Geoscience Reference
In-Depth Information
3.4. Examples of NOAA-AVHRR data used in Western France
3.4.1.
NOAA satellites
NOAA orbiting satellites are American satellites. The NOAA program was
created in 1970 and was the successor of the TIROS program. Today the NOAA
program launches satellites into space approximately every 2 years. The NOAA
satellites are located in low orbits in space, just 900 km above the surface of the
Earth. They are referred to as orbiting satellites as they circle the Earth in a period of
100 minutes and their orbit is almost polar. There is a slight difference in the
location of the ground track that is covered by the satellites and the actual meridians
that exist on the Earth's surface. This means that it is possible for the satellites to fly
over and monitor activity all over the planet, including high latitude areas, which is
not the case for Meteosat satellites. In addition to this, the NOAA satellite is then
capable of monitoring the same point at the same time every day. NOAA satellites
are equipped with an AVHRR radiometer, which has a spatial resolution of
approximately 1 km and is able to carry out measurements in six different channels
that can be found in the satellite, with each channel responding to different needs
[DSO 96]:
- 1: 0.58-0.68 μm, visible light (albedo);
- 2: 0.72-1.1 μm, near infrared (used to study vegetation);
- 3A: 1.58-1.64 μm, medium infrared (used to study ice and snow);
- 3B: 3.53-3.93 μm, medium infrared (used for the differentiation of clouds and
snow/ice);
- 4: 10.3-11.3 μm, thermal infrared (used to study surface temperatures);
- 5: 11.5-12.5 μm, thermal infrared (used to study surface temperatures).
The longevity of this program, as well as the variety of applications created from
recordings made by such applications, explain the importance of the scientific use of
this data. These applications vary in size and can be used on a global scale, for
example they can be used to monitor changes in vegetation cover brought about by
human activity such as deforestation, or activities that influence climate. The
applications can also be used on a regional scale and are also used on a daily basis
for weather forecasting. All of this information will be shown through the examples
of air temperature estimation and the monitoring of drought in the West of France.
3.4.2.
Estimating air temperatures in the region of Brittany, France
Gathering information on local climates that are not equipped with a
meteorological station means that values are recorded by a station in the vicinity and
these are extrapolated and applied to the area that does not have a meteorological
station. However, the values recorded at the nearby station need to be recorded in a
similar environment. It is also possible to use a spatial interpolation method thanks
to a grid of measurement sites created around the area that is being studied, in other
words values from the surrounding areas are also recorded. Several different spatial
