The "H" stands
for Humidity. As the Humidity increases
air pressure decreases. That means as the amount of moisture in
the air increases the air pressure decreases.
The "A" stands
for Altitude. As the altitude increases
the air pressure decreases. That means that there is less air
pressure exerted on you when you are on
the top of a mountain than when you are at sea level.
Finally, the "T" stands
for Temperature. As the temperature
of the air increases the air pressure decreases. Which means
that warm air exerts LESS
pressure than cold air. The tube on the left shows warm air molecules.
how far apart they are. Less pressure.
Hot air is less
dense therefore it rises.
Cold air is
more dense therefore it sinks.
= Low pressure and Cold=High