10.1 Climates

Question 1

What does arid refer to?

Answer 1

Arid refers to areas with a permanent water deficit and less than 250mm of rainfall per annum.

Question 2

Semi-arid is commonly defined as…

Answer 2

Having less than 500mm per annum

Question 3

1)What continent contains the greatest global proportion of arid land?
2)What continent has the most arid land as a proportion of their continent?

Answer 3

1)Africa as it has more land mass than other continents

2) Australia as 75% of the land is classified as arid or semi arid.

Question 4

equation for index of moisture availability. define all values

Answer 4

Im = 100S - 60D/ PE where:

Im: index of moisture availability
S: moisture surplus
D: moisture deficit
PE: potential evapotranspiration.

Question 5

define potential evapotransipration:

Answer 5

how much evaporation would take place if there was an unlimited supply of water.

Question 6

State the Im for the three arid environments.

Answer 6

semi arid: Im between -20 and -40
arid areas: Im between _40 and -56
extreamely arid: Im of less than -56

Question 7

define rainfall effectivness.

Answer 7

potential evapotranspiration subtract actual amount of rainfall in a given time.

if the value is positive: indicates more rainfall than potential evapotranspiration, resulting in a surplus of water

if the value is negative: suggests that potential evaporation exceeds the rainfall, indicating a deficit of water.

Question 8

factors effecting rainfall effectiveness

Answer 8

rate of evaporation:
- effected by temp and wind speeds.
- in hot dry areas ecap losses are high

seasonality:
- winter rainfall is more effective than summer as evap losesse are lower

rainfall intensity:
- heavy, intense rain produces rapid runoff with little infiltration

soil type:
- impermeble clay soils have little capacity to absorb water,
- porous, sandy soild may be susceptible to drought

Question 9

why are porous sand soils susceptible to drought?

Answer 9

Large pore spaces
- so water can quickly penetrate through soil therefore faster drainage and reduced water holding capcity, which tends to dry soils out faster in periods of limited rainfall/ high evapotran rates.

Lower water retention capacity
- rapid drainage due to large pore size also means limited water is retained for plants

Question 10

what are the three/four causes of aridity

Answer 10

• main cause is global atmospheric circulation ( causes aridity in tropics)
• continentality
• cold offshore currents that can be due do continentality
• rain shadow effects

Question 11

explain how global atmospheric circulation causes aridity

Answer 11

-main cause of aridity

dry decending air associated wit the sub tropical high pressure belt at 20-30 degrees celsius

Question 12

explain how continentality causes aridity

Question 13

explain how cold offshore currents causes aridity

Question 14

explain how intense rainshadow effects can cause aridity

Question 15

Describe rainfall in arid environments

Answer 15

• low annual rainfall
• highly variable rainfall variability in the sahara is commonly 0-150% wheras in temperate humid areas just 20%.
• many desert areas recseive low intensity rainfall
• in coastal areas with cold off-shore currents fog formation provides significant amounts of moisture.

Question 16

describe the temperature of arid environments

Answer 16

Deserts exhibit wide variation in temperature.

continental interiors
- exhibit both extremes of temperature, both seasonally and diurnally

coastal areas
- low seasonal and diurnal ranges

Question 17

describe winds in deserts

Answer 17

deserts are high-wind-energy environments
- partly due to lack of vegetation
- reduced friction between wind and surface

Question 18

climate change in desserts