Monitoring interactions between cloud base and the subalpine-alpine environments of the Presidential Range

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Roberti, Joshua Alexander
The exposure to clouds has both positive and negative implications to subalpine and alpine ecosystems. In a negative perspective, clouds deposit pollutants considered harmful to montane environments (Schlesinger and Reiners 1974; Kimball et al. 1988). They also contribute to ice loading and mechanical degradation of the forest, a major determinant of where the treeline-alpine ectone boundary exists in the northeastern United States (Kimball and Weihrauch 2000). The purpose of this research was to determine the frequency of cloud base occurrence near the treeline-alpine ectone boundary of the Presidential Range. Different mathematical procedures were performed to acknowledge height characteristics of cloud bases within the Presidential Range. Statistical comparisons were generated for cloud data on the east and west side of Mt. Washington. It was found that Mt. Washington's western slope was subjected to more cloud base interaction than the eastern slope. Principal Components Analysis (PCA) of cloud heights was produced to determine how the heights varied with each other within a seventy-kilometer radius (mesoscale) of the Presidential Range. This analysis revealed that cloud base heights fluctuated differently at each site, and more importantly, on the two sides of Mt. Washington. PCA of relative humidity was generated for the eastern slope of Mt. Washington (microscale). This analysis exhibited that the eastern slope had three distinct modes of relative humidity. Cloud base height data from nearby ASOS/AWOS ceilometers proved to be inaccurate representations of cloud heights at Mt. Washington. Therefore, cloud base heights from surrounding areas should neither be extrapolated nor interpolated to account for cloud heights within areas of complex terrain. The use of in-situ hygrometers provide an inexpensive solution to the extrapolation / interpolation problem of ceilometer data. However, the high degree of topographic heterogeneity and the lack of a high-density sampling network, particularly hygrometers, limit the ability to accurately extrapolate or interpolate cloud base heights within the Presidential Range. Therefore, hundreds of hygrometers should be deployed throughout the Presidential Range in order to account for topographic effects.