2.4.3 Weather Data Interpretation

Interpreting Weather & Climate Data

Interpreting Weather & Climate Data

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