• Hypothesis of each ideal cases

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A.  When there is a lot of water vapor in high temperature.

The amount of radiant energy incident is greater than that of C and D. In addition, the amount of water vapor in the atmosphere is large, and it cannot be released again, so there is a lot of radiant heat trapped in the atmosphere. Therefore, the heat island strength is stronger than B.

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B. When there is less water vapor in high temperature.

The amount of radiant energy incident is greater than that of C and D, but because the amount of water vapor in the atmosphere is small, the amount of radiant heat trapped by water vapor is less than A. Therefore, the heat island strength will be weaker than that of A.
 

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C. When there is a lot of water vapor in low temperature.

The amount of radiant energy incident is less than that of A and B. However, because the amount of water vapor in the atmosphere is large, and it cannot be released again, so there is a lot of radiant heat trapped in the atmosphere. Therefore, the heat island strength is stronger than D.
 

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D. When there is less water vapor in low temperature.

The amount of solar radiation energy that is incident is less than that of A and B. Also, because the amount of water vapor in the atmosphere is small, the amount of radiant heat trapped by water vapor is small. Therefore, the heat island strength is weaker than C.
 

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• Seasonal hypothesis

 

Since the summer has a higher mixing ratio than the winter, there will be more radiation heat trapped in the atmosphere. Therefore, the heat island strength of summer due to water vapor may be greater than that of winter.