Geoscience Reference
In-Depth Information
study the data used were collected everyday at 18:00 UTC (Coordinated Universal
Time, which corresponded to 15:00 local time in the northeast of Brazil for the
months of September to December 2000). The method involved identifying cloud
cover that was linked to sea-breeze fronts (lines of cumulus clouds on land parallel
to the coastline), and this was followed by plotting the sea-breeze fronts on a map in
order to estimate how often they were created.
In the northeast region of Brazil, the location of the sea-breeze fronts shows that
there is a very steep spatial gradient. The uneven topography of the land exposed to
the East coast (between Salvador and Recife) makes it difficult to identify sea-
breeze fronts because they tend to be hidden by other cloud formations that are
influenced by mountains and orographic effects (Figure 3.5). At 18:00 UTC, the
sea-breeze fronts reach further inland (known as penetration) as the dry season
advances: in September it is common for sea-breeze fronts to be recorded further
inland at a distance of between 40 and 80 km from the coast, with the average
distance being approximately 60 km. The maximum distance from the coast of
between 60 and 100 km was recorded in November 2000. In French Guiana and in
the areas surrounding the mouths of the Amazon River, this distance is at least
100 km. When the sea-breeze front penetrates so far inland this means that the cloud
cover associated with the sea-front breeze starts to mix with cloud cover associated
with the convection currents that occur above forest areas. The slightly indented
nature of the Ceara coastline makes it easier to identify sea-breeze fronts (Figure
4.5) and also makes it possible to determine how the sea-breeze fronts adapt
depending on how far inland they have penetrated. The strongest, most developed
sea-breeze fronts are associated with weak synoptic winds blowing in the opposite
direction of the sea-breeze. A weak synoptic wind that blows in the same direction
as the sea breeze leads to the sea-breeze front moving further and further inland.
Figure 3.5.
A GOES colored composition from the
September 8, 2006, 18:00 GMT (see color section)
