3.1.2 Unare River depression
The Unare River depression is the ~100-km gap in the
Coastal Cordillera that allows the river to discharge into the Caribbean
Sea. This depression is connected to the Venezuelan Llanos and, because
of the lack of prominent topographic features along its corridor (axis L
in Fig. 5), enables the inland penetration of the sea breeze created
therein. Based on an analysis of satellite imagery, Foghin-Pillin (2016)
showed that this sea breeze penetrates up to 250 km in an SSW direction.
A well-established SBF around 10ºN (Fig. 8b), separating the cool
maritime air from the statically-unstable mixed layer over the Llanos,
starts advancing onshore around 1300 LST and reaches the limits of the
Guiana Highlands (~ 7ºN) ten hours later (Fig. 8e);
which implies a propagation speed of 8.3 m s-1.
Interestingly, gravity current theory predicts that under these
atmospheric conditions the sea breeze should propagate at that very same
speed. Once the cool air that has been accelerating behind the SBF
arrives at the location of the C2 core (Fig. 5 and Fig. 8a, e, f), it
merges with the latter so increasing the localized wind speed.