Large data set: weather context

Five stations are in the UK: Camborne, Heathrow, Hurn, Leeming and Leuchars. Three are overseas: Beijing, Jacksonville and Perth. These are selected stations and selected months, not every place or day in the world.

This lesson describes the Pearson Edexcel context. Other awarding bodies may use different data sets.

Reference: Pearson qualification and assessment guide, page 9. Use the official workbook alongside these original explanations when investigating the actual records.

A daily temperature observation needs a station and a date. “July temperature” is incomplete without specifying the location, year and whether you mean one day’s mean, a monthly average, a maximum or another summary.

Each date can have several variables. Temperature, rainfall and wind speed are different measurements for that day; they are not interchangeable observations of one quantity.

The UK, Beijing and Jacksonville are in the Northern hemisphere. Perth is in the Southern hemisphere. May–October includes Northern summer and Southern winter. The full six-month window also crosses seasonal transitions, so it is too crude to label every included day simply “summer” or “winter”.

Latitude, altitude, coastal influence and local conditions can also matter. Hemisphere alone does not predict the actual temperature on a particular day.

Weather variables include daily mean temperature, rainfall totals and wind measurements. Read the exact workbook heading and its unit before calculating or labelling a graph. For example, temperature in °C and wind speed in knots measure different quantities.

A daily mean and a daily maximum are different summaries. Wind direction is directional data: ordinary arithmetic averages of compass bearings can mislead near the wrap from 360° to 0°. Do not silently combine columns with different definitions.

• Wind speed: knots. One knot is one nautical mile per hour, equal to 1.852 km/h.
• Cloud cover: oktas, describing eighths of the sky covered; 0 means clear and 8 means fully covered.
• Visibility: decametres in this data set. One decametre is 10 metres, so 100 decametres is 1 kilometre.
• Pressure: hectopascals (hPa). One hectopascal is 100 pascals.

These definitions help interpret magnitude. They do not make the measurements exact or remove missing values. Distinguish the underlying cloud fraction from a recorded whole-okta value.

Pearson confirms wind-speed units, cloud-cover units, visibility units and pressure units in its assessment materials.

Using every available daily rainfall entry for one station and one period can be a census of that defined set of recorded entries. It does not automatically describe all weather at the station in other years, all of the surrounding region or all UK weather.

To sample ten dates from one station-year period, first define the eligible dates and decide how missing data will be handled. Assign labels and select distinct dates randomly. If comparing two variables, retain their pairing for each chosen date.

For a comparison by month, proportional stratification can help preserve month representation. Choosing the first ten visible rows is an opportunity-style selection of records, not a simple random sample.

A difference between a statistic in 1987 and 2015 describes that comparison. It does not by itself establish a long-term climate trend or prove its cause. A longer, suitably analysed series and relevant scientific evidence would be needed for those claims.

Missing values and unusual records need investigation and clear handling rules; they are not permission to delete inconvenient evidence. The next lesson examines trace rainfall and missing entries.

1. Name the station and year.
2. Check the May–October window.
3. Read the exact variable and unit.
4. Account for season and hemisphere.
5. Define the population and eligible frame.
6. Keep paired observations together.
7. Limit the conclusion to what the design supports.