Explain why air compresses when it sinks.Explain why air compresses when it sinks.

3 Answers

litteacher8's profile pic

litteacher8 | High School Teacher | (Level 3) Distinguished Educator

Posted on

Rising air expands, so it does make sense that sinking cooler air would compress. Air that is already cooler is going to sink, and since it rises when it expands it is not going to expand while sinking. Cooling air also condenses. Then less water vapor is needed to saturate the air
pohnpei397's profile pic

pohnpei397 | College Teacher | (Level 3) Distinguished Educator

Posted on

I assume that you are talking about what happens when air sinks within the atmosphere.  This is the process, for example, that helps to create the eye of a hurricane.

The reason that air compresses as it sinks is that there is more air pressure lower down in the atmosphere.  Down at the bottom of the atmosphere where we are, the air is being compressed by all of the air above it in the atmosphere.  If the air were higher up, there would be less air pushing down on it and compressing it.  So, as the air sinks, there comes to be more air pressing down on it and it compresses.



neela's profile pic

neela | High School Teacher | (Level 3) Valedictorian

Posted on

Pressure, volume and temperature are interrelated. Volume is  inversely proportional to the density. Air has mass and weight and, therefore, pressure at a point in the atmosphere depends upon the air column above. Thus the pressure is more at ground or sea level than on a hilltop. The sinking air pocket, therefore, has a density more than that of its surrounding air. So the sinking air pocket, as it comes down closer to earth has to have higher atmospheric pressure on it and this in turn reduces its volume and increases its density.  The nature has a trick of distributing excess heat energy received from the sun on sea water, which evaporates taking the heat on the sea. The humid air thus possesses the heat energy and goes up and the wind makes the cold air sinks down. This convection helps heat energy flow above and far and wide on the globe.