Submesoscale features and their interaction with fronts and internal tides in a high-resolution coupled atmosphere-ocean-wave model of the Bay of Bengal   总被引：1，自引：1，他引：0  

Tommy G. Jensen  Igor Shulman  Hemantha W. Wijesekera  Stephanie Anderson  Sherwin Ladner 《Ocean Dynamics》2018,68(3):391-410

Large freshwater fluxes into the Bay of Bengal by rainfall and river discharges result in strong salinity fronts in the bay. In this study, a high-resolution coupled atmosphere-ocean-wave model with comprehensive physics is used to model the weather, ocean circulation, and wave field in the Bay of Bengal. Our objective is to explore the submesoscale activity that occurs in a realistic coupled model that resolves mesoscales and allows part of the submesoscale field. Horizontal resolution in the atmosphere varies from 2 to 6 km and is 13 km for surface waves, while the ocean model is submesoscale permitting with resolutions as high as 1.5 km and a vertical resolution of 0.5 m in the upper 10 m. In this paper, three different cases of oceanic submesoscale features are discussed. In the first case, heavy rainfall and intense downdrafts produced by atmospheric convection are found to force submesoscale currents, temperature, and salinity anomalies in the oceanic mixed layer and impact the mesoscale flow. In a second case, strong solitary-like waves are generated by semidiurnal tides in the Andaman Sea and interact with mesoscale flows and fronts and affect submesoscale features generated along fronts. A third source of submesoscale variability is found further north in the Bay of Bengal where river outflows help maintain strong salinity gradients throughout the year. For that case, a comparison with satellite observations of sea surface height anomalies, sea surface temperature, and chlorophyll shows that the model captures the observed mesoscale eddy features of the flow field, but in addition, submesoscale upwelling and downwelling patterns associated with ageostrophic secondary circulations along density fronts are also captured by the model.  相似文献   

Factors controlling high-frequency radiation from extended ruptures     

Igor A. Beresnev 《Journal of Seismology》2017,21(5):1277-1284

Small-scale slip heterogeneity or variations in rupture velocity on the fault plane are often invoked to explain the high-frequency radiation from earthquakes. This view has no theoretical basis, which follows, for example, from the representation integral of elasticity, an exact solution for the radiated wave field. The Fourier transform, applied to the integral, shows that the seismic spectrum is fully controlled by that of the source time function, while the distribution of final slip and rupture acceleration/deceleration only contribute to directivity. This inference is corroborated by the precise numerical computation of the full radiated field from the representation integral. We compare calculated radiation from four finite-fault models: (1) uniform slip function with low slip velocity, (2) slip function spatially modulated by a sinusoidal function, (3) slip function spatially modulated by a sinusoidal function with random roughness added, and (4) uniform slip function with high slip velocity. The addition of “asperities,” both regular and irregular, does not cause any systematic increase in the spectral level of high-frequency radiation, except for the creation of maxima due to constructive interference. On the other hand, an increase in the maximum rate of slip on the fault leads to highly amplified high frequencies, in accordance with the prediction on the basis of a simple point-source treatment of the fault. Hence, computations show that the temporal rate of slip, not the spatial heterogeneity on faults, is the predominant factor forming the high-frequency radiation and thus controlling the velocity and acceleration of the resulting ground motions.  相似文献   

Regional Flood Frequency Analysis Based on L-Moment Approach (Case Study Tisza River Basin)     

Igor Leščešen  Urošev  Marko  Dolinaj  Dragan  Pantelić  Milana  Telbisz  Tamás  Varga  György  Savić  Stevan  Milošević  Dragan 《Water Resources》2019,46(6):853-860

Water Resources - Floods are one of the most common natural hazards and as such, they are causing a great loss of human life as well as great economic damages. Flood frequency analysis (FFA) is...  相似文献   

Mobility and retention of heavy metals, arsenic and sulphur in podzols at eight locations in northern Finland and Norway and the western half of the Russian Kola Peninsula     

Marja Liisa Räisänen  Galina Kashulina  Igor Bogatyrev 《Journal of Geochemical Exploration》1997,59(3):175-195

The mobility and retention of heavy metals, arsenic and sulphur in podzols from eight areas located north of the Arctic Circle in Finland, Norway and Russia were determined by analyzing the < 2.0 mm fraction, using an ammonium acetate (pH 4.5) extraction in addition to a concentrated nitric acid digestion for the humus samples, and a hot aqua regia digestion for the mineral soil samples. Total C, H and N concentrations were determined in humus and mineral soil samples with a CHN analyser.Ni, Cu, Co and As were strongly enriched in the humus layer in the contaminated sites (Monchegorsk, Kurka, Zapoljarnij) when compared to their concentrations in the parent tills and in podzols from the background sites. In most study sites the illuvial layer showed a low capacity to retain the metals and As, the exception included a strongly eroded profile at Monchegorsk, where Ni was tightly fixed in the illuvial layer while Cu was mobile. In contrast to metals, airborne S was not accumulated in the humus layer, but was accumulated in the illuvial layer, more markedly at eroded sites than in places where the humus was covered as at Monchegorsk.  相似文献   

Study of the filamentary infrared dark cloud G192.76+00.10 in the S254–S258 OB complex     

Olga L.Ryabukhina  Igor I.Zinchenko  Manash R.Samal  Petr M.Zemlyanukha  Dmitry A.Ladeyschikov  ANDrej M.Sobolev  Christian Henkel  Devendra K.Ojha 《天文和天体物理学研究(英文版)》2018,(8)

We present results of a high resolution study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex in several molecular species tracing different physical conditions. These include three isotopologues of carbon monoxide(CO), ammonia(NH3) and carbon monosulfide(CS). The aim of this work is to study the general structure and kinematics of the filamentary cloud, and its fragmentation and physical parameters. The gas temperature is derived from the NH3(J, K) =(1,1),(2, 2) and ~(12)CO(2-1) lines, and the ~(13)CO(1-0), ~(13)CO(2-1) emission is used to investigate the overall gas distribution and kinematics. Several dense clumps are identified from the CS(2-1)data. Values of the gas temperature lie in the range 10-35 K, and column density N(H2) reaches the value 5.1 x 10~(22) cm~(-2). The width of the filament is of order 1 pc. The masses of the dense clumps range from ～ 30 M_☉ to ～ 160 M_☉. They appear to be gravitationally unstable. The molecular emission shows a gas dynamical coherence along the filament. The velocity pattern may indicate longitudinal collapse.  相似文献