This change in tropopause height effects the altitude at which clouds occur. Except for low clouds, which are defined as occurring within the first 6,500 feet altitude in each region, the boundaries for mid and high level clouds overlap and vary.
The polar and subtropical jet streams are major dividers between the polar, temperate, and tropical regions. One effect of these cores of strong wind is the maximum altitude of the tropopause decreases in each region as one moves from the equator to the poles.
The traditional division between the Polar and Temperate Regions is the Arctic Circle (66.5°N) in the Northern Hemisphere and the Antarctic Circle (66.5°S) in the Southern Hemisphere. The division between the Temperate and Tropical Regions are the Tropics of Cancer (23.5°N) in the Northern Hemisphere and the Tropics of Capricorn (23.5°S) in the Southern Hemisphere.
The actual division between these regions varies from day to day and season to season. Between the Polar and Temperate Regions lies the jet stream in both hemispheres, while the Sub-Tropical Jet Stream divides the Temperate and Tropical Regions.
|Level||Tropical Region||Temperate Region||Polar Region|
|High Clouds||20,000-60,000 feet (6-18 km)||16,500-45,000 Feet (5-14 km)||10,000-25,000 feet (3-8 km)|
|Mid Clouds||6,500-25,000 feet (2-8 km)||6,500-23,000 feet (2-7 km)||6,500-13,000 feet (2-4 km)|
|Low Clouds||Surface-6,500 feet (0-2 km)||Surface-6,500 feet (0-2 km)||Surface-6,500 feet (0-2 km)|
Since the jet stream follows the sun, it shifts toward the equator as winter progresses. Therefore, the polar region expands and the temperate region moves toward the equator. In summer, the Tropical Region expands shifting the temperate region toward the poles while the polar region shrinks.