Spatial dynamics of estuarine water surface temperature from airborne remote sensing (original) (raw)
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International Journal of Remote Sensing, 2001
The study of surface water velocity éelds through in situ sampling is intrinsically diYcult because they are highly variable in time and space. With airborne remote sensing, however, it is possible to determine changes in velocity éelds because spatially and temporally comprehensive data may be obtained. This letter shows how changes in the statistical properties of successive remotely sensed images may be used to estimate velocity vectors associated with chlorophyll-a and sea surface temperature (SST). The study area is Kirkcudbright Bay, a small estuary in south-west Scotland. Multi-temporal imagery of the study area were acquired by the NERC Daedalus ADDS-1268 Airborne Thematic Mapper (ATM) and processed to show chlorophyll and thermal indices as substitutes for chlorophyll-a and SST. Velocity éelds were estimated by the Maximum Cross Correlation technique. Complex patterns were found, conérming that the comprehensive coverage provided by airborne remote sensing is required for their analysis. The chlorophyll-a velocity éeld diVered from the SST velocity éeld, suggesting that these éelds are relevant to the water quality variable in question, and not necessarily the water body itself.
Near-coastal surface water velocity field estimation using airborne remote sensing
The study of surface water velocity fields through in situ sampling is intrinsically difficult because they are highly variable in time and space. With airborne remote sensing, however, it is possible to determine synoptic changes in velocity fields because spatially and temporally comprehensive data may be obtained. This paper shows how changes in the statistical properties of successive remotely sensed images may be used to estimate velocity vectors associated with chlorophyll-a and sea surface temperature (SST). The study area is Kirkcudbright Bay, a small estuary in south-west Scotland. Multi-temporal imagery of the study area were acquired by the NERC Daedalus ADDS-1268 Airborne Thematic Mapper (ATM) and processed to show chlorophyll and thermal indices as substitutes for chlorophyll-a and SST. Velocity fields were estimated by the Maximum Cross Correlation technique. Complex patterns were found, confirming that the comprehensive coverage provided by airborne remote sensing is required for their analysis. The chlorophyll-a velocity field differed from the SST velocity field, suggesting that these fields are relevant to the water quality parameter in question, and not necessarily the water body itself.
Journal of Coastal Conservation, 1995
This paper deals with the application of satellite images to characterize some aspects of the circulation dynamics of the Tinto-Odiel estuary using turbidity patterns as 'natural tracers'. 15 images (Landsat TM and Spot HRV) were processed to provide synoptic, instantaneous views of the circulation patterns under different environmental conditions. In addition, a comparison was made between results of oceanographic field work, using biplanes and fluorescent tracers, and satellite image turbidity patterns used as 'ground truth' data for specific hydroclimatic situations. This approach allowed (1) the identification and mapping of dynamic processes of interest during a theoretical tidal cycle, (2) the elaboration of additional information on the 'flow schemes' at the mouth of the estuary with improved spatial and temporal resolution, and (3) the supply of basic data to improve the knowledge of exchange processes between estuarine and coastal waters. The results of this study are considered to be useful for the management of the estuarine system.
2015
jm.froidefond(at)epoc.u-bordeaux1.fr The study concerns the quantification of suspended sediments in turbid estuarine waters from high spatial resolution remotely sensed data (SPOT-HRV, Landsat-ETM+). It is applied to the following areas: the Gironde and the Loire estuaries (France), where suspended sediment concentrations (SPM) in surface waters vary from 10 to 2000 mg l-1. The methodology is essentially empirical. Based on in situ optical measurements, calibration rela-tionships are established between the remote sensing reflectance (Rrs) signal and SPM. These relationships, obtained using reflectance ratios between near-infrared (NIR) and visible (VIS) wavebands, are relatively independent of the sediment grain-size and mineralogy, and of the illu-mination conditions (e.g. the cloud cover). Consequently, they can be applied to satellite images, even if no simultaneous in situ measurements were carried out concurrently with the satellite over-pass. A bio-optical model is used to e...
Estimating Coastal Lagoon Tidal Flooding and Repletion with Multidate ASTER Thermal Imagery
Remote Sensing
Coastal lagoons mix inflowing freshwater and tidal marine waters in complex spatial patterns. This project sought to detect and measure temperature and spatial variability of flood tides for a constricted coastal lagoon using multitemporal remote sensing. Advanced Spaceborne Thermal Emission Radiometer (ASTER) thermal infrared data provided estimates of surface temperature for delineation of repletion zones in portions of Chincoteague Bay, Virginia. ASTER high spatial resolution sea-surface temperature imagery in conjunction with in situ observations and tidal predictions helped determine the optimal seasonal data for analyses. The selected time series ASTER satellite data sets were analyzed at different tidal phases and seasons in 2004-2006. Skin surface temperatures of ocean and estuarine waters were differentiated by flood tidal penetration and ebb flows. Spatially variable tidal flood penetration was evaluated using discrete seed-pixel area analysis and time series Principal Components Analysis. Results from these techniques provide spatial extent and variability dynamics of tidal repletion, flushing, and mixing, important factors in eutrophication assessment, water quality and resource monitoring, and application of hydrodynamic modeling for coastal estuary science and management.
Frontiers in Marine Science
Satellite derived sea surface temperatures (SSTs) are often used as a proxy for in situ water temperatures, as they are readily available over large spatial and temporal scales. However, contamination of satellite images can prohibit their use in coastal areas. We compared in situ temperatures to SST foundation (∼10 m depth) at 31 sites inshore of the East Australian Current (EAC), the dynamic western boundary current of the south Pacific gyre, using an area averaging approach to overcome coastal contamination. Varying across-and along-shelf distances were used to area average SST measurements and de-correlation time scales were used to gap fill data. As the EAC is typically anisotropic (dominant along-shore flow) the choice of across-shelf distances influenced the correlation with in situ temperatures more than along-shelf distances. However, the "optimal" distances for both measurements were within known de-correlation length scales. Incorporating both SST area and time averaging (based on de-correlation time scales) produced data for an average of 96% of days that in situ loggers were deployed, compared to 27% (52%) without (with) area averaging. Temperature differences between the in situ data and SSTs varied depending on time of year, with higher differences in the austral summer when daily in situ temperatures can range by up to 4.20 • C. The differences between the in situ and SST measurements were, however, significant with or without area averaging (t-test: p-values < 0.05). Nevertheless, when using the area averaging approaches SSTs were only an average of ∼1.05 • C different from in situ temperatures and less than in situ temperature fluctuations. Linear mixed models revealed that latitude, distance to the coast and nearest estuary did not influence the difference between the in situ and satellite data as much as the water depth. This study shows that using de-correlation length and time scales to inform how to process satellite data can overcome contamination and missing data thereby greatly increasing the coverage and utility of SST data, particularly in coastal areas.
Estuarine, Coastal and Shelf Science, 2004
High spatial resolution hyper-spectral imagery (CASI) and light detection and ranging (LiDAR) imagery acquired for the tidal River Carron and Forth estuary, Scotland, were used in conjunction with field surveys to assess the feasibility of monitoring hydromorphology and human alterations with satellite and airborne remote sensing data. The study was undertaken in the context of the European Union Water Framework Directive (WFD) that requires member states to monitor hydromorphological elements as a component of the ecological status of rivers, estuaries and shorelines. Visual assessment and automated classifications of the imagery were compared with field survey data for an estuarine reach comprising saline waters, mudflats, a tidal reach of a tributary river and an urban/industrialised shoreline.
High spatial resolution sea surface climatology from Landsat thermal infrared data
Remote Sensing of Environment, 2004
High spatial and temporal resolution maps of sea surface temperature (SST) have numerous applications in coastal and estuarine systems. A climatology map, tracking SST as a function of year-day, was produced at Southern New England using 53 Landsat TM and ETM+ thermal infrared data. A recursive curve-fitting algorithm was used to fit these data and eliminate cloud contamination, resulting in an average daily temperature at every 60-m pixel. The climatology was validated against long-term in situ records that were analyzed with the same techniques. The results show, as expected, that isolated and shallow water bodies undergo more extreme temperature variation (À 2 to 25 jC) than deeper, well-connected embayments (1 to 21 jC) or the coastal ocean (4 to 18 jC). The coastal ocean is shown to lag insolation and shallow lakes by up to 44 days, with embayments showing a gradation between these extremes. Despite the subtle temperature range variation, there is rich detail in the spatial patterns which are relevant to the applied sciences of coastal and estuarine systems. The spatial pattern of the climatology reveals anomalous patterns, such as occur where anthropogenic forcing alters climatological patterns. The heat budget of Mount Hope Bay in northeast Narragansett Bay has anthropogenic thermal input from a large power plant, and this input is reflected in the climatology. From the results, it is seen that Narragansett Bay has, on average, a mean annual temperature of 11.86 F 0.41 jC, while the Mount Hope Bay system is consistently warmer at 12.30 F 0.21 jC and shows a delayed response to autumn cooling. The long history of Landsat data acquisition can be used to create a climatology of coastal and estuarine scale dynamics at an order of magnitude finer scale resolution than AVHRR climatologies.