Weather Flashcards
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.
How is rainfall data typically represented?
Rainfall data is always plotted on a bar graph.
What is the minimum duration for calculating mean monthly and annual rainfall?
Mean monthly and annual rainfall is calculated over a minimum of 30 years.
What is the rainfall amount for ‘Very low’ annual rainfall?
0 - 249 mm
Description of the amount.
What is the rainfall amount for ‘Low’ annual rainfall?
250 - 499 mm
Description of the amount.
What is the rainfall amount for ‘Moderate’ annual rainfall?
500 - 999 mm
Description of the amount.
What is the rainfall amount for ‘High’ annual rainfall?
1000 - 1999 mm
Description of the amount.
What is the rainfall amount for ‘Very high’ annual rainfall?
Over 2000 mm
Description of the amount.
What units are used to measure temperature?
Temperature is measured in °C or °F.
How is temperature data typically represented?
Temperature data is always plotted as a line graph.
What are the calculations involved in temperature measurement?
Calculations include diurnal (daily), mean daily temperature, mean monthly temperature, annual range, and mean annual range.
What temperature range is considered ‘Very cold’?
Below -10 °C
Description of temperature.
What temperature range is considered ‘Cold’?
-10 to -1 °C
Description of temperature.
What temperature range is considered ‘Cool’?
0 - 9 °C
Description of temperature.
What temperature range is considered ‘Warm’?
10 - 19 °C
Description of temperature.
What temperature range is considered ‘Hot’?
20 - 29 °C
Description of temperature.
What temperature range is considered ‘Very hot’?
30 °C and above
Description of temperature.
What temperature range is considered ‘Very small’?
0 - 3 °C
Description of temperature ranges.
What temperature range is considered ‘Small’?
4 - 8 °C
Description of temperature ranges.
What temperature range is considered ‘Moderate’?
9 - 19 °C
Description of temperature ranges.
What temperature range is considered ‘Large’?
20 °C and above
Description of temperature ranges.
How is wind speed measured?
Wind is measured in knots (Kts), miles per hour (mph), or kilometres per hour (km/h).
How is wind direction quoted?
Direction is quoted from where the wind is blowing, using compass points.
What is the prevailing wind?
The most frequently occurring wind is called the prevailing wind.
What is the dominant wind?
The direction giving the strongest wind is called the dominant wind.
How is wind plotted?
Wind is plotted on a map with wind barbs.
What wind speed is considered ‘Calm, light, moderate or strong’?
Below 50 km/h
Description of wind speeds.
What wind speed is considered ‘Gale’?
50 - 100 km/h
Description of wind speeds.
What wind speed is considered ‘Storm’?
101 - 118 km/h
Description of wind speeds.
What wind speed is considered ‘Hurricane’?
119 km/h and above
Description of wind speeds.
How is pressure measured?
Pressure is measured in millibars (mb).
What is the mean sea level pressure?
The mean sea level pressure is 1013 mb.
How are pressure readings taken?
Pressure is not totalled over time but measured based on circumstances.
What are isobars?
Isobars are lines joining places with equal sea-level pressures on a weather chart.
What is an anticyclone?
An anticyclone is an area of high pressure.
What is a depression?
A depression is an area of low pressure.
What direction do anticyclone winds blow?
Anticyclone winds tend to blow in a clockwise direction in the northern hemisphere.
What happens to air in a depression?
In depressions, the air rises and blows in an anticlockwise direction around the low in the northern hemisphere.
What is the pressure for sea level?
1013 mb
Description of pressure systems.
What pressure indicates high pressure or anticyclone?
1013 mb and above
Description of pressure systems.
What pressure indicates low pressure or depression?
1013 mb and below
Description of pressure systems.
How is relative humidity measured?
Relative humidity is measured using a relative humidity table.
What determines relative humidity?
Temperature determines relative humidity; higher temperatures allow more water vapour.
What happens when air reaches saturation?
Moisture will start to condense when air reaches saturation.
What happens to relative humidity if temperature rises?
Relative humidity drops if the temperature rises.
What happens to relative humidity if temperature drops?
Excess water is released until equilibrium is reached if the temperature drops.
What does a climate graph show?
A climate graph shows mean monthly temperatures and precipitation rates over 30 years.
How is precipitation represented in a climate graph?
Precipitation is always shown as a bar graph.
How is temperature represented in a climate graph?
Temperature is shown as a line graph.
What should you describe when reading a climate graph?
Describe the overall shape of the graph, noting if the temperature line is steep or gentle and if there are changes throughout the year.
What extremes should be noted in a climate graph?
Note the highest and lowest temperature and rainfall, plus the month in which they occur.
What units should be quoted in a climate graph?
Remember to quote units, like Celsius or millimetres.
How do you calculate the temperature range?
Calculate the temperature range by subtracting the lowest number from the highest.
What is a dispersion graph used for?
Dispersion graphs are useful for comparing sets of data and illustrating whether the data forms groups or is dispersed.
What should you do when reading a dispersion graph?
Read the title, understand each axis, describe the overall pattern, and identify anomalies in the data.
What does a wind rose show?
A wind rose shows the direction of wind for a specific place.
What do wind barbs indicate?
Wind barbs indicate the direction and strength of the wind.
What are isohyets, isotherms, and isobars?
Isohyets are lines joining places with the same amount of rainfall, isotherms join places with the same temperature, and isobars join places with the same pressure.
What is a synoptic chart?
A synoptic chart plots meteorological station readings and can show wind speed, wind direction, pressure patterns, weather fronts, cloud cover, and temperatures.
Stevenson Screen
Wind Vane
Anemometer
Rain gauge
Six’s Thermometer
Thermograph
Hygrometer
Aneroid barometer
Barograph
Sunshine recorder
Cloud cover measurements
Climate graph
Dispersion graph
Wind rose
Wind barbs
Isoline maps
Synoptic weather chart
