FAA Ground School Practice Test

What causes variations in altimeter settings between weather reporting points?

1. Unequal heating of the Earth's surface

2. Changes in elevation

3. Seasonal temperature changes

4. Differences in aircraft types

The correct answer is: Unequal heating of the Earth's surface

Variations in altimeter settings between weather reporting points primarily arise from the unequal heating of the Earth's surface. This phenomenon affects atmospheric pressure, which in turn influences altimeter readings. When different areas of the Earth's surface heat unevenly due to factors like land and water distribution, local weather patterns are created. These variations can lead to differences in air pressure, which altimeters measure to determine altitude. In aviation, altimeters are calibrated to a standard atmospheric pressure; however, regions of high or low pressure directly impact the altimeter settings reported by weather stations. Consequently, pilots must adjust their altimeters according to the local pressure conditions to ensure accurate altitude readings during flight. Understanding this relationship helps pilots navigate safely, particularly when approaching or departing from airports in varying weather conditions. While other factors, such as changes in elevation or seasonal temperature changes, may also influence altimeter readings, they do not directly account for the variation in altimeter settings across different weather reporting points as significantly as the unequal heating of the Earth's surface does.