Which air mass is cool and moist and originates from higher-latitude oceans?

• A. cT
• B. mT
• C. cP
• D. mP

Answer: (D)

Air masses get their characteristics from their source region, so you read them by moisture (maritime vs continental) and temperature (tropical vs polar). An air mass that is cool and moist and originates from higher-latitude oceans is maritime polar. The polar part comes from the cool, high-latitude source region, and the maritime part comes from the ocean, which supplies abundant moisture. That combination is exactly what “cool and moist from polar oceans” describes. The other possibilities would be either dry (continental) or warmer (tropical) or originate from land rather than the ocean, so they don’t fit the given clues.