Scholl, M. A., T. W. Giambelluca, S. B. Gingerich, M. A. Nullet, and L. L. Loope (2007), Cloud water in windward
and leeward mountain forests: The stable isotope signature of orographic cloud water, Water Resour. Res., 43, W12411,
doi:10.1029/2007WR006011.
Abstract:
Cloud water can be a significant hydrologic input to mountain forests. Because it is a
precipitation source that is vulnerable to climate change, it is important to quantify
amounts of cloud water input at watershed and regional scales. During this study, cloud
water and rain samples were collected monthly for 2 years at sites on windward and
leeward East Maui. The difference in isotopic composition between volume-weighted
average cloud water and rain samples was 1.4% d18O and 12% d2H for the windward site
and 2.8% d18O and 25% d2H for the leeward site, with the cloud water samples enriched
in 18O and 2H relative to the rain samples. A summary of previous literature shows
that fog and/or cloud water is enriched in 18O and 2H compared to rain at many locations
around the world; this study documents cloud water and rain isotopic composition
resulting from weather patterns common to montane environments in the trade wind
latitudes. An end-member isotopic composition for cloud water was identified for each site
and was used in an isotopic mixing model to estimate the proportion of precipitation
input from orographic clouds. Orographic cloud water input was 37% of the total
precipitation at the windward site and 46% at the leeward site. This represents an estimate
of water input to the forest that could be altered by changes in cloud base altitude resulting
from global climate change or deforestation.