The orographic rain occurs when moist air is pushed from the sea to a mountain slope in ascending order. It is the core of the interaction between the earth's surface and the atmosphere.
Orographic rainfall is not only important for the conservation of nature's ecosystems and natural resources, such as water for humans, but it is also important for other physical components of the earth system.
For example, floods, landslides and avalanches are affected by the intensity of rain in quite mountainous areas.
As the air rises and cools, orographic clouds form and serve as a source of precipitation, that is, rain. Clouds condense into water vapor and form cumulus clouds. These can produce both rain and strong thunderstorms.
When the flow of air is interrupted by a hill or mountain and is forced up, it can cause changes in the weather system. The rise of humid air over the land is not enough for precipitation to occur, this occurs when there are already storms in the environment.
On the other hand, when the descending air heats up and dries up, both the cloud and the precipitation evaporate. When the air descends on the leeward side (opposite where the wind comes from), it has lost most of its moisture due to rain.
In this case the precipitation is normally low and the area is said to be in a rain shadow.
Places where orographic rain occurs the most
Some places in the world such as the Hawaiian Islands and New Zealand are known for having abundant orographic rainfall.
On these islands, most of the precipitation is on the windward sides (where the wind comes from) and the opposite places remain relatively dry.
However, orographic rain gives rise to some discrepancies. For example, the coast receives less rain than higher elevations, and the leeward coasts are generally dry. That said, Hawaii receives less rainfall per year than highlands like Wai'ale'ale on Kaua'i.
Another place that is known for its orographic rainfall is the Pennine mountain range in the north of England.
In the west of this mountain range, Manchester has more rainfall than Leeds, located in the east. This city has less rain because the precipitation is lower, in other words, it is in the rain shadow area.
This type of rain plays an important role in the type, intensity and duration of precipitation.
Studies have shown that the width of the land barrier, the inclination and the speed at which the air moves upwards, define the amount and intensity of orographic rain.
References
- Abuwala, A. (2017). What Is Orographic Precipitation? Recovered from:
- worldatlas.com Minder, Justin R. and Roe, Gerard, H. (nd). Orographic precipitation. Recovered from:
- earthweb.ess.washington.eduRoe, Gerard H. (2005). Orographic precipitation. Annual Review of Earth and Planetary Sciences, 33. Recovered from:
- earthweb.ess.washington.edu The Editors of the Encyclopaedia Britannica. (2017). Orographic precipitation. Recovered from: britannica.com.