An air mass must be: Group of answer choices homogeneous and small in size uniform in the vertical dimension but may contain different temperatures and moisture contents in the horizontal direction found only in the stratosphere large, uniform in the horizontal direction and travel as a unit

uniform in the horizontal direction and travel as a unit.

Explanation:

Air masses are large portions of air, which can reach 1000 miles or more in size. They have constant internal conditions such as temperature and humidity, in addition they are uniform in the horizontal direction and travel as a unit. From the moment they move, they lose temperature and weight and start to lose strength and impact. Generally, this displacement occurs when the air mass leaves the region of high pressure to a region of low pressure.

answer (a) more rain in u s and less rain in australia and asia