Fog as a Hydrologic Input

Abstract

This article reviews the hydrologic importance of fog in its various forms. Meteorologically, fog is defined as a ground-touching cloud with a visibility in the horizontal of less than 1000 m. The most widely occurring fog types include radiation fog, sea fog and steam fog, and advection fog, but often fog is also referred to by its location of occurrence (coastal, valley, or mountain fog). The physical processes underlying the various types of fog are described briefly. The use, advantages, and limitations of the most common types of fog collectors, fog detectors, and fog droplet spectrometers are dealt with before embarking on a discussion of techniques for the measurement and modeling of fog deposition on forest vegetation. Results of fog deposition measurements made at selected locations (representing coastal vs. inland, lowland vs. montane, and temperate vs. tropical conditions) are compared. The data confirm the importance of fog interception at many coastal and montane sites across the tropical to mediterranean and warm-temperate climatic spectrum. Under more continental conditions, contributions by fog are usually more modest except on windy mountain ridges and summits. Finally, the paper indicates the chief gaps in knowledge regarding the measurement and importance of fog as a hydrologic input.Encyclopedia of Hydrological Sciences. Edited by M G Anderson.

The Influence of Drop Size Distributions on the Relationship between Liquid Water Content and Radar Reflectivity in Radiation Fogs

“…The decrease in the range over the fog life cycle and the simultaneous shift towards higher Z values can be attributed to the small Ω value that was used for the dissipation stage (9.54 × 10 1 g/mm 6 ) compared to 4.07 × 10 2 g/mm 6 and 8.55 × 10 2 g/mm 6 for formation and mature stage. The LWC values derived from typical Z values for each stage showed realistic ranges in the formation stage with a maximum of 4.03 × 10 −1 g/m 3 . For the mature and dissipation stages the maxima of 4.64 × 10 −1 g/m 3 and 1.15 × 10 −1 g/m 3 also lay within the typical values during radiation fog events, which can reach up to 2.15 × 10 −1 g/m 3 [45,46].…”

“…Furthermore, the tops of fog layers reflect solar radiation, which reduces air exchange fluxes when temperature inversions are present [1]. In contrast to these negative effects, fog is often considered as a positive element in hydrology as it can supply otherwise arid ecosystems with moisture [2,3].…”

The role of fog, orography, and seasonality on precipitation in a semiarid, tropical island

“…According to Kaseke et al (2016), fog derived from oceanic vapour (known as advection fog) in Namibia consistently plots along the GMWL, whereas fog formed from local meteoric water (known as radiation fog) falls along the LMWL, and water inputs formed from a combination of two air masses plot between the two meteoric water lines. However, applying this methodology to our study site is difficult because our site is oceanic and not continental; thus, these mechanisms are more spatially concentrated and more difficult to distinguish by looking at fog samples in comparison with LMWLs and GMWLs (Bruijnzeel et al, 2005).…”

“…Whereas rain is a major form of precipitation in the tropics, fog or stratus cloud that resides at the Earth's surface is another key precipitation input in many island ecosystems (Bruijnzeel, Eugster, & Burkard, 2005;Croft, 2003;Gultepe et al, 2007;Koracin et al, 2014;Scholl, Eugster, & Burkard, 2011;Scholl & Murphy, 2014) and can provide much needed moisture to otherwise dry or seasonally dry ecosystems (Bruijnzeel et al, 2005;Scholl et al, 2011). Current climate change predictions suggest that higher air temperatures will lead to an increase in cloud base height, which will move fog cover upward in elevation; this phenomenon has been termed "cloud lifting" (Pounds, Fogden, & Campbell, 1999).…”

“…It is most often formed under stronger trade winds and accompanying low-lying atmospheric inversions (Roe, 2005). Radiation fog, on the other hand, is formed when radiational cooling at night-time reduces the air temperature to or below its dew point (American Meteorological Society, 2012b) and has been found in other tropical regions with surface water bodies (Bruijnzeel et al, 2005). In the tropics, it often takes place in the cool season under low wind conditions (Bruijnzeel et al, 2005).…”