The correct option is 1 and 3 only.
Explanation
Atmospheric pressure is defined as the weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere. The vertical variation of pressure is governed by the physical properties of gases and the gravitational force acting on the atmosphere.
Statement-wise Analysis
- Statement 1 is Correct: Atmospheric pressure decreases with height. Since air is compressible, its density is highest near the surface of the Earth and decreases rapidly with altitude. Consequently, the weight of the air column decreases as one moves upward, leading to a reduction in pressure.
- Statement 2 is Incorrect: The vertical pressure gradient force is much larger than the horizontal pressure gradient force. However, we do not experience strong upward winds because this vertical pressure gradient is generally balanced by an equal and opposite gravitational force. This state of equilibrium is known as hydrostatic balance. The Coriolis force primarily affects horizontal wind movement and is negligible in the vertical context.
- Statement 3 is Correct: At mean sea level, the standard average atmospheric pressure is widely accepted as 1,013.2 millibars (mb) or hectopascals (hPa). This value serves as a reference point for meteorological measurements.
Key Takeaway: While the horizontal pressure gradient force is balanced by the Coriolis force (in geostrophic flow), the vertical pressure gradient force is balanced by the force of gravity (hydrostatic balance).