Abstract
The height of stratocumulus clouds (Sc) in the Northeast Atlantic, off
the coast of Africa in the Central Macaronesian region, has been
examined over the past two decades. We analyzed a dataset of sounding
and surface meteorological data from the islands of Madeira and Tenerife
to investigate cloud base height (CBH) and cloud top height (CTH) using
the lifting condensation level and the height of the trade wind
inversion base as proxies. The results of a Mann-Kendall analysis
indicate a statistically significant downward trend in the height of the
Sc boundaries at both locations. This trend is particularly pronounced
towards the northern end of the Central Macaronesian region (Madeira),
where the decrease is more than double that the observed at the southern
end (Tenerife). The decrease in CTH is consistent with the observed
increase in subsidence at the 850 hPa level over the last two decades,
which may be related to the observed expansion and intensification of
the Azores High (AH). The observed change in the CBH can be attributed
to an increase in the moisture content of the air, in line with the
observed changes in the regional and local sea surface temperature.
However, it cannot be ruled out that changes in the AH, also evidenced
by the observed trend in surface pressure at Central Macaronesia, have
altered the moisture transport patterns. While the observed changes in
the Sc may have significant implications for regional climatic
conditions, the most imminent effects are on the height distribution of
cloud forests.