Weather Flashcards
(99 cards)
What is a Stevenson screen?
A wooden box on four legs, 121 cm high, designed to avoid ground heat affecting thermometer bulbs at 125 cm.
What are the features of a Stevenson screen?
It is painted white to reflect sunlight, made of wood to prevent heat transfer, has slatted sides for air movement, and is double-layered for insulation.
What instruments are found inside a Stevenson screen?
Maximum-minimum thermometer (Six’s thermometer) and hygrometer with wet and dry bulb.
What instruments are found outside a Stevenson screen?
Rain gauge, wind vane, and anemometer.
How is wind direction measured?
With a wind vane, indicating the compass point from where the wind is blowing.
What unit is used to measure wind direction?
Compass direction.
How is wind speed measured?
Using an anemometer, in m/s or km/hr.
What does an anemometer consist of?
3 or 4 cups on metal arms that spin freely on a vertical shaft.
What is precipitation?
Any water that falls to Earth, including hail, mist, rain, sleet, or snow.
How is precipitation measured?
Using a rain gauge, with measurements in millimeters (mm).
What is the unit of temperature measurement?
Celsius (°C) or Fahrenheit (°F).
What type of thermometer is commonly used?
A Six’s thermometer, which houses a maximum and minimum thermometer in a U shape.
What does humidity measure?
The amount of water vapor in a given volume of air.
How is humidity measured?
Using hygrometers with wet and dry bulb thermometers.
What is air pressure?
The weight of air exerting pressure on the Earth’s surface.
What is the unit of measurement for air pressure?
Millibars (mb).
What is a barometer?
An instrument that measures air pressure.
What is a Cambell-Stokes sphere used for?
To calculate the hours and minutes of sunshine a location receives.
How is cloud cover measured?
In units of oktas, where 0 oktas = clear sky and 8 oktas = total coverage.
What are tropical storms?
Deep, low-pressure systems with spirals of strong air, known as typhoons, hurricanes, or cyclones depending on the region.
What scale is used to rate tropical storms?
The five-point Saffir-Simpson scale based on wind speeds.
What wind speed defines a category 3 tropical storm?
Wind speeds between 111-129 miles (178-208 kilometers) per hour.
What is the damage potential of a category 5 storm?
Wind speeds of 157 mph or higher, causing catastrophic damage.
What are the units for measuring rainfall?
Rainfall is always measured in mm.