Unit 1B - Our Changing Weather and Climate Flashcards
2a) Study Fig.6 which shows a Stevenson Screen containing thermometers. Answer the questions which follow.
Thermometer are located in a box called a Stevenson Screen
i) State three reasons why this is the best location for thermometers. [3]
- No direct heat interference from sunlight
- Sheltered from the elements (wind, rain)
- No interference from wildlife
What is weather?
Weather is the day-to-day state of the atmosphere. It is a dynamic process which is constantly changing.
What are the five main gases that make up our atmosphere?
Oxygen (O2) Ozone (O3) Nitrogen (N2) Carbon Dioxide (CO2) Water (H2O)
What is climate?
Climate is more long term. It is the average weather taken over a long period of time (usually over 35 years). Climate is a less dynamic process and does not change as quickly as weather.
What are the seven elements of the weather?
Temperature Precipitation Wind direction Wind speed Air pressure Cloud types Cloud cover
Give a description of temperature
Temperature is a measure of the amount of heat in the atmosphere around us.
Give the method of measurement and units of measurement for temperature
Max and min thermometer (instrument) Degrees centigrade (°C)
Give a description of precipitation
This is the amount of moisture in the atmosphere and usually involves water in all of its states: liquid, solid and gas (vapour). It includes water, dew, hail, rain, sleet and snow.
Give the method of measurement and units of measurement for precipitation
Rain gauge (instrument) Millimetres (mm)
Give a description of wind direction
Wind is the air in motion in a horizontal direction.
Give the method of measurement and units of measurement for wind direction
Wind vane (instrument) 8 compass points
Give a description of wind speed
The speed of wind can range from calm to hurricane force.
Give the method of measurement and units of measurement for wind speed
Anemometer (instrument)
Km per hour (kph)
Give a description of air pressure
What is normal air pressure?
Air pressure (or atmospheric pressure) is the pressure exerted by the weight of the atmosphere on the Earth’s surface. Normal pressure is set at 1000 mb. Low pressure is defined as anything below this and high pressure is anything above.
Give the method of measurement and units of measurement for air pressure
Barometer (instrument)
Millibars (mb)
Give a description of cloud types
What is a cloud?
A cloud is a visible mass of tiny particles floating in the atmosphere, consisting of ice crystals or water formed from the condensation of water vapour.
Where are low clouds found?
0-2 km above the Earth’s surface, within the atmosphere.
Where are middle clouds found?
2-4 km above the Earth’s surface, within the atmosphere.
Where are high clouds found?
4-8 km above the Earth’s surface, within the atmosphere.
What are the five main cloud types?
Cirrus Nimbostratus Stratus Cumulus Cumulonimbus
Give the method of measurement and units of measurement for cloud types
Observation
Cirrus Cirrocumulus Altocumulus Altostratus Nimbostratus Stratocumulus Stratus Cumulus Cumulonimbus
Give a description of cloud cover
Due to an international agreement, the amount of cloud cover (or amount) is reported as eighths (or oktas) of the sky covered.
Give the method of measurement and units of measurement for cloud cover
Observation
Oktas (eighths)
0/8 to 8/8
How does one measure temperature?
Maximum and minimum U-shaped thermometer.
Mercury/Alcohol pushes steel marker.
Markers stay at their highest point.
Use magnet to reset.
How does one measure precipitation?
Read the level of water in the measuring cylinder.
Reposition every 24 hours.
How does one measure wind direction?
Wind vane with four main compass points.
Arrow points to where the wind is coming from.
How does one measure wind speed?
Anemometer.
Small cups spin around with digital readouts.
How does one measure air pressure?
Aneroid barometer.
The pressure is measured when a small metal capsule is squashed when there is lower pressure and is allowed to expand when there is higher pressure. This is linked to a needle which then indicates the amount of pressure in millibars on the dial.
What does aneroid mean?
Without air
How does one measure cloud types?
Cloud type can be measured by determining the altitude of the cloud, and then determining its characteristics to classify it.
How does one measure cloud cover?
An observer should estimate the amount of the blue sky that is visible and identify how much of the sky is covered in cloud (in eighths or oktas).
What factors should be considered when locating a thermometer?
Put thermometers in Stevenson screen.
- Stevenson screen and thermometers should be placed in an area that is shaded from the sun.
- The surface of the screen is painted white to reflect any heat.
- Vents —> Only the air flowing through the box is recorded.
- The shade within the box ensures that direct sunlight cannot give false readings.
What factors should be considered when locating a rain gauge?
- Made of plastic or copper to not rust.
- They need to be anchored securely so that they do not get blown over by the wind.
- The top section of the gauge (where the funnel for collecting the water is) needs to be more than 30 cm above the ground to avoid rain splash when the ground is saturated.
- The rain gauge location needs to be clear of any building, guttering or any other source of potential water that might affect the results.
What factors should be considered when locating a wind vane?
- Verify the position of the direction arrows using a compass
- Wind direction can be checked by throwing some grass into the air to see if it’s movement correlates with that shown by the gauge
- Must be located on top of a roof or high enough for nothing to shelter it from the true wind direction (wind tunnels)
What factors should be considered when locating an anemometer?
- Requires more than 10 knots of airflow to be accurate
- Must be mounted at the top of a building, free from nearby obstructions which might cause shelter (wind tunnels)
- If being held by observer, must be held at arms length above head making sure that the flow of the cups is not disrupted in any way
Identify all five sources of weather data used to create a weather forecast
Land-based weather stations Balloons Buoys Weather ships Geostationary satellites and polar-orbiting satellites
A weather balloon is also known as a …
Radiosonde
The weather balloon will carry a …
Radiosonde package
At what altitude will a weather balloon burst?
20 km
What is an air mass?
An air mass is a large parcel of air (often thousands of kilometres wide) which stays still over a place for a long period of time, picking up the area’s temperature and moisture characteristics.
Name the four air masses that affect the British Isles and broadly identify their moisture and temperature characteristics.
- Tropical maritime - warm and moist
- Tropical continental - warm and dry
- Polar maritime - cold and (fairly) moist
- Polar continental - cold and dry
The air masses are classed according to …
- The latitude where they start, as this affects the temperature of the air.
- The surface over which they develop and move, as this affects the amount of moisture in the air
What is meant by polar?
Air masses from the cold north.
What is meant by tropical?
Air masses from the warm south.
What is meant by maritime?
Air masses that move over the sea will have a higher humidity and will produce more precipitation.
What is meant by continental?
Air masses that develop over a continental land mass will have less opportunity to pick up moisture.
Give a description of polar maritime (Pm)
- This is the most common air mass affecting the British Isles
- It originates over the North Atlantic Ocean
- It reaches the UK from the west or north-west
- It produces unstable air that creates cumulus and cumulonimbus clouds but has good visibility between showers
- It can also cause conventional rainfall in the summer months
Give a description of tropical maritime (Tm)
- This is a very common air mass over the British Isles
- Its air travels from the warm Southern Atlantic Ocean and moves over the south-west of the British Isles
- It brings mild conditions in the winter and warm but wet weather in the summer
- It is responsible for bringing dull skies (nimbostratus clouds), drizzle and fog (poor visibility)
Give a description of polar continental (Pc)
- This is more prevalent in the winter than the summer
- Its air originates over Northern Europe (Norway/Sweden) and moves from the east/north east
- It produces very cold conditions in the winter but milder conditions in the summer
- Its air can be unstable in the winter and can bring snow showers along the east coast of England
- It usually brings dry but cool conditions (with stratus cloud)
Give a description of tropical continental (Tc)
- This is the least common air mass affecting the British Isles and usually only in the summer
- Its air travels from North Africa and the Mediterranean
- It brings very warm and dry air from the south and south east
- It brings mild conditions in the winter but hot weather (heat wave) in the summer
- It can cause thunderstorms to develop if the temperature rises