科学家说，太平洋沿岸夏季雾的减少可能胁迫具有象征意义的沿岸红杉树和其他地方生态系统。利用一种云幕高度以及陆地温度的综合指数，James Johnstone 和Todd Dawson发现了在1901年到2008年间加利福尼亚沿岸雾的频率减少了33%。
海岸红杉是太平洋沿岸包括加利福尼亚红杉在内的巨大树木的成员之一，它是全世界最高和寿命最长的树木之一。这组作者说，这种树在干旱的夏季月份里依靠夏季雾从而帮助保存水，它可能因为对更干燥的空气做出反应而遇到干旱敏感度提高的情况。这项研究挑战了此前一些观测和建模研究提出的北加利福尼亚沿岸雾由于变暖的陆地温度而会变得比此前更加频繁的理论。这组作者发现海洋大气循环以及温度变化很可能压倒由于温室变暖造成的雾增加的假想情况，导致自从20世纪早期开始的雾的净减少。这组作者说，这些发现把大尺度的陆地和东太平洋温度变化与更干燥的空气对加利福尼亚的沿岸环境与生态系统的潜在负面影响联系了起来。
推荐原始出处：
PNAS February 16, 2010, doi: 10.1073/pnas.0915062107
Climatic context and ecological implications of summer fog decline in the coast redwood region
James A. Johnstonea,1 and Todd E. Dawsona,b
aDepartment of Environmental Science, Policy, and Management, and
bDepartment of Integrative Biology, University of California, Berkeley, CA 94720
Biogeographical, physiological, and paleoecological evidence suggests that the coast redwood [Sequoia sempervirens (D. Don) Endl.] is closely associated with the presence of summer marine fog along the Pacific coast of California. Here we present a novel record of summer fog frequency in the coast redwood region upon the basis of direct hourly measurements of cloud ceiling heights from 1951 to 2008. Our analysis shows that coastal summer fog frequency is a remarkably integrative measure of United States Pacific coastal climate, with strong statistical connections to the wind-driven upwelling system of the California Current and the broad ocean temperature pattern known as the Pacific Decadal Oscillation. By using a long-term index of daily maximum land temperatures, we infer a 33% reduction in fog frequency since the early 20th century. We present tree physiological data suggesting that coast redwood and other ecosystems along the United States west coast may be increasingly drought stressed under a summer climate of reduced fog frequency and greater evaporative demand.
