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991.
Relationship Between the Western Pacific Subtropical High and the Subtropical East Asian Diabatic Heating During South China Heavy Rains in June 2005 下载免费PDF全文
Based on the daily NCEP/NCAR reanalysis data, the position variation of the western Pacific subtropical high (WPSH) in June
2005 and its relation to the diabatic heating in the subtropical East Asia are analyzed using the complete vertical vorticity
equation. The results show that the position variation of the WPSH is indeed associated with the diabatic heating in the subtropical
East Asian areas. In comparison with June climatology, stronger heating on the north side of the WPSH and relatively weak
ITCZ (intertropical convergence zone) convection on the south side of the WPSH occurred in June 2005. Along with the northward
movement of the WPSH, the convective latent heating extended northward from the south side of the WPSH. The heating to the
west of the WPSH was generally greater than that inside the WPSH, and each significant enhancement of the heating field corresponded
to a subsequent westward extension of the WPSH. In the mid troposphere, the vertical variation of heating on the north of
the WPSH was greater than the climatology, which is unfavorable for the northward movement of the WPSH. On the other hand,
the vertical variation of heating south of the WPSH was largely smaller than the climatology, which is favorable for the anomalous
increase of anticyclonic vorticity, leading to the southward retreat of the WPSH. Before the westward extension of the WPSH
in late June 2005, the vertical variation of heating rates to (in) the west (east) of the WPSH was largely higher (lower)
than the climatology, which is in favor of the increase of anticyclonic (cyclonic) vorticity to (in) the west (east) of the
WPSH, inducing the subsequent westward extension of the WPSH. Similar features appeared in the lower troposphere. In a word,
the heating on the north-south, east-west of the WPSH worked together, resulting in the WPSH extending more southward and
westward in June 2005, which is favorable to the maintenance of the rainbelt in South China. 相似文献
992.
Global ocean temperature has been rising since the late 1970s at a speed unprecedented during the past century of recordkeeping.This accelerated warming has profound impacts not only on the marine ecosystem and oceanic carbon uptake but also on the global water cycle and climate.During this rapid warming period,the tropical Pacific displays a pronounced La Nin a-like trend,characterized by an intensification of west-east SST gradient and of atmospheric zonal overturning circulation,namely the Walker circulation.This La Nin a-like trend differs from the El Nin o-like trend in warm climate projected by most climate models,and cannot be explained by responses of the global water cycle to warm climate.The results of this study indicate that the intensification of the zonal SST gradient and the Walker circulation are associated with recent strengthening of the upper-ocean meridional overturning circulation. 相似文献
993.
While many surface foraging seabirds ingest plastic, the spatial overlap of these far-ranging predators with debris aggregations at-sea is poorly understood. We surveyed concurrent distributions of marine birds and debris along a 4400 km cruise track within a debris accumulation area in the North East Pacific Ocean using line and strip transect methods. Analysis of debris and bird distributions revealed associations with oceanographic and weather variables at two spatial scales: daily surveys and hourly transects. Hourly bird abundance (densities; 0-9 birds km−2) was higher in lower wind and shallower water. Hourly debris abundance (densities; 0-15,222 pieces km−2) was higher in lower wind, higher sea-level atmospheric pressure and deeper water. These results suggest that debris and seabird abundance and community structure are influenced by similar environmental processes, but in opposing ways, with only three far-ranging seabird species (Black-footed Albatross, Cook’s Petrel and Red-tailed Tropicbird) overlapping with high debris concentrations over meso-scales. 相似文献
994.
A management proposal aims to partly remove a WWII military causeway at Palmyra Atoll to improve lagoon water circulation and alleviate sedimentation stress on the southeast backreef, an area of high coral cover and diversity. This action could result in a shift in sedimentation across reef sites. To provide management advice, we quantified the proximate environmental factors driving scleractinian coral cover and community patterns at Palmyra. The proportion of fine sedimentation was the optimal predictor of coral cover and changes in community structure, explaining 23.7% and 24.7% of the variation between sites, respectively. Scleractinian coral cover was negatively correlated with increases in fine sedimentation. Removing the causeway could negatively affect the Montipora corals that dominate the western reef terrace, as this genus was negatively correlated with levels of fine sedimentation. The tolerance limits of corals, and sediment re-distribution patterns, should be determined prior to complete removal of the causeway. 相似文献
995.
Guitart C Slattery M Ankisetty S Radwan M Ross SJ Letcher RJ Reddy CM 《Marine pollution bulletin》2011,62(3):631-636
Considerable debate surrounds the sources of oxygenated polybrominated diphenyl ethers (O-PBDEs) in wildlife as to whether they are naturally produced or result from anthropogenic industrial activities. Natural radiocarbon (14C) abundance has proven to be a powerful tool to address this problem as recently biosynthesized compounds contain contemporary (i.e. modern) amounts of atmospheric radiocarbon; whereas industrial chemicals, mostly produced from fossil fuels, contain no detectable 14C. However, few compounds isolated from organisms have been analyzed for their radiocarbon content. To provide a baseline, we analyzed the 14C content of four O-PBDEs. These compounds, 6-OH-BDE47, 2′-OH-BDE68, 2′,6-diOH-BDE159, and a recently identified compound, 2′-MeO-6-OH-BDE120, were isolated from the tropical marine sponges Dysidea granulosa and Lendenfeldia dendyi. The modern radiocarbon content of their chemical structures (i.e. diphenyl ethers, C12H22O) indicates that they are naturally produced. This adds to a growing baseline on, at least, the sources of these unusual compounds. 相似文献
996.
Laure Moulin Ana Isabel Catarino Thomas Claessens Philippe Dubois 《Marine pollution bulletin》2011,62(1):48-54
The effect of pH ranging from 8.0 to 6.8 (total scale - pHT) on fertilization, cleavage and larval development until pluteus stage was assessed in an intertidal temperate sea urchin. Gametes were obtained from adults collected in two contrasting tide pools, one showing a significant nocturnal pH decrease (lowest pHT = 7.4) and another where pH was more stable (lowest pHT = 7.8). The highest pHT at which significant effects on fertilization and cleavage were recorded was 7.6. On the contrary, larval development was only affected below pHT 7.4, a value equal or lower than that reported for several subtidal species. This suggests that sea urchins inhabiting stressful intertidal environments produce offspring that may better resist future ocean acidification. Moreover, at pHT 7.4, the fertilization rate of gametes whose progenitors came from the tide pool with higher pH decrease was significantly higher, indicating a possible acclimatization or adaptation of gametes to pH stress. 相似文献
997.
We investigated the plastics ingested by short-tailed shearwaters, Puffinus tenuirostris, that were accidentally caught during experimental fishing in the North Pacific Ocean in 2003 and 2005. The mean mass of plastics found in the stomach was 0.23 g per bird (n = 99). Plastic mass did not correlate with body weight. Total PCB (sum of 24 congeners) concentrations in the abdominal adipose tissue of 12 birds ranged from 45 to 529 ng/g-lipid. Although total PCBs or higher-chlorinated congeners, the mass of ingested plastic correlated positively with concentrations of lower-chlorinated congeners. The effects of toxic chemicals present in plastic debris on bird physiology should be investigated. 相似文献
998.
999.
1000.
The onset of South China Sea summer monsoon in 1998 occurred on May 21st. Using the U.S. National Centers for Environmental Prediction reanalysis data, this paper examines the physical process of the weakening of a subtropical anticyclone in West Pacific during the onset period using the Zwack-Okossi vorticity equation. Results show that during the pre-onset period, the positive vorticity advection in front of an upper tropospheric trough was the most dominant physical mechanism for the increase of the cyclonic vorticity on the 850-hPa layer over the South China Sea and its nearby region. The secondary contribution to the increase of the cyclonic vorticity was the warm-air advection. After the onset, the magnitude of the latent-heat warming term rapidly increased and its effect on the increase of the cyclonic vorticity was about the same as the positive-vorticity advection. The adiabatic term and divergence term contributed negatively to the increase of the cyclonic vorticity most of the time. Thus, the positive vorticity advection is the most important physical mechanism for the weakening of the West Pacific subtropical anticyclone over the South China Sea during the onset period. 相似文献