1B.1 Weather Elements

Question 1

Define weather.

Answer 1

The hour to hour, day to day state of the atmosphere. It includes sunshine, precipitation, cloud cover, temperature and wind. Weather is short term and localised in an area.

Question 2

Define climate.

Answer 2

The average weather conditions for a place taken over a period of time, usually 30 years. It is the expected rather than actual atmospheric conditions and is long term, often applied to large sections of the globe.

Question 3

Define temperature.

Answer 3

A measure of the amount of heat in the atmosphere around us.

Question 4

What unit is temperature measured in?

Answer 4

Degrees Celsius

Question 5

Describe in detail how temperature is measured.

Answer 5

It is measured using a maximum and minimum thermometer. This is filled with mercury and alcohol and contains 2 metal index pins, one on either side.

1. The alcohol heats up during the day and expands, which pushes the mercury higher on the maximum side. This pushes a pin up the tube, and the pin stops and stays at the highest point reached.
2. At night, the alcohol cools down and contracts, pulling the mercury up the minimum column where it leaves the minimum pin at the minimum temperature.
3. We can read off the highest and lowest temperatures during the previous 24 hours by reading the Degrees Celsius scale at the bottom of the metal index. The pins can be reset to the mercury using a magnet once the measurements have been taken or by pressing the reset button.
4. The current temperature can be taken at any time by simply recording the scale at the end of the mercury.

Question 6

Why is it important that temperatures are recorded at the same time every day?

Answer 6

To ensure a fair recording and to have a measurement of the past 24 hours.

Question 7

Describe the features of a Stevenson Screen, and explain how these make it suitable to store thermometers.

Answer 7

❄️ Its slatted sides mean only the air flowing through the screen is recorded.

❄️ It is painted white to reflect sunlight.

❄️ The thermometers are stored in the shade to ensure that direct sunlight doesn’t give a false reading.

❄️ It is raised 1 metre above ground in order to avoid extremes caused by ground frost, etc.

❄️ It is sited away from buildings or large trees as these may interrupt the air flow, radiate heat or create a shadow effect which may increase or decrease the temperature.

Question 8

Define precipitation.

Answer 8

The amount of moisture in the atmosphere usually involving water in all of its states: liquid, solid and gas. It includes rain, dew, hail, sleet and snow.

Question 9

How is precipitation measured?

Answer 9

Using a rain gauge - a copper cylinder sunk into the ground with a funnel on top. The rain in the gauge should be carefully poured into a measuring cylinder and the amount of water can be read off the scale on the side in millilitres.

Question 10

Why are rain gauges normally made of copper or plastic?

Answer 10

It doesn’t rust.

Question 11

Why are rain gauges anchored securely?

Answer 11

It doesn’t get knocked over by the wind, animals, etc.

Question 12

Why should rain gauges be positioned with the top 30cm above ground level?

Answer 12

To prevent rain splash due to saturated ground and high surface runoff.

Question 13

How is wind speed measured?

Answer 13

Using an anemometer - this can either be hand held or ideally mounted on a roof top or mast 10 metres above ground. It is made up of cups attached to a handle with a scale. The stronger the wind the faster the cups rotate and the higher the reading on the scale.

Question 14

What unit is wind speed measured in?

Answer 14

Knots or km/h

Question 15

Why is a roof top the best location for an anemometer?

Answer 15

It avoids shelter and thus false results.

Question 16

If an anemometer is hand held, why must it be at arm’s length?

Answer 16

It reduces shelter and the effect of your breath.

Question 17

How is wind direction measured?

Answer 17

Using a wind vane - ideally this should be mounted on a rood top or mast 10 metres above ground. It is made up of an arrow mounted on top of a spindle, allowing the arrow to move with the wind. The arrow always points in the direction from which the wind is blowing. It is measured using the 8 main compass points.

Question 18

What is air pressure?

Answer 18

The pressure exerted by the weight of the atmosphere on the earth’s surface. Normal pressure is set as 1000 mb. Low pressure is defined as anything below this, and high pressure as anything above.

Question 19

What is an aneroid barometer and how does it work?

Answer 19

It contains a capsule which is a vacuum. As the pressure rises and falls the capsule contracts and expands and this is indicated by a needle on a dial at the front. The pressure can then be read in millibars.

Question 20

What is a barograph and how does it work?

Answer 20

It contains a metal vacuum cyclinder which contracts when the pressure increases. This moves a metal arm with a pen that leaves a trace of the pressure on a revolving drum.

Question 21

What is a cloud?

Answer 21

A visible mass of tiny particles floating in the atmosphere, consisting of ice crystals or water formed from the condensation of water vapour.

Question 22

Describe stratus clouds.

Answer 22

These appear as light grey clouds that look like a blanket stretching across the sky. They tend to be low in the atmosphere and are composed of fine water droplets, causing some drizzle.

Question 23

Describe nimbostratus clouds.

Answer 23

Thick layers of rain bearing clouds found low in the atmosphere.

Question 24

Describe cumulus clouds.

Answer 24

These are often low in the air and look like cotton wool floating in the sky. Clusters of small, white cumulus clouds are usually a sign of good weather. However if they turn grey at the base, they can bring rain.

Question 25

Describe cumulonimbus clouds.

Answer 25

Cumulus clouds can develop into large, stormy clouds which bring lightning and thunder. These clouds stretch into the upper atmosphere (8-10 km high). They can bring heavy rain due to the rapid uplift of air and water vapour leading to cooling, condensation and precipitation.

Question 26

Describe cirrus clouds.

Answer 26

These are the whitest, highest, and often wispy clouds made of tiny ice crystals.

Question 27

How is cloud cover measured?

Answer 27

In oktas (eighths of the sky)

Question 28

What do meteorologists do?

Answer 28

They study the weather and use computers along with records of past weather patterns to predict current weather. Forecasters use data collected from many sources to produce a sypnotic chart showing the predicted weather conditions.

Question 29

What are weather forecasts?

Answer 29

Predictions of the weather, usually accurate for a period of 24 hours and reasonably accurate for up to 5 days ahead. Beyond this they become increasingly unreliable.

Question 30

Describe how land based stations are used as a source of weather data.

Answer 30

There are more than 10,000 land based stations located in countries all over the world. Meteorologists collect data for all weather elements every 3 hours and every day of the year.

Question 31

Describe how weather balloons work.

Answer 31

Weather balloons filled with helium are released from ground level. As they rise, the balloons gather data on temperature, pressure and wind speeds using a small digital device suspended under the balloon. This device transmits the data back to a computer on the ground.

Question 32

How do weather buoys work?

Answer 32

Weather buoys are stationed in mid-ocean locations. They transmit weather data via satellite to weather centres for use in forecasting and climate study. Both moored buoys and drifting buoys are used.

Question 33

Describe weather ships.

Answer 33

Weather ships have a weather station attached to them so they can record weather data in remote ocean locations and send the data back to weather centres using satellites.

Question 34

What are satellites?

Answer 34

Small spacecraft that carry specific weather instruments. They are launched into space and orbit the Earth recording its weather data. The radiometer provides colour images of clouds while the scatterometer uses microwaves to detect the speed and direction of winds.

Question 35

How do geostationary satellites work?

Answer 35

These are positioned over one place and move at the same speed as the Earth so provide weather data for the same place, 365 days a year. They take visible light and infrared images of cloud formations, allowing us to predict wind speed and changing weather.

Question 36

How do polar satellites work?

Answer 36

These offer daily worldwide coverage because they orbit the Earth 14 times a day.