AS Statistics

• The UK weather stations: Camborne, Heathrow, Hurn, Leeming and Leuchars.
• The overseas weather stations are Beijing, Jacksonville and Perth.
• The data set contains data for 11 variables:

  • Daily Maximum Temperature
  • Daily Total Rainfall
  • Daily Total Sunshine
  • Daily Maximum Relative Humidity
  • Daily Mean Windspeed
  • Daily Maximum Gust
  • Daily Mean Wind Direction
  • Daily Maximum Gust Direction
  • Cloud cover
  • Visibility
  • Pressure
• Values for the daily maximum temperature are given in Degrees Celsius and to one decimal place.
• For the daily maximum temperature, a negative value indicates a reading below 0 degrees celsius. If a reading is not available, it is listed as ‘n/a’.
• Daily Total Rainfall totals given are in millimetres (mm).
• If the total amount of rainfall collected is less than 0.05 mm, it is referred to as a trace of rain. These values are indicated by ‘tr’ in the data set.
• If a reading is not available, it is listed as ‘n/a’.
• Daily Total Sunshine values are given in hours and to one decimal place.
• Relative humidity is a measure of how close the air is to being saturated with water vapour.
• Daily Maximum Relative Humidity values are recorded as percentages (%).
• Relative humidities above 95% are associated with mist and fog.
• The daily mean windspeed is given in knots.
• 1 knot is 1.15 mph.
• The windspeeds are also categorised according to the Beaufort scale. This is an empirical and discrete scale.
• The maximum gust speed is the maximum instantaneous speed that occurred over a 24 hour period.
• Daily Maximum Gust is calculated as an average over a 24 hour period.
• For Daily Mean Wind Direction, two data processes are used to obtain it. The mean direction of the wind is calculated each hour. The value for the daily mean wind direction is then recorded in the LDS as the most frequently recorded (i.e. modal) wind direction of these hourly data captures.
• For Daily Mean Wind Direction, the value is given in degrees relative to the true north. The corresponding cardinal direction is also given.
• Daily Maximum Gust Direction is the direction the wind was blowing in the hour the corresponding daily maximum gust occurred.
• For Daily Maximum Gust Direction, values are given in degrees relative to the true north.
• Cloud cover is a discrete variable in the data set. It is measurement of the fraction of the celestial dome covered by cloud.
• Cloud cover is measured in eighths. The technical unit used in this case is called oktas. 0 oktas indicates a completely clear sky, while 8 oktas indicates complete overcast.
• Visibility is measured horizontally. Readings are given in metres. A dash indicates unavailable data.
• Pressure is recorded in hectopascals (hPa).The previous unit for measuring pressure was the millibar (mb). 1 bar is 1000 millibars and 1 millibar = 1 hectopascal.
• The large data set also only contains weather information from May–October.
• Jacksonville:

  This is located in Florida in the USA, close to the sea. It is in the Northern hemisphere. We expect high temperatures here. More rainfall here than in the UK and moderate windspeeds.
• Beijing:

  This is located in China and is in the Northern hemisphere. High temperatures are expected here with values similar to Jacksonville. However, we expect a lower average temperature than Jacksonville and much more variation in the temperature we see.
• Perth:

  This is located in Australia. A key difference is that Perth is in the Southern Hemisphere. The significance of this is that the seasons are reversed in the Southern Hemisphere, so between June-August, it is winter. It is located next to the sea, so we expect high windspeeds here.
• Daily total rainfall:

  • Measured in millimetres (mm) given to 1dp
  • Measured for the 24 hours starting at 0900 GMT
  • A trace of rain 'tr' is an amount less than 0.05mm
• Daily mean (air) temperature:

  • Measured in degrees Celsius (°C) given to 1dp
  • Average of hourly temperature readings between 0900 - 0900 GMT
• Daily total sunshine:

  • Measured in hours (hr) given to 1dp
• Daily maximum relative humidity:

  • Given as a percentage given to the nearest integer
  • A reading above 95% is associated with mist and fog
• Daily mean windspeed and direction:

  • Mean measured in knots (1 kn = 1.15 mph) given to nearest integer and is described using the Beaufort conversion (calm, light, etc)
  • Direction measured in degrees rounded to the nearest 10 and is given as a cardinal direction (north, south, etc)
  • Averaged for 24 hours starting at 0000 GMT
• Daily maximum gust and direction:

  • Measured using the same units as windspeed
  • The maximum instantaneous speed over the 24 hours
• Cloud cover:

  • Measured in Oktas (eighths of the sky covered by cloud)
• Daily mean visibility:

  • Measured in decametres (1 Dm = 10 m) horizontally
• Daily mean pressure:

  • Measured in hectopascals (1 hPa = 100 Pa = 1 millibar)
• The total daily total sunshine, mean windspeed and maximum gust is unknown for the first half of May 1987 for the UK cities.
• The three international cities only contain data for daily mean temperature, daily total rainfall, daily mean pressure and daily mean windspeed.