Measurements of Fog Water Deposition on the California Central Coast

Abstract

Fog deposition is a notable component of the water budget of herbaceous-shrub ecosystems on the central and southern coastal regions of California. This paper presents an analysis of fog water deposition rates and meteorological controls in Big Sur, California. Mesh-screen fog collectors were installed the Brazil Ranch weather station sites to measure fog water during the summer seasons of 2010 and 2011. Fog deposition occurred during 73% of days recorded in 2010 and 87% of days recorded in 2011. The daily average deposition rate was 2.29 L/m<sup>2</sup> in 2010 and 3.86 L/m<sup>2</sup> in 2011. The meteorological variables which had the greatest influence on prediction of fog deposition were wind speed, wind direction, and the dew-point depression (difference between air temperature and dew point). Based on these results, we hypothesize that high rates of summer fog deposition help sustain the productivity of California coastal vegetation through periods of low rainfall

Understanding Climate Change on the California Coast: Accounting for Extreme Daily Events among Long-Term Trends

“…Nevertheless, it is common to observe temperature inversions on the Central Coast that frequently result from the persistent marine layer, and which remain very stable between May and October [8]. Summer fog is common below about 600 m (2000 feet) elevation [4]. Nonetheless, diurnal heating and cooling of ecological habitats along the Big Sur coast and higher into the Santa Lucia mountains involves a complex series of elevational gradients and topographic variations.…”

“…This can lead to the formation of steep elevation gradients in air temperature regimes, humidity and other climate factors. The advection of marine stratus layers over land profoundly moderates the coastal climate by reducing insolation and temperatures, raising humidity, and supplying water directly to the landscape [4]. Lebassi [5].…”

“…The setting for this analysis is arguably located at the nexus of modern climate change geography in the Western United States. The Central Coast of California is constantly subjected to extreme climate events [4], frequent wildfires, and human development impacts, together affecting wildlife populations, native plant communities, soil conservation, riparian zones, and water quality.…”

“…Big Sur is generally delineated by the 140 km (90 miles) of coastline from the Carmel River in Monterey County south to the San Carpoforo Creek in San Luis Obispo County, and extends about 30 km inland to the eastern foothills of the Santa Lucia Mountains. The region has a Mediterranean climate of warm, dry summers and cool, wet winters, with localized summer fog near the coast [4]. Annual rainfall is highly variable and ranges from 400 to 1520 mm throughout the region, with highest event totals generally falling on the higher mountains in the northern extreme of the study area during winter storms.…”

“…Mean annual temperature ranges between 10 °C and 15 °C, from shaded canyon bottoms to exposed ridge tops, respectively. Plant growth on the Central Coast can be highly variable from year-to-year and is generally limited by declines of soil moisture in the summer and by cool temperatures in the winter [4]. The annual production pattern for coastal grasses is rapid growth in the late fall (November) after the first rains have returned, slow winter growth (December-February), and rapid growth again in spring (March-May) [7][8][9].…”