What is an air mass?

Most air masses form over cold areas called polar regions or warm tropical areas.
In addition, they will form over oceans and be moist. Air masses that form over the ocean are called maritime and they form over continents. Air masses that form over continents are dry and are called continental air masses.
Remember air masses take on the conditions of where they are formed.
Let’s take a look at all of the air masses the Earth has
Maritime tropical are warm and moist
Maritime equatorial are hot and moist
Maritime polar cold and moist
Continental tropical warm and dry
Continental polar cold and dry
Continental arctic and Antarctica very cold and dry

Video of Jet Stream
Title: Aerial Superhighway.ogv
Author: NASA/Goddard Space Flight Center
Date: 24 January 2012