Deserts and Wind Flashcards
What is a desert?
a region that receives less than 25cm of precipitation per year
Life support in a desert
deserts are unable to support significant populations of animals because the vegetation is so sparse, and water is so rare
Temperature in a desert
Extreme temperature ranges because the atmosphere contains little humidity to block the Sun’s rays or retain heat at night
Natural Climate Change
climates can change naturally, i.e the Sahara region was humid 5k to 10k years ago
Deserts may be hot or cold, but
low precipitation is a common trait
Top 3 largest deserts
Antarctic desert, Arctic desert, and Sahara
Some would argue that the “Arctic Desert” isn’t really a desert. Why do most cool dry areas have more vegetation than hot dry areas?
Life is better at dealing with cool than hot, can conserve water better
Atmospheric moisture circulation determines the location of most deserts
arid belts are where deserts are because of the way air moves up then cools off and precipitates
Formation of Deserts
- Air warms and contracts as it sinks closer to Earth’s surface
- Evaporation exceeds condensation
- Deserts form, clustered around 30ºN and 30ºS latitudes
Not all deserts lie around 30º latitude. Several other factors contribute to desert locations:
- Orographic effect
- Dry, cold air descending over polar regions
- The distance atmospheric moisture is transported
- Cold ocean current adjacent to a tropical coast
- Poor management of farmland
- Deforestation
Orographic effect
- When air masses are forced to flow over high topography.
- As air rises over mountains, it cools and water vapour condenses.
- As a result, it is common for rain to be concentrated on the windward side of mountains, and for rainfall to increase with elevation in the direction of storm tracks.
- The other side of the mountain has arid conditions
Rainshadow
The side of the mountain that has arid conditions b/c precipitation is on the other side of the mountain
The distance atmospheric moisture is transported, more distance =
less precipitation further away/further inland b/c it’s precipitated out as it travels
Cold ocean current adjacent to a tropical coast = warm currents are much more likely to:
evaporate and precipitate, cold currents create much less
Poor management of farmland = decertified by:
removing all the foliage via agriculture
Deforestation = removal of
biomass, dries out soil
Everything comes back to the ocean because:
it is the heat sink on the planet and distributes the heat around.
What dictates the ocean current?
Location of the continents.
- As they move they change the ocean currents’ routes and changes the distribution of heat = changing the climate
Trade Wind Deserts
An area of very little rainfall and high temperature occurs where the trade winds or their equivalent (such as the harmattan) blow over land.
Mid-latitude Deserts
near the equator basically
Rain Shadow Deserts
A patch of land that has been forced to become a desert because mountain ranges blocked all plant-growing, rainy weather. On the rain shadow side has all precipitation is blocked.
Coastal Deserts
- Occur in cool to warm areas along the coast.
- Cool winters and long, warm summers.
- Located on the west coasts of continents between 20° to 30° latitude.
- Winds off the coast blow in an easterly pattern and prevent the moisture from moving onto the land
Wind is an important geological agent, has much less
carrying capacity, but can still move a lot and create structures
Stoss slope
Windward slope (less steep)
