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Figure 8.14. Recreation of daytime wind speed, by using the
process of kriging, on July 5, 2005 at 15:00 UTC
Carrying out the same procedure during the day (data collected at 15:00 UTC)
leads to the production of different results, because although the water reserve might
be considered as being the same, relative humidity is lower during the day due to the
higher temperatures (Figure 8.13). Relative humidity can be very low, reaching
values of less than 30% along the French Riviera, these values can sometimes reach
below 20%, whereas at night-time the values can range anywhere between 50 and
80%. The reason for the sharp decrease in relative humidity during the day is due to
the fact that there is a southwest to west-southwest wind, which rises and is similar
to the Foehn wind. This wind affects mainly the coastal area around Nice, and the
areas to the west of Nice. The wind becomes stronger because during the day the
cushion of stable air, which is established during the night and protects the ground
from any synoptic winds, is not present (Figure 8.14).
The meteorological risks recreated during the daytime (at 15:00 UTC) are
different to those created during the night because the effects of the bumps and
hollows are less evident. This is due to the fact that wind gradients are more regular
and homogeneous during the day, especially as far as the synoptic wind is
concerned. This is not the case for the thermal breeze. It is possible to see the effect
that wind has on the meteorological risk that reaches 19/20 in the windiest area, in
other words on the coast (Figure 8.15).
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