VALLEY CLIMATES
MACRO & MICROCLIMATES:
Macro climates - systems that affect large areas of the earth
Microclimates - factors that affect local climates on a much smaller scale
(where variations in atmospheric heating, pressure & winds can influence
the weather of a small area)
FACTORS THAT AFFECT THE MICRO CLIMATE OF VALLEYS
Temperature differences
1. Latitude: how far north or south of the equator the area is
2. Slope aspect: north or south facing slope
3. Angle of incidence: angle at which the suns rays strike the
earth
4. Seasons: winter or summer
5. Vegetation: what’s found on the slopes & valleys
Variations in air density & pressure
1. Effect of pressure belts: eg. Anticyclonic circulation
2. Local winds: katabatic, anabatic, land & sea breezes
THE EFFECT OF ASPECT
ANGLE OF INCIDENCE
Changes throughout the day and according to the season
An area receiving sunlight at a
perpendicular angle will be warmer
than an area receiving sunlight at
an oblique angle
Hence the equator is warmer than
the poles
, There are times in the year where the suns rays strike a valley directly
(summer), and times where the suns rays will strike the land obliquely -
casting a shadow in the valley
Called a shadow zone
In the southern hemisphere:
The sun moves from east to west
North facing slopes are warmer &
sunnier than south facing slopes
Farmers plant their crops according
to how much sunlight they need year
round
NORTH FACING SOUTH FACING
Grains Pine trees
Vegetables Eucalyptus
Fruit trees
WINDS RELATED TO VALLEYS
Winds that blow due to a difference in temperature between the top and
bottom of the slopes of a valley
DAY-TIME WINDS
During the day, upper slopes receive more
insolation and thus, are warmer & have a
lower pressure than the lower slopes
ANABATIC WINDS - the higher pressure on
the valley floor causes a wind to blow
from the valley floor up the slopes
MACRO & MICROCLIMATES:
Macro climates - systems that affect large areas of the earth
Microclimates - factors that affect local climates on a much smaller scale
(where variations in atmospheric heating, pressure & winds can influence
the weather of a small area)
FACTORS THAT AFFECT THE MICRO CLIMATE OF VALLEYS
Temperature differences
1. Latitude: how far north or south of the equator the area is
2. Slope aspect: north or south facing slope
3. Angle of incidence: angle at which the suns rays strike the
earth
4. Seasons: winter or summer
5. Vegetation: what’s found on the slopes & valleys
Variations in air density & pressure
1. Effect of pressure belts: eg. Anticyclonic circulation
2. Local winds: katabatic, anabatic, land & sea breezes
THE EFFECT OF ASPECT
ANGLE OF INCIDENCE
Changes throughout the day and according to the season
An area receiving sunlight at a
perpendicular angle will be warmer
than an area receiving sunlight at
an oblique angle
Hence the equator is warmer than
the poles
, There are times in the year where the suns rays strike a valley directly
(summer), and times where the suns rays will strike the land obliquely -
casting a shadow in the valley
Called a shadow zone
In the southern hemisphere:
The sun moves from east to west
North facing slopes are warmer &
sunnier than south facing slopes
Farmers plant their crops according
to how much sunlight they need year
round
NORTH FACING SOUTH FACING
Grains Pine trees
Vegetables Eucalyptus
Fruit trees
WINDS RELATED TO VALLEYS
Winds that blow due to a difference in temperature between the top and
bottom of the slopes of a valley
DAY-TIME WINDS
During the day, upper slopes receive more
insolation and thus, are warmer & have a
lower pressure than the lower slopes
ANABATIC WINDS - the higher pressure on
the valley floor causes a wind to blow
from the valley floor up the slopes
