Theme 2 - 2.4 - Weather Flashcards
(60 cards)
1
Q
What are the design features of a Stevenson Screen and what are the reasons for this?
A
- Above ground level -> Doesn’t receive heat form the ground
- White -> Reflects solar radiation
- Away from buildings -> Avoids heat or shadows
- Slats -> Allows air to circulate
- On grass -> Grass doesn’t reflect the sun’s heat much
2
Q
What is a Stevenson Screen?
A
A wooden box standing on four legs in which instruments are kept for weather measurements.
3
Q
Define weather.
A
The short-term changes and state of the atmosphere in regards to temperature, cloud cover, wind speed, precipitation, humidity, etc.
4
Q
Define climate.
A
The average weather conditions that a region or country experiences over a number of years.
5
Q
What instruments are found inside and outside a Stevenson Screen?
A
INSIDE • Thermometer • Hygrometer • Barometer OUTSIDE • Rain gauge • Anemometer • Wind vane
6
Q
What is a barometer?
A
- Measures air pressure
- Kept inside Stevenson Screen
- Has adjustable pointer to note the previous day’s pressure
7
Q
What is air pressure measured in?
A
Millibars
8
Q
What is a max./min. thermometer?
A
- Records the maximum and minimum temperature of a day
- Contains Mercury and alcohol
- One side of the U-bend shows the max temperature, while the other shows the min temperature.
9
Q
How does the maximum side of a max-min thermometer work?
A
- When temperature rises, the mercury expands, pushing the metal index up the scale
- When the temperature cools, the mercury contracts, but the index remains
- The bottom of the metal index can be used to check the maximum temperature for that day
- Magnet is used to reset pin
10
Q
How does the minimum side of a max-min thermometer work?
A
- When temperature cools, the alcohol contracts and its meniscus pulls the index up the tube
- When the temperature rises, the alcohol expands, but leaves the metal index behind
- The bottom of the index can be used to check the minimum temperature for that day
- Magnet is used to reset pin
11
Q
Check that you know how to read a max-min thermometer.
A
Online
12
Q
What is a max-min thermometer used to calculate?
A
Calculating:
• Mean daily temperature
• Temperature range for the day
13
Q
Which side of the pins is used when taking readings from a max-min thermometer?
A
Bottom
14
Q
What is a wet/dry bulb thermometer (hygrometer)?
A
- Measure air humidity
- Has a wet and dry thermometer
- Air humidity is calculated by looking at the difference between the two
15
Q
What is the difference between a wet-bulb and a dry-bulb thermometer?
A
- Dry-bulb -> Glass thermometer which measures the actual temperature
- Wet-bulb -> Similar thermometer, but with the bulb enclosed in a muslin bag which dips into a bottle of water
The wet-bulb generally gives a lower reading, unless the humidity is near to 100%.
16
Q
What is a rain gauge?
A
- Measures rainfall
- Consists of a cylindrical container, in which there is a collecting can containing a glass or plastic jar and a funnel which fits onto the top of the container
- Placed on grass, so water doesn’t splash in
17
Q
What is rainfall measured in?
A
mm
18
Q
What is a wind vane?
A
- Shows wind direction
- Consists of a horizontal rotating arm pivoted on a vertical shaft
- Compass points are used to show direction
19
Q
In which direction is wind measured?
A
The direction the wind is coming from.
20
Q
What is an anemometer?
A
- Measures wind speed
- Consists of three or four metal arms that rotate freely on a vertical shaft -> The faster the rotation, the faster the wind
- Normally placed on top of buildings
21
Q
Which way does a wind vane point?
A
The direction the wind is coming FROM.
22
Q
What is a sunshine recorder?
A
- Measures minutes of sunshine during the day
- Can’t be in shade
- Sun’s rays pass through a glass sphere, burning a path on a piece of paper. This shows when the Sun was in a specific place.
23
Q
Define diurnal.
A
Daily
24
Q
How does a barometer work?
A
- Tube of mercury that is open is placed into a dish of mercury
- The density of air above the dish is constantly changing
- As air pressure increases, it pushes the mercury further up the tube
- As air pressure decreases, the mercury sinks down the tube
25
Can digital instruments be use instead of normal ones when taking weather measurements?
Yes, they are more precise and give a reliable reading.
26
How do clouds form?
* Water on the ground evaporates and the air it is in cools as it rises
* When the air cools below the dewpoint, the water condenses
* It condenses around dust particles
* As more and more condenses around a particle, a raindrop forms
* If these become large enough, you can see them as a cloud or as fog
27
What factors determine the name of a cloud?
1. Height
| 2. Shape
28
What are high clouds usually composed of?
Ice crystals
29
What are medium clouds usually composed of?
• Water droplets
OR
• Mixture of water and ice crystals
30
What are low clouds usually composed of?
Water droplets
| Except cumulonimbus
31
What is the height of the base of high clouds?
5500 - 14000m
32
What is the height of the base of medium clouds?
2000 - 7000m
33
What is the height of the base of low clouds?
Below 2000m
34
What are the form main cloud types?
* Nimbus
* Stratus
* Cumulus
* Cirrus
35
Name some high clouds.
• Cirrocumulus
• Cirrostratus
• Cirrus
(Cumulonimbus clouds can also grow very high)
36
Name some medium clouds.
* Altocumulus
| * Altostratus
37
Name some low clouds.
* Stratus
* Cumulus
* Statocumulus
38
What is special about cumulonimbus clouds?
The are very tall. Their base can be below 2000m but the top can reach 6000m. This makes it hard to classify them into a specific height category.
39
What does the Latin word "cirro" mean?
Curl of hair
40
What does the Latin word "cumulo" mean?
Heap or pile
41
What does the Latin word "strato" mean?
Layer or sheet
42
What does the Latin word "nimbo" mean?
Rain
43
Describe cirrus clouds.
* Very high level (12000m)
| * Mimic curls of hair + very wispy
44
What are cirro and alto used as a prefix for?
Cirro: Describing high clouds.
Alto: Describing medium clouds.
E.g. Cirrostratus are like stratus clouds except very high up
45
Describe cumulus clouds.
* Low level (Below 2000m)
* Fluffy cotton-ball-like
* Look detached
46
Describe status clouds.
* Low level (Below 2000m)
| * Hazy layer without a shape
47
Describe altostratus clouds.
* Medium level
| * Like stratus clouds, but slightly higher up
48
Describe cirrostratus clouds.
* High level
| * Like stratus clouds, but very high up
49
Describe nimbostratus clouds.
* Low level
* Layered clouds
* Produce precipitation
50
Describe cumulonimbus clouds.
* Extends from low level to high levels of the troposphere
| * Known as thunderstorm clouds
51
Describe cirrocumulus clouds.
* High level
* Resemble a shoal of fish
* Fluffy
52
Describe altocumulus clouds.
* Medium level
* Like cirrocumulus but lower
* Fluffy
53
Describe stratocumulus clouds.
* Low level
| * In layers + fluffy
54
Remember to practice cloud types.
Google an image which has to be labelled + Pg 49 of revision guide
55
What are the 4 types of cloud you need to know?
* Stratus
* Cumulus
* Cirrus
* Cumulonimbus
56
How is cloud cover calculated?
* A mirror is divided into squares and it is placed on the ground
* Count the number of squares completely or partially covered by cloud
* Repeat several times to avoid anomalies
* Calculate a percentage cloud cover
* Convert this to oktas
57
What is the unit for cloud cover?
Oktas
58
What is an okta?
An eighth of the sky in cloud cover.
59
What does each number of oktas mean?
```
0 - Complete absence of cloud
1 - 1/8th cloud cover or less
2 - 2/8th cloud cover
3 - 3/8th cloud cover
4 - 4/8th cloud cover
5 - 5/8th cloud cover
6 - 6/8th cloud cover
7 - 7/8th cloud cover or more
8 - Complete cloud cover
9 - Sky obscured for some reason (e.g. fog)
```
60
Remember to revise wind roses, dispersion diagrams and climate graphs.
Online + Pg 50 of revision guide
