Where are deserts formed and why? - The Hadley cell, rain shadows and continental interiors

Summary

This educational video explores the geographical factors behind desert formation. It explains that deserts typically occur between 15 and 30 degrees latitude north and south of the equator, where the Hadley cell's atmospheric circulation leads to dry air descending. The script also highlights the role of continental interiors and rain shadows created by mountain ranges, such as the Himalayas, in desert development. The video uses maps and visualizations to illustrate how precipitation patterns and the rain shadow effect contribute to arid regions.

Takeaways

• 🌍 Deserts typically form in specific geographic regions characterized by low precipitation and high potential evaporation rates.
• 🌧️ Precipitation rates, including rain, snow, sleet, or hail, are crucial in defining arid regions where deserts are likely to form.
• 🌡️ Deserts are commonly found between 15 and 30 degrees north and south of the equator due to atmospheric circulation patterns.
• 🔄 The Hadley cell, a large-scale atmospheric convection cell, plays a significant role in desert formation by influencing air movement and precipitation.
• 🏜️ Major deserts are often located in the subtropics where air masses descend, leading to dry conditions and minimal precipitation.
• 🌊 Deserts can also form in the interior of continents, far from the ocean, which are the primary sources of moist air.
• 🏞️ The rain shadow effect, caused by large mountain ranges, creates deserts by blocking moist air and causing dry conditions on the leeward side.
• 🏔️ Examples of rain shadow deserts include those found north of the Himalayas, such as the Tibetan Plateau, where dry air results from the rain shadow of the mountains.
• 🌿 The contrast in landscape, vegetation, and color is stark between the windward and leeward sides of mountain ranges due to the rain shadow effect.
• 🌍 The script uses a combination of maps and visualizations, like Google Earth Pro, to illustrate the geographic distribution and causes of desert formation.

Q & A

What is the relationship between precipitation rates and desert formation?

Deserts tend to form in regions where the potential rates of evaporation are much greater than the rates of precipitation, leading to low precipitation areas.

Why do major deserts of the world closely match the regions with lower rates of precipitation?

Major deserts are located in areas with lower precipitation rates because these regions have high potential rates of evaporation, creating an environment conducive to desert formation.

What are the common geographic locations where deserts are formed?

Deserts are typically formed between 15 and 30 degrees north and south of the equator, in the interior of continents, and in the rain shadows of large mountain belts.

How does the Hadley cell influence the formation of deserts?

The Hadley cell, a large-scale atmospheric convection cell, contributes to desert formation by causing air to rise near the equator, flow poleward, and descend in the subtropics, leading to dry conditions in these regions.

Why do deserts often form between 15 and 30 degrees north and south of the equator?

Deserts form in these latitudinal positions due to the atmospheric circulation patterns, specifically the descending dry air in the subtropics as part of the Hadley cell circulation.

How do interior continental locations contribute to desert formation?

Interior continental locations are far from the main sources of moist air, typically the oceans, leading to less precipitation and the formation of deserts.

What is the rain shadow effect and how does it lead to desert formation?

The rain shadow effect occurs when moist air masses are forced to rise over mountains, leading to precipitation on the windward side and dry conditions, or a rain shadow, on the leeward side where deserts can form.

Can you provide an example of a desert formed in a rain shadow region?

An example of a desert formed in a rain shadow region is the Tibetan Plateau north of the Himalayas, where the air masses crossing the Himalayas become dry, resulting in an arid landscape.

How does the distance from the ocean affect precipitation and desert formation?

Areas far from the ocean receive less moisture from the main source of moist air, leading to dry conditions and the potential for desert formation.

What role does temperature play in the process of desert formation?

Temperature affects desert formation by influencing the air's capacity to hold moisture. Warmer air near the equator can hold more moisture, leading to higher humidity and precipitation, while cooler air in subtropical regions results in less moisture retention and drier conditions.

What is the significance of the 10 to 15-kilometer height in the context of desert formation?

The height of 10 to 15 kilometers is significant as it represents the altitude where air masses, influenced by the Hadley cell, flow poleward and start to descend, contributing to the dry conditions typical of desert regions.

Outlines

00:00

🌍 Desert Formation and Geographic Characteristics

This paragraph explains the formation of deserts and their geographic characteristics. Deserts typically form in regions with high potential evaporation rates and low precipitation, often seen between 15 and 30 degrees north and south of the equator. The atmospheric circulation, particularly the Hadley cell, plays a significant role in desert formation. Warm air rises near the equator, cools and precipitates as it moves towards the poles, leading to dry conditions in the subtropics. The paragraph also mentions the role of continents' interiors and rain shadows of large mountain belts in desert formation, where moist air from the ocean is blocked by mountains, creating dry conditions on the leeward side.

05:00

🌏 Influence of Continental Position and Rain Shadow Effect

The second paragraph delves into how deserts form in the interior of continents and the rain shadow effect. Deserts are prevalent in continental interiors due to the distance from the ocean, which is the primary source of moist air. As air masses move inland, they lose moisture, leading to arid conditions. The rain shadow effect is illustrated by the example of the Himalayas and the Tibetan Plateau, where moist air from the ocean is forced to rise and cool as it encounters the mountains, leading to precipitation on the windward side. On the leeward side, the air is dry, creating a desert-like environment. The paragraph emphasizes the importance of geographic location and atmospheric processes in shaping desert landscapes.

Keywords

💡Deserts

Deserts are large, dry areas of land that receive very little precipitation, typically less than 250 millimeters (10 inches) of rain per year. They are characterized by their arid conditions and sparse vegetation. In the video, deserts are discussed in relation to their formation due to geographic and atmospheric conditions, such as low precipitation rates and high evaporation rates.

💡Precipitation

Precipitation refers to any product of the condensation of atmospheric water vapor that falls under gravity from clouds, including rain, snow, sleet, and hail. The video uses a map to illustrate areas with varying rates of precipitation, highlighting how regions with less precipitation are more likely to be deserts.

💡Evaporation

Evaporation is the process by which water changes from a liquid to a gas or vapor and returns to the atmosphere. The video explains that deserts form in areas where the potential rates of evaporation are much greater than the rates of precipitation, leading to dry conditions.

💡Latitude

Latitude refers to the angular distance of a place north or south of the equator, measured in degrees. The video mentions that deserts are typically formed between 15 and 30 degrees north and south of the equator due to specific atmospheric circulation patterns.

💡Hadley Cell

The Hadley Cell is a large-scale atmospheric circulation that moves air from the equator towards the subtropics. In the video, it is described as a process where air rises near the equator, flows poleward, and descends in the subtropics, contributing to the formation of deserts in these regions.

💡Subtropics

The subtropics are the regions of the Earth immediately north and south of the tropics, lying roughly between 23.5 and 40 degrees latitude. The video explains that deserts often form in the subtropics due to the descending air masses associated with the Hadley Cell, which results in dry conditions.

💡Interior of Continents

The interior of continents refers to the areas far from the coastlines. The video discusses how deserts can form in these regions because they are farther from the main sources of moist air, which typically come from the oceans, leading to less precipitation.

💡Rain Shadow

A rain shadow is a干燥 area on the leeward side of a mountain range due to the orographic effect, where the windward side receives more precipitation. The video uses the rain shadow effect to explain how deserts can form on the downwind side of mountain ranges, such as the Tibetan Plateau north of the Himalayas.

💡Orographic Lift

Orographic lift is the process by which air is forced to rise along the windward side of a mountain range, leading to cooling and precipitation. The video describes how this lift causes moist air to rise and cool, dropping its moisture as precipitation on the windward side, leaving the leeward side dry and prone to desert formation.

💡Tibetan Plateau

The Tibetan Plateau is a vast, elevated plateau in Central Asia and the world's highest and largest plateau. The video uses it as an example of a rain shadow region, where the air masses crossing the Himalayas become dry, leading to an arid landscape on the plateau's north side.

💡Atmospheric Circulation

Atmospheric circulation refers to the large-scale movement of air in the Earth's atmosphere. The video connects desert formation to specific patterns of atmospheric circulation, particularly the Hadley Cell, which influences precipitation and evaporation rates.

Highlights

Deserts form in regions with specific geographic characteristics and high potential rates of evaporation.

A map illustrating global precipitation rates helps identify areas where deserts are likely to form.

Deserts are typically located in areas with low precipitation rates, matching the dark blue areas on the map.

Major deserts are found between 15 and 30 degrees north and south of the equator.

Deserts also form in the interior of continents and in the rain shadows of large mountain belts.

The Hadley cell, a large-scale atmospheric convection cell, influences desert formation near the subtropics.

Warm air near the equator rises, leading to high humidity and precipitation.

Air masses become drier and colder as they move away from the equator towards the poles.

At around 30 degrees latitude, air masses descend, creating dry conditions conducive to desert formation.

Deserts in continental interiors form due to distance from moist air sources, typically oceans.

Rain shadow effect caused by mountains leads to dry conditions and desert formation on the leeward side.

The Tibetan Plateau north of the Himalayas is an example of a rain shadow desert.

The video showcases a Google Earth Pro visualization of the Himalayas and Tibetan Plateau, illustrating the rain shadow effect.

Desert formation is influenced by a combination of geographic factors, including latitude, continental position, and orographic lift.

Deserts are characterized by a lack of precipitation and an environment where evaporation rates exceed rainfall.

The presentation concludes with an overview of the geographic conditions that create a perfect environment for deserts.

Transcripts

there's a discover a vast area of our

continents and they usually form over

regions with the specific geographic

characteristics do you know where

deserts form and why

[Music]

here is a map that shows the rates of

precipitation in millimeters per month

over the year in the world precipitation

is just rain snow sleet or hail that

falls to the ground note that the dark

blue colors represent more rain per

month than areas shown as white or green

the rates of precipitation are used to

define the zyrtec regions deserts are

locations where the potential rates of

evaporation are much greater than the

rates of precipitation and where the

deserts tend to form that is where are

the major deserts located today in our

planet here is the same map will be seen

previously with the rates of

precipitation and now we will look at

the locations of the main deserts in the

world do you know any relationship

between these maps if you observe the

maps closely you will note that the

regions with lower rates of

precipitation closely match the

locations of the deserts because these

are regions where we have high potential

rates of evaporation

they are the regions where deserts may

form so what are the common geographic

locations where deserts are formed well

deserts are usually formed between 15

and 30 degrees north and south of the

equator in the interior of continents

and in rain shadows of large mountain

belts here I'm showing the locations of

the major deserts of the plain that

you've just seen on map now using Google

Earth Pro note how large they are they

do cover a very large area of our

continents but why did this deserts form

on those locations let's go over what is

happening in each of these geographic

locations we've listed before and let's

start with the latitudinal position

where a lot of deserts form between 15

and 30 degrees north and south of the

Equator

major deserts forum between 15 degrees

and 30 degrees north and south of the

equator because of the characteristics

of the atmospheric circulation in our

planet particularly we are looking at

how air is transported by the healthy

South the Hadley cell is a large-scale

atmospheric convection cell that

features air rising near the equator

flowing poleward at a height of 10 to 15

kilometers above the Earth's surface

descending in the subtropics

and then returning ecuator world near

the surface this whole process starts

out because the equator region receives

a higher amount of sun radiation so we

have warmer air and lots of evaporation

there the whole region is usually very

humid because warm air is capable of

holding more moisture than cool air so

as we know warmer air tends to rise and

it will do so until it gets to about 10

to 15 kilometers high as the air rises

temperature decreases so there will be a

lot of precipitation events as the air

masses rise and start their trip towards

the north and south take a look at the

map that shows the rates of

precipitation in the world and note how

there is much more rain near the equator

following their path within the hardly

south air masses will continue flowing

southward and northward but as they do

they will get drier and drier because of

the rain events and also colder and

colder since they are leaving the

equator and going towards the poles at

around 30 degrees south and 30 degrees

north air masses tend to descend towards

the planet's surface so these regions

will be dominated by dry air without

much precipitation and this creates the

perfect environment for deserts to form

take a look again at the map that shows

the locations of the major deserts in

our planet and note how most of them are

located around

degrees south and 30 degrees north some

deserts are also located in the interior

of continents in a very simplistic way

this is because they may be farther from

the main sources of moist air the main

source of moist air that promotes rain

is the ocean far from the interior of

continents so there is usually more rain

occurring near the coasts and once the

air masses reach the interior of

continents they are already dry but this

effect includes a lot of other factors

and one of them is the rain shadow

effect this figure shows an example of

how a ridah D is increased in the rain

shadow of mountains the moist warm air

comes from the ocean and as it moves

towards the Continental interior it

encounters high mountains then the air

masses are forced from a low elevation

where temperatures are higher to a

higher elevation where temperatures are

colder in the process with NOAA's

orographic lift the air masses tend to

rise in elevation in order to cross the

mountains and as they rise they become

cooler and able to hold less and less

moist so we have precipitation occurring

on the side of the mountain above which

air masses are rising when the air

masses are finally able to cross the

high elevation terrain they are already

pretty dry if they cross the high

terrain towards a much lower terrain

temperatures tend to become much higher

which helps to prevent further

precipitation this is why we say these

regions are rain shadows of mountains

rain shadow regions are perfect settings

for deserts to form one example of rain

shadow is the Tibetan Plateau north of

the Himalayas here is a video showing a

Google Earth Pro visualization of the

Himalayas and Tibetan Plateau in

Southeast Asia the winds mainly come

from the south so when they encountered

the Himalayas the air masses tend to

rise and a lot of precipitation tends

over there note how all this region is

pretty green

now when the air masses cross the

Himalayas towards the Tibetan Plateau

they are already very dry so this region

is much more arid note how the landscape

vegetation and colors change all right

so today we've talked about the

locations where deserts form we went

over the specific geography

characteristics of these regions and why

they create a perfect environment for

desert formation

[Music]