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Arid And Semi Arid > Hot Arid And Semi-Arid Climates > Flashcards

Hot Arid And Semi-Arid Climates Flashcards

1
Q

HOT ARID AREAS

A
  • less than 250mm of rain a year
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2
Q

HOT ARID EXAMPLES

A
  • Cairo, Egypt: mean annual rainfall of 33mm
  • Areas of Atacama desert have experienced no rainfall at all
  • Luderitz, Namibia: total average rainfall in a year is 125mm
  • Khartoum, Sudan: total average rainfall in a year is 161.5mm
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3
Q

GOBI DESERT

A
  • largest Asian desert
  • covers Mongolia and China
  • surrounded by Mongolian grasslands &;Altai mountains
  • covers 800 km north-west
  • lies in a rainshadow caused by Himalayas
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4
Q

ATACAMA DESERT

A
  • in South America
  • driest in the world; no rain from 1570-1971
  • average rainfall is 1mm
  • Arica & Iquique get 1-3mm in a year
  • located between Andes & Chilean coast range mountain chains
  • day temp: 40 degrees
  • night temp: 5 degrees
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5
Q

SAHARA DESERT

A
  • in North Africa
  • worlds largest hot desert
  • 3.6 million miles big
  • half of it gets less than 1 inch of rain a year
  • covers big parts of Chad, Libya, Algeria, Mali
  • bordered by Atlantic on West
  • bordered by Atlas Mountains & Med Sea on North
  • bordered by Red Sea on East
  • bordered by Niger River & Sudan on South
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6
Q

TROPIC OF CANCER

A
  • line of latitude in northern hemisphere
  • approx 23.5 degrees north of equator
  • Sun’s rays appear directly overhead at local noon
  • marks northern boundary of tropics
  • passes through Hawaii
  • passes through parts of central USA
  • passes through Northern Africa
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7
Q

TROPIC OF CAPRICORN

A
  • line of latitude in Southern Hemisphere
  • goes around Earth at approx 23.5 degrees south of equator
  • southernmost point on Earth where Sun’s rays are directly overhead at local noon
  • passes mainly thought water
  • crosses through Rio, Madagascar, Australia, Brazil
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8
Q

LOCATION OF DESERTS

A
  • cover 25-30% of earths land surface
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9
Q

SEMI- ARID DESERT

A
  • between 250-500mm of rain a year
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10
Q

SEMI-ARID EXAMPLES

A
  • Great Basin, North USA: 300mm of rain a year in East

- N’Djamena, Chad: annual precipitation of 580mm

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11
Q

MOJAVE DESERT

A
  • smallest in USA
  • lies between 1500m above sea level. Is 86 m below sea level
  • gets between 50-330mm of rain per year
  • temp as high at 49 degrees in summer
  • temp can be below 0 in winter
  • plants adapt; Joshua tree found on edge of desert. Creosote bush is common
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12
Q

WHAT DO PLANTS NEED TO GROW

A
  • nutrients
  • heat
  • water
  • Sun
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13
Q

WHAT ARE 3 CHARACTERISTICS OF DESERTS

A
  • Climate:
    Rainfall= low when climate =hot
  • Soil:
    Dry, sandy, lack of organic matter, thin, poorly developed
  • Vegetation:
    Xerophytes adapt to conditions, plants have long roots, leaves are small &tough, vegetation found near oases
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14
Q

VEGETATION IN A DESERT

A
  • density = low
  • desert soils are poor, alkaline
  • salts are common within soil. Plants that can handle soil are halophytic- eg, saltbush
  • when it rains vegetation changes. Seeds from last period of rainfall germinate & blossom
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15
Q

PLANTS IN A DESERT

A
  • adapt to high temps
  • growth is limited by high levels of evaporation or transpiration
  • lots have long tap roots that burrow down up to 15m into ground to reach an underground water supply. Known as xerophytic plants
  • plants are normally small. Gives hem smaller SA & reduces transpiration
  • leaves are replaced by thorns; give more protection
  • leaves are replaced by small wax cuticles; reduces rate of transpiration
  • aqueous tissue is fleshy & stores water. Common in cacti
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16
Q

HOW DO CACTI ADAPT IN A DESERT

A
  • known as succulents
  • they absorb & store water in their tissue
  • have low rate of transpiration
  • eg cottontop cactus
  • eg barrel cactus
  • eg beavertail cactus
  • eg beavertail prickly pear
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17
Q

ESSAY QUESTION:

‘Outline the characteristics of a desert’ (6)

A
  • climate:
  • soils
  • vegetation
  • LINK ALL 3 FACTORS TOGETHER
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18
Q

WHAT SORT OF EVAPORATION IS THERE AT THE EQUATOR

A
  • lots of evaporation is at the Equator
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19
Q

WHAT HAPPENS WHEN THERES HIGH PRESSURE

A
  • no clouds

- no rain

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20
Q

WHAT IS THE WEATHER LIKE IN THE TROPICS

A
  • dry

- due to the tri- cellular model

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21
Q

WHAT INFLUENCES THE TEMPERATURE IN ARID & SEMI- ARID ENVIRONMENTS

A
  • latitude

- distance from the sea

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22
Q

HOT ARID LOCATIONS

A
  • occur in centre of desert areas
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23
Q

SEMI- ARID LOCATIONS

A
  • occur on margins
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24
Q

A.A.MILLER’S ARIDITY THEORY

A
  • said deserts had areas with mean annual rainfall of less than 250mm
  • distinction between hot deserts & mid- latitude deserts
  • said hot had no month with a mean temp of less than 6 degrees
  • most hot are located in latitudes from 15 to 30 degrees
  • said mid- latitude have a cold season with at least 1 month with a mean of temp of less than 6 degrees. Include Great Basin of N.USA & Gobi
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25
Q

W.KÖPPEN’S THEORY

A
  • based on P:Etp balance
  • arid climates are shown by letter B
  • BW: desert climate. Annual rainfall is less than 50% of Etp value
  • BS: steppe climate. Annual rainfall is 50-100% of Etp value
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26
Q

EXAMPLE OF KÖPPEN’S BW

A
  • hot arid environment
  • a hot arid environment follows Köppen’s BW desert climate
  • means annual rainfall is less than 50% of the Etp value
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27
Q

EXAMPLE OF KÖPPEN’S BS

A
  • semi-arid environment
  • a semi-arid environment follows Köppen’s BS steppe climate
  • means annual rainfall is between 50-100% of the Etp
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28
Q

HOW TO CALCULATE KÖPPEN’S DEGREE OF ARIDITY

A
  • MULTIPLY average annual temperature in degrees by 20
  • ADD:
  • 280 if 70% of more of total rainfall is in April-September in n.hemisphere or October-March in s.hemisphere
  • 140 if 30-70% of total rainfall is received during applicable time
  • 0 if less than 30% of total rainfall is received during applicable time
29
Q

PRECIPITATION + MOISTURE IN HOT ARID ENVIRONMENTS

A
  • annual precipitation is less than 0.2 times the potential evapotranspiration
  • precipitation: v.low
  • little moisture available for plant growth
  • rainfall is less than 250mm
  • in some areas there’s been no rain at all
30
Q

PRECIPITATION + MOISTURE IN SEMI- ARID ENVIRONMENTS

A
  • annual precipitation is 0.2-0.5 times the potential evapotranspiration
  • precipitation is low
  • moisture is available for plant growth
31
Q

LYSIMETER

A
  • the way in which actual evapotranspiration is measured

- also measured using a pan of soil & vegetation

32
Q

ISOHYET

A
  • a line of equal precipitation on a map
33
Q

WHAT DETERMINES ARIDITY IN AN AREA

A
  • depends on amount of precipitation

- depends on effectiveness of precipitation; moisture available for plant growth

34
Q

WHAT THINGS INCREASE THE AMOUNT OF EVAPORATION LOST

A
  • high temps
  • direct sun
  • strong desiccating winds
35
Q

CENTRAL SAHARA

A
  • continental area
  • v.high diurnal temp ranges
  • mainly exceed 30 degrees
  • daytime temps are highest in world
  • shade temps above 50 degrees
  • eg 1922: Aziza, Libya: 58 degrees
  • eg Salah, Algeria: July has mean temp of 37 degrees
36
Q

COASTAL AREAS

A
  • eg Namib
  • eg Atacama
  • climates are influenced by sea + cold ocean currents
  • have cooler summers
  • eg Walvis Bay, Namibia: mean temp of hottest month is only 19 degrees. BUT: humidity is v.high
37
Q

HORSE LATITUDES

A
  • where hot arid areas lie
  • areas of sub-tropical high pressure systems
  • roughly 30-35 degrees north & south of equator
  • areas of descending air
  • have gentle pressure gradients
38
Q

CLIMATES IN HOT ARID + SEMI- ARID ENVIRONMENTS

A
  • both have similar climates
39
Q

SEMI- ARID CLIMATES

A
  • areas near Equator have a transitional climate with savannas. Summer rainfall happens due to low pressure & monsoon
  • areas on mid- latitude side have transitional climate on poleward side with Mediterranean climate. Have winter rainfall
40
Q

HOT ARID CLIMATE

A
  • has little seasonality

- rare, extreme rainfall occurrences can happen in any season

41
Q

PRESSURE + WINDS

A
  • causes aridity in deserts
  • air around tropics of Cancer & Capricorn is dry
  • this is a zone of high air pressure where air sinks
  • air at Equator rises + cools + condensation forms rain
  • air moves north + south until it gets to 30 degrees north + south of equator where it sinks
  • this air is dry + no condensation can form
  • known as Hadley Cell
42
Q

COLD OCEAN CURRENTS

A
  • causes aridity in deserts
  • most hot arid + semi- arid areas occur on west coast of continents with a cold ocean current offshore
  • when onshore winds blow onto west coasts of deserts they are cooled for condensation to occur over current, leads to FOG hanging in air near surface
  • coastal places have foggy days + high humidity when winds are onshore
  • condensation removes moisture from air
  • foggy air moves inland, leads to water droplets evaporate
43
Q

RELIEF + RAINSHADOW

A
  • causes aridity in deserts
  • small amounts of orographic rainfall + rainshadow happens in deserts
  • low areas in lee of mountains are v.dry. Eg Turfan Basin, China
  • some deserts form in rainshadow of mountains. Eg Atacama desert is located in the rain shadow of the Andes
  • air is forced to rise over mountains, air cools + condensation occurs
  • rain falls over mountains
  • dry air sinks down other side of mountain
44
Q

WHAT HAPPENS TO SEA + LAND IN DAY

A
  • high pressure causes a colder sea

- sea breeze leads to low pressure + warmer land

45
Q

WHAT HAPPENS TO SEA + LAND AT NIGHT

A
  • high pressure causes colder land

- sea breeze causes low pressure + warmer sea

46
Q

TEMPERATURE

A
  • rain isn’t common in deserts
  • when it does it can cause FLASH FLOODS
  • eg. Parts nearest Equator where occasional convectional storms occur in summer heat
47
Q

LATITUDE

A
  • influences temp in deserts
  • hot arid + some semi area have overhead Sun in summer
  • leads to EXTREMELY HIGH TEMPS
  • 21st June: Sun is overhead Tropic of Cancer
  • 22nd December: Sun is overhead Tropic of Capricorn
  • there’s a TEMP LAG as temp builds up so hottest + coolest month is a month later
  • tropical deserts: Sun is never v.low. Wingers are hot + so are summers
  • length of day is longer in summer away from Equator
48
Q

ALTITUDE

A
  • influences temp in deserts
  • air is thinner + has less water vapour + dust to absorb Earths LW radiation
  • this causes temp to decrease to 0.6 degrees every 100m of height gained
  • contributes to cooler temps at Keetmanshoop, Namibia
49
Q

DISTANCE FROM SEA

A
  • influences temp in deserts
  • when water heats + cools slower than land coastal areas have warmer winters + cooler summers than in inland areas
  • known as maritime influence as air from sea brings temps of sea to land
  • continental areas don’t experience this effect + land heats up fast in summer + cools fast in winter
  • continental areas in hot deserts have v.hot summer temps. Eg Salah, Algeria: July mean temp is 37 degrees
50
Q

DAY THAT THE SUN IS OVERHEAD THE TROPIC OF CANCER

A
  • 21st June
51
Q

DAY THE SUN IS OVERHEAD THE TROPIC OF CAPRICORN

A
  • 22nd December
52
Q

MARITIME INFLUENCE

A
  • when air from sea brings temp of sea to the land
53
Q

COLD OCEAN CURRENTS

A
  • influences the temp in deserts
  • there are cold ocean currents off coasts of hot deserts
  • are bodies of water moving through oceans from areas nearer Poles to areas near Equator
  • winds that blow over cold Benguela current off Namibia coast are chilled by contact with current. They carry cooler air onto land. This lowers temp on coastal strip
54
Q

LACK OF CLOUD

A
  • influences temp in deserts
  • desert air has v.low relative humidity. So skies are cloudless. Leads to extreme DIURNAL TEMP
  • in hot deserts temp can be 50 degrees in summer shade
  • at night: without clouds temp drop to 15 degrees in summer + 5 in winter
  • low night time temp can lead to condensation of water vapour. Forms dew. Helps weathering process
55
Q

RELATIVE HUMIDITY

A
  • how much humidity there is in the air

- compared to how much there could be

56
Q

ABSOLUTE HUMIDITY

A
  • measure of water vapour (moisture) in air

- doesn’t matter what the temp is

57
Q

POTENTIAL EVAPOTRANSPIRATION

A
  • amount of evaporation that would occur if a sufficient water source was available
58
Q

ACTUAL EVAPOTRANSPIRATION

A
  • quantity of water removed from a surface due to evaporation + transpiration
59
Q

2 COOL COASTAL DESERTS

A
  • Atacama

- Namib

60
Q

10 SUBTROPICAL DESERTS

A
  • Mojave, California
  • Sonoran, N.USA
  • Chihuahuan, N.USA. Extends into parts of New Mexico, Texas + southeastern Arizona
  • Sahara, N.Africa. Covers large parts of Algeria, Chad, Egypt, Libya, Mali, Niger, Mauritania
  • Kalahari, S.Africa. Covers most of Botswana
  • Arabian, W.Asia. Covers from Yemen to Persian Gulf + Oman to Jordan + Iraq
  • Thar, Rajasthan
  • Great Sandy, NW of W.Australia
  • Gibson, W.Australia
  • Great Victoria, S.Australia
61
Q

7 COLD WINTER DESERTS

A
  • Colorado, California
  • Patagonian, Argentina
  • Iranian, Iran
  • Kyzyl-Kum, Kazakhstan + Uzbekistan
  • Kara-Kum, Turkmenistan
  • Taklamakan, Central Asia, China
  • Gobi, Mongolia + China
62
Q

DIURNAL TEMPERATURE RANGE DEFINITION

A
  • difference between daily max temp + daily min temp
63
Q

CAUSES OF CHANGES IN DIURNAL TEMPERATURE RANGE

A
  • cloud cover
  • urban heat
  • land use change
  • aerosols, greenhouse gases
64
Q

DIURNAL TEMPERATURE RANGE DEFINITION

A
  • difference between daily max temp + daily min temp
65
Q

CAUSES OF CHANGES IN DIURNAL TEMPERATURE RANGE

A
  • cloud cover
  • urban heat
  • land use change
  • aerosols, greenhouse gases
66
Q

DO ALL CONTINENTS HAVE A DESERT

A
  • no
  • all continents do
  • except Europe
67
Q

WHY DO DESERTS TEND TO BE LOCATED IN THE WEST

A
  • due to Coriolis effect
68
Q

HYPER-ARID DEFINITION

A
  • when areas have a mean annual precipitation value of less than 100mm

Arid And Semi Arid (4 decks)

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