Complex Relationships Between the Spatial and Temporal Patterns of Climate in Mountainous Terrain

A complex interplay between the spatial and temporal patterns of climate is known to exist at the regional scale in the Pacific Northwest. For example, there is a surprising lack of relationship between maximum temperature in winter and minimum temperature in all seasons on mountain tops vs. those in valley bottoms. This lack of relationship exists at time scales ranging from sub-daily to monthly and longer. Recent analysis of temperature data from the H.J. Andrews Experimental Forest in Oregon's Cascade Mountains provides a case study from a small (10x12 km) watershed. Initial results suggest that: (1) Temporal variations in climate do not always occur in lock-step across the landscape - they are often asynchronous; (2) much of this asynchrony appears to be controlled by susceptibility to cold air flowing down drainages and pooling in valley bottoms; (3) the patterns and degrees of climatic asynchrony (i.e., cold air drainage) vary strongly with weather regime, season, time of day, topographic position, and other factors; and (4) effects of cold air drainage on the spatial patterns of snowpack persistence may produce positive feedbacks that can reinforce cold air pooling. This has great implications for long-term ecosystem monitoring and analysis in complex terrain. It suggests that terrestrial and aquatic ecosystems in very close proximity may be exposed to markedly different regimes of weather and climate trends and variability across scales ranging from seconds to months, and perhaps longer.