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Response of the tropical ocean to a uniform zonal wind is studied numerically and analytically. In addition to the Equatorial Undercurrent and surface westward flows on both sides of the equator, an eastward flow at the pycnocline depth is formed at several degrees latitude in both hemispheres. This subsurface eastward flow first appears in the eastern part of the ocean and extends to the west. Then it gradually decreases in speed, and at a steady state the speed is of the order of 1cm sec–1. The spatial distribution of this subsurface flow is similar to the Subsurface Countercurrent, but the speed is one order smaller than that observed. The obtained thermostad is obscure compared with that observed. Whole of the time evolution produced by a numerical model can be accounted for by linear wave dynamics in a multi-layer model including vertical diffusion and friction. Although diffusion and friction are essential to maintain this subsurface flow, changes in the values of coefficients for vertical viscosity and diffusivity and also in initial density stratification lead only to a minor change in the speed of the subsurface eastward flow. It is concluded that a subsurface eastward flow with speed exceeding 10 cm sec–1 accompanied by a distinctive thermostad structure cannot be explained by linear wave dynamics including vertical dissipation. 相似文献
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G. Spindler T. Gnauk A. Grüner Y. Iinuma K. Müller S. Scheinhardt H. Herrmann 《Journal of Atmospheric Chemistry》2012,69(2):127-157
Size-segregated particle samples were collected using a Berner 5-stage impactor (stages 1?C5: 0.05?C0.14?C0.42?C1.2?C3.5?C10???m aerodynamic diameter). The means for all 169?days and for different categories of days were used for a characterization. The sorting criteria were (a) the distinction between winter (Wi, November to April) and summer (Su, May to October), (b) the distinction between air mass inflow from a sector West (W, 210?°?C320?°) and from a sector East (E, 35?°?C140?°). For the assignment of the air mass origin 96-h backward trajectories were used and four categories (WiW, WiE, SuW and SuE) with 48, 18, 42 and 29?days were established. The lowest mean particle mass concentrations were found for SuW and the highest for WiE with relative mass concentration distributions of 5.9, 28.2, 36.5, 18.0, and 11.4?% and 3.5, 22.7, 52.6, 16.7, and 4.5?% for stages 1?C5, respectively. The mass closure for water soluble ions, water, organic material (OM) and elemental carbon (EC) accounts for 81?C99?% of the gravimetric mass in Wi and for 60?C81?% for Su, depending on the stage. The fractions of nitrate were relatively high for WiW while sulphate fractions are high for WiE. The estimated concentrations of secondary organic carbon (SOA) on stage 3 for WiW, WiE, SuW and SuE were 0.32, 1.25, 0.27 and 0.58???gm?3, respectively. The highest amount of SOA is found for WiE, representing 59?% of organic carbon (OC). The highest difference in the percentages of SOA in OC was found between winter (WiW 55?%, WiE 59?%) and summer (SuW and SuE 74?%) indicating photochemical processes during long-range transport. The mean Carbon Preference Indices (CPI) are highest for SuE (stage 4: 7.57 and stage 5: 9.82) resulting mainly from plant wax abrasion in the surrounding forests. For WiE the mean PAH concentration on stage 3 (9.7?ngm?3) is about five times higher than for WiW, indicating long range transport following domestic heating and other combustion processes. 相似文献
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The behavior of low density fresh water injected at the surface of a uniformly rotating saline water was investigated on the basis of a tank experiment. The injected water mass shows a clockwise circulation and grows gradually with an axisymmetric convex shape, until it breaks into two vortices at a critical size. An experimental formula for the change of radius of the water mass with time for the axisymmetric stage is obtained. It is shown that within our experimental range of values the radius of the water mass increases almost in proportion tot 1/2, wheret is the elapse time, while the inviscid theory indicates that the radius should increase in proportion tot 1/4. The dependence of the radius on elapse time is essential for forecasting the extent of discharged waters. The position of the maximum azimuthal velocity is fixed at \(V = - ge^{ - a^2 q^2 } \) within our experimental range of values wherer is the radial coordinate,f the Coriolis parameter,v the viscosity coefficient andQ the flow rate of injection, respectively. This radius corresponds to the radial scale derived by Gillet al. (1979). The steadiness of the position of the maximum azimuthal velocity may be essential in partition of the water mass into inner and outer regions and in the understanding the derived experimental formula. The critical radius for breaking is also investigated. The radius is shown to be independent ofQ and to be almost proportional to (Δ ρ / ρ )1/2 f -1 whereρ is the density of the saline water andΔρ the density difference between the saline and injected waters. Even after the water supply is cut off in the axisymmetric stage, the radius of the water mass increases at almost the same rate as before, while its thickness decreases. The behavior after supply cut-off is discussed in the Appendix. 相似文献
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Long-Term Variability of North Pacific Subtropical Mode Water in Response to Spin-Up of the Subtropical Gyre 总被引：1，自引：0，他引：1
The Meteorological Research Institute's ocean general circulation model (MRI-OGCM) has been used to investigate the temperature
variability of the North Pacific Subtropical Mode Water (NPSTMW) over a time series longer than 5 years via the spin-up of
the subtropical gyre. Besides an interannual variation, the wintertime sea surface temperature in the area where the NPSTMW
is formed, and the temperature of the NPSTMW itself, both change remarkably in a >5-year time scale. An analysis of heat budgets
showed that the long-term changes in NPSTMW temperature are due mainly to a leading advection of heat by the Kuroshio Extension
and compensating surface heat flux. As a result of a dynamical adjustment to the wind stress fields, the transports of the
Kuroshio and the Kuroshio Extension increased in the mid 1970s with a lag of 3 years after the wind stress curl in the central
North Pacific. The increased heat advection by the Kuroshio Extension induces a warming in the mixed layer in the NPSTMW formation
area, followed by a warming of the NPSTMW itself. Both these warming actions increase the heat release to the atmosphere.
These results imply that the surface heat flux over the Kuroshio Extension area varies in response to the change in the ocean
circulation through the spin-up of the subtropical gyre.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Summary. The thickening plate theory proposed by Yoshii and Parker & Oldenburg for the oceanic lithosphere is extended to include the continental lithosphere. The theory is based on the assumption that the lithosphere—asthenosphere boundary is a solidus and that as a result solidification of the top of the asthenosphere is occurring. Observational data imply that the relationship between the plate thickness and basement age for the North American continent is y = 1.7 √ t + (50 ± 10), where y (km) is the plate thickness and t (Myr) is the basement age.
The theory is tested against changes with basement age of the observed surface heat-flow and seismic estimate of plate thickness. The following conclusions are inferred:
(1) The changes both of the observed heat flow and plate thickness with basement age are explained by this theory.
(2) The surface erosion and vertical distribution of radiogenic heat sources are important factors in controlling the thickening process of the continental lithosphere.
(3) The equality of the average surface heat-flow over the oceans and over the continents is a consequence of a faster release of latent heat at the lithosphere—asthenosphere boundary under the oceans, instead of a higher heat production in the continental crust. 相似文献
The theory is tested against changes with basement age of the observed surface heat-flow and seismic estimate of plate thickness. The following conclusions are inferred:
(1) The changes both of the observed heat flow and plate thickness with basement age are explained by this theory.
(2) The surface erosion and vertical distribution of radiogenic heat sources are important factors in controlling the thickening process of the continental lithosphere.
(3) The equality of the average surface heat-flow over the oceans and over the continents is a consequence of a faster release of latent heat at the lithosphere—asthenosphere boundary under the oceans, instead of a higher heat production in the continental crust. 相似文献
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R. Hino D. Inazu Y. Ohta Y. Ito S. Suzuki T. Iinuma Y. Osada M. Kido H. Fujimoto Y. Kaneda 《Marine Geophysical Researches》2014,35(3):181-190
Ocean-bottom pressure records obtained near the epicenter of the 2011 Tohoku-Oki earthquake were examined to test whether the earthquake was preceded by substantial precursory crustal deformation. The seafloor data enabled us to search for small-scale preslip near the epicenter that would be difficult to identify from terrestrial geodetic data. After treating the data to reduce nontectonic fluctuations, we obtained a time series of seafloor vertical deformation in the epicentral region with a noise level of 2–4 cm. No significant crustal deformation related to preslip was detected in the period of roughly a day before the mainshock, whereas postseismic deformation associated with the largest foreshock 2 days before the mainshock was apparent. From our quantitative estimate of the sensitivity of the seafloor network in detecting slip on the plate interface, we conclude that the Tohoku-Oki earthquake was not preceded by preslip with moment release greater than moment magnitude (Mw) 6.2 in the vicinity of the hypocenter or greater than Mw 6.0 along the subduction interface near the trench. 相似文献
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XU Jiren ZHAO Zhixin Institute of Geology Chinese Academy of Geological Science Beijing China Kono Yoshiteru Faculty of Science Kanazawa University Kanazawa - Japan 《Continental Dynamics》2000,(1)
1. IntroductionThe Nankai Trough region (Fig. 1.1) of southwest Japan is one of the most tectonically complex subduction zones in the world. The subduction of the Philippine Sea plate (PH) beneath the Eurasian plate (EU) has caused a series of large and great interplate earthquakes. It is generally accepted that great earthquakes have occurred at intervals of 100-150 years along the Nankai subduction zone since the 684 Hakuho earthquake (Fig. 1.2). However, a large earthquake (M>7.5) has… 相似文献
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