Onde os desertos são formados e por quê? - Célula de Hadley, sombras de chuva e mais!

Geologia da Terra

14 Dec 201808:10

Summary

TLDRThe video script explores the formation of deserts, highlighting their prevalence between 15 and 30 degrees north and south of the equator. It explains how deserts form in regions with high evaporation rates and low precipitation, often influenced by atmospheric circulation patterns like the Hadley Cell. The script also discusses the role of rain shadow effects from mountains, where moist air is forced to rise, cool, and precipitate on one side, leaving the other side dry and desert-like. Examples include the Sahara, the Gobi, and the Tibetan Plateau's arid conditions due to the rain shadow of the Himalayas.

Takeaways

🌍 Deserts cover vast areas of our continents and typically form in regions with specific geographical characteristics.
💧 Deserts are areas where potential evaporation rates are much higher than precipitation rates.
🌧️ The dark blue areas on the world precipitation map indicate higher monthly rainfall, while white and green areas show less.
🏜️ Deserts tend to form between 15 and 30 degrees north and south of the equator, in the rain shadow of large mountain ranges, and in the interiors of continents.
🌡️ Atmospheric circulation, particularly the Hadley cell, plays a significant role in desert formation near the equator.
☀️ Regions near the equator receive more solar radiation, leading to hotter air, more evaporation, and generally more humidity.
🔼 Hot air near the equator rises to about 10 to 15 kilometers above the Earth's surface, leading to precipitation as it cools at higher altitudes.
🌀 As air masses move away from the equator towards the poles, they become drier and cooler, leading to less precipitation and the creation of desert conditions.
🏞️ Deserts also form in continental interiors because they are farther from the main sources of moist air, typically oceans.
⛰️ The rain shadow effect caused by mountains creates arid regions where deserts can form, as moist air is forced to rise and cool, leading to precipitation on the windward side and dry conditions on the leeward side.

Q & A

What are deserts and how are they typically formed?
-Deserts are vast areas that form in regions with specific geographical characteristics, typically in areas where potential evaporation rates are much higher than precipitation rates.
What is precipitation and how is it depicted on the world map mentioned in the script?
-Precipitation refers to rain, snow, or hail that falls on the Earth's surface. On the world map, it is depicted in millimeters per month, with dark blue areas representing more rainfall than white or green areas.
Why are deserts often located between 15 and 30 degrees north and south of the equator?
-Deserts are often found between 15 and 30 degrees north and south of the equator due to the atmospheric circulation patterns, particularly the Hadley Cell, which causes air to rise near the equator and descend around 30 degrees latitude, creating dry conditions.
How does the Hadley Cell contribute to the formation of deserts?
-The Hadley Cell is a large-scale atmospheric convection cell where air rises near the equator, moves towards the poles, and descends around 30 degrees latitude. This descending air creates arid conditions, which are conducive to desert formation.
What is the rain shadow effect and how does it influence desert formation?
-The rain shadow effect occurs when mountains cause moist air to rise and cool, leading to precipitation on the windward side and dry conditions on the leeward side, creating a perfect environment for deserts to form.
Why are some deserts located in the interiors of continents?
-Deserts are located in the interiors of continents because these areas are farther from the main sources of moist air, typically oceans, and receive less precipitation.
How does the position of a continent relative to the ocean affect its precipitation levels?
-The position of a continent relative to the ocean affects its precipitation levels because oceans are the primary source of moist air that leads to rainfall. Areas closer to the coasts tend to receive more rain than those in the interior.
What is the significance of the Tibetan Plateau in relation to desert formation?
-The Tibetan Plateau is significant because it acts as a barrier for moist air coming from the south, causing the air to rise and precipitate on the windward side of the Himalayas, while the leeward side, the plateau itself, becomes very dry, creating arid conditions.
How does the script explain the relationship between low precipitation areas and the location of major deserts?
-The script explains that regions with low precipitation rates correspond to the locations of major deserts because these areas have high evaporation rates and less moisture, leading to desert formation.
What is the role of geography in the formation of deserts, as described in the script?
-Geography plays a crucial role in desert formation by influencing factors such as atmospheric circulation, proximity to oceans, and the presence of mountain ranges that create rain shadows, all of which contribute to arid conditions.

Outlines

00:00

🌍 Formation of Deserts and Geographical Factors

This paragraph discusses the formation of deserts across the globe, highlighting their prevalence in specific geographical regions. It begins with an introduction to deserts and the factors that contribute to their formation, such as low precipitation rates. A world map is referenced to illustrate annual precipitation rates, with darker blues indicating higher rainfall and lighter colors signifying less. The concept of potential evaporation rates exceeding precipitation is introduced as a key characteristic of desert regions. The paragraph then connects these geographical patterns to the locations of major deserts, suggesting a correlation between low precipitation areas and desert formation. It concludes with an invitation to examine the map closely to understand the relationship between rainfall and desert locations, hinting at the role of atmospheric circulation and the Hadley Cell in desert formation, particularly between 15 and 30 degrees north and south of the equator.

05:04

🏜️ Deserts in Continental Interiors and Rain Shadow Effects

The second paragraph delves into why deserts often form in the interior of continents and the role of rain shadow effects. It explains that these regions are distant from the primary sources of moist air, typically oceans, which are the main contributors to rainfall. The text describes how air masses, once they reach the continental interiors, are already dry, having lost much of their moisture near the coasts. The concept of rain shadow is introduced with an example, illustrating how mountains can create arid regions by forcing air masses to rise and cool, leading to precipitation on the windward side and leaving the leeward side dry. The paragraph uses the example of the Tibetan Plateau, north of the Himalayas, to show how air masses become dry after crossing the mountain range, resulting in a stark contrast in vegetation and landscape. The video script ends by summarizing the discussion on desert locations, emphasizing the importance of understanding the geographical characteristics that create suitable environments for desert formation.

Mindmap

Keywords

💡Desert

A desert is a barren area of landscape where little precipitation occurs and living conditions are hostile for plant and animal life. In the context of the video, deserts are formed in specific geographic regions with low rainfall. The script explains that deserts are characterized by high potential evaporation rates compared to precipitation, leading to dry conditions.

💡Precipitation

Precipitation refers to any product of the condensation of atmospheric water vapor that falls under gravity. This includes rain, snow, sleet, or hail. The video script uses a world map to illustrate areas with varying levels of monthly precipitation, highlighting that deserts form in regions with low precipitation rates.

💡Evaporation

Evaporation is the process by which water changes from a liquid to a gas or vapor. The script mentions that deserts are areas where evaporation rates are much higher than precipitation, contributing to their arid nature. This is a key factor in the formation and sustenance of deserts.

💡Latitude

Latitude refers to the angular distance of a place north or south of the equator. The script points out that deserts commonly form between 15 and 30 degrees north or south of the equator, which is significant for understanding the geographic distribution of deserts.

💡Hadean Cell

The Hadean Cell, also known as the Hadley Cell, is a large-scale atmospheric circulation that moves air along a horizontal path. The video script describes how the Hadean Cell contributes to desert formation by transporting moist air upward near the equator and causing it to descend dry and cool at about 30 degrees latitude, which is typical of desert regions.

💡Rain Shadow

A rain shadow occurs when mountains block moist air, causing one side of the mountain to be much drier than the other. The script uses the rain shadow effect to explain how deserts form on the leeward side of mountain ranges, where air masses lose their moisture as they rise and cool, leading to less precipitation on the other side.

💡Orographic Lifting

Orographic lifting is the process where air is forced to rise along the windward side of a mountain range. As the air rises, it cools and the moisture condenses, leading to precipitation on the windward side. The video script uses this concept to explain how deserts form in areas that are on the leeward side of mountains, where the air is dry after crossing the range.

💡Tibetan Plateau

The Tibetan Plateau is a vast elevated plateau in Central Asia and the world's highest plateau. The script uses the Tibetan Plateau as an example of a rain shadow region, where air masses crossing the Himalayas become dry, leading to the formation of a desert-like environment on the plateau.

💡Geographic Location

Geographic location refers to the specific place or position of a feature on Earth's surface. The video script discusses how the geographic location of deserts, particularly between 15 and 30 degrees latitude and in the interiors of continents, influences their formation due to atmospheric circulation patterns and distance from moisture sources.

💡Atmospheric Circulation

Atmospheric circulation is the large-scale movement of air in the Earth's atmosphere. The video script explains how deserts form in areas affected by specific patterns of atmospheric circulation, such as the Hadean Cell, which influences temperature, humidity, and precipitation.

💡Continental Interior

The continental interior refers to the regions far from the ocean within a continent. The script mentions that deserts often form in continental interiors because these areas are distant from the ocean, which is a primary source of moisture. This results in less precipitation and a drier climate.

Highlights

Desertos cobrem uma vasta área dos nossos continentes e são formados em regiões com características geográficas específicas.

Desertos são locais onde as taxas de evaporação potenciais são muito maiores do que as taxas de precipitação.

As regiões desérticas são definidas por taxas de precipitação baixas, com áreas azuis escuras representando mais chuva e áreas brancas menos.

Desertos tendem a se formar entre 15 e 30 graus norte ou sul da linha do equador, em sombras de chuva de grandes massifs montanhosos.

A circulação atmosférica, particularmente a célula de Hadley, é fundamental para a formação de desertos.

A região perto da linha do equador recebe mais radiação solar, resultando em ar mais quente e evaporação.

A arquitetura de Hadley envolve massas de ar quentes ascendendo na região do equador e fluindo para os pólos.

As massas de ar se tornam mais secas e frias à medida que se movem para norte ou sul, resultando em menos precipitação.

As regiões em torno de 30 graus norte e sul são dominadas por descensão de ar, criando um ambiente seco ideal para desertos.

Desertos também se formam no interior dos continentes, longe das fontes de ar úmido do oceano.

O efeito da sombra de chuva das montanhas é um fator chave na aridez e formação de desertos.

Levantamento orográfico ocorre quando massas de ar quentes e úmidos são forçadas a subir pelas montanhas, resultando em precipitação.

As regiões de sombra de chuva são aquelas que, após o levantamento orográfico, se tornam muito secas e propensas a formar desertos.

O Planalto Tibetano, norte dos Himalaias, é um exemplo de região de sombra de chuva que se torna árida devido à influência das montanhas.

A paisagem e a vegetação mudam drasticamente em regiões de sombra de chuva, indicando a transição para ambientes desérticos.

A discussão aborda como as características geográficas específicas criam um ambiente perfeito para a formação de desertos.