What aspect of atmospheric conditions can lead to erroneous altimeter readings?

Erroneous altimeter readings are primarily influenced by changes in atmospheric pressure. An altimeter measures altitude by comparing the current atmospheric pressure outside the aircraft with a standard pressure value at sea level. When atmospheric pressure changes—due to weather systems like high or low-pressure fronts—it directly affects the altimeter's readings, which can lead pilots to misinterpret their altitude relative to the ground.

While humidity levels, temperature changes, and wind direction can have varying effects on flight and performance, they do not directly impact the fundamental operation of the altimeter in the same way that atmospheric pressure changes do. For instance, temperature changes can alter air density, but the altimeter primarily reacts to pressure. Therefore, understanding the dynamics of atmospheric pressure is crucial for accurate altitude measurement and aviation safety.