Understanding the Stevenson Screen and Weather vs. Climate
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Questions and Answers

What is the primary purpose of placing the Stevenson screen on grass?

  • To provide a stable foundation
  • To minimize heat absorption from the ground (correct)
  • To make it more visible to the public
  • To prevent moisture from affecting the instruments

Why are the sides of the Stevenson screen slatted?

  • To allow free movement of air around the instruments (correct)
  • To enhance the aesthetic appeal of the structure
  • To provide extra insulation from heat
  • To prevent rain from entering the screen

At what height is the Stevenson screen placed to avoid ground heat affecting the thermometer?

  • 175 cm
  • 150 cm
  • 100 cm
  • 121 cm (correct)

Which of the following instruments is NOT typically found inside a Stevenson screen?

<p>Anemometer (C)</p> Signup and view all the answers

What is the required distance for wind vanes and anemometers from the nearest obstacle?

<p>Three times the height of the obstacle (A)</p> Signup and view all the answers

What type of thermometer is used inside a Stevenson screen?

<p>Maximum-minimum thermometer (Six's thermometer) (C)</p> Signup and view all the answers

How often are readings taken from the instruments inside the Stevenson screen?

<p>Once a day (C)</p> Signup and view all the answers

What is a critical factor for the placement of the rain gauge?

<p>It must be in an open space at least twice its height from any object (B)</p> Signup and view all the answers

What device measures wind speed?

<p>Anemometer (B)</p> Signup and view all the answers

What is the primary unit of measurement for precipitation?

<p>Millimetres (B)</p> Signup and view all the answers

Which thermometer is used to measure the minimum and maximum temperatures?

<p>Six's thermometer (B)</p> Signup and view all the answers

What is the correct formula to calculate the mean daily temperature?

<p>$\frac{max + min}{2}$ (B)</p> Signup and view all the answers

How is the diurnal temperature range calculated?

<p>Maximum temperature - Minimum temperature (B)</p> Signup and view all the answers

What does a hygrometer measure?

<p>Relative humidity (B)</p> Signup and view all the answers

What happens to the wet bulb temperature of a hygrometer when air is saturated?

<p>It is equal to the dry bulb temperature (C)</p> Signup and view all the answers

For the accurate measurement of wind speed, where should an anemometer be placed?

<p>Far from buildings and trees (A)</p> Signup and view all the answers

What is recorded if a precipitation reading is too small?

<p>Trace (C)</p> Signup and view all the answers

What does a thermograph use to record temperature changes?

<p>An exposed bimetallic strip (D)</p> Signup and view all the answers

What weather is commonly associated with nimbostratus clouds?

<p>Steady rain or drizzle (A)</p> Signup and view all the answers

Which type of clouds typically extends to high levels and is known for dense storm activity?

<p>Cumulonimbus (C)</p> Signup and view all the answers

At what wind speed does a tropical storm become classified as a category 3 storm?

<p>111-129 mph (C)</p> Signup and view all the answers

What is the maximum wind speed for a category 5 tropical storm?

<p>157 mph or higher (A)</p> Signup and view all the answers

What is the typical altitude range for stratocumulus clouds?

<p>0-2 km (A)</p> Signup and view all the answers

Which disaster is NOT typically caused by tropical storms?

<p>Earthquakes (B)</p> Signup and view all the answers

What is the primary purpose of a barometer?

<p>To measure air pressure (D)</p> Signup and view all the answers

What characterizes the center of a hurricane?

<p>Calm area known as the eye (A)</p> Signup and view all the answers

Which type of tropical storm is referred to as a typhoon?

<p>In the South China Sea (B)</p> Signup and view all the answers

Which instrument continuously records atmospheric pressure changes over a week?

<p>Barograph (C)</p> Signup and view all the answers

At what pressure level is the sea level pressure approximately measured?

<p>1.03 kg/cm² (A)</p> Signup and view all the answers

What does the term 'isobar' refer to on a weather map?

<p>Lines connecting areas of equal air pressure (C)</p> Signup and view all the answers

What feature primarily characterizes an aneroid barometer?

<p>It has a corrugated metal chamber (B)</p> Signup and view all the answers

What type of cloud is associated with precipitation?

<p>Cumulonimbus (B)</p> Signup and view all the answers

How is cloud cover quantified?

<p>Using oktas (D)</p> Signup and view all the answers

What distinguishes the Campbell-Stokes sunshine recorder?

<p>It records sunshine duration (A)</p> Signup and view all the answers

What type of clouds typically form at high altitudes, above 6 km?

<p>Cirrus (D)</p> Signup and view all the answers

What happens to the mercury in a mercury barometer when atmospheric pressure increases?

<p>It rises in the tube (C)</p> Signup and view all the answers

What type of clouds are characterized by having a thick, white, or gray appearance and could produce fine weather?

<p>Altostratus (B)</p> Signup and view all the answers

What is the maximum visibility indicated by 8 oktas of cloud cover?

<p>Total coverage (A)</p> Signup and view all the answers

What process leads to the formation of clouds?

<p>Rising, cooling, and condensing air (D)</p> Signup and view all the answers

The feature used to determine sunshine duration in a Campbell-Stokes recorder is primarily:

<p>Glass sphere focusing sunlight (C)</p> Signup and view all the answers

Flashcards

Stratocumulus

A low-level cloud made of water droplets, appearing as white and grey partly heaped formations.

Nimbostratus

A thick, dark grey layered cloud consisting of water droplets, often bringing steady rain or drizzle.

Cumulonimbus

A towering, dense, dark grey cloud that extends to high levels. They form from cumulus clouds and have a billowy head that flattens into an anvil shape at the top. Composed of ice crystals at high levels and water droplets at lower levels.

Tropical Storm

A collective name for deep, low-pressure systems with spirals of strong air known as typhoons, hurricanes, or cyclones depending on their location.

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Eye of a Tropical Storm

The calm central area of a tropical storm, characterized by clear skies and relatively low wind speeds.

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Eyewall of a Tropical Storm

The outer edge of a tropical storm's eye, where winds are strongest and most destructive.

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Saffir-Simpson Scale

A five-point scale used to categorize tropical storms based on their wind speeds.

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Major Tropical Storm

A tropical storm reaching category 3 or higher on the Saffir-Simpson scale, characterized by wind speeds between 111-129 miles (178-208 kilometres) per hour.

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Stevenson Screen

A wooden box, usually painted white, with louvred sides and an air space for insulation, used to house weather instruments like thermometers and hygrometers. It is elevated to avoid ground heat and placed in an open area away from buildings and trees.

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Wind Direction

The direction from which the wind is blowing, measured using a wind vane. It is expressed as compass points, such as north, south, east, west, northeast, etc.

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Anemometer

A device used to measure wind speed. It rotates as wind strikes its cups, with the speed of rotation indicating wind velocity.

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Barometer

An instrument that measures atmospheric pressure. It is typically used to predict weather changes.

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Barograph

An instrument that records atmospheric pressure over time. It graphically displays changes in pressure.

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Hygrometer

A device used to measure humidity, usually by comparing the temperature of a wet bulb thermometer to a dry bulb thermometer.

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Rain Gauge

A device used to collect and measure rainfall. It typically consists of a funnel that directs rainwater into a graduated cylinder.

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Wind Vane

A device that indicates wind direction. It is shaped like an arrow with a counterbalanced tail, and the arrow points into the wind.

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How do we measure wind speed?

Wind speed is measured using an instrument called an anemometer.

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What are anemometers?

An anemometer consists of three or four cups mounted on metal arms that rotate freely around a vertical shaft.

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Where should anemometers be placed?

Anemometers are placed in open areas, away from obstructions like buildings and trees, to ensure the wind is not blocked or distorted.

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What is precipitation?

Precipitation refers to any form of water falling to Earth, including rain, snow, sleet, hail, and mist.

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How do we measure precipitation?

A rain gauge is a tool used to measure the amount of precipitation that falls within a specific time period.

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What unit is used to measure temperature?

Temperature is measured in degrees Celsius (°C) or Fahrenheit (°F), depending on the location.

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What tools are used to measure temperature?

A thermometer is a device used to measure temperature, while a thermograph continuously records temperature changes over time.

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What is the daily mean temperature?

The daily mean temperature calculates the average temperature for a day by adding the daily maximum and minimum temperatures and dividing by two.

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Define humidity.

Humidity is the amount of water vapor present in the air.

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How do we measure humidity?

A hygrometer is a device used to measure humidity. It typically consists of two thermometers: a dry-bulb thermometer and a wet-bulb thermometer.

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What is air pressure?

Air pressure is the force exerted by the weight of air on the Earth's surface.

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What is standard air pressure?

Sea level pressure, approximately 1.03 kg/cm², is the standard pressure at sea level.

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How does altitude affect air pressure?

Air pressure decreases as altitude increases. The higher you go, the less air is above you, resulting in lower pressure.

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How does temperature affect air pressure?

Air pressure increases with temperature. Warm air is less dense and exerts less pressure, while cold air is denser and exerts more pressure.

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What is the standard unit for measuring air pressure?

Millibars (mb) are the standard units for measuring air pressure.

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What are isobars?

Isobars are lines on a weather map connecting areas of equal air pressure.

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What is a barometer?

A barometer is an instrument used to measure atmospheric pressure.

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How does a mercury barometer work?

A mercury barometer uses a column of mercury to measure air pressure. The height of the mercury column changes with air pressure.

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How does an aneroid barometer work?

An aneroid barometer uses a sealed, flexible metal chamber that expands and contracts with changes in air pressure.

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What is a barograph?

A barograph is a type of barometer that continuously records air pressure over time, typically for a week.

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What is a sunshine recorder?

A sunshine recorder measures the duration of sunshine at a location by focusing sunlight onto a recording card.

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How is cloud cover measured?

Cloud cover is measured in oktas, with each okta representing one-eighth of the sky covered by clouds.

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How are clouds classified?

Clouds are classified based on their shape and height.

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What are cirrus clouds?

Cirrus clouds are wispy, high-altitude clouds made of ice crystals. They are associated with fair weather.

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What are cumulonimbus clouds?

Cumulonimbus clouds are large, towering clouds that produce thunderstorms.

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Study Notes

Stevenson Screen

  • Constructed of wood, painted white to reflect sunlight
  • Four legs, 121 cm high, to avoid ground heat
  • Sides are louvred (slatted) to allow air circulation.
  • Double-layered wood with airspace for insulation to prevent heat transfer.
  • Located on grass to minimize ground heat absorption.
  • Instruments within the screen are placed to protect from direct sunlight and heat from the ground.
  • Readings taken at the same time daily.
  • Modern stations use digital recording equipment connected to the Met Office computers.

Weather vs. Climate

  • Weather: Daily variations of rain, sun, snow, etc., measured over days.
  • Climate: Long-term average conditions (e.g., warm summers, cold winters) measured over 30 years.

Ideal Stevenson Screen Location

  • Open area: Avoid heat from buildings.
  • Clear of trees: Prevent shade and undisturbed airflow.
  • Grass: Reduces heat absorption from ground.
  • Away from public: Minimizes tampering.

Wind Vane

  • Measures wind direction.
  • Unit of measurement: compass points (north, south, etc.)
  • The broad end catches the wind, indicating the wind's origin.
  • Positioned away from buildings and trees to avoid blocked airflow that affects reading accuracy.

Anemometer

  • Measures wind speed.
  • Units of measurement: m/s or km/hr.
  • Consists of 3 or 4 cups on metal arms that rotate freely, speed recorded using calibrated dials and mechanisms.
  • Positioned away from buildings and trees to avoid blockages.

Precipitation

  • Any form of water falling to Earth (rain, snow, hail, sleet).
  • Unit of measurement: millimetres (mm).
  • Measured using a rain gauge.
  • Water collected is poured into a graduated cylinder to measure the level.

Temperature

  • Measured using a thermometer or thermograph to determine the daily minimum, maximum, and average temperatures.
  • Measurements are in °C or °F.
  • Shade temperature is recorded to exclude direct sunlight.
  • Six's thermometer measures both maximum and minimum temperatures
  • Thermographs measure and record temperature continuously.
  • Diurnal temperature range is the difference between the maximum and minimum temperatures in a 24-hour period.

Humidity

  • Hygrometer measures relative humidity.
  • Relative humidity is the amount of water vapor in the air compared to the maximum it can hold at a given temperature.
  • Warm air holds more water vapor than cold air.
  • Wet bulb thermometer measures the effect of evaporation on air temperature.
  • Water vapor evaporation from the wet bulb muslin causes cooling and lowering of the reading.

Air Pressure

  • Air exerts pressure on Earth's surface.
  • Unit of measurement: millibars (mb).
  • Barometer measures atmospheric pressure; there are:
    • Mercury barometer
    • Aneroid barometer
    • Barograph
  • Mercury barometer measures pressure by the height of the mercury column.
  • Aneroid barometer uses a partially vacuumed metal chamber to measure pressure changes.
  • Barograph records atmospheric pressure continuously over time on a chart.

Sunshine Recorder (Campbell-Stokes)

  • Measures sunshine hours.
  • Consists of a glass sphere that focuses sunlight onto a recording card below it.
  • Positioned in an open space, facing south in northern hemisphere, north in southern hemisphere.
  • The burn length on the card represents the hours of sunshine.

Clouds

  • Cloud cover is measured in oktas (1/8ths of the sky).
  • Different cloud types have different descriptions, heights and shapes.
  • Cloud formation relies on rising, cooling, and condensation of air.
  • Cloud type dictates likelihood of precipitation.
  • Cumulonimbus and nimbostratus are the primary precipitation clouds.

Tropical Storms

  • Collective name for low-pressure systems (typhoons, hurricanes, cyclones).
  • Rated on the Saffir-Simpson scale based on wind speed categories.
  • Category 3 and above are considered major.
  • Formation occurs over warm tropical ocean waters.
  • Wind speed categorized to assess hurricane risk.

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Description

This quiz explores the construction and significance of the Stevenson Screen in weather measurement, as well as the difference between weather and climate. Discover how proper placement of the screen impacts data collection and why long-term climate assessment is crucial. Test your knowledge on these fundamental meteorological concepts.

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