Factors affecting suspended‐solids concentrations in South San Francisco Bay, California
Factors affecting suspended‐solids concentrations in South San Francisco Bay, California
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DOI：
10.1029/96jc00747
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发表时间：
1996-05
影响因子：
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通讯作者：
D. Schoellhamer
中科院分区：
文献类型：
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作者：
D. Schoellhamer
为了确定影响悬浮物浓度的因素，在南旧金山湾的三个地点进行了两个深度的悬浮物浓度(SSC)测量。从1991年底或1992年底至1993年9月，收集了28段可靠的、连续的14天以上的SSC时间序列数据。利用谱分析和奇异谱分析将这些数据段与几个潜在强迫因素的时间序列联系起来，包括全日和半日潮、春潮-小潮周期、风切变、淡水径流和纵向密度差。夏季，当下午的海风对南湾施加陆向风切变时，SSC最大。SSC的变化约有一半是由春潮周期引起的，SSC比春潮周期滞后约2天。相对较短的枯水时间限制了潮汐周期中悬浮固体的沉积和新沉积床沙的固结，因此，随着大潮的到来，悬浮固体在水柱中积累，随着小潮的到来，悬浮固体缓慢沉积。在研究期间，风和冬季风暴造成的局地径流对SSC的扰动通常比春季-小潮周期引起的SSC变化小得多。研究地点在潮汐时间尺度上的SSC变化是潮汐强迫的，并且具有显著的非线性物理过程。大潮期间以平流输送为主，当风浪再悬浮产生的水从浅水平流到主航道时，平流输送占主导地位，而在小潮期间，平流输送作用较小。这项研究和其他研究的结果表明，悬浮物的潮汐平均输送响应于南湾风切变的季节变化。
Measurements of suspended-solids concentration (SSC) were made at two depths at three sites in South San Francisco Bay (South Bay) to determine the factors that affect SSC. Twenty-eight segments of reliable and continuous SSC time series data longer than 14 days were collected from late 1991 or 1992 through September 1993. Spectral analysis and singular spectrum analysis were used to relate these data segments to time series of several potential forcing factors, including diurnal and semidiurnal tides, the spring-neap tidal cycle, wind shear, freshwater runoff, and longitudinal density differences. SSC is greatest during summer, when a landward wind shear is applied to South Bay by the afternoon sea breeze. About one half the variance of SSC is caused by the spring-neap cycle, and SSC lags the spring-neap cycle by about 2 days. Relatively short duration of slack water limits the duration of deposition of suspended solids and consolidation of newly deposited bed sediment during the tidal cycle, so suspended solids accumulate in the water column as a spring tide is approached and slowly deposit as a neap tide is approached. Perturbations in SSC caused by wind and local runoff from winter storms during the study period were usually much smaller than SSC variations caused by the spring-neap cycle. Variations of SSC at the study sites at tidal timescales are tidally forced, and nonlinear physical processes are significant. Advective transport dominates during spring tides, when water with higher SSC due to wind wave resuspension is advected to the main channel from shallow water, but, during neap tides, advective transport is less significant. The findings of this and other studies indicate that the tidally averaged transport of suspended solids responds to seasonal variations of wind shear in South Bay.