An air mass is a large volume of air defined by its consistent temperature and moisture properties. These air masses influence the weather of entire regions for days or weeks. To effectively track and forecast their movement, meteorologists use a standardized, shorthand classification system on weather maps. This system communicates an air mass’s fundamental characteristics and its likely impact on local conditions.
The Standard Air Mass Classification Framework
The universal meteorological system uses a two-part code to classify any air mass. This designation is based on its source region, which determines its inherent properties. The first letter relates to the air mass’s moisture content, and the second letter describes its thermal characteristic, or temperature. The moisture component divides air masses into those that form over land and those that form over water. The thermal component classifies the air mass based on the latitude of its origin.
Identifying Continental Air Masses
The lowercase letter ‘c’ designates a continental air mass, signifying that it originates over a large landmass, or continental source region. This letter stands for “continental” and indicates the air mass is inherently dry. It acquires low moisture content because it forms over a surface that lacks a large, readily available water source. In contrast, a maritime air mass forms over water and is designated with the letter ‘m’ for high humidity. Continental air masses typically develop over vast land areas, such as the interior of North America, where the lack of surface water limits evaporation.
Interpreting Full Continental Designations on a Map
A continental air mass designation is completed by pairing the ‘c’ with a second capital letter that indicates the air mass’s temperature. The thermal characteristics are determined by the latitude of the source region. These include ‘P’ for Polar (cool or cold), ‘T’ for Tropical (warm or hot), and ‘A’ for Arctic (extremely cold). Combining these symbols results in three primary continental air mass types that appear on weather maps.
The symbol ‘cP’ stands for Continental Polar, a cold and dry air mass. This type forms over high-latitude land areas, such as northern Canada, bringing clear skies and stable atmospheric conditions. When this air mass moves south in winter, it can cause prolonged periods of below-freezing temperatures.
The designation ‘cT’ represents Continental Tropical, characterized as hot and dry. This air mass originates over low-latitude deserts, such as the southwestern United States or the Sahara Desert. It is often associated with heatwaves and drought conditions.
The ‘cA’, or Continental Arctic, is the most extreme type, signifying air that is exceptionally cold and dry. This air mass forms over the permanently frozen arctic regions. It is responsible for the most severe cold outbreaks.
These two-letter designations, such as ‘cP’ or ‘cT’, are placed directly on the weather map, usually near the geographic center of the air mass. This placement provides an immediate understanding of the weather conditions prevalent across that region. The movement of these symbols across the map helps predict changes in temperature, humidity, and the potential for precipitation as one air mass replaces another.