True or False: Fronts have a vertical structure and do not exist solely at the Earth's surface.

Fronts are indeed characterized by vertical structures that extend through the atmosphere, not just at the Earth's surface. A front is defined as a boundary between two different air masses, which have varying temperatures and humidity levels. This boundary often leads to significant weather changes, including precipitation and changes in wind patterns.

In a typical frontal system, the air masses interact in complex ways, leading to vertical development of clouds and precipitation. This vertical structure can extend several kilometers into the atmosphere, which affects weather phenomena well above ground level. Therefore, stating that fronts do not exist solely at the Earth's surface accurately reflects the reality of how fronts operate in the atmosphere.

The other options do not accurately capture the behavior of fronts; they either imply restrictions in their presence that do not apply or suggest variability that isn't typical. Therefore, asserting that fronts have a vertical structure and are present throughout the atmosphere supports a better understanding of meteorological phenomena and their implications for weather forecasting.