What does ground effect describe in relation to an aircraft?

Ground effect refers to the increased lift and decreased aerodynamic drag that an aircraft experiences when it is flying close to the ground, usually within a wingspan’s distance above the surface. This phenomenon occurs because the presence of the ground disrupts the airflow around the wings, reducing the amount of wingtip vortices and the resulting induced drag. As a result, the aircraft requires a shorter distance to achieve takeoff and landing speeds, contributing to a more efficient ascent and descent.

In contrast, the other options focus on aspects not specifically related to the aerodynamic interaction between the wings and the ground. Increasing speed during takeoff pertains to the thrust generated by engines rather than the aerodynamic effects of ground proximity. The effect of altitude on lift is relevant in discussions about air density and pressure but isn’t directly connected to the ground effect experienced during low flight. Enhanced control during steep turns involves different aerodynamic principles related to the yawing and rolling moments of the aircraft, which are unrelated to ground effect. Thus, the focus on decreased induced drag when near the ground succinctly captures the essence of ground effect in aviation.