Geoscience Reference
In-Depth Information
In the other example where a 10 m raster is used (example C in Figure 2.2) the
situation is worse because the size of the inaccuracy is bigger than the size of the
pixel. The exact point of location (depending on the moment when the measurement
was taken) may be in one of the nine pixels that surround the theoretical center point
from where the measurement was taken. In this example, a clear error has been
produced.
2.2.2. Endogenous information
Endogenous information relates to all climatological data that can be mapped.
Many organizations, in France and in other countries, measure, archive and transmit
climatological information. Météo-France is the only organization in France that is
entirely dedicated to meteorology and climatology. Météo-France makes several of
its databases available to the general public in the form of its “CLIMATHEQUE”,
which is the only source of homogenous information that has been verified and
validated and which is available throughout the whole of France.
Within the CLIMATHEQUE it is possible to access basic data, such as precise
hourly, daily, 10-day or monthly data, etc. The different variables that are available
include temperature (maximum and minimum daily temperatures, average
temperature or frequency of high (>30ºC) or low (<-5ºC) temperature) precipitation
(frequency, amount), sunshine, frequency of fog, windspeed, etc. Other types of
data, which are the result of specific processes, are also available and they include
climate tables, calculations of degree-days, which are to be issued to the École
Spéciale des Travaux Publics (ETP), a prestigious university in Paris. Only the basic
data will be used in the following examples.
2.2.3. Exogenous information
Ever since the end of the 1980s exogenous information as information layers,
covers all space and is capable of explaining the spatial modifications being
experienced by different climate variables. Transferring information using spatial
analysis tools makes it possible to recreate continuous spatial fields from precise
endogenous data.
These layers of exogenous information are stored within the GIS and make
extensive use of digital elevation models (DEMs) as well as remote sensing which
are the two main initial data sources.
2.2.3.1. DEMs
The DEM is an altitude matrix that is provided in France by the French National
Geographic Institute (IGN). The database in question provides a DEM with different
resolutions which range from 50 to 500 m, even 1 km. In this chapter, we will use
different resolutions due to the fact that the climate models in the following
examples using different scales. By calculation applied to a DEM, it is possible to
Search WWH ::




Custom Search