Norwegian cyclone model
The older of the models of
Development of the theory
Polar front theory is attributed to Jacob Bjerknes, derived from a coastal network of observation sites in Norway during World War I. This theory proposed that the main inflow into a cyclone was concentrated along two lines of convergence, one ahead of the low and another trailing behind the low. The convergence line ahead of the low became known as either the steering line or the warm front. The trailing convergence zone was referred to as the squall line or cold front. Areas of clouds and rainfall appeared to be focused along these convergence zones. The concept of frontal zones led to the concept of air masses. The nature of the three-dimensional structure of the cyclone would wait for the development of the upper air network during the 1940s.[2][3][4]
Evolution
A wave along a frontal boundary, in the form of a broad area of
Conveyor belt
A conveyor belt, also referred to as the warm conveyor belt, describes the flow of a stream of warm moist air originating within the warm sector of an extratropical cyclone ahead of the cold front which slopes up above and north of the surface warm front. The idea of the conveyor belt originated in 1969.[6] The left edge of the conveyor belt is sharp due to the higher density air moving in from the west forcing a sharp slope to the cold front. An area of stratiform precipitation develops north of the warm front along the conveyor belt. Active precipitation north of the warm front implies potential for greater development of the cyclone. A portion of this conveyor belt turns to the right (left in the Southern Hemisphere), aligning with the upper level westerly flow. However, the western portion of this belt wraps around the northwest (southwest in the Southern Hemisphere) side of the cyclone, which can contain moderate to heavy precipitation. If the air mass is cold enough, the precipitation falls in the form of heavy snow.[2] Theory from the 1980s talked about the presence of a cold conveyor belt which originates north of the warm front and flows along a clockwise path (in the northern hemisphere) into the main belt of the westerlies aloft, but there has been conflicting evidence as to whether or not it actually exists.[6]
See also
References
- ^ Shaye Johnson. The Norwegian Cyclone Model. Archived September 1, 2006, at the Wayback Machine Retrieved on 2006-10-11.
- ^ a b University of Oklahoma. The Norwegian Cyclone Model. Archived September 1, 2006, at the Wayback Machine Retrieved on 2007-05-17.
- ^ "Norwegian Cyclone Model". oceanservice.noaa.gov. Archived from the original on 11 May 2009. Retrieved 25 September 2023.
- ^ "Archived copy" (PDF). Archived from the original (PDF) on 10 May 2017. Retrieved 10 June 2016.
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: CS1 maint: archived copy as title (link) - ^ JetStream. Norwegian cyclone model. Archived 2016-01-04 at the Wayback Machine Retrieved on 2007-05-17.
- ^ a b University of Oklahoma. Reexamining the Cold Conveyor Belt. Retrieved on 2007-05-17.