Which air mass is classified as the coldest on the planet?

The coldest air mass on the planet is classified as Continental Antarctic. This air mass forms over the Antarctic continent, which experiences extremely low temperatures due to its high elevation and ice cover. The cold air is dense and can result in very frigid conditions, especially when it spills out and interacts with other air masses.

Continental Antarctic air is characterized by its origin over land in polar regions, allowing it to acquire low temperatures and minimal moisture. This contrasts with Maritime Polar, which while cold, originates over oceans and carries more moisture. Similarly, the Continental Arctic air mass is also cold but not as frigid as Continental Antarctic, primarily because it is sourced from the Arctic regions rather than the Antarctic. Maritime Tropical, on the other hand, is warm and humid, significantly differing in characteristics compared to the frigid air masses mentioned.

Overall, the extreme cold of Continental Antarctic gives it the distinction of being the coldest air mass on the planet.