Passage VI

Air at its dew point temperature (or dew point) is saturated with water vapor. Air temperature usually decreases with increasing altitude. When air cools to its dew point, the water vapor in the air can begin to condense and form clouds.

Air temperatures and dew points were measured every 600 m from the surface (0 m) to an altitude of 3,000 m at 4 cities (A-D). Data, including the altitude of the cloud base over each city, were taken at 2 P. M. on every summer day that clouds were present. Figures 1-4 show the average air temperatures, the average dew points, and the average cloud-base altitudes at each city.

33. Assume that the cloud layer at City C extends from an altitude of 3,000 m up to an altitude of 4,000 m. Based on this assumption and the observed trends within cloud layers for the 4 cities, which of the following would be the best approximation of the air temperature and dew point in the cloud layer at an altitude of 3,600 m over City C?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

According to figure 3, the air temperature at altitude 3000m is 43°F, and the higher the altitude, the lower the temperature, so the temperature at 3600 m must be lower than 43°F, excluding D;

Look at the dew point also decreases slowly with the increase of altitude, so the dew point at 3600 m should also be less than 43°F, excluding C;

And according to figures 1-4, it can be seen that the average Above the cloud-base altitude, the dew point is always less than or equal to the air temperature, so exclude A