Composition and Structure of Atmosphere | Class 11 Geography Notes

Distribution of Temperature

Global temperature distribution is best understood by studying temperature maps for January and July, represented by isotherms—lines joining places of equal temperature. Generally, isotherms run parallel to latitudes, reflecting the dominant influence of latitude on temperature. However, deviations occur due to land-sea contrasts and ocean currents. In January, the northern hemisphere shows more pronounced deviations because of its larger landmass. For example, warm ocean currents like the Gulf Stream cause isotherms to bend northward over the North Atlantic Ocean, while cold continental interiors like Siberia show sharp temperature drops. The southern hemisphere, with more oceanic area, shows more gradual temperature variations and isotherms are more parallel. In July, isotherms generally run parallel to latitude with warmer temperatures over equatorial oceans and subtropical continental regions. Figure 8.4 (a) and (b) illustrate these distributions for January and July respectively. Figure 8.5 shows the temperature range between these months, with the highest range over northeastern Eurasia due to continentality and the least range near the equator.

📊 Diagram: Figure 8.4 (a): The distribution of surface air temperature in the month of January; Figure 8.4 (b): The distribution of surface air temperature in the month of July; Figure 8.5 : The range of temperature between January and July

🔗 Connection: This section leads to the concept of temperature inversion and its effects on atmospheric stability.