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The relationship between satellite-derived low cloud frequency and the occurrence of tropical montane cloud forest (TMCF) in Taiwan was investigated. From daily MODIS cloud mask products between 2003 and 2012 the low cloud class was extracted and mean low cloud frequency was calculated for Taiwan. This low cloud frequency map was blended with an existing plot-based vegetation classification for Taiwan to analyze the relationship between low cloud frequency and TMCF occurrence. Receiver operating characteristics curves and the area under the ROC curve (AUC) were used to analyze if a relationship exists. No relationship was found for all four TMCF types taken together (AUC = 0.61) and for the dominant TMCF type, Quercus montane evergreen broad-leaved cloud forest (AUC = 0.5). Strong relationships were found for the two spatially-restricted TMCF types, Fagus montane deciduous broad-leaved cloud forest (AUC = 0.91) and Pasania-Elaeocarpus montane evergreen broad-leaved forest (AUC = 0.84), as well as for the second dominant type Chamaecyparis montane mixed cloud forest (AUC = 0.74). The results show that low cloud frequency thresholds might be associated with specific cloud forest types in Taiwan. Further studies should incorporate information about cloud base height, cloud density, and cloud immersion time as well as satellite-based cloud frequency information with a higher temporal resolution. Combination with satellite-based land cover classifications for Taiwan would allow quasi-continuous observation of TMCF changes. Such knowledge would be the precondition for effective protective actions concerning this exceptional but threatened ecosystem.

http://dx.doi.org/10.3390/rs71012986

Masks of ground fog in the taiwanese mountains (2002 - 2014) processed based on data of all MODIS overflights using the algorithm DOGMA (Schulz, M.; Thies, B.; Chang, S. & Bendix, J. (2016): Detection of ground fog in mountainous areas from MODIS (Collection 051) daytime data using a statistical approach. Atmospheric Measurement Techniques 9, 1135 - 1152 DOI: http://dx.doi.org/10.5194/amt-9-1135-2016.)

Map of montane cloud forest in Taiwan derived from MODIS based ground fog frequency data, ASTER GDEM 2 and Landsat 7 data.

Resolution: 250 m per pixel

The map was created as described in 
Schulz, H.M., Li, C.F., Chang, S.C., Thies, B., and Bendix J.: Mapping the montane cloud forest of Taiwan using 12 year MODIS-derived ground fog frequency data, PLOS ONE, manuscript submitted for publication.

Presence and absence of montane cloud forest in Taiwan. Compiled from the National Vegetation Database of Taiwan.

Ground fog masks were created from MODIS data from 2003 to 2014 using the method DOGMA. From those masks the ground fog frequency was calculated for each month separately.