Question 1135Navigation General

A) the ground over which it moves is cooler than the air is the correct answer. An air mass is considered "warm" when the ground over which it is moving is cooler than the air within the air mass. This causes the air mass to warm up as it moves over the cooler surface, creating a warm air mass. The other answer choices are incorrect because: B) an air mass can originate in either a high or low pressure area, not specifically a high pressure area. C) the temperature threshold of 70°F is not the defining factor for a "warm" air mass. D) the origin of the air mass in a low pressure area does not necessarily make it "warm".