Lee cyclogenesis: Difference between revisions

Latest revision as of 05:34, 29 March 2024

(Also called orographic cyclogenesis.) The synoptic-scale development of an atmospheric cyclonic circulation on the downwind side of a mountain range.

The "lee" side is relative to the mean background airflow. Weak development can occur due to a redistribution of uniform vorticity as large-scale flow passes over a mountain barrier (
see lee trough). Stronger cases of lee cyclogenesis occur when the mountain range interacts with a developing baroclinic wave. In this instance the mountain acts to position the cyclone or generate a secondary cyclone in the lee. Often this leaves a weaker parent cyclone that is typically poleward of the development and far from the mountains. Lee cyclogenesis is a multistage process involving a phase of rapid deepening followed by a transition to slower baroclinic deepening. The mountain barrier disrupts the orderly advection of low-level cold air that would occur behind the cyclone over flatter terrain and induces a quasigeostrphic imbalance. As it tends to restore this imbalance (
see geostrophic adjustment), the atmosphere produces the beginnings of a cyclonic system near the surface. The lack of cool air at low levels and the descending upper-level air make the mountain lee environment statically less stable than the surroundings. This enhances the possibility for vertical coupling of potential vorticity maxima associated with the approaching upper-level trough and the incipient lee disturbance at lower levels. Lee cyclogenesis is common on the leeward side of the major mountain ranges of the world including the Alps, the Himalayas, the Rockies (both east and west), and the Andes. Many minor ranges support lee cyclogenic activity.
See also Genoa cyclone, Colorado low, Alberta clipper, pampero.

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+{{Term
+|Display title=lee cyclogenesis
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+|Definitions={{Definition
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+|Meaning=(''Also called'' orographic cyclogenesis.) The synoptic-scale [[development]] of an atmospheric  [[cyclonic circulation]] on the [[downwind]] side of a mountain range.
-<div class="termentry">
+|Explanation=The "lee" side is relative to the mean background airflow. Weak development can occur due to  a redistribution of uniform [[vorticity]] as large-scale flow passes over a mountain barrier (<br/>''see'' [[lee trough|lee  trough]]). Stronger cases of lee cyclogenesis occur when the mountain range interacts with a developing  [[baroclinic wave]]. In this instance the mountain acts to position the [[cyclone]] or generate  a [[secondary cyclone]] in the lee. Often this leaves a weaker parent cyclone that is typically poleward  of the development and far from the mountains. Lee cyclogenesis is a multistage process involving  a phase of rapid [[deepening]] followed by a transition to slower [[baroclinic]] deepening. The mountain  barrier disrupts the orderly [[advection]] of low-level cold air that would occur behind the cyclone  over flatter terrain and induces a quasigeostrphic imbalance. As it tends to restore this imbalance  (<br/>''see'' [[geostrophic adjustment]]), the [[atmosphere]] produces the beginnings of a [[cyclonic]] system near  the surface. The lack of cool air at low levels and the descending upper-level air make the mountain  lee [[environment]] statically less stable than the surroundings. This enhances the possibility for  vertical coupling of [[potential vorticity]] maxima associated with the approaching [[upper-level trough]]  and the incipient lee [[disturbance]] at lower levels. Lee cyclogenesis is common on the [[leeward]] side  of the major mountain ranges of the world including the Alps, the Himalayas, the Rockies (both  east and west), and the Andes. Many minor ranges support lee cyclogenic activity. <br/>''See also'' [[Genoa cyclone|Genoa  cyclone]], [[Colorado low]], [[Alberta clipper]], [[pampero]].
-  <div class="term">
+}}
-== lee cyclogenesis ==
+}}
-  </div>
-<div class="definition"><div class="short_definition">(''Also called'' orographic cyclogenesis.) The synoptic-scale [[development]] of an atmospheric  [[cyclonic circulation]] on the [[downwind]] side of a mountain range.</div><br/> <div class="paragraph">The "lee" side is relative to the mean background airflow. Weak development can occur due to  a redistribution of uniform [[vorticity]] as large-scale flow passes over a mountain barrier (<br/>''see'' [[lee  trough]]). Stronger cases of lee cyclogenesis occur when the mountain range interacts with a developing  [[baroclinic wave]]. In this instance the mountain acts to position the [[cyclone]] or generate  a [[secondary cyclone]] in the lee. Often this leaves a weaker parent cyclone that is typically poleward  of the development and far from the mountains. Lee cyclogenesis is a multistage process involving  a phase of rapid [[deepening]] followed by a transition to slower [[baroclinic]] deepening. The mountain  barrier disrupts the orderly [[advection]] of low-level cold air that would occur behind the cyclone  over flatter terrain and induces a quasigeostrphic imbalance. As it tends to restore this imbalance  (<br/>''see'' [[geostrophic adjustment]]), the [[atmosphere]] produces the beginnings of a [[cyclonic]] system near  the surface. The lack of cool air at low levels and the descending upper-level air make the mountain  lee [[environment]] statically less stable than the surroundings. This enhances the possibility for  vertical coupling of [[potential vorticity]] maxima associated with the approaching [[upper-level trough]]  and the incipient lee [[disturbance]] at lower levels. Lee cyclogenesis is common on the [[leeward]] side  of the major mountain ranges of the world including the Alps, the Himalayas, the Rockies (both  east and west), and the Andes. Many minor ranges support lee cyclogenic activity. <br/>''See also'' [[Genoa  cyclone]], [[Colorado low]], [[Alberta clipper]], [[pampero]].</div><br/> </div>
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