Temporal and Spatial Coherence of Wind Profiles over Terrain of Diverse Complexity

Observed wind profiles are used for many purposes, such as initializing and validating numerical weather prediction models, studying phenomena and processes in the boundary layer and free atmosphere, estimating wind resources, characterizing climate, predicting the transport of airborne material, and monitoring the threat of hazardous weather. This study uses observed profiles of horizontal winds from profilers, lidars, and rawinsondes, and simulated profiles from model analyses over terrain of various complexity to assess how the coherence of wind profiles decreases with time and distance. Overall, mean time-lagged autocorrelations of horizontal wind in the lower troposphere remain high for many hours after a sounding, and spatial correlations can be high to horizontal distances of 100 km and beyond. However, from place to place and season to season, the temporal and spatial trends are varied. At the mountainous locations in the study, spatial coherence, which is lowest near the ground, changes with altitude more quickly than over less complex terrain. There is also more heterogeneity in horizontal patterns of coherence at the mountainous locations, reflecting the influence of underlying terrain. This study is a step toward assessing how well a sounding taken at a given time and location in mountainous terrain is representative of a sounding at some other time and location when/where a sounding is not possible.