🎒 Base knowledge and understanding

✅ Tasks

🔑 Key terms

🎯 Context

The weather in Geneva now

Weather Conditions - CdN Console

Geneva’s climate

World Weather Information Service

Weather vs Climate

Climate describes atmospheric conditions over relatively long periods of time, whereas weather describes the conditions in the atmosphere over a short period of time.

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Weather and climate describe the same set of atmospheric variables, but over very different timescales.

Weather is what you experience when you step outside: the temperature, humidity, air pressure and wind speed at a particular moment or over a short period (hours to days). It is variable and changes rapidly.

Climate is the average of these same conditions over a much longer period, approximately 30 years. Climate tells you what to expect in a region; weather tells you what is actually happening right now.

A useful way to think about it: weather is your mood today; climate is your personality.

Key atmospheric variables

Variable	Weather example	Climate example
Temperature	It is 14°C outside right now	The average July temperature in London is 18°C
Humidity	It feels muggy today	Tropical regions have consistently high humidity
Air pressure	A low-pressure system is moving in	Subtropical regions are dominated by high pressure
Wind speed	Gusts of 50 km/h expected tonight	Mid-latitude regions experience prevailing westerlies
Precipitation	20 mm of rain fell yesterday	The annual average rainfall in the Amazon is 2,300 mm

A news report says: "Tomorrow will be 28°C with scattered showers." Is this describing weather or climate?
A geography textbook says: "The mean annual temperature in this region is 12°C with 750 mm of rainfall per year." Is this describing weather or climate?
Why is 30 years used as the standard period for defining climate?

Abiotic Factors and Biome Distribution

Abiotic factors are the determinants of terrestrial biome distribution. For any given temperature and rainfall pattern, one natural ecosystem type is likely to develop.

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Precipitation, temperature and insolation are the major abiotic factors influencing the distribution of terrestrial biomes. For any given combination of temperature and rainfall, one natural ecosystem type is likely to develop.

This relationship is shown on a biome distribution graph (sometimes called a Whittaker diagram), which plots mean annual temperature against mean annual precipitation. Each region of the graph corresponds to a different biome.

[Source]

Why do these factors matter?

Water is needed for photosynthesis, transpiration and the structural support of plants
Sunlight (insolation) provides the energy for photosynthesis
Temperature affects the rate of photosynthesis (it is a chemical reaction)
Together, these factors determine the productivity of an ecosystem, which in turn determines its structure and the biome that develops

Using the biome distribution graph, which biome would you expect at 25°C average temperature and 2,500 mm annual precipitation?
What happens to the biome type as precipitation decreases at high temperatures (e.g. moving from 2,500 mm down to 250 mm at 25°C)?
Why does tundra develop at low temperatures even when precipitation is also low?

Hint: Think about evaporation rates and the availability of liquid water.
The graph shows that for a given temperature and rainfall, one biome is predicted. Can you think of any reasons why the predicted biome might not actually develop?

🎒 Base knowledge and understanding

✅ Tasks

🔑 Key terms

🎯 Context

The weather in Geneva now

Geneva’s climate

Weather vs Climate

A news report says: "Tomorrow will be 28°C with scattered showers." Is this describing weather or climate?

A geography textbook says: "The mean annual temperature in this region is 12°C with 750 mm of rainfall per year." Is this describing weather or climate?

Why is 30 years used as the standard period for defining climate?

Abiotic Factors and Biome Distribution

Using the biome distribution graph, which biome would you expect at 25°C average temperature and 2,500 mm annual precipitation?

What happens to the biome type as precipitation decreases at high temperatures (e.g. moving from 2,500 mm down to 250 mm at 25°C)?

Why does tundra develop at low temperatures even when precipitation is also low?

The graph shows that for a given temperature and rainfall, one biome is predicted. Can you think of any reasons why the predicted biome might not actually develop?

The Tricellular Model of Atmospheric Circulation