Impacts of Advection Fog and Marine Layer on Aircraft Movement (Credit: Meteorologist Jessica Olsen)

Image Courtesy: FlightAware

DISCUSSION: Fog, a relative to the cloud, only in that the base of fog is located at the earth’s surface, is something that can be both pleasant by breaking through to such a beautiful sky, or leave a day to seem dull in certain locations. It’s a question I have to mentally prepare myself to answer to the general public nearly every few weeks as advection fog or a large marine layer coupled with stratus and fog approach the coast of Monterey Bay. Why does fog impact aircraft?
 
Monterey Bay is home to unique weather patterns that many residents enjoy as a coolness to the air lingers, due to the effects of fog and the marine layer. Monterey often experiences a marine layer, an air mass that develops over the Pacific in the presence of a temperature inversion. Fog is likely to form within a marine layer, where humidity is high enough and there is cooling sufficient enough to support the production of condensation.
 
Visibility is the most common impact in aviation, however not in the typical way most would predict. Fog has the ability to cause operational delays which can impact arrival to a destination. The result of fog can restrict both ground and airborne movement at an airport. Often most aircraft are able to land and take off in low surface visibility by utilizing LVP (Low Visibility Procedures), a set of standards to ensure safe operations during specific approaches and take-offs. Limitations become challenging as the operational goal is most difficult to maintain the safety of aircraft during ground movement. Aircraft will often need additional space when landing and when taxiing on the ground, meaning the distance between an aircraft that will have landed will be well clear of the runway before the next lands, thus utilizing LVP to reduce the chance for a runway incursion and costly aircraft damage.
 
Advection fog is most prone in Monterey Bay as the air surrounding the airport can be impacted by this quick moving event. This fog is formed when warm, moist and stable air moves across a cooler surface, where the air temperature decreases to dew point and condensation can occur. Advection fog and other fog types have the potential to rapidly reduce visibility from visual flight rules (VFR) to instrument flight rules (IFR) within a span of minutes, often in coastal cities like that of Monterey or most known San Francisco. It is conceivable that diversions can occur and pilots are likely to plan for alternative runways, and increased fuel consumption as the weather at the destination deteriorates rapidly.
 
For more information on aviation meteorology and weather impacting your area visit the Global Weather and Climate Center.
 
 
© Meteorologist Jessica Olsen
 
 
Resources:
 
"Low Visibility Procedures (LVP)." Low Visibility Procedures (LVP) - SKYbrary Aviation Safety. N.p., n.d. Web. 06 Aug. 2017.