Advancing Water Resources Research and Management

World Wide Web Access to
Great Lakes CoastWatch Environmental Data ^*

George A. Leshkevich , David J. Schwab , Glenn C. Muhr , and Songzhi Liu

Table of Contents

Abstract

Introduction

AVHRR Imagery (NOAA 14 & NOAA 15 AVHRR Imagery)

GLSEA (Great Lakes Surface Environmental Analysis)

GOES Imagery (GOES 8 Imagery)

Image Products (Channel 1 / Channel 2 Reflectance Products)

In Situ Data (Great Lakes NOAAPORT Marine Observation Data)

Statistics (Great Lakes Average Surface Water Temperature)

Future Plans

References

Abstract

CoastWatch is a nationwide National Oceanic and Atmospheric Administration (NOAA) program within which the Great Lakes Environmental Research Laboratory (GLERL) functions as the Great Lakes regional node. In this capacity, GLERL obtains, produces, and delivers environmental data and products for near real-time monitoring of the Great Lakes to support environmental science, decision making, and supporting research. This is achieved by providing Internet access to near real-time and retrospective satellite observations, in-situ Great Lakes data, and derived products to Federal, state, and local agencies, academic institutions, and the public via the Great Lakes CoastWatch web site (http://coastwatch.glerl.noaa.gov). The goals and objectives of the CoastWatch Great Lakes Program directly support agency statutory responsibilities in estuarine and marine science, living marine resource protection, and ecosystem monitoring and management. Great Lakes CoastWatch data are used in a variety of ways including monitoring of algal blooms, plumes, ice cover and water temperatures, two and three dimensional modeling of Great Lakes physical parameters such as wave height and currents, damage assessment modeling, research, and for educational and recreational activities.

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Introduction

In response to an occurrence of "Red Tide" off the coast of North Carolina in late 1987, a program was developed within NOAA's National Environmental Satellite, Data and Information Service (NESDIS) to provide the NOAA National Marine Fisheries Service Laboratory at Beaufort, North Carolina with satellite-derived sea surface temperature (SST) maps of the Gulf Stream and other types of data so that future occurrences of this phenomenon or other coastal environmental events could be better anticipated and monitored (Pyke, 1989). Within the NOAA Coastal Ocean Program, this program was extended to other coastal regions of the U.S., including the Great Lakes, to become the NOAA CoastWatch Program, now a part of NESDIS (Leshkevich et al., 1997, Leshkevich et al, 1993, Schwab et al., 1992). The original goal of the CoastWatch Program, to develop and deliver environmental data and products for near real-time monitoring of U.S. coastal waters to support environmental science and decision making, has expanded to include research, educational, and recreational uses.

The CoastWatch Great Lakes Node is currently receiving a suite of 33 enhanced digital image products including satellite-derived surface temperature, visible and near-infrared reflectance, brightness temperatures, cloud masks, and satellite/solar zenith angle data from the NOAA/AVHRR (Advanced Very High Resolution Radiometer) series of satellites, as well as GOES (Geostationary Operational Environmental Satellites) visible, near infrared, and water vapor imagery. These near real-time products are acquired at GLERL from NESDIS via the Internet.

The Great Lakes environmental data received at the CoastWatch Great Lakes Node are processed within 30 minutes after download. Several types of the products are produced and stored on the CoastWatch Great Lakes Node web site, including AVHRR imagery in GIF, PostScript, and CoastWatch raw data format, AVHRR interactive SST imagery (SatView), Great Lakes Surface Environmental Analysis (GLSEA), subtraction or histogram equalized reflectance imagery, and GOES imagery (see Figure 1). Currently, the AVHRR imagery on the web site are updated twice a day (2AM and 9PM local time). GLSEA, subtraction and histogram equalized reflectance imagery are updated once a day. AVHRR satellite data and products are kept on the web site for two weeks. Access to a retrospective archive beginning in 1990 via the NOAA CoastWatch Active Access System (NCAAS) is also available.

The CoastWatch Great Lakes Node also receives raw marine observations for the Great Lakes region via satellite transmission from the NOAAPORT broadcast system. The information extracted from NOAAPORT observations includes: air temperature, dew point, wind direction, wind speed, maximum wind gust, cloud cover, air pressure, water temperature, wave height, and wave period. The raw marine observations are available on the CoastWatch Great Lakes Node web site and are updated hourly. In addition, other in-situ data and modeled data including marine and meteorological observations, NDBC buoy observations, water level gauge measurements received from the National Ocean Service (NOS), and Great Lakes Forecasting System (nowcast and forecast) products are made available to Great Lakes CoastWatch data users via links on the CoastWatch Great Lakes web site.

Access to near real-time AVHRR satellite imagery received at GLERL is available at no cost after submitting an electronic registration form via the CoastWatch Great Lakes web site. Other data and products (with the exception of the proprietary RADARSAT data) do not require registration for access.

In a cooperative project with the Great Lakes Sea Grant Network, CoastWatch AVHRR imagery is downloaded from the CoastWatch Great Lakes Node by Michigan Sea Grant and the Michigan State University (MSU) Institute of Water Research and processed to produce a contoured surface water temperature product of regional areas on the Great Lakes. This product is available on the CoastWatch Great Lakes web site via a link to the Michigan Sea Grant web site at MSU (http://www.coastwatch.msu.edu).

Figure 1. NOAA CoastWatch Great Lakes Node Web Site
(118.9Kbytes, 642x538 pixels)

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AVHRR Imagery (NOAA 14 & NOAA 15 AVHRR Imagery)

CoastWatch image products, i.e., water surface temperature imagery, visible (Ch.1) and near-infrared (Ch.2) reflectance data, cloud mask, and satellite/solar zenith angle data are obtained from NOAA polar-orbiting weather satellites. There are currently two operational polar-orbiting weather satellites (NOAA 14 and NOAA 15) which each carry (among other sensors) the Advanced Very High Resolution Radiometer (AVHRR). Each satellite passes over a given area twice a day (about 4 AM and 2:30 PM local time for NOAA 14 and about 8:30 AM and 7:30 PM local time for NOAA 15) The AVHRR scans a swath of approximately 2700 km on the earth's surface beneath the satellite in five radiometric bands, Ch.1 - visible (0.58-0.68 µm), Ch.2 - reflected infrared (0.725-1.0 µm), and three thermal infrared channels (Ch.3 - 3.55-3.93 µm, Ch.4 - 10.3-11.3 µm, Ch.5 - 11.5-12.5 µm) (Koczor, 1987). AVHRR data are processed at two resolutions, 4 km Global Area Coverage (GAC) and 1 km High Resolution Picture Transmission (HRPT). The HRPT data are used for Great Lakes CoastWatch imagery. These data are downloaded to a satellite receiving station then transmitted to NESDIS facilities in Suitland, Maryland where they are calibrated, geo-located, quality controlled, and made available as AVHRR level 1b data sets (see Kidwell, 1991 and Pichel et al., 1991 for details of this process). For the CoastWatch program, the level-1b data are mapped to a Mercator projection and resampled to a 512x512 pixel grid. Four scenes or "windows" are extracted for the Great Lakes region as listed in Table 1. One synoptic scene covers all five lakes at a 2.56 km resolution. The other three scenes focus on Lake Superior, Lakes Michigan and Huron, and Lakes Erie and Ontario at twice the resolution of the five-lake scene. Actual resolution is determined by d cos f, where d is the spatial resolution at the equator, and f is the latitude. The grid spacing for the three high resolution Great Lakes scenes ranges from 1.24 to 1.30 km as indicated in Table 1.

Table 1. CoastWatch Windows for the Great Lakes

Full resolution (1.3 km) synoptic scenes on a 1024x1024 pixel grid are currently being received and will be made available in the near future.

• select the synoptic scene or one of the three subscenes (see Figure 2).

  
  
  Figure 2. The Laurentian Great Lakes
  (11.99Kbytes, 512x512 pixels)
  

• select daytime or nighttime SST or Ch.1 (visible) or Ch.2 (near-infrared) scenes from the thumbnail images of the past two weeks. (see Figure 3).

  
  
  Figure 3. Thumbnail Images of the Past Two Weeks
  (55.96Kbytes, 547x501 pixels)
  

• view or download selected images (see Figure 4).

  
  
  Figure 4. Selected Image
  (75.58Kbytes, 576x445 pixels)
  

• run a Java applet program to interactively retrieve temperature (C or F) and Lat/Long at the cursor position (see Figure 5).

  
  Figure 5. Run a Java Satview program
  (To run Java Applet, you need an Internet connection. Downloading an imagery may take 4 minutes for a 28.8K modem)
  (489.6Kbytes, 512x721 pixels)
  

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GLSEA (Great Lakes Surface Environmental Analysis)

The Great Lakes Surface Environmental Analysis (GLSEA) is a daily, cloud free digital map of the Great Lakes surface water temperature (with ice cover overlay during the winter) produced at the NOAA CoastWatch Great Lakes Node. The GLSEA is stored as a 512x400 pixel map in GIF format, suitable for viewing on PCs and workstations (see Figure 6). Software for accessing and viewing CoastWatch image data and products is available for download from the "Software" page on the CoastWatch Great Lakes web site.

Figure 6. Great Lakes Surface Environmental Analysis (GLSEA)
(23.79Kbytes, 512x400 pixels)

The lake surface temperatures are derived from the near real-time AVHRR satellite imagery obtained by the Great Lakes CoastWatch program. The addition of ice cover concentration information provided by the National Ice Center (NIC) was implemented in late 1997 (see Figure 7). Lake surface temperatures are updated daily with information from the cloud-free portions of the previous day's satellite imagery. If no imagery is available, a smoothing algorithm is applied to the previous day's map (see Schwab et al., in press). During the winter season, ice concentration information is then added, using the most recent Great Lakes Ice Analysis produced by the NIC, nominally three times per week during the ice season.

Figure 7. Great Lakes Surface Environmental Analysis with Ice Cover (GLSEA)
(25.76Kbytes, 512x400 pixels)

Yearly and previous 365 day animations of the daily GLSEA chart in QT, FLC, and AVI formats are also available (see Figure 8).

Figure 8. Previous 365 days GLSEA animation (AVI format)
(4597.06Kbytes, 512x400 pixels)

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GOES Imagery (GOES 8 Imagery)

The GOES spacecraft is designed to operate in geosynchronous orbit, 35,790 km (22,240 statute miles) above the earth, thereby remaining stationary relative to the earth's surface. The spacecraft continuously views the continental U.S., neighboring environs of the Pacific and Atlantic Oceans, and Central and South America. The three-axis, body stabilized spacecraft design (GOES-8, onward) enables the sensors to image clouds, monitor earth's surface temperature and water vapor fields, and sound the atmosphere for its vertical thermal and water vapor structures.

The main mission is carried out by the primary payload instruments, the Imager and the Sounder. The Imager is a multichannel instrument that senses radiant energy and reflected solar energy from the earth's surface and atmosphere. The Sounder provides data for vertical atmospheric temperature and moisture profiles, surface and cloud top temperature, and ozone distribution.

Two advanced GOES satellites are in use: GOES-8, and -10 (Series I-M). Currently the CoastWatch Great Lakes Node recieves three types of GOES-8 satellite imagery (3 km resolution): Visible Channel (Ch.1) (see Figure 9), Infrared Channel (Ch.2) (see Figure 10), and Water Vapor (see Figure 11).

Figure 9. GOES-8 Satellite Imagery (Visible Channel 1)
(136.26Kbytes, 576x432 pixels)

Figure 10. GOES-8 Satellite Imagery (Infrared Channel 2)
(87.16Kbytes, 576x432 pixels)

Figure 11. GOES-8 Satellite Imagery (Water Vapor)
(50.31Kbytes, 576x432 pixels)

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Image Products (Channel 1 / Channel 2 Reflectance Products)

Great Lakes CoastWatch visible reflectance products are produced using two types of Advanced Very High Resolution Radiometer (AVHRR) satellite data. AVHRR Channel 1 (visible, 0.58-0.68 µm) and Channel 2 (reflected infrared, 0.725-1.0 µm) from daytime passes of NOAA polar orbiting satellites.

The CoastWatch Great Lakes Node currently provides two types of reflectance imagery products: Subtraction (Ch.1 - Ch.2) (see Figure 12) which is useful in the detection of suspended solids (plumes) and algal blooms in the Great Lakes, and Histogram Equalized Ch.1 (see Figure 13) which is useful for ice cover detection and monitoring during the winter season.

Figure 12. Subtraction (Ch.1 - Ch.2)
(83.37Kbytes, 639x617 pixels)

Figure 13. Histogram Equalized Ch.1
(54.53Kbytes, 642x600 pixels)

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In Situ Data (Great Lakes NOAAPORT Marine Observation Data)

Marine observations for the Great Lakes region are obtained via satellite transmission from the NOAAPORT broadcast system. The NOAAPORT broadcast system provides a one-way broadcast communication of NOAA environmental data and information in near real-time to NOAA and external users. This broadcast service is implemented by a commercial provider of satellite communications utilizing C-band.

These NOAAPORT observations, acquired hourly by the CoastWatch Great Lakes node, are decoded and processed to produce various data files, timeseries plots, and interactive imagemaps (see Figure 14).

Figure 14. Buoys data interactive imageMap
(13.2Kbytes, 760x570 pixels)

The Great Lakes surface observation network is comprised of 205 fixed stations including 18 moored buoys, 11 Coastal Marine Automated Network (CMAN) stations, 35 US Coast Guard stations, 21 Other Marine Reports (OMR) stations, and 120 surface airways stations. In addition, many commercial cargo ships and Coast Guard vessels provide regular meteorological reports. Frequency of observational reporting ranges from about once every 3 hours to 3-5 times per hour depending on the type of station.

The Great Lakes CoastWatch data base includes the following information extracted from NOAAPORT observations: air temperature, dew point, wind direction, wind speed, maximum wind gust, cloud cover, air pressure, water temperature, wave height, and wave period. During a typical summer day, the marine observation data includes about 300 buoy observations, 3500 observations from land stations, and about 300 reports from vessels.

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Statistics (Great Lakes Average Surface Water Temperature)

Great Lakes average surface water temperature derived from the daily Great Lakes Surface Environmental Analysis (GLSEA) is displayed in three formats:

• Previous 365 day GLSEA Average Surface Water Temperature for each lake.
• Average GLSEA Surface Water Temperature Graphs (see Figure 16) for each lake for the previous 5 years and for all lakes for each of the previous 5 years.
• Average GLSEA Surface Water Temperature Data for each lake for the previous 5 years.

The average GLSEA surface water temperature graphs and data will help data users compare the Great Lakes surface water temperature for the past 5 years.

Figure 16. Average GLSEA Surface Water Temperature Graph
(15.71Kbytes, 640x480 pixels)

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Future Plans

To enhance the accessibility and utility of NOAA CoastWatch Great Lakes data, future plans include interactive retrieval of physical parameters such as surface water temperature, ice cover concentration, water depth , etc., at a given location. Plans also include enhancing the present product suite with products derived from new satellite sensors such as synthetic aperture radar (SAR) and ocean color sensors. Figure 17 is an example of a chlorophyll map derived from the SeaWiFS ocean color sensor.

Figure 17. Chlorophyll Map Derived from SeaWiFS Image. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE
(34.31Kbytes, 648x405 pixels)

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References

Kidwell, K.B. (ed.), 1991.

NOAA Polar Orbiter Data Users Guide (TIROS-N, NOAA-6, NOAA-7, NOAA-8, NOAA-9, NOAA-10, NOAA-11, NOAA-12). National Environmental Satellite, Data and Information Service, National Climatic Data Center, Satellite Data Services Division, Washington, D.C. 20233. pp. 280.

Koczor, R.J., 1987.

Multispectral sensing with the AVHRR. ITT Aerospace Optical Division, Fort Wayne, Indiana, 9pp. (presented at the North American NOAA Polar Orbiters Users Group Meeting, Boulder, Colorado, July, 1987).

Leshkevich, G.A., Schwab, D.J. and Muhr, G.C., 1993.

Satellite Environmental Monitoring of the Great Lakes: A Review of NOAA's Great Lakes CoastWatch Program. Photogrammetric Engineering & Remote Sensing 59(3):371-379(1993).

Leshkevich, G.A., Schwab, D.J. and Muhr, G.C., 1997.

Satellite environmental monitoring of the Great Lakes: Great Lakes CoastWatch Program update. Marine Technology Society Journal 30(4):28-35.

Pichel, W., Weaks, M., Sapper, J., Tadepalli, K., Jandhyala, A., and Ketineni, S., 1991.

Satellite mapped imagery for CoastWatch. In Proceedings, 7th Symposium on Coast & Ocean Management, pp.2531-2545. Long Beach, ASCE.

Pyke, T.N., 1989.

CoastWatch: New mission for NOAA weather satellites. Sea Technology 30(4):27-32.

Schwab, D.J., Leshkevich, G.A. , and Muhr, G.C., 1992.

Satellite measurements of surface water temperature in the Great Lakes - Great Lakes CoastWatch. Journal of Great Lakes Research 18(2):247-258(1992).

Schwab, D.J., Leshkevich, G.A., and Muhr, G.C., (in press)

Automated Mapping of Surface Water Temperature in the Great Lakes.   Journal of Great Lakes Research.

Author

Co-Authors

Glenn C. Muhr
NOAA/ Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, MI 48105-2945

Songzhi Liu
Cooperative Institute for Limnology and Ecosystems Research
University of Michigan
2200 Bonisteel Blvd.
Ann Arbor, MI 48109

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