Final answer:
The three letters such as 'cPk' in an air mass designation signify the moisture characteristics, the latitude or thermal properties, and the stability and geographic area of the source region.
Step-by-step explanation:
The three letters that specify the source region of an air mass, such as cPk, represent the following characteristics in order:
- The first letter indicates the moisture characteristics of the air mass. c stands for continental, suggesting a dry air mass originating over land. m would mean maritime, indicating a moist air mass coming from over the ocean.
- The second letter designates the latitude or thermal properties of the source region. P represents polar, implying cold characteristics, while T would stand for tropical, indicating warm characteristics.
- The third letter denotes the stability and geographic area of the air mass source. k represents continental polar, specifying that it originates from a colder, high latitude continental region. w would indicate a milder, typically maritime influence.