Final answer:
The altitude of the 500 mb level is higher at the equator than at the North Pole because of higher temperatures and the shape of the Earth affected by its rotation, causing a more expanded atmosphere at the equator.
Step-by-step explanation:
At the equator, the altitude of the 500 mb level is always larger than it is at the North Pole due to atmospheric temperature variations and Earth's rotation.
Earth's equator experiences higher temperatures because it receives direct sunlight throughout the year. This results in thermal expansion of the atmosphere, causing the altitude at which you find a pressure of 500 millibars (mb) to be higher. Moreover, the equatorial regions are warmer due to the angle of incoming solar radiation, which is more direct compared to the poles.
Additionally, Earth's oblateness—due to its rotation—causes the equatorial radius to be about 30 km larger than at the poles, which contributes to the higher altitude of pressure levels at the equator. This is partially because gravity is slightly weaker at the equator due to centrifugal force from Earth's rotation, leading to a less dense atmosphere. Consequently, pressure levels such as the 500 mb level are found at higher altitudes. In contrast, the air is colder and denser over the poles, contributing to the lower altitude of the same pressure level.
Last, temperature gradients present across the globe due to geographic and solar reasons play a role too. As the temperature declines with altitude, the warmer equatorial temperatures mean that these levels will be found at higher altitudes than over the cold polar regions.