基于FY-3A的湛江湾及其邻近海域叶绿素a遥感监测研究

叶绿素a质量浓度是水体水环境一个重要指标。本文结合实测的叶绿素a质量浓度、水体的光谱数据和FY-3A中等分辨率成像光谱仪的数据,研究利用FY-3A遥感监测湛江湾及其邻近海域叶绿素a质量浓度的可行性。研究结果表明,湛江湾海域大部水体接近一类水体,二类水体主要集中在湛江港附近的狭小封闭海域;OC4算法可以用于湛江湾海域的叶绿素a质量浓度的遥感监测,实测叶绿素a质量浓度与反演的叶绿素a质量浓度具有较好的相关性,相关系数R达到0.7以上;FY-3A中等分辨率成像光谱仪的数据可以较好地反映湛江湾海域叶绿素a质量浓度的空间分布。     

Remote sensing of particle backscattering in Chesapeake Bay: A 6-year SeaWiFS retrospective view

Traditional field techniques to monitor water quality in large estuaries, such as boat-based surveys and autonomous moored sensors, generally provide limited spatial coverage. Satellite imagery potentially can be used to address both of these limitations. Here, we show that satellite-based observations are useful for inferring total-suspended-solids (TSS) concentrations in estuarine areas. A spectra-matching optimization algorithm was used to estimate the particle backscattering coefficient at 400 nm, b_bp(400), in Chesapeake Bay from Sea-viewing Wide-Field-of-view Sensor (SeaWiFS) satellite imagery. These estimated values of b_bp(400) were compared to in situ measurements of TSS for the study period of September 1997–December 2003. Contemporaneous SeaWiFS b_bp(400) values and TSS concentrations were positively correlated (N = 340, r² = 0.4, P < 0.0005), and the satellite-derived b_bp(400) values served as a reasonable first-order approximation for synoptically mapping TSS. Overall, large-scale patterns of SeaWiFS b_bp(400) appeared to be consistent with expectations based on field observations and historical reports of TSS. Monthly averages indicated that SeaWiFS b_bp(400) was typically largest in winter (>0.049 m⁻¹, November–February) and smallest in summer (<0.031 m⁻¹, June–August), regardless of the amount of riverine discharge to the bay. The study period also included Hurricanes Floyd and Isabel, which caused large-scale turbidity events and changes in the water quality of the bay. These results demonstrate that this technique can provide frequent synoptic assessments of suspended solids concentrations in Chesapeake Bay and other coastal regions.     

基于遥感影像的浙江省三门湾近40年海岸线及海岸带时空变化分析

根据1985、1995、2005、2013和2020年的Landsat卫星图像,采用人机交互手段将三门湾海岸线分为基岩岸线、砂质岸线、淤泥质岸线、人工岸线和河口岸线。采用交互式监督分类将三门湾海岸带的土地利用分为水体、林地、裸地、建设用地和农业用地。研究结果表明：近40年三门湾人工岸线和基岩岸线变化最大,分别增加了80.3 km和减少了79.3 km;近40年三门湾海岸带面积累计增加了130 km2,建设用地和水体是围填海新增土地的主要利用类型,主要的土地转移形式为裸地向建设用地、农业用地的转变以及林地转为建设用地;近40年三门湾岸线分形维数由1.22减小至1.201,人工岸线比例和建设用地占比分别上升了13%和22.57%,总体上呈现向海推进、人工化加强的趋势。人类活动是造成三门湾岸线及海岸带变化的主要原因,随着对海岸带保护与合理利用的推进,三门湾海岸带开发利用格局正逐渐稳中向好。     

1986—2017年胶州湾水体透明度时空变化及影响因素研究

借助遥感技术能够获取长时序大范围数据的特点,利用1986—2017年的Landsat TM/ETM+/OLI影像,通过构建基于实测数据的定量反演模型,分析了32年来胶州湾海域水体透明度的时空分布特征和变化规律,并探究其主要影响因素。结果表明,年均水体透明度的变化范围为1.55～2.55m,且空间分布规律稳定,呈现东南高西北低的特点;季均水体透明度从高到低依次为冬季(2.09m)、春季(1.83 m)、秋季(1.82 m)、夏季(1.43 m)。利用气象数据及胶州湾流域的土地利用分类/景观格局数据,从自然环境和人类活动两方面分析影响胶州湾水体透明度时空分布的因素,发现胶州湾水体透明度与入海径流量、降水量存在显著的负相关关系,并受到近海养殖区破碎化程度和修建大型人工设施等人为因素的影响。     

Short-term variability of suspended sediment and phytoplankton in Tampa Bay,Florida: Observations from a coastal oceanographic tower and ocean color satellites

We examined short-term phytoplankton and sediment dynamics in Tampa Bay with data collected between 8 December 2004 and 17 January 2005 from optical, oceanographic, and meteorological sensors mounted on a coastal oceanographic tower and from satellite remote sensing. Baseline phytoplankton (chlorophyll-a, Chl) and sediment concentrations (particle backscattering coefficient at 532 nm, bbp(532)) were of the order of 3.7 mg m⁻³ and 0.07 m⁻¹, respectively, during the study period. Both showed large fluctuations dominated by semidiurnal and diurnal frequencies associated with tidal forcing. Three strong wind events (hourly averaged wind speed >8.0 m s⁻¹) generated critical bottom shear stress of >0.2 Pa and suspended bottom sediments that were clearly observed in concurrent MODIS satellite imagery. In addition, strong tidal current or swells could also suspend sediments in the lower Bay. Sediments remained suspended in the water column for 2–3 days after the wind events. Moderate Chl increases were observed after sediment resuspension with a lag time of ˜1–2 days, probably due to release of bottom nutrients and optimal light conditions associated with sediment resuspension and settling. Two large increases in Chl with one Chl > 12.0 mg m⁻³ over ˜2 days, were observed at neap tides. For the study site and period, because of the high temporal variability in phytoplankton and sediment concentrations, a monthly snapshot can be different by −50% to 200% from the monthly “mean” chlorophyll and sediment conditions. The combination of high-frequency observations from automated sensors and synoptic satellite imagery, when available, is an excellent complement to limited field surveys to study and monitor water quality parameters in estuarine environments.     

Suspended particulate matter in the St. Lawrence estuary and Gulf surface layer and development of a remote sensing algorithm

Remote sensing of chlorophyll concentration is potentially affected by the presence of inorganic matter in the water column. Seasonal variability of total suspended particulate matter (SPM) concentration and its partition into organic and inorganic fractions was thus measured in the estuary and Gulf of St. Lawrence during five cruises. These measures were made in the surface layer down to the depth of the 0.1% light level. Results indicate that vertical variability was small for the entire study area. Data analysis lead to the definition of two main regions having different SPM characteristics: 1) the estuary zone characterized by a strong spatial variability, intermediate SPM concentrations and a clear spring phytoplankton bloom that is combined to an increased inorganic matter load; 2) the gulf region characterized by a relatively low SPM concentration and phytoplankton blooms in the spring and fall periods. Combined with in situ measurements of remote sensing reflectances, the database was used to validate existing inorganic matter retrieval algorithms and develop a new one better adapted to the low concentrations encountered in the St. Lawrence estuary and Gulf.     

大连湾及邻近海域水体叶绿素浓度荧光遥感算法研究

叶绿素荧光遥感算法为探测近岸海域二类水体叶绿素浓度开辟了新途径．基于大连湾及邻近海域的实测数据,本文研究了海水叶绿素浓度的荧光遥感算法．结果表明：随着海水叶绿素质量浓度的增高,荧光峰出现显著的红移现象,叶绿素质量浓度与荧光峰波长存在着正相关关系．此外,基于MODIS、MERIS及GLI传感器荧光波段建立的荧光基线高度算法较差,不适用于该研究海域．选择680、685、690、695、700、705nm作为荧光峰波长建立的荧光基线高度算法,随着选定波长的增大,该算法拟合的相关性逐渐增高,最大相关系数（R2）可达0．91;而以实测荧光峰波长建立的荧光基线高度算法最佳,乘幂函数拟合优于线性拟合,拟合方程为P（chl）=3．167×10^5 FLH^1.45（R2=0．93）．本研究为新一代海洋水色卫星传感器的开发、建造提供了科学依据,并为已有高光谱传感器在叶绿素荧光遥感反演方面的应用打下了基础．     

Combined Use of Remote Sensing and Continuous Monitoring to Analyse the Variability of Suspended-Sediment Concentrations in San Francisco Bay, California

Analysis of suspended-sediment concentration data in San Francisco Bay is complicated by spatial and temporal variability. In situ optical backscatterance sensors provide continuous suspended-sediment concentration data, but inaccessibility, vandalism, and cost limit the number of potential monitoring stations. Satellite imagery reveals the spatial distribution of surficial-suspended sediment concentrations in the Bay; however, temporal resolution is poor. Analysis of thein situ sensor data in conjunction with the satellite reflectance data shows the effects of physical processes on both the spatial and temporal distribution of suspended sediment in San Francisco Bay. Plumes can be created by large freshwater flows. Zones of high suspended-sediment concentrations in shallow subembayments are associated with wind-wave resuspension and the spring-neap cycle. Filaments of clear and turbid water are caused by different transport processes in deep channels, as opposed to adjacent shallow water. Crown     

Variations of the Nutrients Loads to the Mainland U.K. Estuaries: Correlation with Catchment Areas, Urbanization and Coastal Eutrophication

The annual loads of nutrients (TO_xN equal to nitrate+nitrite; ammonium, phosphate, silicate) to all the estuaries on the mainland of the United Kingdom were estimated from data on water flow through gauging stations at the tidal limits of estuaries, and from concentration measurements under the Harmonised Monitoring Scheme of nutrient concentrations in water samples from these stations. The annual loads of nutrients showed distinct regional variations, with estuaries along the west coast of Wales and northern Scotland having much smaller loads than those along the east coast of England. The largest nitrogen loads were of TO_xN, and ammonium loads were usually small in comparison. The Severn, Mersey, Humber and Thames had the highest loads, although these were small in relation to the larger continental European estuaries. Loads of TO_xN per unit of catchment area were surprisingly constant (about 10⁵ moles N km⁻² y⁻¹). The nutrient loads showed that most U.K. catchments were influenced by human activity, the majority being in the ‘ moderately influenced ’ category. Nutrient loads were also normalized for the area of each estuary, as a measure of the relative influence of nutrients on the receiving estuaries. The ratios of N:P, N:Si and P:Si in the annual loads suggested that most estuaries were likely to be, if anything, P limited rather than N or Si limited. However, crude annual loads may conceal significant seasonal variations.The spring maximum chlorophylla concentrations in coastal waters adjacent to each estuary were significantly correlated with the log total annual loads of TO_xN, ammonium and phosphate (but not silicate) for each estuary, providing a direct link between a measure of the degree of biological response in coastal waters and the nutrient load through the estuaries. There were no significant correlations between spring maximum chlorophyll a concentrations and either catchment-normalized or estuary-normalized nutrient loads. There was significant correlation between catchment area-normalized loads of phosphate and an urbanization index for the catchments, but not with the catchment area-normalized loads of the other nutrients.     

Modeling water quality and hypoxia dynamics in Upper Charlotte Harbor,Florida, U.S.A. during 2000

Hypoxia has occurred in Upper Charlotte Harbor, a shallow (∼3 m) estuary in Southwest Florida, during moderate to high freshwater flows from the Peace and Myakka Rivers and after hurricanes, due to nutrient loading and vertical stratification. This paper studies the annual hypoxia and water quality dynamics in Upper Charlotte Harbor in 2000, using CH3D-IMS, an integrated modeling system which includes coupled models of circulation, wave, sediment transport, and water quality. The CH3D-IMS simulations showed that bottom-water hypoxic conditions occur during periods with relatively steady moderate to high (5–40 m³/s) freshwater inflows and sediment oxygen demand (SOD). During periods of relatively steady moderate to high river discharge, strong vertical salinity stratification results in reduced vertical mixing which prevents surface water from supplying dissolved oxygen (DO) to bottom water where SOD continuously consumes DO. There was significant temporal fluctuation of the hypoxic water volume, as a result of significant temporal variation in vertical turbulent mixing associated with combinations of spring-neap tides and river discharge. The validated modeling system could be used to forecast hypoxia.