The Large Data Set
Understanding the Edexcel LDS: locations, variables, and limitations
SPEC 1.1 • STATISTICAL SAMPLING
What is the Large Data Set?
Definition
The Large Data Set (LDS) is a collection of weather data from the Met Office that you must be familiar with for your A-Level exam.
Here's what a section of the actual LDS looks like:
HEATHROW - Daily Weather Data (June 2015)
DateMean Temp (°C)Rainfall (mm)Sunshine (hrs)Wind (kn)Pressure (hPa)
01/06/201514.20.08.371024
02/06/201515.82.45.191018
03/06/201516.4tr10.261021
04/06/201517.10.012.551025
Exam Expectation
You don't need to memorise values, but you must know the locations, variables, units, and limitations.
8 Locations in the LDS
UK Camborne
Coastal, South-West England
UK Heathrow
Inland, South-East England
UK Hurn
Coastal, South England
UK Leeming
Inland, North England
UK Leuchars
Coastal, Scotland
OVERSEAS Beijing
China
OVERSEAS Jacksonville
USA, Florida
OVERSEAS Perth
Australia (Southern Hemisphere)
Memory Tip
5 UK + 3 Overseas = 8 Total. The overseas locations span three continents: Asia, North America, and Oceania.
Time Periods Covered
Period 1
May - October 1987
Period 2
May - October 2015
Which Months Have Data?
JanFebMarAprMayJunJulAugSepOctNovDec
✗✗✗✗✓✓✓✓✓✓✗✗
Critical Limitation
Only 6 months of data. You cannot make conclusions about full-year weather patterns!
Historical Note
The Great Storm of October 1987 is in the data - expect extreme wind readings!
Weather Variables
Here's how the variables appear as column headers in the spreadsheet:
UK LOCATION - Column Headers
Daily Mean TempDaily Max TempDaily Total RainfallDaily Total SunshineDaily Mean WindDaily Max GustDaily Mean PressureCloud Cover
°C°CmmhoursknotsknotshPaoktas
1 d.p.1 d.p.1 d.p.1 d.p.integerintegerinteger0-8
Key Units
Wind: knots (not mph!) - 1 knot = 1.15 mph
Cloud: oktas (0 = clear, 8 = overcast)
Pressure: hPa (hectopascals)
Data Availability by Location
Not all variables are available for overseas locations!
VariableUK (All 5)BeijingJacksonvillePerth
Daily Mean Temperature✓✓✓✓
Daily Total Rainfall✓✓✓✓
Daily Mean Pressure✓✓✓✓
Daily Mean Windspeed✓✓✓✓
Daily Total Sunshine✓✗✗✗
Daily Maximum Gust✓✗✗✗
Cloud Cover✓✗✗✗
Exam Trap
If asked to compare sunshine, gust, or cloud between UK and overseas - you can't! The data doesn't exist.
Special Value: n/a
When data wasn't recorded, the LDS shows "n/a" (not available):
LEEMING - Early May 1987 (Missing Data)
DateMean TempRainfallSunshineWindspeedMax Gust
01/05/19878.40.2n/an/an/a
02/05/19879.10.0n/an/an/a
03/05/198710.21.4n/an/an/a
n/a
= Data not available / not recorded
Data Cleaning
You must remove n/a values before calculating statistics. State how many values were excluded.
Known Issue: Sunshine, windspeed, and gust missing for UK locations in early May 1987.
Special Value: tr (Trace)
When rainfall is less than 0.05mm, the LDS records "tr" (trace):
HEATHROW - Rainfall Data
DateDaily Total Rainfall (mm)Meaning
15/06/20150.0No rain
16/06/2015trTrace: < 0.05mm
17/06/20152.82.8mm of rain
18/06/2015trTrace: < 0.05mm
19/06/201515.215.2mm of rain
tr
= Trace of rain: less than 0.05mm fell
How to Handle "tr"
Option 1: Treat as 0 mm (most common)
Option 2: Treat as 0.025 mm (midpoint)
Option 3: Exclude from sample
Always state your method!
Wind Speed: Knots to mph
Conversion
1 knot = 1.15 mph
Beaufort Scale Reference
BeaufortDescriptionKnotsmph
0Calm< 1< 1
1-3Light1-101-12
4-5Moderate11-2113-24
6-7Strong22-3325-38
8+Gale/Storm34+39+
Quick Calculation
To convert knots → mph: multiply by 1.15
Example: 20 knots × 1.15 = 23 mph
Key Facts to Remember
Temperature
Heathrow = warmest UK
Jacksonville = hottest overall
2015 warmer than 1987
Rainfall
Camborne = wettest UK
Heathrow = driest UK
October = wettest month
Wind
Coastal windier than inland
Great Storm: Oct 1987
Geography
Perth = Southern Hemisphere (seasons reversed!)
Jacksonville = near equator (hottest)
Limitations of the LDS
Time
Only May-October - cannot generalise to winter or make annual comparisons.
Location
Only 8 locations - cannot generalise to all UK or worldwide. No rural/mountain data.
Years
Only 1987 and 2015 - cannot identify long-term climate trends from just 2 years.
Variables
Overseas has fewer variables - cannot compare sunshine/gust/cloud between UK and overseas.
Worked Example01
Aisha wants to compare daily total sunshine between Camborne and Beijing in June 2015. Explain why she cannot do this.
Aisha cannot make this comparison because daily total sunshine is not recorded for overseas locations.
Looking at the availability matrix:
•
Camborne (UK): Sunshine ✓ available
•
Beijing (Overseas): Sunshine ✗ not available
Beijing only has: temperature, rainfall, pressure, windspeed.
Answer
Worked Example02
Ben concludes that "Heathrow has the highest average temperature in the UK throughout the year." Explain why this may not be valid.
This conclusion may not be valid because the LDS only contains data for May to October.
•
No winter data (November - April)
•
Temperature patterns may differ in winter
•
Another location might be warmer annually
Valid conclusion: "Heathrow has the highest average temperature from May to October."
Answer
Worked Example03
The daily mean windspeed at Hurn is 12 knots. Convert this to mph.
1
Use: 1 knot = 1.15 mph
2
12 × 1.15 = 13.8
Answer: 13.8 mph
Worked Example04
A student finds 5 days with rainfall 'tr'. Explain what 'tr' means and how to handle it when calculating mean rainfall.
'tr' = "trace" - less than 0.05mm of rain fell.
Options:
•
Treat 'tr' as 0 mm (most common)
•
Treat 'tr' as 0.025 mm (midpoint)
•
Exclude days with 'tr'
Always state which method you use!
Worked Example05
Claire takes a stratified sample of 40 days from Leuchars 2015, stratified by month (May-Oct). How many from each month?
1
Total: 31+30+31+31+30+31 = 184 days
2
Sample per month = (days/184) × 40
3
May: 6.74≈7, Jun: 6.52≈7, Jul: 6.74≈7
Aug: 6.74≈7, Sep: 6.52≈6, Oct: 6.74≈6
Answer: 7, 7, 7, 7, 6, 6 = 40 total
Worked Example06
David notices Perth is cooler in July than January. Explain why.
Perth is in Australia (Southern Hemisphere).
Seasons are reversed:
•
July = winter in Australia (colder)
•
January = summer in Australia (warmer)
This is opposite to the UK where July is summer.
Answer
Worked Example07
Ella compares 1987 and 2015 temperatures to investigate climate change. Give two limitations.
Limitation 1: Only two years of data. Differences could be natural variation, not climate change. Need many more years.
Limitation 2: Only May-October. Climate change effects may differ in winter.
Other valid answers: Only 5 UK locations; local factors (urbanisation) could affect readings.
Practice
Question 1: Fiona wants to compare daily maximum gust between Heathrow and Jacksonville. Explain why she cannot do this.
Daily maximum gust is not recorded for overseas locations.
Jacksonville only has: temperature, rainfall, pressure, mean windspeed.
Gust data is only available for UK locations.
Answer
Practice
Question 2: George samples every 5th day from Leeming sunshine data in May 1987. What problem will he encounter?
George will find missing data (n/a values).
Sunshine data for UK locations in early May 1987 is missing.
He must clean the data by removing n/a values or adjust his sample.
Answer
Practice
Question 3: Convert 18 knots to mph and describe using the Beaufort scale.
Conversion: 18 × 1.15 = 20.7 mph
Beaufort: 18 knots is in range 11-21 (Beaufort 4-5)
Answer: 20.7 mph, Moderate wind
Summary
Key Points
AspectDetails
Locations5 UK + 3 Overseas = 8 total
TimeMay-Oct 1987 and May-Oct 2015
Wind1 knot = 1.15 mph
Specialn/a = missing, tr = trace (<0.05mm)
OverseasOnly: temp, rain, pressure, wind
Main Limitations
Only 6 months - can't generalise to full year
Only 8 locations - can't generalise everywhere
Only 2 years - can't identify long-term trends
Overseas has fewer variables
Next: What is the Large Data Set?