Which effect can atmospheric conditions NOT have on GPS signals?

Atmospheric conditions can have a significant impact on GPS signals, primarily through interference, delays, and inaccuracies caused by various factors in the atmosphere, such as ionospheric and tropospheric effects.

Improving accuracy, however, is not something that atmospheric conditions can do regarding GPS signals. Instead, the atmosphere tends to complicate the signal's journey, leading to various distortions and delays that ultimately reduce the precision of the positioning data provided by GPS systems. For instance, when GPS signals pass through the ionosphere, they can be delayed and refracted, which can lead to less accurate position fixes. Similarly, tropospheric delays affect the signals as they traverse through the lower atmosphere, further contributing to inaccuracies rather than enhancing them.

The other choices directly relate to the typical effects of atmospheric conditions on GPS signals. Thus, acknowledging that atmospheric conditions consistently hinder, rather than help, accuracy elucidates why the answer points to an improvement being unattainable in this context.