Large data set

• The large data set consists of weather data samples provided by the Met Office for five UK weather stations and three overseas weather stations.
• The data is from May to October. There are two sets of data for each weather station, one from 1987 and one from 2015.
• The UK weather stations are Camborne, Heathrow, Hurn, Leeming, and Leuchars.
• The overseas weather stations are Jacksonville in the USA, Beijing in China, and Perth in Australia.
• Camborne, Hurn and Leuchars are on the coast.
• Perth is the only location in the southern hemisphere.
• Daily mean temperature is measured in degrees Celsius. Air temperatures are measured by thermometers in a louvered screen 1.25 metres above short grass, except at some weather centres and climate data logger stations where observations are made from a non-standard rooftop exposure.
• Values for the daily mean temperature are recorded in degrees celcius, to one decimal place.
• The daily mean air temperature (0000-0000GMT) is the average of the hourly temperature readings during this period.
• Daily total rainfall is measured in millimetres.
• For daily total rainfall, daily totals refer to 24-hour periods commencing at 0900GMT on the day of entry.
• Daily total rainfall includes precipitation such as snow or hail as well, which is melted and measured in the same way as rainfall.
• A trace (tr) of rain is an amount less than 0.05mm.
• Daily total sunshine is measured in hours to one decimal place.
• At most Met Office stations, sunshine is measured using an instrument that measures the amount of solar radiation exceeding a threshold.
• Daily maximum relative humidity is a measure of how close the air is to being saturated with water vapour.
• Relative humidities of above 95% are associated with mist and fog.
• Daily mean windspeed is measured in knots. 1 knot = 1.15mph.
• The daily mean windspeed is averaged over the 24 hours from 0000GMT on the date given.
• The maximum daily gust speed is the maximum instantaneous speed that occured during the 24 hours from 0000GMT on the date given.
• The daily mean wind direction is measured in degrees, rounded to the nearest 10 degrees. It is averaged over the 24 hour period from 0000GMT.
• The daily maximum gust direction is measured in degrees. The direction of the daily maximum gust is the direction that the wind was blowing in when the maximum gust during the hour commencing at the time of entry occurred.
• For all locations, the speed of the wind is also categorised according to the Beauford scale.
• For the UK locations, the wind and gust directions are also listed as cardinal directions.
• Cloud cover is measured in oktas (eights). Cloud cover is the fraction of the celestial dome covered by cloud.
• Visibility is measured in decameters (dm) and is defined as the greatest distance at which an object can be seen and recognised in daylight, or at night could be recognised if the general illumination was raised to daylight level.
• Visibility is measured using a visiometer at automatic sites, but used to be done by observers at manual stations, except at some weather centres and climate data logger stations where observations are made from a non-standard rooftop exposure.
• Visibility is measured horizontally.
• For visibility, a dash indicates that data is not available.
• Pressure is measured in hectopascals (hPa). The mean sea level pressure has been calculated from a measurement made at station level.
• The unit used to measure pressure was previously the millibar. One hectopascal = one millibar.
• The Beauford Scale (used for windspeeds):

  0 = calm (<1kn)

  1-3 = light (1-10kn)

  4 = moderate (11-16kn)

  5 = fresh (17-21kn)
• The UK great storm occured on the night of the 15-16th October 1987. Gusts up to 100kn were recorder.
• Florida hurricanes:

  • 12 October 1987 - Hurricane Floyd
  • 1-2 October 2015 - Hurricane Joaquin
• A hurricane is defined as 64kn or more.