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Fig. 4
Vertical cross section of potential temperature and wind field at La Palma (
top
) at 18:00 UTC
November 28, 2005 and Tenerife (
bottom
) at 00:00 UTC November 29, 2005 at 9km resolution
(
left
), 3km resolution (
middle
), and 1km resolution (
right
). The cross sections are depicted in
bottom-left
of Fig.
3
, La Palma: AA', and Tenerife: BB (color map: wind speed (m/s); vector map:
wind field; contour map: potential temperature (K))
The increase of the horizontal resolution brings high winds to the bottom of the
mountain, in agreement with Durran (
1986
) who attributes this behaviour to the
finite amplitude effects (increase of mountain height), and more in agreement with
the often observed strongest winds near the base of a mountain. In summary, if the
horizontal resolution is decreased, the mountain wave activity lessens, even though
the mountain-top winds present no major differences. As noted by other authors
(e.g., Doyle and Shapiro
2000
; Zhang et al.
2005
) the horizontal resolution of the
mesoscale models need to be higher than 9-10 km to develop the details of the wave.
In La Palma cross section, it is also noticeable the effect of Tenerife island in the
flow, provoking a plume of low wind speed at low levels downwind of La Palma.
Finally, the 10m hourly wind speeds modelled were compared against meteoro-
logical observations available in the area (Fig.
5
). Due to power loss of the automatic
meteorological stations related to the damage of the energy supply provoked by the
intense Delta wind field, the meteorological stations stopped measuring after 22:00
UTC of November 28 and no information is available after then. The model results
show a good agreement with the observations in places where the major wind speeds
were registered. The stations of La Palma-E145 and Tenerife Sur-E276 reached max-
imum wind speeds of 90-108 km/h at 10magl that are accurately reproduced by the
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