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A general pattern for turbulent mixing in the upper layer of the South China Sea (SCS) is presented based on TurboMAP measurements in April and May 2010. The turbulence level decreased significantly overall from north to south, and weakened from east to west in the northern SCS. The average dissipation rate north of 18°N reaches 1.69 × 10?8 W/kg, approximately six times larger than that south of 18°N. The mean mixing efficiency in the SCS is 0.2, with a maximum of 0.31 near the Luzon Strait. At one repeatedly occupied station located in the central deep basin, the dissipation rate varies diurnally in the mixed layer and pycnocline due to diurnal heating and cooling by solar radiation and local barotropic tide, respectively. 相似文献
94.
Anatoly?AleksaninEmail author Vladimir?Kim Vasily?Kachur 《Journal of Oceanography》2016,72(5):801-810
Microwave satellite images used for retrieving sea surface temperatures often have such distortions as noise and blurring of the thermal fronts. An image processing approach based on the Mumford-Shah model of optimal image approximation is considered for the solution to this problem. We divide images into flat areas and frontal zones, and then process these areas separately. Image fragmentation is based on automatic detection of the thermal front lines. SST enhancement in frontal zones is achieved by using image deconvolution methods. It has been shown that SST errors in high gradient areas reach 1–3 °C. The proposed approach can decrease this discrepancy. 相似文献
95.
Yoshihisa?MinoEmail author Chiho?Sukigara Makio?C.?Honda Hajime?Kawakami Kazuhiko?Matsumoto Masahide?Wakita Minoru?Kitamura Tetsuichi?Fujiki Kosei?Sasaoka Osamu?Abe Jan?Kaiser Toshiro?Saino 《Journal of Oceanography》2016,72(6):819-836
Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ 15N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ 15N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ 15N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ 15N(SUS) signature was reflected by δ 15N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ 15N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ 15N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ 15N(DST) vs. PP regression to δ 15N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully. 相似文献
96.
Zhao-Jun?LiuEmail authorView authors OrcID profile Shoshiro?Minobe Yoshi?N.?Sasaki Mio?Terada 《Journal of Oceanography》2016,72(6):905-922
The future regional sea level (RSL) rise in the western North Pacific is investigated by dynamical downscaling with the Regional Ocean Modeling System (ROMS) with an eddy-permitting resolution based on three global climate models—MIROC-ESM, CSIRO-Mk3.6.0, and GFDL-CM3—under the highest greenhouse-gas emission scenario. The historical run is forced by the air-sea fluxes calculated from Coordinated Ocean Reference Experiment version 2 (COREv2) data. Three future runs—ROMS-MIROC, ROMS-CSIRO, and ROMS-GFDL—are forced with an atmospheric field constructed by adding the difference between the climate model parameters for the twenty-first and twentieth century to fields in the historical run. In all downscaling, the RSL rise along the eastern coast of Japan is generally half or less of the RSL rise maxima off the eastern coast. The projected regional (total) sea level rises along the Honshu coast during 2081–2100 relative to 1981–2000 are 19–25 (98–104), 6–15 (71–80), and 8–14 (80–86) cm in ROMS-MIROC, ROMS-CSIRO, and ROMS-GFDL, respectively. The discrepancies of the RSL rise along the Honshu coast between the climate models and downscaling are less than 10 cm. The RSL changes in the Kuroshio Extension (KE) region in all downscaling simulations are related to the changes of KE (northward shift or intensification) with climate change. 相似文献
97.
In the southwestern United States, precipitation in the high mountains is a primary source of groundwater recharge. Precipitation patterns, soil properties and vegetation largely control the rate and timing of groundwater recharge. The interactions between climate, soil and mountain vegetation thus have important implications for the groundwater supply. This study took place in the Sacramento Mountains, which is the recharge area for multiple regional aquifers in southern New Mexico. The stable isotopes of oxygen and hydrogen were used to determine whether infiltration of precipitation is homogeneously distributed in the soil or whether it is partitioned among soil-water ‘compartments’, from which trees extract water for transpiration as a function of the season. The results indicate that “immobile” or “slow” soil water, which is derived primarily from snowmelt, infiltrates soils in a relatively uniform fashion, filling small pores in the shallow soils. “Mobile” or “fast” soil water, which is mostly associated with summer thunderstorms, infiltrates very quickly through macropores and along preferential flow paths, evading evaporative loss. It was found that throughout the entire year, trees principally use immobile water derived from snowmelt mixed to differing degrees with seasonally available mobile-water sources. The replenishment of these different water pools in soils appears to depend on initial soil-water content, the manner in which the water was introduced to the soil (snowmelt versus intense thunderstorms), and the seasonal variability of the precipitation and evapotranspiration. These results have important implications for the effect of climate change on recharge mechanisms in the Sacramento Mountains. 相似文献
98.
Corner-point gridding is widely used in reservoir and basin modeling but generally yields approximations in the representation of geological interfaces. This paper introduces an indirect method to generate a hex-dominant mesh conformal to 3D geological surfaces and well paths suitable for finite-element and control-volume finite-element simulations. By indirect, we mean that the method first generates an unstructured tetrahedral mesh whose tetrahedra are then merged into primitives (hexahedra, prisms, and pyramids). More specifically, we focus on determining the optimal set of primitives that can be recombined from a given tetrahedral mesh. First, we detect in the tetrahedral mesh all the feasible volumetric primitives using a pattern-matching algorithm (Meshkat and Talmor Int. J. Numer. Meth. Eng. 49(1-2), 17–30 2000) that we re-visit and extend with configurations that account for degenerated tetrahedra (slivers). Then, we observe that selecting the optimal set of primitives among the feasible ones can be formalized as a maximum weighted independent set problem (Bomze et al. 1999), known to be \(\mathcal {N}\mathcal {P}\)-Complete. We propose several heuristic optimizations to find a reasonable set of primitives in a practical time. All the tetrahedra of each selected primitive are then merged to build the final unstructured hex-dominant mesh. This method is demonstrated on 3D geological models including a faulted and folded model and a discrete fracture network. 相似文献
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