Chapter 3: Weather and climate

• Aardrijkskunde
• Middelbare school
• havo, vwo
• Leerjaar 3

Chapter 3:
 

Weather and climate

Section 3.1.: Weather
Section 3.2.: Dutch climate

Section 3.3.: Climates in Europe
Section 3.4.: Tropical climates
Section 3.5.: Dry climates
Section 3.6.: Cold climates

What is the difference between weather and climate?

Section 3.1. The weather

Learning goals:

1. Define the keyword weather 

2. Explain the four most important parameters when it comes to weather.

Weather is the current state of the atmosphere. It's measured on a time in a certain place.

 

Climate is the average weather over an extended period.

Longer period and larger area

We'll watch the BBC weather forecast of today. 

Which different elements of weather do you recognize? 

https:

Which different elements of weather did you recognize?

In the weather forecast you've recognised the four charecteristics or elements of weather:

• Temperature
• Precipitation
• Wind (speed and direction)
• Cloud cover 

With these four elements you can express the difference in weather between places.

Temperature

In the Netherlands measured in degrees Celsius using a thermometer.

Location influences the temperatures:

Further away from the equator the temperatures becomes less. 

The higher on a mountain the lower the temperature.

Isotherm temperature map of 

the USA 

Precipitation

There a two types of precipitation:

solid (e.g. hail and snow) 

and 

fluid (e.g. rain, fog).

Three important processes that make precipitation possible:

- Evaporation
- Transpiration

- Condensation

Precipitation always needs rising air!

Very very important!

When air rises it gets colder, cold air can't hold as much water vapour then warm air so precipitation.

When air falls it gets warmer, so less precipitation

Very important!

When air rises it gets colder, cold air can't hold as much water vapour then warm air so precipitation.

When air falls it gets warmer, so less precipitation

What is the difference between the small and large water cycle?

Wind

Wind is the movement of air through the atmosphere. 
In the forecast they mention wind speed (in Beaufort) and wind direction.
Wind always is named after the direction it comes from, in the Netherlands that's mainly Western wind.

Buys Ballot

Important law of Buys Ballot
1. Wind always moves from high pressure areas to low pressure areas;

2. Wind is deflected to the right in the Northern Hemisphere and to left in the Southern Hemisphere.

Coriolis effect

Also wind goes the opposite direction in the Northern Hemisphere, but why?

That's because the Coriolis effect.

Air pressure

Is expressed in hectopascal hPa and on a map of the air pressure you see isobars.

Section 3.2. The Dutch climate

Learning goals:

1. Explain the difference between weather and climate 

2. Use a climate graph to describe the Dutch climate 

3. Draw a climate graph 

4. Explain why the earth has different seasons

What's the difference between weather and climate?

Why is the temperature near the tropics warmer then near the poles (figure 3.17)?

1. Distance from the sun is shorter near the equator;

2. The surface that is heated near the equator is smaller.

The climate of the Netherlands is influenced by it's location near the sea.

Seawater slowly warms up and slowly cools down compared to land surface. 
Therefore places near the sea have less differences in summer and winter temperatures.

Typically Dutch is also our annual rainfall. 

This rainfall is also caused by the location near the sea but also thanks to frontal rainfall.

The temperature of the Atlantic Ocean near Western Europe is higher than could be expected because it's location. 

That's because of the Gulf stream a warm sea current that originates from the Gulf of Mexico.

Section 3.3. Europe's climates

Learning goals:

1. Describe Köppen’s climate classification system.

2. Describe differences between climates in Europe.

3. Explain the effect of mountains on the climate 

4. Explain the different height belts in mountains. 

5. Determine using a climate graph which climate according Köppen’s classification system a place has 

The Netherlands has a maritime climate, but Europe has also different climates.

Köppens'climate classification

The German geographer Wladimir Köppen ordered all the climates in the world in his climate classification by investigating the vegetation in the world

Köppen uses letters for his climate classification. 

The first letter is always a capital, so:
A. tropical climates
B. Dry climates
C. Maritime climates

D. Continental climates

E. Cold climates

The second letter is a lower case letter with A, C en D.

f: no dry period

s: dry summer

w: dry winter

First determine which hemisphere a place is located

Dry (B) climates and cold (E) climates get a second capital letter:

BW (desert) and BS (steppe)

EH (high mountain range), ET (tundra) and EF (snow and ice on higher latitude).

What is the difference between BW and BS?

Annual rainfall:

BW: less then 200 mm rainfall per year
BS: more then 200 mm rainfall per year 

How do you determine the climate? 

Learn this scheme!
1. What is the temperature of the coldest month (can be January or July)?:
Warmer then 18 degrees = A

Between -3 degrees and 18 degrees = C

Colder then -3 degrees = D or E

2. For D or E
What is the temperature of the warmest month (January or July)?
Warmer then 10 degrees = D
Cooler then 10 degrees = E

3. for A, C or E
When is the dryest month?
Summer: s

Winter: w

No dry month: f

If you compare temperatures on mountains you'll see that the temperature in the valley is always warmer then on the top.

Why?

The atmosphere is heated up by sun beams that are reflected by the earth's surface.

Every 1000 meters the temperature drops with 6 degrees.

Temperature also influences the vegetation (fig 3.30)

On a summer day I decide to walk up on a mountain. Temperature in the Valley is 18 degrees. What is the temperature on 1500 metres?

1. 18 degrees
2. 27 degrees
3. 9 degrees
4. 6 degrees

In the afternoon i've reached the top at 2000 metres. The temperature at the top is 3 degrees. What is the temperature in the valley ( 500 metres)?

1. -6 degrees
2. 3 degrees
3. 9 degrees
4. 12 degrees

Air that rises becomes

1. Colder
2. Warmer

Orographic rainfall

Air rises gets colder and precipitates. 
Decending air gets warmer so there is no precipitation.

Section 3.4. The tropical climate

Learning goals:

1. Locate the tropic and subtropics

2. Describe the two types of tropical climate

3. Explain how the sun causes the wet and dry seasons in the savannah climate 

4. Describe convectional rainfall

5. Describe frontal, orographic and convectional rainfall

6. Describe the wind system between the subtropics and the tropics 

7. Describe and explain the monsoon in India

The area between the Tropic of Cancer (23.4 N) and Tropic of Capricorn (23.4 S) is called the tropics. Area north and south of the tropics are subtropics.

The tropical region can have two different climates:

Af: tropic climate with no dry periods or tropical rainforest climate

Aw/As: Savannah climate or Monsoon climate (tropical climate with a dry period)

Why are the tropics warm and why does is rain that often?

Convectional rainfall

Air rises at the equator and descends around the 30 degrees N and S. 

So low pressure (rain) at the equator and high pressure (drought) around the 30 degrees.

According Buys Ballot's physical law the winds blows from the subtropics towards the tropics. These winds are called trade winds. The meeting point of this wind is called the intertropical convergence zone (ITCZ).

Moving ITCZ

The ITCZ moves with the Sun; in June, July and August the northern hemisphere receives more sunlight and the ITCZ moves also to the north. In December, January and February the ITCZ moves more to the south.

Section 3.5. Arid climates

Learning goals:

1. Describe two different arid climates 

2. Explain why the world’s deserts are arid 

3. Describe the atmospheric circulation 

4. Explain the effect of sea currents on the precipitation 

5. Explain the Coriolis effect 

Two B or dry climates

BW: Desert climate

BS: Steppe climate

Desert

Steppe

Atmospheric circulation

The different cells:

1. Hadley cell

2. Ferrel cell
3. Polar cell

Annotate the diagram with:

- Different cells and their names

- Areas of high and low pressure

- Direction of prevailing wind

Section 3.6. Polar climates

Learning goals:

1. Describe the polar climates. 

2. Explain the location of the polar climates. 

3. Describe the way the way of life in the polar climate 

Three E or cold climates

ET: Tundra climate

EF: Snow and ice near the poles 
EH: (Height) Mountain ranges 

All these climates have a low temperature in common.

Because of this cold temperatures isn't possible for trees to grow in these regions.

Tundra: 

Landscape with shrubs, grasses and mosses.  Winter temperature is below 0 degrees. In the summer is above 0, then the soil does not  thaw completely. This is called permafrost.
Because of the permafrost it can be marshy