Editing Orography (section)

==Orographic precipitation==
{{See also|Orographic lift}}
{{Split|Orographic precipitation|date=November 2020|discuss=Talk:Orography#Splitting proposal|section=y}}
[[Image:Steigungsregen.jpg|thumb|right|Orographic precipitation occurs when moist air is forced upwards by terrain.]]
Orographic precipitation, also known as relief precipitation, is [[precipitation (meteorology)|precipitation]] generated by a forced upward movement of air upon encountering a physiographic upland (see [[anabatic wind]]). This lifting can be caused by:

# Upward deflection of large-scale horizontal flow by the orography.
# Anabatic or upward vertical propagation of moist air up an orographic slope, caused by daytime heating of the mountain barrier surface.

Upon ascent, the air that is being lifted expands and cools adiabatically. This [[Adiabatic lapse rate|adiabatic cooling]] of a rising moist air parcel may lower its temperature to its [[dew point]], thus allowing for condensation of the water vapor contained within it, and hence the formation of a [[cloud]]. If enough water vapor condenses into cloud droplets, these droplets may become large enough to fall to the ground as precipitation.

[[Terrain|Terrain-induced]] precipitation is a major factor for [[meteorologists]] to consider when they forecast the local weather. Orography can play a major role in determining the type, amount, intensity, and duration of precipitation events. Researchers have discovered that barrier width, slope steepness, and [[updraft]] speed are major contributors when it comes to achieving the optimal amount and intensity of orographic precipitation. [[Computer model]]s simulating these factors have shown that narrow barriers and steeper slopes produce stronger updraft speeds, which in turn increase orographic precipitation.

Orographic precipitation is known to occur on oceanic [[island]]s, such as the [[Hawaiian Islands]] and [[New Zealand]]; much of the rainfall received on such islands is on the windward side, and the [[leeward]] side tends to be quite dry, almost [[desert]]-like. This phenomenon results in substantial local gradients in the amount of average rainfall, with coastal areas receiving on the order of {{convert|20|to|30|in|mm}} per year, and interior uplands receiving over {{convert|100|in|mm}} per year. Leeward coastal areas are especially dry&mdash;less than {{convert|20|in|mm|abbr=on}} per year at [[Waikiki]]&mdash;and the tops of moderately high uplands are especially wet&mdash;about {{convert|475|in|mm|abbr=on}} per year at [[Wai'ale'ale]] on [[Kaua'i]].

Another area in which orographic precipitation is known to occur is the [[Pennines]] in the north of [[England]]: the west side of the Pennines receives more rain than the east because the clouds are forced up and over the hills and cause the rain to tend to fall on the western slopes. This is particularly noticeable between [[Manchester]] (to the west) and [[Leeds]] (to the east); Leeds receives less rain due to a rain shadow of {{convert|12|mi}} from the Pennines.