Chapter 13 Weather (Weather instruments)

Question 1

What is a Stevenson screen?

Answer 1

A box with slatted sides that holds thermometers, a hygrometer and a barograph

Question 2

How is temperature measured?

Answer 2

With a maximum and minimum thermometer

Question 3

How does a maximum and minimum thermometer work?

Answer 3

As the temperature increases, the Mercury expands and pushes the marker up on the maximum side
As the temperature decreases, the marker rises up the tube on the minimum side
The markers remain at the lowest and highest points
Temperature is shown in degrees Celsius

Question 4

What are the lines that join places of equal temperature called?

Answer 4

Isotherms

Question 5

How is average daily temperature calculated?

Answer 5

Adding the highest and lowest temperature of the day and dividing by 2

Question 6

With what instrument is atmospheric pressure measured?

Answer 6

Barograph/barometer

Question 7

How does a barograph work?

Answer 7

The corrugated drum is partially emptied of air
When the pressure of the air increases, the drum contracts slightly
When the pressure of the air falls, the drum expands slightly
The movement of the drum is transferred to a pointer by a series of levers
Another drum slowly rotates with graph paper attached
The end of the pointer has an inked in that records the pressure on the graph paper

Question 8

What is the unit of atmospheric pressure?

Answer 8

Millibars

Question 9

What are the lines that join places of equal pressure called?

Answer 9

Isobars

Question 10

What instruments are used to measure wind direction and speed?

Answer 10

Wind vane

Anemometer

Question 11

How does a wind vane work?

Answer 11

The head of the arrow points towards the direction from which the wind blows
The fin is large and is blown forward by the wind

Question 12

How does an anemometer work?

Answer 12

Three cups spin in the wind
They rotate faster when wind is stronger
The speed of the wind is read from a dial on a meter

Question 13

Which direction is wind direction named from?

Answer 13

The direction it comes from

Question 14

What is the unit of wind speed?

Answer 14

Km/hr

Question 15

What are the lines that join places of equal wind speed called?

Answer 15

Isotachs

Question 16

What scale its wind strength measured on?

Answer 16

The Beaufort scale

Question 17

How is wind strength measured on the Beaufort scale?

Answer 17

By observing the damage it causes to the landscape

There are 12 strengths

Question 18

What instrument is used to measure precipitation?

Answer 18

Rain gauge

Question 19

How does a rain gauge work?

Answer 19

Rain gauge is buried in the ground away from buildings not (so water does not fall into it from buildings)
Rain enters cylinder through funnel
Cylinder is marked in millimetres

Question 20

What are lines that join laces of equal rainfall called?

Answer 20

Isohyets

Question 21

What instrument is used to measure relative humidity?

Answer 21

Hygrometer

Question 22

How does a hygrometer work?

Answer 22

The dry bulb temperature is read from the dry bulb thermometer
The wet bulb thermometer gives the temperature of saturated air
A muslin bag dipped in water covers the wet bulb
The difference in temperature between the two thermometers is used to find the relative humidity (greater difference= lower RH)
The measurement is expressed as a percentage

Question 23

What instrument is used to measure sunshine?

Answer 23

The Campbell stokes sunshine recorder

Question 24

How does the Campbell stocks sunshine recorder work?

Answer 24

The glass ball or sphere directs the Suns Ray’s onto the strip of paper at the back
The sun burns a mark on the paper which is divided into hourly intervals

Question 25

What are the lines that join places of equal sunshine called?

Answer 25

Isohlels