Question

1. You and a friend decide to take a hike in the Sierras this Fall. Fortunately your smartphone has a barometric pressure app and you notice that when you leave Davis it reads 1000 mb. Later after hiking uphill all morning you arrive at a beautiful vista and check the pressure. It reads 680 mb and your friend freaks out. "Woah! That's seriously low pressure, there must be a storm coming, let's get out of here." How do you reason with your friend in order to save the day's outing?

Answer 1

A convincing explanation to your friend would be that he is mistaking the decreasing pressure with altitude for a low pressure which leads to a storm.Generally with increasing altitude , pressure decreases because the density of air molecules decreases with increase in height above the ground.The air pressure is a measure of the total weight of the air above a unit area at any elevation. Since most of the atmosphere's molecules are held close to the earth's surface by the force of gravity, air pressure decreases rapidly at first, then more slowly at higher levels.

SO, no need to worry, and carry on with hiking.