Question

Pressure is about 1000 hPa at sea level and about 500 hPa at an altitude of 5.5 km. Why doesn’t this vertical pressure gradient cause permanent upward acceleration and motion?A. The upward pressure gradient force is balanced by gravity.B. The upward pressure gradient force is balanced by friction.C. The upward pressure gradient force is balanced by the Coriolis force.D. The upward pressure gradient force is too small to have any noticeable effect.E. Upward motion is prevented by the temperature inversion.

Answer 1

Answer:

A. The upward pressure gradient force is balanced by gravity.

Explanation:

A. is correct because the pressure difference is actually generated by gravity. As in the following formula for the pressure at different points:

$p = p_0 + \rho g h$

where $p, p_0$ are the pressure at 2 points, ρ is the density of the fluid, g is the gravitational constant, and h is the height difference.

B is incorrect because friction in air is too small to make an effect.

C is incorrect because the Coriolis force is horizontal, not vertical.

D is incorrect because a difference of 500 hPa = 50000 Pa, this is half of the atmospheric pressure.

E is incorrect because temperature cannot generate force.