Weather Data Interpretation (CIE IGCSE Geography)

Climate graphs

• A climate graph shows mean monthly temperatures and precipitation rates over 30 years
• They can be local, national, or global  
• Precipitation is always shown as a bar graph and temperature as a line graph
• Describe the overall shape of the graph:
  • Is the temperature line steep or gentle?
  • Are there changes throughout the year?
  • Always mention the months but do not give a month-by-month account

• Look for extremes: 
  • Note anomalies - something that isn't following a trend
  • Summer has the hottest months and winter the coolest (Spring and Autumn are not usually discussed)
  • Note the highest and lowest temperature and rainfall plus the month in which they occur
  • Remember to quote units, e.g. Celsius or millimetres
• Identify the seasons when most rain or least rain falls:
  • Equitorial climate regions have no seasons, but refer to seasons in other locations
  • Remember that the southern hemisphere's seasons are reversed compared to the northern hemisphere
    • Summer in Australia is Nov - March 
    • Summer in Europe is June - Sept 
• Work out the temperature range by subtracting the lowest number from the highest
• Add the rainfall totals for each month together to work out the total annual rainfall
  • Divide this by 12 to find the average monthly rainfall

Dispersion graphs

• Useful for comparing sets of data 
• Also illustrates whether the data forms groups or is dispersed (spread)
• Values are plotted on the vertical axis
• Can also be used to present the upper and lower values along with the mean, median, mode and extreme values
• Reading a dispersion graph:
  • Read the title to see what the graph is showing
  • Read and understand what each axis represents
  • Describe the overall pattern of the graph
  • Identify anomalies in the data
  • Complete any statistical analysis such as the mean, median and range 

Wind rose

• The direction of wind for a specific place is shown on a wind rose
• Made of circles that radiate rectangles representing points of a compass
• Lengths of the rectangles show number of days or time that the wind blew from that direction
• The number of days or hours when there is zero wind is shown in the centre of the rose

Wind barbs

• When looking at a weather map, wind direction and strength are shown using wind barbs
• Barbs point to the direction the wind is travelling from
• The arrow tip points to the direction of the wind
• Half barbs represent 5 knots, full barbs = 10 knots and flags = 50 knots
• A combination of these symbols shows overall speed of the wind and from where it originates from
  • A double flag = 100 knots
  • A double flag and 3 full barbs with a half barb = 135 knots

Isoline and choropleth maps

• Isohyets are lines joining places with the same amount of rainfall
• Isotherms join places with the same temperature
• Isobars join places with the same pressure
• Isoline maps become choropleth isoline maps when shaded between the isolines
  • Shading is progressive from light to dark
  • The heaviest (darkest) shading is for the largest value

Synoptic charts

• Meteorological station readings are plotted on synoptic charts
• They can show some or all of the following:
  • Wind speed
  • Wind direction
  • Pressure patterns
  • Weather fronts
  • Cloud cover
  • Temperatures