The Influence of Cloudiness on Hydrologic Fluctuations in the Mountains of the Western United States

Abstract

AbstractThis study investigates snowmelt and streamflow responses to cloudiness variability across the mountainous parts of the western United States. Twenty years (1996–2015) of Geostationary Operational Environmental Satellite‐derived cloud cover indices (CC) with 4‐km spatial and daily temporal resolutions are used as a proxy for cloudiness. The primary driver of nonseasonal fluctuations in daily mean solar insolation is the fluctuating cloudiness. We find that CC fluctuations are related to snowmelt and snow‐fed streamflow fluctuations, to some extent (correlations of <0.5). Multivariate linear regression models of daily snowmelt (MELT) and streamflow (ΔQ) variations are constructed for each month from February to July, when snowmelt is most active. Predictors include CC from five antecedent days up to the current day. The CC‐MELT and CC‐ΔQ associations vary with time and location. The results show the dominance of negative correlations between CC and MELT, exemplifying the cloud‐shading (or clear‐sky) effect on snowmelt. The magnitude of the CC‐MELT association (R2) amounts to 5–61%, typically peaking in May. These associations fade earlier in summer during dry years than wet years, indicating the differing responses of thicker versus thinner snowpack. The CC‐ΔQ association displays a less consistent pattern, with R2 amounting to 2–47%. Nevertheless, MELT and ΔQ fluctuations exhibit spatially extensive patterns of correlations with daily cloudiness anomalies, indicating that the effects of cloudiness often operate over regional spatial scales.