Description of the Maps





OCEAN FEATURES
ANALYSIS (OFA): GULF STREAM SOUTH This map provides currents, temperatures
and ocean floor data. A Celsius to Fahrenheit conversion chart appears
on the map key, as well as information about the aspects of ocean surface
features.. During the heightened time of sailing to America by countries
such as England, it was noticed that some ships made the journey across
the Atlantic Ocean in much less time than others. These "quicker" ships
first sailed south from England toward the equator and then traveled parallel
to the equator toward America. This enabled them to avoid going against
a strong current that flowed from what is now the northern tip of the United
States across the Atlantic towards England. This current is called the
Gulf Stream and is labeled "GS" at various points on the map. The Gulf
Stream: A description Trade winds blowing from the northeast and southeast
near the equator off the western coast of Africa, coupled with the Coriolis
effect start a current of Atlantic ocean water that moves parallel to the
equator. This warm stream of water is pushed into the Gulf of Mexico. Because
of the shape of the Gulf of Mexico, a loop current, labeled "LC", is created.
Warm eddies, labeled "WE", also spin off. The Gulf Stream continues its
way northward along the eastern coast of the United States, and eventually
turns east towards England, and crosses the Atlantic Ocean. This eastward
current is the one mentioned above that slowed ships that tried to sail
directly across the ocean from England to America. Off the coast of Europe,
the Gulf stream turns south to follow the western coasts of Europe and
Africa until it gets to the equator where it completes its circular pattern.




MULTI-CHANNEL
SEA SURFACE TEMPERATURE(MCSST) This activity opens a window to visualizing
sea surface temperature. The oceans have been monitored for the past 17
years using remote sensing satellites that measure the temperature of the
sea very accurately from space. Current satellites do this to within .3
degrees Celsius of the actual sea surface temperature. Accuracy is important
because it is believed that small changes in the temperature of the sea
can have significant impacts on world-wide weather patterns. The scientific
data that you will use was collected by the Advanced Very High Resolution
Radiometer (AVHRR) on board a NOAA (National Oceanic and Atmospheric Administration)
satellite. The Multi-Channel Sea Surface Temperature Map provides temperature
data in a color-coded form. The Very High Resolution Radiometer (AVHRR)
orbits collect data and are validated by ground truthing through comparison
with high-quality global drifting buoy data. The buoys drifting on the
ocean surface provide data within four hours of the satellite data and
the location of the buoy is within 25 kilometers of that taken by the AVHRR
satellite. By looking at the temperature maps students can easily identify
the differences in temperatures of the currents. This map when used in
conjunction with the Ocean Features Analysis Map shows how numeric data
can be visualized using colors. It provides a bridge for visualization
of data using images.




SPECTRAL WAVE ANALYSIS (SWAPS)
The Spectral Wave Prediction System maps provide forecasts of wave height,
period, and direction. This information is important in sailing because
wave action is directly related to wind. Generally, the higher the waves,
the greater the wind in the vicinity. There are many variables in this
generality however. For instance, the smaller the body of water, the smaller
the waves produced by the same velocity or speed of wind. Also, waves can
be generated by winds located some distance from the wave located. Waves
will travel over great distances unless interrupted by some obstacle such
as land. Since wave direction generally follows wind direction, this map
will be useful for predicting wind direction. Of course wind direction
is important in sailing since it is the wind that provides the power to
move the sailboat. Attempting to sail into the wind with a sailboat results
in many "tacking" maneuvers. Doing this results in slower overall speed.
While it seems apparent that sailing in the direction the wind is blowing
would provide the greatest speed, this is in fact a false assumption. A
sailboat will actually move faster in a cross wind. One would probably
want to avoid areas or points on the map where arrows point in different
directions. This may indicate unstable air which would result in unpredictable
winds.




ALTIMETRY Altimetry is the technique for obtaining
sea surface information using data collected from the combination of satellites
and drifter buoys. There are currently three satellites used to collect
information about the sea surface. As each of these satellites orbit the
earth, they collect information from drifter buoys located under their
path, then transmit data back to ground stations for analysis. Drifter
buoys are used to collect information about the sea surface, especially
wave and wind data, which is transmitted to a satellite. Information about
the height of the sea surface is obtained by the satellite sending out
a signal to the buoy and then measuring the response time for the echo
to return. This is referred to as nadir sensing. In this way scientists
are able to study the geophysics associated with sea surface height. Bulges
in the sea surface are caused by gravity anomalies associated with differences
in the crust's density. This supplies information about the topography
of the crust under the ocean. As buoys drift in the currents, they provide
useful information about ocean currents. The data they collect for wave
height and wind speed are used in both industry and scientific research.
The Altimetry map used in this lesson shows the last seven tracks of the
orbital tracking satellite and the information collected from the buoys.
While the SWAPS map indicates the data for wave height, the Altimetry map
shows sea surface wind conditions. Data is given using standard wind flags,
used in weather map applications. The tail of the flag indicates wind speed.
Each complete bar of the flag represents winds of 10 knots. A half flag
indicates 5 knots. For land lovers, a knot is equal to approximately 1.15
miles per hour. The map used for this lesson also shows wind speed by color
coding, which is explained in the key at the bottom of the map. Wind direction
is as important to understand as speed. The flags shown on the map indicate
the direction of the wind, from the flag to the point end. Using the wind
speed and direction information shown on the Altimetry map, in combination
with the wave height shown on the SWAPS map, information is provided about
sea surface conditions necessary to plan shipping or sailing.