Thornthwaite Classification:

Thornthwaite was an American climatologist. He presented his first climate classification in 1931. In 1931, his classification looked similar to Koeppen. Like Koeppen, Thornthwaite also thought that vegetation is the indicator of climate type. Two basic features of this classification are (i) Precipitation Effectiveness, (ii) Temperature Efficiency. On the basis of these two indicators, Thornthwaite divided the world into five humidity regions. Each region had its own special type of vegetation as shown in the table below:

On the basis of distribution of seasonal rainfall the above types of humidity regions were further divided into following subdivisions:

Y = Heavy rainfall in all seasons

s = Scarcity of rainfall in summer season w = Scarcity of rainfall in winter season d = Scarcity of rainfall in all seasons

After linking precipitation effectiveness and seasonal distribution of rainfall to temperature anomalies, the climates could be of 120 different types.