Sky view and weather controls on nocturnal surface moisture deposition on grass at urban sites

摘要

Water from dew has relevance to several topics in physical geography, including climatology, pollution deposition, and plant-water relations. There is growing scientific interest in urban dew, but urban dew data are rare. Weather is a primary control on dew wherever it forms but, especially in cities, site geometry can be important. In this paper sky view and weather controls on nocturnal surface moisture deposition are explored using data collected in Vancouver, British Columbia, Canada, during summer. For residential lawns and grassed parks in the city, similar spatial trends were evident in surface moisture amount measured at dawn by blotting and the sky view factor W. That is, more water accumulated where sky view was large, less under trees, and near buildings. Moisture accumulation at open sites was strongly controlled by weather conditions. Correlation was seen between moisture accumulation and wind and cloud conditions expressed as the semi-empirical "weather factor," Phi(w). Results suggest psi and Phi(w) may together have potential to predict surface moisture accumulation, provided humidity is not limiting. Given the several important implications of surface moisture for urban physical systems, more studies of urban dew seem warranted.