Abstract:
The detection of clouds and the analysis of cloud frequency play an
important role for operational weather prediction as well as for climate–
ecological studies. A threshold technique for cloud detection in the tropical
mountainous area of Ecuador is presented which is based on National Oceanic
and Atmospheric Administration Advanced Very High Resolution Radiometer
(NOAA-AVHRR) data. Cloud classification is performed for both day and
night overpasses by applying several threshold tests which also include ancillary
terrain information. From a set of 155 images, maps of relative cloud frequency
are calculated for Ecuador and adjacent areas as well as the central study area of
an ecological project in southern Ecuador (Loja). Results show a clear relation
between topography, main airflow and cloudiness due to barrage and lee-effects.
The spatial extension of high mountain ecosystems such as the Ecuadorian
Pa´ramo has been proven to be significantly influenced by the spatial pattern of
cloud frequency.
