283. doi: 10.26464/epp2022022
In a recent paper (Luo H et al., 2022), we found that the peak amplitudes of diurnal magnetic variations, measured during martian days (sols) at the InSight landing site, exhibited quasi Carrington-Rotation (qCR) periods at higher eigenmodes of the natural orthogonal components (NOC); these results were based on ~664 sols of magnetic field measurements. However, the source of these periodic variations is still unknown. In this paper we introduce the neutral-wind driven ionospheric dynamo current model (e.g., Lillis et al., 2019) to investigate the source. Four candidates — the draped IMF, electron density/plasma density, the neutral densities, and the electron temperature in the ionosphere with artificial qCR periodicity, are applied in the modeling to find the main factor likely to be causing the observed surface magnetic field variations that exhibit the same qCR periods. Results show that the electron density/plasma density, which controls the total conductivity in the dynamo region, appears to account for the greatest part of the surface qCR variations; its contribution reaches about 67.6%. The draped IMF, the neutral densities, and the electron temperature account, respectively, for only about 12.9%, 10.3%, and 9.2% of the variations. Our study implies that the qCR magnetic variations on the Martian surface are due primarily to variations of the dynamo currents caused by the electron density variations. We suggest also that the time-varying fields with the qCR period could be used to probe the Martian interior's electrical conductivity structure to a depth of at least 700 km.
A two-dimensional energy balance climate model on Mars
YaoKun Li, JiPing Chao
2022, 6(3): 284-293. doi: 10.26464/epp2022026
A two-dimensional energy balance climate model has been built to investigate the climate on Mars. The model takes into account the balance among solar radiation, longwave radiation, and energy transmission and can be solved analytically by Legendre polynomials. With the parameters for thermal diffusion and radiation processes being properly specified, the model can simulate a reasonable surface atmospheric temperature distribution but not a very perfect vertical atmospheric temperature distribution compared with numerical results, such as those from the Mars Climate Database. With varying solar radiation in a Martian year, the model can simulate the seasonal variation of the air temperature on Mars. With increasing dust content, the Martian atmosphere gradually warms. However, the warming is insignificant in the cold and warm scenarios, in which the dust mixing ratio varies moderately, whereas the warming is significant in the storm scenario, in which the dust mixing ratio increases dramatically. With an increasing albedo value of either the polar cap or the non-ice region, Mars gradually cools. The mean surface atmospheric temperature decreases moderately with an increasing polar ice albedo, whereas it increases dramatically with an increasing non-ice albedo. This increase occurs because the planetary albedo of the ice regions is smaller than that of the non-ice region.
Groove formation on Phobos from reimpacting orbital ejecta of the Stickney crater
XiangYu Xi, Min Ding, MengHua Zhu
2022, 6(3): 294-303. doi: 10.26464/epp2022027
Numerous linear grooves have long been recognized as covering the surface of Phobos, but the mechanisms of their formation are still unclear. One possible mechanism is related to the largest crater on Phobos, the Stickney crater, whose impact ejecta may slide, roll, bounce, and engrave groove-like features on Phobos. When the launch velocity is higher than the escape velocity, the impact ejecta can escape Phobos. A portion of these high-velocity ejecta are dragged by the gravitational force of Mars, fall back, and reimpact Phobos. In this research, we numerically test the hypothesis that the orbital ejecta of the Stickney crater that reimpact Phobos could be responsible for a particular subset of the observed grooves on Phobos. We adopt impact hydrocode iSALE-2D (impact-Simplified Arbitrary Lagrangian Eulerian, two-dimensional) to simulate the formation of the Stickney crater and track its impact ejecta, with a focus on orbital ejecta with launch velocities greater than the escape velocity of Phobos. The launch velocity distribution of the ejecta particles is then used to calculate their trajectories in space and determine their fates. For orbital ejecta reimpacting Phobos, we then apply the sliding boulder model to calculate the ejecta paths, which are compared with the observed groove distribution and length to search for causal relationships. Our ejecta trajectory calculations suggest that only ~1% of the orbital ejecta from the Stickney crater can reimpact Phobos. Applying the sliding boulder model, we predict ejecta sliding paths of 9−20 km in a westward direction to the east of the zone of avoidance, closely matching the observed grooves in that region. The best-fit model assumes an ejecta radius of ~150 m and a speed restitution coefficient of 0.3, consistent with the expected ejecta and regolith properties. Our calculations thus suggest the groove class located to the east of the zone of avoidance may have been caused by reimpact orbital ejecta from the Stickney crater.