This project used data collected by the Advanced Very High Resolution Radiometer (AVHRR) on water reflectance for the Florida Bay region over the 12-year period from July 1985 to September 1997, and field data on light attenuation and changes in bottom cover.
Richard P. Stumpf (no longer with USGS) Megan L. Frayer, 2005, Remote Sensing of Water Turbidity and Sedimentation in Florida Bay and Biscayne Bay.Online Links:
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The project is conducting comparisons between chlorophyll values collected from the shipboard monitoring programs and pre-cruise reflectances to assess whether there is a link between resuspension events and algal blooms. The next stage in the project is to expand the AVHRR data set backward to before the seagrass dieoffs and to incorporate Landsat data for limited high resolution analysis.
In the dataset the typical month has 3-9 nominally cloud-free scenes prior to a1994 and 8-16 scenes starting in 1995. Winter 1994 had only four acceptable scenes owing to the extremely late overpass time of NOAA-11 (1600 local standard time). Scenes with solar angles >70 degrees were discarded. Gaps occur in late summer months for 1988-1989. From the available images, monthly average images were determined using the cloud-free pixels. Then the mean winter reflectance from December to March and the mean summer reflectance June to September were determined.
Field ecologists in the project area document light attenuation using scalar radiometers that measure photo-synthetically-active radiation (PAR, 400-700nm). We used a Licor 4pi PAR sensor for profiles of scalar irradiance at 0.25-m increments from 0.25 m (or 0.5m) depth to the bottom.
SEAGRASSES Bottom coverage of Thalassia testudium in Rankin Lake, Johnson Key Basin, and Rabbit Key Basin was determined using a modified Braun-Blanquet cover-abundance method (Mueller-Dombois and Ellerberg, 1974). Coverage for 1991 was obtained by randomly sampling 10 locations per basin from a 0.5-nautical (nmi) grid. Coverage for 1994-1996 was obtained by systematic random sampling within 30-35 tessellated hexagons per basin. All data were obtained by sampling four 0.25 meter square quadrats per station (north, east, south and west of the vessel). The density values correspond to the following modified Braun-Blanquet cover-abundance scale: 5=cover of more than 75% of the quadrat; 4=50-75% cover; 3=25-50% cover; 2=5-25% cover, 1=numerous stems with less than 5% cover or scattered with up to 5% cover; 0.5=few stems with small cover; 0.1=solitary, with small cover, and 0=not present. Frequency of occurrence and density information for each species within a particular basin was calculated using the formulas: Frequency = no. of occupied quad/total no. of quads and Density = sum of B-B scale values/total no. of quads. The areal extent of each cover was estimated by kriging the mean station data for each basin using Surfer software package Golden Software. With the nominal 1-km spacing of the samples, each 1-m sq sample site fell in a different pixel. Reflectances for all pixels with sites in a basin were averaged; the combination of kriging and averaging dampens out the scaling problems between the 1-m sq samples with the individual 1.2 km sq pixels.
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Person who carried out this activity:
727 803-8747 ext. 3045 (voice)
727 803-2030 (FAX)
rwertz@usgs.gov
Ransibrahmanakul, Varis Stumpf, Richard P., 2002, The Use of AVHRR Satellite Data for Estimating Spatially Varying Critical Wind Stress in Florida Bay: Journal of Coastal Research v. 18, no. 2, p. 267-273, Coastal Education and Research Foundation (CERF), Royal Palm Beach, FL.Online Links:
The full article is available via journal subscription or single article purchase. The first page of the article may be viewed on the website below.
Stumpf, R. P. Frayer, M. L.; Durako, M. J, 1999, Variations in water clarity and bottom albedo in Florida Bay from 1985 to 1997: Estuaries v.22, n. 2B, p. 431-444, Springer New York, New York, New York.Online Links:
Mueller-Dombois, D. Ellerberg, H., 1974, Aims and Methods of Vegetation Ecology: John Wiley and Sons, New York, NY.
Stumpf, R. P. Pennock, J. R., 1989, Calibration of a general optical equation for remote sensing of suspended sedimetns in a moderately turbid estuary: Journal of Geophysical Research - Oceans v. 94, n. C10, p. 14363-14371, American Geophysical Union, Washington, DC.Online Links:
The full article is available via journal subscription or single article purchase. The abstract may be viewed on the website below.
Stumpf, R. P. Pennock, J. R., 1991, Remote estimation of the diffuse attenuation coefficient in a moderately turbid estuary: Remote Sensing of Environment v. 38, n. 3, p.183-191, Elsevier Science B. V., Amsterdam, The Netherlands.Online Links:
The full article is available via journal subscription or single article purchase. The abstract may be viewed on the website below by selecting the volume and issue number.
Iverson. R. L. Bittaker, H. F., 1986, Seagrass distribution and abundance in eastern Gulf of Mexico coastal waters: Estuarine, Coastal and Shelf Science v. 22, n. 5, p. 577-602, Elsevier B. V., Amsterdam, The Netherlands.Online Links:
The full article is available via journal subscription or single article purchase. The abstract may be viewed on the website by selecting the volume and issue number.
Rao, C. R. N. Chen, J., 1995, Inter-satellite calibrations for the visible and near-infrared channels of the Advanced Very High Resolution Radiometer on the NOAA-7, NOAA-9, and NOAA-11 spacecraft: International Journal of Remote Sensing v. 16, n. 11, p. 1931-1942, Taylor & Francis Gourp, online.Online Links:
The full article is available via journal subscription or single article purchase. The abstract may be viewed on the website below.
Rao, C. R. N. Chen, J., 1996, Post-launch calibraiton of the visible and near-infrared channels of the Advanced Very High Resolution Radiometer on the NOAA-14 spacecraft: International Journal of Remote Sensing v. 17, n. 14, p. 2743-2747, Taylor & Francis Group, online.Online Links:
The full article is available via journal subscription or single article purchase. The abstract may be viewed on the website below.
Stumpf, R. P., 1992, Remote sensing of water quality in coastal waters: Environmental Research Institute of Michigan, Ann arbor, MI.
The datasets were mapped to a Mercator projection with a pixel size of 1.13 km at latitude 25 deg North and residual navigational errors were removed by registering the image within a pixel of the NOAA digital shoreline.
Nearly 1700 scenes were used from over 2000 scenes processed with about 1000 nominally cloud-free scenes. The analysis used the afternoon satellites, NOAA-9, NOAA-11, and NOAA-14, as these have the best relative calibration and provided more robust datasets in the winter when the sun is lowest.
The failure of NOAA-13 on launch in 1993 left NOAA-11 as the primary satellite in 1994. The orbit of NOAA-11 had precessed to late afternoon precluding quality imagery in winter 1994 due to low sun angles. NOAA-11 failed in September 1994 and an afternoon satellite was not available till the launch of NOAA-14 in late December.
The AVHRR on the National Oceanic and Atmospheric Administration’s polar-orbiting meteorological satellite provides almost daily imagery at 1-km pixel resolution.
Monthly average image values were corrected month-by-month for a systematic bias for greater offsets with earlier scenes at the Gulf Stream site (Stumpf et al. 1997). In addition to reflectance calculations, cloud-contaminated pixels were flagged using a combination of techniques: thresholds on sea-surface temperature and channel 2, and spatial variations on channel 2 and a thermal band.
While each AVHRR sensor is calibrated prior to launch, the lack of onboard calibration raised concerns for post-launch calibration and sensor deterioration. The problem was resolved when a relative calibration of the sensors on the afternoon satellites was developed (Rao and Chen, 1995 & 1996)
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727 803-8747 ext. 3045 (voice)
727 803-2030 (FAX)
rwertz@usgs.gov
Florida Bay satellite images
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