Answer to Question 1
ANSWER: Answers will vary, but should address the following:
To correct some of the Kppen deficiencies, the American climatologist C. Warren Thornthwaite devised a new classification system in the early 1930s. Both systems utilized temperature and precipitation measurements and both related natural vegetation to climate. However, to emphasize the importance of precipitation (P) and evaporation (E) on plant growth, Thornthwaite developed a P/E ratio, which is essentially monthly precipitation divided by monthly evaporation. The annual sum of the P/E ratios gives the P/E index. Using this index, the Thornthwaite system defines five major humidity provinces and their characteristic vegetation: rainforest, forest, grassland, steppe, and desert. To better describe the moisture available for plant growth, Thornthwaite proposed a new classification system in 1948 and slightly revised it in 1955. His new scheme emphasized the concept of potential evapotranspiration (PE), which is the amount of moisture that would be lost from the soil and vegetation if the moisture were available.
Answer to Question 2
ANSWER: Kppens system has been criticized primarily because his boundaries (which relate vegetation to monthly temperature and precipitation values) do not correspond to the natural boundaries of each climatic zone. In addition, the Kppen system implies that there is a sharp boundary between climatic zones, when in reality there is a gradual transition.