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Weather

Define weather (1)

  • Short term atmospheric conditions, including temp, rainfall & humidity
  • Can vary from day to day / place to place

Weather instruments

Stevenson Screen

Characteristics

Contains:

  • Max-min thermometer
  • Wet & dry bulb thermometer
  • Barometer

Explain why the thermometers are kept in a Stevenson Screen (4)

  • Not affected by direct sunlight & wind
  • Measure condition of air not ground
  • Not sheltered or shaded by trees/buildings
  • Avoid damage
  • Painted white – reflect solar radiation to prevent false temp readings
  • Slatted sides / vents – allow air circulation
  • Made of wood – avoid absorbing too much solar radiation
  • Double layer wooden roof – protect against solar radiation & conduction, air space maintains constant temp
  • 1.25m above ground level – instruments not affected by heat from ground
  • Door opens to N/S in northern/southern hemisphere – avoid sun’s rays

Site

  • In open area to avoid heat from building / shelter
  • On grass to avoid heat absorption from concrete
  • In a protected area to prevent damage from ppl / animals
  • On flat land
  • Door face away from direct sunlight

Rain gauge

What it measures

  • Amount of precipitation

Site

  • In open area to avoid heat from building / shelter
  • On flat land
  • Partly buried in the ground – stop it spilling

Describe the ground surface where rain gauge is located (1)

  • Flat land of grass / short vegetation

How features help to measure rainfall accurately (3)

  • Sharp rim – measure from precise area
  • Enclosed collecting vessel – prevent evaporation
  • Deep funnel – prevent rain splashing out
  • Partly buried in the ground – stop it spilling
  • 30cm above surface – avoid surface water entering into it

How to use

  1. Rainfall collected through funnel into container
  2. Pour water into measuring cylinder
  3. Take measurement from measuring cylinder in mm
  4. Read at eye level
  5. Pour water away before reuse
  6. Take measurements every 24 hours

Maximum – minimum thermometer (Six’s thermometer)

What it measures

  • Highest & lowest temp

How to use

  1. Read min & max temp off the bottom of indices at eye level
  2. Rest indices with magnet
  3. Check every 24 hours

Wet-and-dry bulb thermometer (hygrometer)

What it measures

  • Relative humidity

Characteristics

Explain why 2 thermometers show different temp in a wet & dry thermometer. (4)

(If temp ↑, dry bulb ↑)

  • Dry bulb exposed to air giving the air temp
  • Wet bulb
  • Bulb linked to container of water & wrapped in muslin
  • Keep bulb continuously moist
  • Heat lost in moisture

If wet & dry bulb same reading – humidity is 100% ( air is saturated)

Which temp reading decreases when there’s a low humidity & why?

  • Wet bulb coz as humidity is low, more evaporation takes place while latent heat is used which reduces the temp of air and bulb, so temp on wet lower than dry bulb.

Depression of wet bulb – dry bulb – wet bulb

How to use

  1. Read both temperatures
  2. Use relative humidity table
  3. Subtract wet from dry bulb
  4. Read off figure at intersection of dry & wet bulb depression figures

Sunshine recorder

What it measures

  • Hours of sunshine

Site

  • Placed south facing in northern hemisphere
  • Put in open area

How to use

  1. A sunshine recorder is a glass sphere with a piece of card located behind it which is marked in minutes and hours.
  2. The glass sphere focuses sun’s rays onto the piece of card.
  3. As the sun’s rays pass through the glass, it burns a line in the card paper. The marks on the paper indicate at which hour this happened
  4. As the position of the sun changes, the burn line will extend across the card.
  5. At the end of each day, measure the length of the burnt line which shows the hours of sunlight.
  6. Replace the card paper each day.

Barometer

What it measures

Atmospheric pressure

How to use

  1. Index pointer shows previous recorded value
  2. Pointer moves on dial when pressure changes
  3. Read value on dial
  4. Find difference between index pointer & arrow in mb (milibar)

Anemometer

What it measures

Wind speed

Site

  • On the roof
  • High up above trees/buildings
  • Wind won’t be blocked or sheltered

How to use

  1. Cups which catch wind & rotate
  2. Record electronic display screen in km per hr
  3. Observe at set times

Wind vane

What it measures

Wind direction

Site

  • On the roof
  • High up above trees/buildings
  • Wind won’t be blocked or sheltered

How to use

  1. Arrow with compass points around
  2. Observe direction arrow is pointing
  3. Arrow points to direction wind is blowing from
  4. Observe at set times

 Explain why there’s a fence around weather station (1)

  • Keep ppl / animals away

Explain why weather station is sited on grass not concrete (1)

  • To prevent splash back from concrete
  • To prevent increased heat from concrete

To what extent do you think the weather station is located in a good position? (4)

  • Not covered by buildings
  • On grass
  • Open area – readings aren’t affected by shelter
  • Not many ppl living close by
  • Flat land
  • (Dis) trees on one side – causes shade

Paper 2

Describe influence of cloud cover on temp (2)

  • More cloud higher maximum temp
  • More cloud higher minimum temp
  • More cloud smaller range

Define mb (units of pressure)

  • milibars

Paper 4

Give 3 advantages of using digital instruments  (3)

  • Sensitive
  • Easy to read
  • Precise
  • Less chance of making mistake in reading

Suggest two ways that students could check temperature measurements were correct. (2)

  • Use another thermometer
  • Compare readings with other students
  • Take more readings and compare

Suggest two ways to improve reliability of their investigation. (2)

  • Take temp readings at more sites on the day / at more times in the day / on different days

Why is it important to collect data at the same time each day? (1)

  • For comparison

Suggest two ways in which secondary data is more reliable than primary data collected by students. (2)

  • Professional ppl – less error
  • Measurements done with advanced instruments

Suggest why they decided to use six rain gauges at each location. (2)

  • More results
  • Avoid student error
  • Calculate mean

Suggest reasons for the difference in temperatures between built-up and rural areas (4)

  • In built-up area
  • Concrete absorb radiate heat
  • Air conditioning control temp
  • In rural area
  • Vegetation gives more shade
  • More humidity in woodland
  • Fluffy / flat bottomed / low
  • Thick / thin
  • Dark / grey / white
  • Not much cloud

How data collected & recorded at digital weather station

  • No need to visit station
  • Signals & results are sent to a receiver in a building eg a computer

Clouds

Describe cloud type and cover

Characteristics of clouds

Cumulonimbus clouds
  • Tall, cauliflower & wide top, grey, flat & low base, thunder
Cumulus
  • Like cotton wool, dense, domed tops
Cirrus
  • High altitude, thin, wispy
Stratus
  • Layer, uniform

Explain how clouds are formed (3)

  • Overhead sun causes large amounts of evaporation & transpiration
  • Air cools as it rises to upper atmosphere 
  • Lots of condensation occur
  • Cumulus & cumulonimbus clouds form

Paper 4

Describe how students measure the amount of cloud cover and type. (4)

  • Look at clouds
  • Estimate how much sky is covered
  • Measured in oktas
  • Identify type of cloud from chart

Explain how and why an increase in amount of cloud cover might affect daytime temp (2)

  • Reduce temp
  • Clouds block sun’s ray