28th March 2008 - 01:02 AM
air usually has water dissolved in it...= water vapour, or a water vapour-pressure
Now we could weigh that water ( condense a volume of air and weigh the liquid water or ice.
[I weigh the absolute water content of air, I use a fixed volume container.. 3 L which I expose to the air... closed the lid and I place the lot in a deep freeze... where the water vapour freezes out onto a metal place as ice crystals... I weigh the metal plate ... then calculate the ABSOLUTE humidity]
the amount of water vapour dissolved in the air is referred to as humidity...
hot air can hold more water than cold air.
Wiki:- The term humidity is usually taken in daily language to refer to relative humidity.
Relative humidity is defined as the amount of water vapor in a sample of air compared to the maximum amount of water vapor the air can hold at any specific temperature in a form of 1 to 100%.
so if we take a volume of cold air with water vapour and heat it (prevent extra water evaporation into that volume of air), the relative humidity goes down... you tell me why ! but the amount of water in that air has not changed.
So a confusing term for many.
In weather reports daily temperature fluctuations cause the local air-mass to gain or lose relative humidity.
The air acts as a pipe for water.... evaporated water here can be transported there a long way off.
The poles is the usual end poin.
Now at the poles the absolute humidity is very very low... very very dry air because it is very cold air.
hope this sparks your interest in Ice Clouds.