Chapter 13: Weather Flashcards
Atmosphere
Is a thin layer of gases that surrounds the Earth.
Layers within the atmosphere
Troposhere
Stratosphere
Troposhere
The lowest layer in the Earths atmosphere.
It reaches from sea level to about 17km
Weather and clouds occur in the troposhere
The temperature decreases the higher the altitude.
The stratosphere
It extends from 17km to 50km from the Earths surface
The ozone layer is located in the stratosphere.
Some of the highest clouds can be found in the lower stratosphere.
Solar heat
The amount of heat kept in the atmosphere depends on the amount of greenhouse gases in the atmosphere.
The uneven heating of the Earth
Latitude
The Earths adis
Latitude
The earth is divide into the Northern hemisphere and the southern hemisphere.
Because of the spherical shape, the equator is closest to the sun.
The sun rays have a shorter distance to travel to the equator.
The sun rays shine directly on the equator and so are concentrated on a smaller area. The rays at higher latitudes are slanted and therefore cover a larger area and are less intense.
The Earths axis
During our summer, the northern hemisphere is tilted towards the sun.
During our winter, the northern hemisphere begins to tilt away from the sun.
How winds are formed
The unequal heating of the atmosphere and the Earth’s surface leads to movements of air.
When air is heated, it expands. This makes it lighter and so it rises. This creates areas of low pressure at the equator.
At about 30 degrees north and south of the equator, the warm air begins to cool. When air is cooled it becomes heavy and sinks towards the surface of the Earth. This creates areas of high pressure.
Between 30 degrees latitude and the equator, most of the cooling, sinking air moves back to the equator. The rest of the air flows towards the poles.
Global winds
Trade winds The doldrums The prevailing westerlies The horse latitudes The polar easterlies
Trade winds
Trade winds are air movements towards the equators. They are warm, steady breezes that blow almost continuously. The rotation of the Earth on its axis causes what is known as the Coriolis effect.
The Coriolis effect
It makes the trade winds appear to curve towards the west, regardless of whether they are travelling to the equator from the south or north
The doldrums
The doldrums is an area of calm weaher. The trade winds coming from the south and the north meet near the equator. As they are heated, these converging trade winds blow upwards so there is little movement of air near the surface, and so little wind
The prevailing westerlies
Between 30 degrees and 60 degrees latitude, the wind that move towards the poles appear to curve to the east. These winds are called westerlies. Prevailing westerlies in the Northern hemisphere are responsible for many of the weather movements across Europe, and especially in Ireland
The horse latitude
The horse latitude are found at 30 degrees north and south of the equator. They form a belt that blows between the trade winds and the prevailing westerlies. Horse latitude winds tend to be weak and encourage clear, bright weather.
The polar easterlies
At about 60 degrees latitude in both hemispheres, the prevailing westerlies meet the polar easterlies. The polar easterlies form when the atmosphere over the poles cools. This cool air then sinks and spreads over the surface. As the air flows away from the poles, it is turned to the west by the Coriolis effect.
Ocean currents
Ocean waters are always moving. The movement of water is referred to as a current. Ocean currents occur due to:
Differences in temperature
The Earth rotating on its axis
Wind
Warm currents
Currents flowing from the equator are warm. The Gulf Stream originates in the Gulf of Mexico and turns north-eastwards into the Atlantic Ocean, where it splits to form the warm North Atlantic Drift (NAD) and the cold Canary Current. The NAD flows past the west coast of Ireland where it helps to keep ports ice-free.
Cold currents
Cold currents flow from areas in high latitudes towards the equator. The Labrador Current, which flows south along the coast of north-east America, reduces the temperature of the ocean and many ports freeze over as a result.
Air masses
Air masses are large moving pockets of air that are distinct from the surrounding atmosphere. Warm air masses carry more moisture or water vapour then cold air masses.
All air masses have the following characteristics
They are large, often stretching more than 1500 km across the landscape and extending several kilometres into the atmosphere.
The temperature, pressure and moisture are similar at any point within the air mass.
They travel across the atmosphere as a single unit
Polar maritime
These air masses from the north-west Atlantic bring cold, wet air and showery conditions.
