排序方式： 共有56条查询结果，搜索用时 171 毫秒
41.
Steven E. Lohrenz Donald G. Redalje Wei-Jun Cai James Acker Michael Dagg 《Continental Shelf Research》2008
Long-term patterns in riverine nutrient flux in the lower Mississippi River were examined in relationship to spatial and temporal patterns in surface nutrient concentrations, chlorophyll, and primary productivity in the outflow region in the northern Gulf of Mexico. A retrospective analysis of dissolved inorganic nutrient fluxes based on USGS water quality data and US Army Corps of Engineers discharge data from the 1950s to mid-2004 showed an increase in river-borne dissolved inorganic nitrogen (DIN) flux after 1967. Flux of DIN peaked in the early 1980s and has since fluctuated and shown a general decreasing trend since the early 1990s. Records for total phosphorus (total P) fluxes beginning in mid-1974 exhibited a variable but slight increasing trend up to 2004. The increase in fluxes during the 1970s and into the 1980s can be attributed to increases in both nutrient concentrations and river discharge. DIN concentrations since the 1980s have shown a decreasing trend. Total P concentrations exhibited large fluctuations, with no consistent long-term trend. Dissolved organic nitrogen (DON) concentrations and orthophosphate (Ortho P) peaked in the 1980s, declined relative to DIN and remained relatively low. DIN:Ortho P ratios were consistently well above the Redfield N:P ratio of 16:1. DIN:Total P ratios were variable and lower, fluctuating around the Redfield 16:1 value. Both DIN:Ortho P and DIN:Total P ratios were weakly, but significantly, correlated with river discharge and fluctuations were largely a reflection of higher DIN concentrations during high-discharge events. DIN:Ortho P ratios in surface waters of the outflow region adjacent to the birdfoot delta were higher in spring, consistent with seasonal variation in riverine DIN:Ortho P ratios. The seasonal signal diminished with increasing distance to the west of the delta, indicating a selective removal of DIN or source of Ortho P along the shelf. DIN fluxes and SeaWiFS satellite-derived chlorophyll showed seasonally elevated values during the first half of the year followed by generally lower values in late summer and fall. This seasonal signal diminished from east to west. The observed relationship between DIN flux and chlorophyll was consistent with ship-based observations of a linkage between riverine nutrient inputs and productivity. Long-term trends in river discharge were correlated with the Multivariate ENSO (El Niño Southern Oscillation) Index (MEI) (r=−0.281, p<0.0001), evidence that river discharge was influenced by global climatic trends. 相似文献
42.
SeaWiFS与HY-1卫星COCTS的系统交叉辐射校正 总被引：6，自引：0，他引：6
海洋一号(HY-1)卫星是中国第一颗海洋环境遥感卫星。由于卫星上没有太阳定标装置,而且其上搭载的水色水温扫描仪(COCTS)一直存在漂移的问题,所以必须不断对其进行辐射校正,所述内容就是其辐射校正方法之一。美国宽视场水色扫描仪(SeaW iFS)提供了高精度的水色数据,如一类水体上的离水辐亮度及叶绿素浓度等被国际水色遥感界作为参照的基准。以SeaW iFS反演的归一化离水辐亮度和气溶胶参数对COCTS遥感器的辐射校正系数进行了系统校正。该方法可以对COCTS的定标系数进行长期监测。结果表明,校正后的COCTS水色数据产品精度得到了很大的提高。 相似文献
43.
Variation in Lake Baikal's phytoplankton distribution and fluvial input assessed by SeaWiFS satellite data 总被引：1，自引：0，他引：1
Birgit Heim Hedi Oberhaensli Susanne Fietz Hermann Kaufmann 《Global and Planetary Change》2005,46(1-4):9
The current behaviour of selected climate proxies in Lake Baikal was assessed by remote sensing analyses of ‘Sea viewing Wide Field of view Sensor’ (SeaWiFS) satellite data. Suitable proxies include optically visible water constituents such as phytoplankton, suspended terrigenous matter and yellow substance. These limnological parameters reflect the present-day climate bioproductivity and the river discharge in the catchment area.A biological and geochemical ground truth data set for Lake Baikal was established with the help of members of the paleoclimate project ‘high-resolution CONTINENTal paleoclimate record in Lake Baikal’ (CONTINENT). For processing the SeaWiFS satellite data, the atmospheric correction was adapted to the case of Lake Baikal. Chlorophyll as a proxy for phytoplankton was quantified using global NASA ocean colour algorithms OC2 and OC4. In cases of no optical interferences by terrigenous input, the calculated chlorophyll concentrations in clear pelagic waters were within ±30% accuracy with the CONTINENT cruise data during the summers of 2001 and 2002. Within this range of accuracy, the SeaWiFS time series will be able to show the seasonal variations of chlorophyll of specified bio-optical provinces of Lake Baikal and of CONTINENT sites. In this study, the suspended matter as a proxy for the terrigenous input was calculated according to an empirical algorithm using ground truth data in the time frame of flooding events in summer 2001. The approach chosen correlates the suspended matter concentration with the remotely sensed parameter of ‘attenuation coefficient’ to account for the organic-rich terrigenous input that originates from the swampy watersheds.Seasonal and spatial information that is provided by the analyses of the SeaWiFS satellite data will assist paleoclimate researchers to interpret the autochthonous and allochthonous influences at the CONTINENT coring sites. 相似文献
44.
1998年冬季台湾海峡的暖水入侵及其生态响应 总被引：6，自引：0，他引：6
就1998年2－3月台湾海峡AVHRR表层水温和SeaWiFS叶绿素数据以及当年2月20日至3月8日在台湾海峡北部海区所实施的多学科现场调查资料进行综合分析，着重探讨暖水入侵的过程及其生态响应。结果表明，1998年冬季由澎湖水道北上进入台湾海峡的高温高盐黑潮入侵水强度大于往年，在2月8日－3月13日期间不断增强，直至侵占整个海峡东侧海域，迫使低温低盐且富含营养盐的闽浙沿岸水主流顺大陆沿岸南下。这一过程向海峡西侧海域输入营养盐并使之达到适宜的水温，极可能是西侧海域出现叶绿素高值区、呈现出与往年相反的叶绿素分布态势的主控机制。分析这一现象与1997－1998年的E1 Nino事件可能存在着某种关联。 相似文献
45.
1998年冬季台湾海峡遥测叶绿素分布特征 总被引：12，自引：1，他引：12
结合1998年2－3月台湾少峡的SeaWiFS水色数据与现场观测Chla数据，对遥测与实测数据进行了初步的对照分析，同时比较了遥测与实测叶绿素的分布状况，以期利用丰富的水色遥感信息掌握海域时绿素的时空变化，进而进行海域初级生产力的研究，分析结果表明，SeaWiFS水以民现场实测数据的相关性良好（r^2=0.81,n=7)，初步说明，SeaWiFS水色数据能够在相当程度上反映海域的实际Chla含量，另一方面，遥测沿岸水对营养盐的输送，贫瘠的黑潮水自海峡南部的入侵是造成一分布况的主要原因，黑潮水经由澎湖水道进入海峡的现象在SeaViFS图像的得到佐证。 相似文献
46.
47.
Remote sensing of particle backscattering in Chesapeake Bay: A 6-year SeaWiFS retrospective view 总被引：1，自引：0，他引：1
David G. Zawada Chuanmin Hu Tonya Clayton Zhiqiang Chen John C. Brock Frank E. Muller-Karger 《Estuarine, Coastal and Shelf Science》2007,73(3-4):792-806
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, bbp(400), in Chesapeake Bay from Sea-viewing Wide-Field-of-view Sensor (SeaWiFS) satellite imagery. These estimated values of bbp(400) were compared to in situ measurements of TSS for the study period of September 1997–December 2003. Contemporaneous SeaWiFS bbp(400) values and TSS concentrations were positively correlated (N = 340, r2 = 0.4, P < 0.0005), and the satellite-derived bbp(400) values served as a reasonable first-order approximation for synoptically mapping TSS. Overall, large-scale patterns of SeaWiFS bbp(400) appeared to be consistent with expectations based on field observations and historical reports of TSS. Monthly averages indicated that SeaWiFS bbp(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. 相似文献
48.
我国海区SeaWiFS资料大气校正 总被引：13，自引：1，他引：13
利用光谱辐射传输理论，结合海上同步实测资料，开发出我国海区SeaWiFS资料大气校正模型。经卫星资料处理结果比对，本模型在一类水体，基本消除了412nm和443nm波段离水辐射率小于0的现象；在二类水体，利用临近一类水体的大气条件进行了有效的大气校正；同时建立了670nm,765nm,865nm波段的大气校正模型，这三个面适用于高浓度悬浮泥沙的信息提取。本模型用于处理我国海区的SeaWiFS资料比美国NASA模型更适合我国海区特定的大气和海洋环境，为SeaWiFS资料海洋水色信息提取和我国海洋一号（HY－1）及风云一号（FY－1C）卫星资料的大气校正研究提供了技术基础。 相似文献
49.
Yu -Hwan Ahn Palanisamy Shanmugam Kyung- Il Chang Jeong -Eon Moon Joo -Hyung Ryu 《Ocean Science Journal》2005,40(2):67-71
Complex physical, chemical and biological interactions off the Korean coast created several striking patterns in the phytoplankton
blooms, which became conspicuous during the measurements of ocean color from space. This study concentrated on analyzing the
spatial and temporal aspects of phytoplankton chlorophyll variability in these areas using an integrated dataset from a Sea-viewing
Wide Field-of-view Sensor (SeaWiFS), Advanced Very High Resolution (AVHRR) sensor, and Conductivity Temperature Depth (CTD)
sensor. The results showed that chlorophyll concentrations were elevated in coastal and open ocean regions, with strong summer
and fall blooms, which appeared to spread out in most of the enclosed bays and neighboring waters due to certain oceanographic
processes. The chlorophyll concentration was observed to range between 3 and 54 mg m-3 inside Jin-hae Bay and adjacent coastal bays and 0.5 and 8 mg m-3 in the southeast sea offshore waters, this gradual decrease towards oceanic waters suggested physical transports of phytoplankton
blooms from the shallow shelves to slope waters through the influence of the Tsushima Warm Current (TWC) along the Tsushima
Strait. Horizontal distribution of potential temperature (θ) and salinity (S) of water off the southeastern coast exhibited
cold and low saline surface water (θ<19°C; S<32.4) and warm and high saline subsurface water (θ>12°C; S>34.4) at 75dBar, corroborating
TWC intrusion along the Tsushima Strait. An eastward branch of this current was called the East Korean Warm Current (EKWC),
tracked with the help of CTD data and satellite-derived sea surface temperature, which often influenced the dynamics of mesoscale
anticyclonic eddy fields off the Korean east coast during the summer season. The process of such mesoscale anticyclonic eddy
features might have produced interior upwelling that could have shoaled and steepened the nutricline, enhancing phytoplankton
population by advection or diffusion of nutrients in the vicinity of Ulleungdo in the East Sea. 相似文献
50.
选取VGPM模式对南海北部海域初级生产力进行反演,通过SeaWiFS和AVHRR提供的Chl a,K490,PAR和SST等遥感数据产品计算得到了模式所需的各项参数,结合现场实测数据对模式进行了修订和误差分析.在此基础上通过反演计算获得了南海北部海域7 a平均(1998～2004年)初级生产力逐月分布图像.研究结果表明,研究海域初级生产力(C)分布趋势为由沿岸带向陆架以及外海逐渐降低,其中沿岸带区高于400 mg/(m2·d),外海区大致在100～300 mg/(m2·d);初级生产力水平冬季最高[平均为608 mg/(m2·d)]、夏季最低[平均为292 mg/(m2·d)],春、秋季基本持平.控制初级生产力时空分布的因子主要有营养盐、温度、光照,其中又以季风和环流驱动下的营养盐变化对初级生产力的调控最为显著. 相似文献