In the context of Koeppen’s scheme of classification of climate, which of the following variables were selected to define climatic groups?

The correct option is Mean monthly temperature and mean monthly precipitation.

Explanation

Vladimir Koeppen’s climate classification is an empirical system based on the observation that the distribution of natural vegetation is the best expression of climate. To scientifically map these zones, he established quantitative criteria based on climatic data.

Analysis:

• Koeppen selected specific numerical values to define the boundaries between climatic groups. The variables selected were temperature and precipitation.
• Specifically, the system utilizes mean monthly temperature and mean monthly precipitation data.
• Using monthly means is essential to determine seasonality, such as the temperature of the coldest month (e.g., to distinguish between Tropical and Temperate climates) or the precipitation of the driest month (e.g., to distinguish between Rainforest and Monsoon climates).
• Mean annual temperature and mean monthly precipitation only is incorrect because relying solely on mean annual temperature would fail to account for the seasonal variations critical to the scheme.
• Mean annual precipitation and evaporation rates is incorrect because evaporation rates are a primary variable in Thornthwaite’s classification, not Koeppen’s.
• Atmospheric pressure and wind direction is incorrect because atmospheric pressure and wind direction are dynamic factors used in genetic classifications, whereas Koeppen’s system is empirical.

Key Takeaway:
Koeppen’s classification is strictly based on the empirical values of mean monthly temperature and mean monthly precipitation.