Understanding the role of fog in forest hydrology: stable isotopes as tools for determining input and partitioning of cloud water in montane forests

Scholl, Martha A.; Eugster, Werner; Burkard, R.

doi:10.1017/cbo9780511778384.025

Cited by 41 publications

(92 citation statements)

References 61 publications

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“…2). Fog has been reported to be isotopically enriched relative to local rainfall (if they are from the same source) because it is a first stage condensate and formed at generally higher temperatures than rainfall (Gonfiantini and Longinelli, 1962;Ingraham and Matthews, 1988;Scholl et al, 2011). However, local rainfall can be more enriched isotopically than fog in some arid environments because sub-cloud evaporation could result in enrichment beyond that observed in the first stage condensates alone .…”

Section: Resultsmentioning

confidence: 99%

Fog Spatial Distributions over the Central Namib Desert - An Isotope Approach

Kaseke

Tian

Wang

et al. 2018

Aerosol Air Qual. Res.

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Fog is a characteristic feature of the Namib Desert and is essential to life in this fog dependent system. It is often acknowledged that advective fog from the ocean is the dominant fog type over the Namib Desert fog-zone but recent evidence suggests that other fog types occur in this area. Knowledge of the existence and spatial distribution of different fog types will enhance the mechanistic understanding of fog formation and potential changes in this region, but such knowledge is limited in literature. In this study, we investigated fog spatial variations within the Namib Desert fog-zone by applying stable isotope (δ 18 O and δ 2 H) techniques to differentiate various fog types and identify their source waters. Isotope based results showed that at least three types of fog (advective, radiation and mixed) occurred in this region and what appears as a single fog event may include all three types. Results suggest that radiation fog was the dominant fog type during our study period. The results also suggest that advective fog (with Atlantic Ocean origins) either dissipated 30-50 km inland and the residual humidity combined with locally derived moisture to form mixed fog or advective fog incorporated local moisture along its trajectory inland resulting in mixed fog. Fog in the Namib Desert was consistently depleted in 18 O and 2 H compared to rainfall and this was attributed to sub-cloud evaporation of the rainfall as well as different sources of fog and rainfall. Sub-cloud evaporation led to enrichment of 18 O and 2 H in rainfall beyond that of the first stage condensate, fog. Advective fog is often considered the architect of the fog-zone in the Namib Desert, but our results demonstrated multiple dominant fog types during the study period, suggesting knowledge of both fog frequency and fog type is needed to better predict climate change impacts on the fog-zone.

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Section: Resultsmentioning

confidence: 99%

Fog Spatial Distributions over the Central Namib Desert - An Isotope Approach

Kaseke

Tian

Wang

et al. 2018

Aerosol Air Qual. Res.

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“…Some of these previous studies were multiyear efforts, notably the ones done in California [ Ingraham and Matthews , 1990, 1995; Dawson , 1998; Corbin et al , 2005; Fischer and Still , 2007], but most of the studies in tropical mountain environments with orographic precipitation involved short‐term data collection or are not published in the peer‐reviewed literature [ te Linde , 2000; Eugster et al , 2002; Schmid , 2004; Scholl et al , 2006]. Fog or cloud water isotope values measured worldwide have a large range, from −10.4 to +2.7‰ δ 18 O and −71 to +13‰ δ 2 H, depending on the temperature range and vapor sources in the study areas [ Scholl et al , 2007]. Most of the studies used sample collection methods similar to this study, and reported average fog or cloud water isotopic composition to be more enriched than average rain isotopic composition at the same site.…”

Section: Resultsmentioning

confidence: 99%

Cloud water in windward and leeward mountain forests: The stable isotope signature of orographic cloud water

Scholl

Giambelluca

Gingerich

et al. 2007

Water Resources Research

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[1] 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% d 18 O and 12% d 2 H for the windward site and 2.8% d 18 O and 25% d 2 H for the leeward site, with the cloud water samples enriched in 18 O and 2 H relative to the rain samples. A summary of previous literature shows that fog and/or cloud water is enriched in 18 O and 2 H 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.

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“…In general, topographical exposure was the most significant parameter explaining the geographical differences between cloud forests and montane forests, followed by distance to coast, montane range size, and altitude [11]. Despite the occurrence of TMCFs in a wide range of climatic and landscape conditions [11], the main common climatic attribute for every TMCF is frequent and persistent cloud immersion [6,15,16] and the factors that influence cloud formation. Temperature, moisture, and nature of the cloud condensation nuclei govern cloud condensation.…”

Section: Discussionmentioning

confidence: 99%

Frequency of Low Clouds in Taiwan Retrieved from MODIS Data and Its Relation to Cloud Forest Occurrence

et al. 2015

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Abstract: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 PasaniaElaeocarpus 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 OPEN ACCESSRemote Sens. 2015, 7 12987 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.

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Understanding the role of fog in forest hydrology: stable isotopes as tools for determining input and partitioning of cloud water in montane forests

Cited by 41 publications

References 61 publications

Fog Spatial Distributions over the Central Namib Desert - An Isotope Approach

Fog Spatial Distributions over the Central Namib Desert - An Isotope Approach

Cloud water in windward and leeward mountain forests: The stable isotope signature of orographic cloud water

Frequency of Low Clouds in Taiwan Retrieved from MODIS Data and Its Relation to Cloud Forest Occurrence

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