History and Background

Fog is the dominant characteristic of warm-season weather along coastal, western North America— literally and figuratively permeating most aspects of coastal life, especially in coastal California. Humans directly experience fog through its impacts on daily temperatures, tourist activities, driving hazards, flight delays, and social media (e.g., @karlthefog!). Fog supplies a substantial source of water during an otherwise dry season, enabling rainforest-like ecosystems to inhabit a climate that receives essentially no rainfall for half the year. These coastal ecosystems support ecologically keystone vegetation with un usual characteristics–such as direct uptake of water through the needles of Sequoia sempervirens (the iconic redwoods)–that specifically evolved for using fog water during the otherwise dry season. In addition to the direct benefit of water, and even if fog is not present, the presence of low cloud cover aloft reduces evaporation and transpiration, thereby allowing natural vegetation and critical agriculture to use less water.