The Orographic Effect And Its Effect On The Weather

What affects the weather?

As we live on planet earth, we are surrounded by the weather. Weather is constant, and it is constantly changing.

Everything we see can affect the weather, climate change, mountains pushing up, temperatures going down, or the position of the moon in the sky. 

When we watch the weather channel, we know that temperatures and wind can affect the weather around us.

But the land can too. Vast deserts or mighty forests, but most of all, mountains.

an illustration of the orographic effect

With their climbing peaks, the weather is forced up higher, to deviate its path around these large, natural obstacles, creating unique weather systems that morph, becoming unique to that specific climate.

What Is The Orographic Effect?

The orographic effect is the reason that mountains receive greater rainfall than other terrains, and, why, in turn, they also have a greener, lusher vegetation. Orography technically refers to the study of the formation and relief of mountains. 

This effect is a weather condition triggered by upward moving air masses that come into contact with mountains or elevated terrains. The upward movement of air created by this lift in terrain is known as “orographic lift”. 

As this air mass rises it encounters something called adiabatic cooling, which is the cooling of air without addition or subtraction of any thermal energy. This phenomenon of a temperature decrease due to heightening altitudes means that the air will eventually condense. 

Warm and moist air climbs the side of the mountain. As it scales the side of this obstruction, the air will start to cool and the air will lose its moisture through precipitation. 

To put it in its simplest definition, a cloud or warm moist air will rise up the side of a mountain, losing body through rainfall as it climbs. The side of the mountain that meets the air is known as the windward side, this side meets the rainfall.

The other side is known as the dry rain shadow or leeward side. Unmet by rainfall, the air that will descend on the other side is dry and warm.

Orographic Rainfall

When humidity is at 100%, a cloud is formed and this will result in rainfall or precipitation. This is referred to as Orographic precipitation, some of the best examples of regions that receive this type of rainfall would include the Appalachian Mountains in West Virginia and the lesser Himalayas in India. 

Regions on the windward side of an affected mountain will experience very heavy rainfall, somewhere between 80 and 100 inches.

While the leeward side of the mountain gets a dry spell, known as the ‘rain-shadow effect’, these areas, rarely even 10 or more miles receive minimal rainfall if they are lucky, usually a maximum of 10 inches. 

Orographic rainfall happens when the air going up the windward side of the mountain reaches the temperature at which it can no longer stay in its gaseous state, as it rises.

Depending on the water content of the cloud, the condensed air will form water droplets and become precipitation. Depending on the size of the cloud, air,  the variation of water hitting this side of the mountain can range from a light drizzle to torrential rainfall. 

How it affects the weather

The Orographic effect has an effect on certain climates. This basically means that mountainous areas will receive greater rainfall.

he weather in these climates, with vast mountain ranges or tall terrains, will face an entirely different weather pattern, and therefore an entirely unique climate in comparison to the landscapes and weather found in flatter terrain areas. 

The orographic effect is simply the effect of high terrains on air masses or clouds. That results in heavy rainfall in one place and dry warm conditions in another. 

How it affects the weather scapes and the world below

The orographic effect also grants changes to the landscape below the air masses it directly affects. Moreso, it actually creates two very different weather conditions in its wake.

By the time that the air that was forced up the side of the raised terrain reaches its peak, it is cold and dry, as a result of the aforementioned adiabatic cooling, and the precipitation that took place on the windward side. 

In most cases, the leeward side will have a terrain decrease at the same rate that the windward side elevated. With this lowering of terrain, the gravity will force the dry air down the side. As this dry air descends the air will get compressed and warm through adiabatic heating.

This opposition of two different weather conditions, in very close proximity to one another, results in outstanding oppositional landscapes. The orographic rainfall on the windward side grants this mountain slope with lush vegetation and green landscapes.

These windward slopes make up some of the lushest and densest vegetation on the planet, including many of the tropic and rainforests of South America and Africa. 

Whereas the Leeward side, gets the cool, dry air, receiving as little as 10 inches of rainfall. This part of this spectacular phenomenon results in large arid or semi-arid landscapes, in some of the most extreme cases this can result in desert-like climates that can extend over vast regions.

Summary

The Orographic effect affects mountain regions or elevated terrains, that interrupt the typical flow of air masses, which results in condensation and intense rainfall on the windward side, resulting in lush, green vegetation.

While the leeward side, after the peak altitude the air mass is met with, is granted by cool, dry airs, that gradually warm as they are pulled back to earth by the natural gravitational pull of our planet. 

This natural phenomenon is one of the many wonders of weather. Our mountain ranges are met with beautiful landscapes that are a constant wonder to the human eye.

Met with vast rainfalls and covered in dense vegetation, the orographic effect is just one of the factors attributed to the unmet beauty of this climate. 

Our weather is changed by many factors, and the physical terrain of our landscape is just as capable as the wind and temperature of producing outstanding weather phenomena, just like this. 

About the Author Marvin J. Snyder

I'm the research analyzer and data interpretation here at Weather Station Lab. I test various weather stations and share my conclusion here. Since my childhood, I had a passion towards weather and I'm always fascinated by that. Eventually, I pursued Ph.D. in Atmospheric Science from the University of Arizona. I hope my contribution will help you to know more about weather stations. Read more about us, here