海拔与气压折线图：为何该图呈曲线而非直线？

Great question—this curve isn’t a flaw in your graph, it’s a direct reflection of how Earth’s atmosphere behaves. Let’s break this down in plain terms:

First, remember that atmospheric pressure is the weight of all the air above a given point pressing down. The key difference between air and, say, water is that air is compressible. Unlike liquid (which has nearly constant density no matter how deep you go), air gets less dense as you climb higher because there’s less weight squeezing it from above.

Here’s why that creates a curved relationship:

• Exponential decay is the natural rule
  The pressure-altitude relationship follows the barometric formula, which is an exponential equation (not linear):
  P(h) = P₀ * e^(-mgh/(kT))
  Where:

  • P(h) = pressure at altitude h
  • P₀ = sea-level pressure
  • m = average mass of air molecules
  • g = gravitational acceleration
  • k = Boltzmann constant
  • T = average atmospheric temperature (simplified for a constant-temperature scenario)

  Exponential functions produce curves by nature: pressure drops quickly at lower altitudes (where dense air is packed tight) and slows down as you climb higher (since there’s less dense air left to contribute to downward pressure).

• Density decreases with altitude
  At sea level, the air is compressed by the entire weight of the atmosphere above. Each meter you climb, the air above you is less dense than the layer below. So each 100-meter ascent doesn’t reduce pressure by the same amount—you lose more pressure per meter near the ground, and less as you go up. That non-uniform drop is what creates the curve.

• Real-world temperature shifts make it even more curved
  In reality, atmospheric temperature isn’t constant (the troposphere cools as you climb, then the stratosphere warms). These temperature changes adjust the exponential rate, making the graph’s curve even more pronounced than the simplified formula predicts.

To sum it up: If air were incompressible (like water), pressure would drop in a straight line with altitude. But because air compresses under its own weight, the pressure decay slows down as you ascend—resulting in that curved line you’re seeing.

内容的提问来源于stack exchange，提问作者user65035