Surface Influences 8.3

Fog/mist is only recorded at the

surface

Fog/mist is merely

clouds at ground levels, even though the depth could be anywhere from 1 m to 1000

Synoptic observations of fog are based on what?

The obstruction to horizontal visibility instead of liquid water content

Intensity of rain or snow is based on what?

Visibility criteria instead of precipitation accumulation

What is some of the many challenges with understanding and forecasting fog?

The several different ways fog may form.

Fog occurring at night, in complex terrain, and under high static stability

Little is still known of the interactions of fog in ______ ______ environments and in ______ canopies

urban built; forest

Fog can also result in

differential thermal patterns

a lack of insolation that keeps daytime temperatures cooler

surface cooling is reduced during the night

Obstruction to visibility by dust occurs most often during

periods of high winds

Blowing dust is commonly associated with either…

strong thunderstorm outflow winds or large-scale gradient winds associated with synoptic-scale weather systems

Dust sources

Unvegetated dunes

Dry lake bed deposits

seasonally bare farmland

river deposits

land disturbed by construction projects

Haboobs

Dust lofted by the density current of a convective cold pool, giving it a shallow frontal character

How can the intensity of dust events be described

Visibility

Aerosol optical depth

concentrations of particulate matter

Two size criteria for particulate matter

PM_2.5 and PM₁₀, for particles that are below 2.5 and 10 um diameter

Satellite imagery and dust

Satellite imagery can help track dust plumes, but often requires specific enhancements

May fail to detect shallow layers of blowing dust

What parts of the world could be considered a “global mega-source for dust transport”?

The Sahara and Sahel

High latitude dust sources

Often from river and glacial deposits during seasons of low water