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1.
《大气与海洋》2013,51(4):173-193
Abstract New observations in the Strait of Georgia, British Columbia, Canada show that temperature and dissolved oxygen have a pronounced seasonal cycle, with a spatially varying phase. Phase lags in oscillating systems arise due to internal time scales which can be interpreted in fluid systems as residence times. Exploiting phase we construct a quantitative and internally consistent circulation scheme for this body of water after dividing it into four regions: the Fraser River plume, the surface waters down to 50 m, the intermediate waters down to 200 m, and the deep water. In this scheme the intermediate water, the largest region by volume, is continually renewed, and its characteristics change in response to continuous changes in the characteristics of source waters. The dependence of the estuarine circulation on variations in fresh inflow is weak. The deep water is volumetrically less important, but seasonal changes in the density of oceanic source waters can produce a variation in the overall circulation by driving an additional inflow which leads to both deep renewal and increased upwelling. In turn, this increased upwelling results in lower surface temperatures than might otherwise be expected. Intermediate water residence times are about 160 days. Deep water is renewed once per year in summer and is affected only by vertical diffusion during the rest of the year. Surface water residence times for the entire Strait are a few months at most, but the Fraser River plume has a freshwater residence time of approximately 1 day. In addition, we find that the residence time of oceanic source waters in the Strait is 1.7 years due to a substantial recirculation in Haro Strait. Other consequences of this scheme are consistent with independent estimates of horizontal transports, air‐sea heat fluxes, subsurface oxygen (O2) utilization, and primary production. Finally, analysis of the spatial phase variations suggests that the intermediate inflow enters the Strait as a boundary current along the slopes of the Fraser delta. 相似文献
2.
A. G. Andreev 《Russian Meteorology and Hydrology》2010,35(9):633-640
The interannual variations of the sea level at the coastal stations of the Sea of Japan and of the water discharge through
the Korea (Tsushima) Strait are studied. It is demonstrated that the interannual variations of the water discharge through
this strait are determined by the water discharge of the Oyashio (in the subarctic Pacific) and the Kuroshio (in the East
China Sea) currents and by the zonal wind stress component over the Sea of Japan in winter period. It is revealed that the
variations in the East China Sea water transport through the Korea (Tsushima) Strait cause the interannual variations of the
dissolved oxygen content in intermediate (500 m) and deep (1000 m and more, σθ = 27.35) waters of the Sea of Japan. 相似文献
3.
Abstract The mid‐to‐bottom waters of the Labrador Shelf are shown to exhibit an anomalous along‐shelf temperature gradient, with warmer waters found in the north. This feature is present in summer and autumn but appears to reverse in December. Inadequate data are available during winter and spring to draw firm conclusions regarding this feature. A time averaged heat loss of the shelf waters to the atmosphere would result on average, in colder waters in the south (because of north‐south advection); however, it is shown that there is a net annual‐mean input of heat to the shelf waters. An examination of the seasonal temperature cycle at standard depths reveals that its phase is almost uniform below 30‐m depth on the northern banks of the Labrador Shelf. The limited phase variation suggests the influence of a plume of well mixed water originating near Hudson Strait. It thus appears that mixing at the entrance to Hudson Strait imparts a phase anomaly to the seasonal cycle in the north that contributes to the observed inversion of the expected latitudinal temperature gradient. 相似文献
4.
《大气与海洋》2013,51(1):45-58
Abstract An intensive study of the water column distributions of the dissolved nutrients silicate, phosphate, nitrate, ammonia and of dissolved oxygen in Ship Harbour, Nova Scotia in 1991 and 1992, has revealed details of, and some of the mechanisms responsible for, nutrient distributions in temperate inlets. Ship Harbour is ～10km by ～1 km wide and has a deeper (～25 m) inner basin separated from coastal waters by a shallow sill (～7 m). Nutrient distributions here result from a combination of processes within the inlet and the typical seasonal cycle expected for temperate shelf waters. Different sources and processes control each of the nutrients. In Ship Harbour, offshore nutrient supply is important for nitrate and phosphate, but is not important for silicate and ammonia. Biological uptake during the spring is important for nitrate, silicate and phosphate. Remineralization of organic matter in the deep water or the sediments of the inner basin causes concentrations of silicate, phosphate and ammonia to be unusually high, and dissolved oxygen to be unusually low, in the deep water of the inner basin in the late summer and fall. A time‐dependent model of this regeneration shows that the partial isolation of the inner basin, whose turnover time is no longer than a few months, is the determining factor. Neither the supply of organic matter to inner basin sediments, nor the ensuing regeneration rates, is unusual for inlets in the region. This finding is consistent with other recent work showing the dominance of sills in determining eutroph‐ication status of inlets in the region. In Ship Harbour, high silicate levels are found in surface waters near the head of the inlet throughout the year, despite the fact that the concentrations of reactive silicate in the rivers entering the inlet are very low. Even so, the discharges of the rivers are still the most likely external source for the silicate in the surface waters of the inlet, which must be delivered in a non‐reactive form and are probably cycled through sediments near the head of the inlet. Finally, calculations based on the biomass of cultured mussels in Ship Harbour and their clearance rate show that mussels can filter ～5–20% of the volume of the inner basin per day and, in recent years, may be starting to have a detectable impact on ambient levels of ammonia and phosphate in the inner basin. 相似文献
5.
东亚太平洋地区近地面臭氧的季节和年际变化特征及其与东亚季风的关系 总被引：1，自引：0，他引：1
朱彬 《南京气象学院学报》2012,(5):513-523
利用东亚清洁背景站近地面臭氧观测资料,结合风场和降水资料,分析东亚各地区臭氧的多年季节变化特征,并探讨东亚太平洋地区臭氧的季节和年际变化与季风的关系以及影响近地层臭氧的主要因子。结果表明：东亚大部分地区与北半球背景站观测一致,近地层臭氧季节变化表现为春季最高、夏季最低的特征;但在东亚中纬度33～43°N,臭氧表现为夏季最高,而在东亚20°N以南地区臭氧则表现为冬末、春初最高。东亚太平洋沿岸近地面臭氧的季节变化主要受东亚冬、夏季风环流的季节变化控制。该地区不同纬度上春季峰值出现时间的差异与亚洲大陆春季不同时期污染物输送路径的差异有关。对东亚太平洋沿岸对流层顶附近位势涡度、高空急流和垂直环流季节变化的分析表明,冬春季可能是平流层向对流层输送的最强期,对近地面臭氧贡献最大。初夏至秋季（5-11月）,平流层向对流层输送较弱,对近地面臭氧贡献较小。东亚太平洋地区夏季风爆发的时间和强度以及季风环流型的年际差异是导致该地区春、夏季臭氧年际变化的主要原因;而季风降水和云带位置以及平流层一对流层交换是造成臭氧年际变化的其他原因。 相似文献
6.
7.
The relation of interannual anomaly of East Asian monsoon to the ENSO cycle is investigated in terms of even and odd symmetry analysis over a tropical heating field based on the past 30-year data. Evidence suggests that odd and even symmetry components related to the monsoon and Walker heating, respectively, effectively describe the East Asian monsoon circulation and Pacific Walker analog, with the monsoon intensity index corresponding to its heating vigor and western Pacific Walker heating vigor to ENSO phase change, both types of heating marked by pro-nounced seasonal variation and phase-locking; the key region for linking monsoon-ENSO interaction is the western Pacific warm pool; the monsoon effect upon ENSO cycle is affected jointly by the seasonal evolution and interannual anomaly of the heating components; the superimposition of an anti-Walker circulation phase produced by interannual winter monsoon perturbation upon a weaker Walker phase on a seasonal basis leads to an El Nino hap-pening in March-April and plays a significant role in maintaining a warm ENSO phase. 相似文献
8.
Chatham Sound, a semi-enclosed inland sea located off northern British Columbia, is an important waterway due to many proposed industrial activities related to the Port of Prince Rupert, along with its high levels of marine productivity. The oceanographic forcing in Chatham Sound is complex due to a combination of large tides, seasonally strong winds, and large freshwater discharges. Although much oceanographic data have been collected over the past six decades, past studies of the oceanographic regime of the full Chatham Sound area have been very limited. Using these extensive forcing datasets, high-resolution three-dimensional numerical modelling using the Coastal Circulation model for Sediment transport was conducted to investigate the tidal and wind-driven currents in the stratified waters of Chatham Sound. The numerical study shows the progression of the river-dominated lower salinity near-surface waters being advected northward, especially on the eastern side of Chatham Sound, with more saline waters on the western side of the Sound, especially in areas of exchanges with the waters of Hecate Strait through side channels. These surface circulation results are in good agreement with the large-scale representation of the outer diffuse Skeena River plume as seen in high-resolution Landsat satellite imagery. The model was operated over a representative year with four seasonal model runs. Southern Chatham Sound was found to be dominated by large tidal currents. Seasonal variations of residual flow were also investigated. Significant correlation between non-tidal current speeds and Skeena River discharges was found in the Skeena River delta area and through narrow tidal channels in southern Chatham Sound. In other offshore areas, non-tidal currents were found to be constrained near the surface and driven mainly by winds. 相似文献
9.
Yu. V. Artamonov E. A. Skripaleva A. V. Fedirko 《Russian Meteorology and Hydrology》2017,42(2):105-112
The regional features oflong-term variability ofsea surface temperature (SST) in the Black Sea are analyzed using the satellite data for 1982-2014. It is demonstrated that the maximum intraannual and interannual variability of SST is registered on the northwestern shelf of the Black Sea. The high level of interannual variability of SST and maximum linear trends are observed in the northeastern part of the sea. The qualitative connection is revealed between the long-term variability of SST and the variations in the intensity of the Black Sea Rim Current in the long-term seasonal cycle. An increase in the level of interannual variability of SST is observed in summer, when the Black Sea Rim Current weakens. The significant negative correlation is revealed between the interannual anomalies of SST and the NAO index. The highest correlation coefficients are obtained for the eastern part of the Black Sea and near the Crimean coast. 相似文献
10.
热带太平洋和印度洋海面高度季节循环和年际变化的数值模拟 总被引：3，自引：1，他引：2
利用卫星海面高度计资料,分析了赤道太平洋和印度洋海面高度变化的季节和年际变化特征,并与一个耦合气候系统模式FGCM0模拟的海面高度进行比较,评估模式模拟海面高度季节和年际变化的能力.结果表明,尽管耦合模式存在一定的系统误差,但仍然能在相当程度上模拟出海面高度季节和年际变化的基本特征.同时为检验模式中印度尼西亚贯穿流(ITF)对海面高度季节和年际变化的影响,还进行了印度尼西亚海道完全关闭的敏感性试验,与控制试验结果对比表明,印度尼西亚贯穿流可以显著影响热带太平洋和印度洋年际变化的特征. 相似文献
11.
The influence of interannual variability of water transport by the East Kamchatka Current, the Oyashio, and the East Sakhalin Current on the dissolved oxygen concentration in the western subarctic Pacific and the Sea of Okhotsk is considered for studying climate change impact on sea water chemical parameters. It is shown that statistically significant relation is observed between the calculated with the Sverdrup equation interannual variations in water transport with the East Kamchatka Current, the Oyashio, and the East Sakhalin Current and changes in mean sea water level at coastal stations in winter. It is found that the main reason of interannual variability of the dissolved oxygen concentration at isopycnic surfaces in the intermediate water layer (100–800 m) of the Sea of Okhotsk and in the western subarctic Pacific is caused by variations in water transport by the East Kamchatka Current, the Oyashio, and the East Sakhalin Current. 相似文献
12.
Summary Annual and interannual variations of rainfall over Brazil are discussed. First, rainy and dry seasons for several stations of Brazil are determined using the data of 21 years (1958–1978). The progressive movement of the Intertropical Convergence Zone seems to be associated with the progresive variation of rainfall seasons in the equatorial eastern Brazil. The annual migration of deep tropical convection from Central and Southern Portion of the Amazon basin in austral summer to the northwestern sector of South America in austral winter seems to be responsible for the annual cycle of rainfall in the Amazon basin. The conncection between the interannual variation of rainfall over Brazil and the Southern Oscillation is also discussed. The correlation coefficient between the Southern Oscillation index and the rainfall is generally small over most of Brazil except over Rio Grande do Sul. The correlation between the spring rainfall of Rio Grande do Sul and the Southern Oscillation index of the same or of the previous season is significantly high and shows prospects for seasonal rainfall prediction.With 5 Figures 相似文献
13.
This study investigates the seasonal scale variability of the East Asian winter monsoon (EAWM), which is distinguished from the seasonal cycle with temporal variation throughout winter. Winters lasting 120 days (Nov. 17–Mar. 16) for a period of 64 years from the NCEP daily reanalysis data set are used to study the seasonal scale variability of the EAWM. Cyclostationary empirical orthogonal function (CSEOF) analysis is adopted to decompose the variability of the EAWM. The second CSEOF mode of 850-hPa temperature exhibits a seasonal scale variation, the physical mechanism of which is explained in terms of physically consistent variations of temperature, geopotential height, sea level pressure, wind, and surface heat fluxes. The seasonal-scale EAWM exhibits a weak subseasonal and a strong interannual variability and has gradually weakened during the 64 years. In a weak EAWM phase, the land-sea contrast of sea level pressure declines in East Asia. Consistent with this change, low-level winds decrease and warm thermal advection increases over the eastern part of mid-latitude East Asia. Latent and sensible heat fluxes are reduced significantly over the marginal seas in East Asia. However, during a strong EAWM phase, the physical conditions in East Asia reverse. A large fraction of the variability of the EAWM is explained by the seasonal cycle and the seasonal scale variation. A two-dimensional EAWM index was developed to explain these two distinct components of the EAWM variability. The new index appears to be suitable for measuring both the subseasonal and the interannual variability of the EAWM. 相似文献
14.
An ocean circulation model for the British Columbia continental shelf is run with future initial conditions and forcing fields downscaled from the North American Regional Climate Change Assessment Program archive. Average seasonal sea surface temperatures for the period 2065 to 2078 are projected to increase by between 0.5° and 2.0°C with respect to analogous averages from 1995 to 2008. Seasonal sea surface salinities are projected to decrease by as much as 2.0 over the same period, though there are some regions where and periods when small increases are projected. Though stronger winter winds result in larger Haida Eddies, slightly stronger summer winds along the western Vancouver Island shelf do not result in appreciable changes to either the cross-shelf upwelling or to the magnitude of Juan de Fuca Eddies or the timing of their formation. However, increased flows are projected in some seasons for the Rose Spit, Middle Bank, and Goose Island Bank eddies. More precipitation over the watersheds emptying into coastal waters produces larger freshwater discharges and, in particular, a stronger estuarine flow in Juan de Fuca Strait and a stronger Vancouver Island Coastal Current. Generally increasing winds and decreasing density mean that the winter minus summer range of sea surface heights is projected to increase all along the coast. 相似文献
15.
青藏高原是我国的水塔,西风与季风及其相互作用是导致亚洲天气和气候变化最重要的环流系统。本文基于1981～2020年大气再分析资料,采用经验正交函数分解方法（Empirical Orthogonal Function,EOF）提取了西风与季风季节循环分量在青藏高原的耦合模态,并对其季节变化特征进行分析。研究发现,第一主模态方差贡献率高达78.39%,主要反映的是东亚季风、南亚季风和对流层高层中纬度西风的季节循环特征及各个季节的年际变化特征。夏季在对流层高层高原及其南侧主要为东风气流,范围从北纬5°至35°,对流层低层则表现为典型的绕高原气旋式季风环流系统,热带和副热带地区为西南季风控制,冬季的环流结构刚好相反。耦合模态的冬、夏季节转换节点与东亚季风和南亚季风的季节转换时间基本一致。从年际变化的角度来看,各个季节耦合模态的强度偏强时,东亚季风和南亚季风均偏强,西风带位置偏北;反之,季风偏弱,西风带位置偏南。厄尔尼诺—南方涛动（El Ni?o–Southern Oscillation,ENSO）是影响西风与季风耦合模态年际变化的关键外强迫,拉尼娜（La Ni?a）事件发生的前夏、前秋和次年夏季耦合模态的强度均增强,冬季至次年春季耦合模态的强度均减弱。西风与季风耦合的第二主模态主要表现为对流层高层高原上的东风及其南侧西风,以及低层南亚季风区的西南季风和西北太平洋反气旋的协同变化特征。该模态的方差贡献率为4.68%,表现出明显年际差异的同时还呈现显著减弱的长期趋势,尤其是在冬季。 相似文献
16.
Sea-level variability in the South China Sea was investigated based on satellite altimetry, tide-gauge data, and temperature and salinity climatology. The altimetric sea-level results clearly reveal three distinct amphidromes associated with the annual cycle. The annual sea level is higher in fall/winter in the coast and shelf region and in summer/fall in the central sea, agreeing well with independent tide-gauge data. Averaged over the deep basin (bottom depth>2,000 m), the annual cycle can be approximately accounted for by the steric height relative to 700 db. Significant interannual sea-level change is observed from altimetry and tide-gauge data. The interannual and longer-term sea-level variability in the altimetric data is negatively correlated (significant at the 95% confidence level) with the El Niño - Southern Oscillation (ENSO), attributed in part to the steric height change. The altimetric sea-level rise rate is 1.0 cm/year for the period from 1993 to 2001, which is consistent with the rate derived from coastal tide-gauge data and approximately accountable for by the steric height calculated relative to 700 db. The altimetric sea-level (steric height) rise rate of 1.05 (0.9) cm/year from 1993 to 2001 is much larger than that of 0.22 (0.12) cm/year for the period from 1979 to 2001, implying the sensitivity to the length of data as a result of the decadal variability. Potential roles of the ENSO in the interannual and longer-term sea-level variability are discussed in terms of regional manifestations such as the ocean temperature and salinity. 相似文献
17.
Through an Australia-China climate change bilateral project, we analyzed results of 51-year global offline simulations over China using the Australian community atmosphere biosphere land exchange (CABLE) model, focusing on integrated studies of its surface energy, water and carbon cycle at seasonal, interannual and longer time-scales. In addition to the similar features in surface climatology between the CABLE simulation and those derived from the global land-surface data assimilation system, comparison of surface fluxes at a CEOP reference site in northeast China also suggested that the seasonal cycles of surface evaporation and CO2 flux are reasonably simulated by the model. We further assessed temporal variations of model soil moisture with the observed variations at a number of locations in China. Observations show a soil moisture recharge–discharge mechanism on a seasonal time scale in central-east China, with soil moisture being recharged during its summer wet season, retained in its winter due to low evaporation demand, and depleted during early spring when the land warms up. Such a seasonal cycle is shown at both 50- and 100-cm soil depths in observations while the model only shows a similar feature in its lower soil layers with its upper layer soil moisture varying tightly with rainfall seasonal cycle. In the analysis of the model carbon cycle, the net primary productivity (NPP) has similar spatial patterns as the ones derived from an ecosystem model with remote sensing. The simulated interannual variations of NPP by CABLE are consistent with the results derived from remote sensing-based and process-based studies over the period of 1981–2000. Nevertheless an upward trend from observations is not presented in the model results. The model shows a downward trend primarily due to the constant CO2 concentration used in the experiment and a large increase of autotrophic respiration caused by an upward trend in surface temperature forcing data. Furthermore, we have compared river discharge data from the model experiments with observations in the Yangtze and Yellow River basins in China. In the Yangtze River basin, while the observed interannual variability is reasonably captured, the model significantly underestimates its river discharge, which is consist with its overestimation of evaporation in the region. In the Yellow River basin, the magnitudes of the river discharge is similar between modeled and observed but its variations are less skillfully captured as seen in the Yangtze River region. 相似文献
18.
Sea-level variability in the South China Sea was investigated based on satellite altimetry, tide-gauge data, and temperature and salinity climatology. The altimetric sea-level results clearly reveal three distinct amphidromes associated with the annual cycle. The annual sea level is higher in fall/winter in the coast and shelf region and lower in summer/fall in the central sea, agreeing well with independent tide-gauge data. Averaged over the deep basin (bottom depth?>?2,000 m), the annual cycle can be approximately accounted for by the steric height relative to 700 db. Significant interannual sea-level change is observed from altimetry and tide-gauge data. The interannual and longer-term sea-level variability in the altimetric data is negatively correlated (significant at the 95% confidence level) with the El Niño - Southern Oscillation (ENSO), attributed in part to the steric height change. The altimetric sea-level rise rate is 1.0 cm/year for the period from 1993 to 2001, which is consistent with the rate derived from coastal tide-gauge data and approximately accountable for by the steric height calculated relative to 700 db. The tide-gauge sea-level (steric height) rise rate of 1.05 (0.9) cm/year from 1993 to 2001 is much larger than that of 0.22 (0.12) cm/year for the period from 1979 to 2001, implying the sensitivity to the length of data as a result of the decadal variability. Potential roles of the ENSO in the interannual and longer-term sea-level variability are discussed in terms of regional manifestations such as the ocean temperature and salinity. 相似文献
19.
Causes and impacts of changes in the Arctic freshwater budget during the twentieth and twenty-first centuries in an AOGCM 总被引：2，自引：1，他引：1
The fourth version of the atmosphere-ocean general circulation (AOGCM) model developed at the Institut Pierre-Simon Laplace
(IPSL-CM4) is used to investigate the mechanisms influencing the Arctic freshwater balance in response to anthropogenic greenhouse
gas forcing. The freshwater influence on the interannual variability of deep winter oceanic convection in the Nordic Seas
is also studied on the basis of correlation and regression analyses of detrended variables. The model shows that the Fram
Strait outflow, which is an important source of freshwater for the northern North Atlantic, experiences a rapid and strong
transition from a weak state toward a relatively strong state during 1990–2010. The authors propose that this climate shift
is triggered by the retreat of sea ice in the Barents Sea during the late twentieth century. This sea ice reduction initiates
a positive feedback in the atmosphere-sea ice-ocean system that alters both the atmospheric and oceanic circulations in the
Greenland-Iceland-Norwegian (GIN)-Barents Seas sector. Around year 2080, the model predicts a second transition threshold
beyond which the Fram Strait outflow is restored toward its original weak value. The long-term freshening of the GIN Seas
is invoked to explain this rapid transition. It is further found that the mechanism of interannual changes in deep mixing
differ fundamentally between the twentieth and twenty-first centuries. This difference is caused by the dominant influence
of freshwater over the twenty-first century. In the GIN Seas, the interannual changes in the liquid freshwater export out
of the Arctic Ocean through Fram Strait combined with the interannual changes in the liquid freshwater import from the North
Atlantic are shown to have a major influence in driving the interannual variability of the deep convection during the twenty-first
century. South of Iceland, the other region of deep water renewal in the model, changes in freshwater import from the North
Atlantic constitute the dominant forcing of deep convection on interannual time scales over the twenty-first century. 相似文献
20.
IPCC AMIP模式对西南澳类季风环流的模拟 总被引：2，自引：1，他引：1
以西南澳类季风环流为出发点,考察了IPCC第四次评估报告AMIP提供的12个大气环流模式对于澳大利亚西南部(SWWA)地区降水的季节演化特征,西南澳类季风环流(SWAC)的季节特征、季节演化、对应的异常环流型及其年际变率的模拟性能进行了评估。结果表明,除了NCAR_CAM3模式以外,其余模式均能较好的再现SWWA地区近地层盛行风向季节性反转及副热带高压脊线的季节性跳跃特征。对副热带高压脊线的季节演化特征,虽然大部分模式可以模拟出其季节移动特征,但是对于副热带高压脊线的北跳、南撤时间、到达位置和年内振幅均不能很好模拟。其次,除了NCAR_CAM3,其余模式基本能刻画出与SWAC相联系的异常环流型结构;而对于SWAC的年际变率,基本所有模式均不能较好模拟。整体权衡,GISS_MODEL_E_R在模拟SWAC环流的年际变率方面表现出较其它模式稍好的性能,大致可以模拟出与观测SWAC相似的特征,对SWWA地区的冬季降水显示出了与观测相似的显著影响。 相似文献