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Advection fog occurs when moist air passes over a cool surface by advection (wind) and is cooled. [21] It is common as a warm front passes over an area with significant snow-pack. It is most common at sea when moist air encounters cooler waters, including areas of cold water upwelling , such as along the California coast .
Using the classical definition of advection, moisture advection is defined as: =in which V is the horizontal wind vector, and is the density of water vapor. However, water vapor content is usually measured in terms of mixing ratio (mass fraction) in reanalyses or dew point (temperature to partial vapor pressure saturation, i.e. relative humidity to 100%) in operational forecasting.
The advection equation is a first-order hyperbolic partial differential equation that governs the motion of a conserved scalar field as it is advected by a known velocity vector field. [1] It is derived using the scalar field's conservation law , together with Gauss's theorem , and taking the infinitesimal limit.
Fog is commonly considered a surface-based cloud layer. [21] The fog may form at surface level in clear air or it may be the result of a very low stratus cloud subsiding to ground or sea level. Conversely, low stratiform clouds result when advection fog is lifted above surface level during breezy conditions.
Also actiniform. Describing a collection of low-lying, radially structured clouds with distinct shapes (resembling leaves or wheels in satellite imagery), and typically organized in extensive mesoscale fields over marine environments. They are closely related to and sometimes considered a variant of stratocumulus clouds. actinometer A scientific instrument used to measure the heating power of ...
Advection is fluid motion created by velocity instead of thermal gradients. Convective heat transfer is the intentional use of convection as a method for heat transfer . Convection is a process in which heat is carried from place to place by the bulk movement of a fluid and gases.
Fog over the Golden Gate Bridge (May 2009). Fog is a common weather phenomenon in the San Francisco Bay Area and the entire coastline of California extending south to the northwest coast of the Baja California Peninsula.