地球科学最新文献

An algorithm for obtaining ion vector velocities and neutral winds in the lower thermosphere (100–150 km) was applied to the Sanya incoherent scatter radar (SYISR; located at 18.3°N, 109.6°E) for the first time. The observational experiment transmitted alternating code pulses with a code width of 20 μs. The ion vector velocities and neutral winds were derived from multiple-beam line-of-sight ion velocities. To verify the reliability, we first analyzed the variations and errors of the ion vector velocity and the neutral wind at different time scales. Then, we used an empirical model (HWM) and a theoretical model (NCAR-TIEGCM) for comparison. Both comparisons exhibited good consistency in terms of neutral wind velocity. Furthermore, we compared the SYISR neutral winds with the meteor radar and ICON/MIGHTI winds. The zonal (meridional) wind speeds of the meteor radar and SYISR are 24.95 m/s (13.95 m/s) and 20.68 m/s (16.85 m/s), respectively, at 6:30 LT at 100 km. The amplitudes and phases of the tides derived from the SYISR data are in accordance with those of the meteor radar. The ICON/MIGHTI and SYISR showed consistencies in terms of the wind velocity when ignoring interannual variation.

During the summer season, deep convection over the central United States has a significant impact on the dynamics and composition of the upper troposphere and lower stratosphere (UTLS). These storms transport tropospheric air containing trace gases, ice particles, and aerosols into the UTLS, which can affect chemical and radiative processes over a large region. Because overshooting storms necessarily have strong updrafts, there is a marked correlation between overshooting and the occurrence of severe weather at the surface. Heat released by these storms also helps to drive the North American Monsoon Anticyclone (NAMA) in the UTLS, which partially confines air injected into the stratosphere by overshooting storms. In support of the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) project, this study is a climatological analysis of the environmental factors that affect the occurrence of deep and overshooting storms. Using hourly analyses of overshooting storms based on GridRad radar data and ERA5 reanalyzes, we focus on the roles of convective available potential energy (CAPE), convective inhibition (CIN), jet location, and other relevant dynamical and thermodynamic variables. The results show that northward intrusion of airmasses containing moist high CAPE air from the Gulf of Mexico into the central plains plays a major role in producing the conditions necessary for overshooting storms with other factors playing secondary roles.

Faulting and folding of basement rocks together accommodate convergence within continental orogens, forming complex zones of intraplate deformation shaped by the fault interaction. Here we use the river terraces along the Dongda river to examine the tectonic deformation patterns of the hinterland and the foreland of the eastern North Qilian Shan, a zone of crustal shortening located at the northeast margin of the Tibetan Plateau. Five Late Pleistocene–Holocene terraces of Dongda river are displaced by three major reverse faults: Minle-Damaying fault, Huangcheng-Ta'erzhuang fault, and Fengle fault, from south to north. Based on displaced terrace treads, we estimated vertical slip rates along the Minle-Damaying fault as 0.7–0.8 mm/a, and along the Fengle fault as 0.5–0.7 mm/a. Deformed terraces suggest an additional uplift of ∼0.2 mm/a through the folding of the Dahuang Shan anticline. Inhomogeneous uplift of the intermontane basins between the Minle-Damaying fault and the Dahuang Shan anticline indicates a 0.9 ± 0.2 mm/a uplift rate along the Huangcheng-Ta'erzhuang fault. Kinematic modeling of this thrust system shows that deformation propagated northward toward the foreland along a south-dipping 10° décollement rooted into the Haiyuan fault at the depth of ∼20 km. This system accommodates 2.7–3.4 mm/a total crustal shortening rate. We suggest this broad thrust belt and the relatively high rate of shortening within this part of the eastern Qilian Shan is a result of the oblique convergence along a restraining bend of Haiyuan fault system. The elevated shortening rate within this area indicates high potential seismic hazard.

Lunar mare basalts represent melting of mantle material, buoyant ascent in dikes, and eruption onto <20% of the surface. Global mare distribution is distinctly asymmetrical, with a paucity on the farside, plausibly interpreted to be related to thicker farside low-density crust inhibiting buoyant magma rise to the surface. Challenging this hypothesis is the presence of the huge, ancient farside South Pole-Aitken (SPA) basin, site of the thinnest crust and deepest depression observed on the Moon. We hypothesize that an oblique impact stripped the farside crust within the SPA basin, permitting early mare basalt emplacement as cryptomaria due to thin/absent crust. However, removal of the SPA thermally insulating megaregolith/crust accelerated lithosphere thickening beneath the basin. This deepening rheological barrier inhibited buoyant rise of mantle diapirs below SPA, resulting in early abatement of mare basalt extrusions compared to the nearside, and retention of the deep, underfilled SPA impact basin observed today.