Physical and Earth Science NOTES: WATER in the AIR Physical and Earth Science

Several things in the atmosphere make us feel warm . . . The radiation from the sun The radiation reflected back up from the ground The CO2 in the air traps heat from the sun. The amount of WATER VAPOR in the air has the most influence on warmth and daily weather . . . It transfers heat to your skin so you can feel it, and prevents the air from heating up or cooling down too rapidly.

Water and Air are both FLUIDS Water is denser than air, so it has more collisions with other molecules in the atmosphere, and also your skin! Water vapor in the air is HUMIDITY. The more humid it is, the amount of heat you feel will be exaggerated. (you feel hotter, sticky, curly hair, like you can’t dry off)

Relative Humidity THE AIR USUALLY HAS 0.5 – 4% WATER VAPOR IN IT Relative humidity is the % of water vapor in the air NOW compared to what the air COULD hold

Warm air can hold more water vapor compared to cold air!!!! WHY?

Even though humidity makes humans uncomfortable, it adds beauty to a climate. . .

An instrument used to measure humidity is called a psychrometer. There is a wet and Dry thermometer that Are spun around. The difference Between them after the wet One dries indicates humidity.

CLOUDS form from Water Vapor in the air. . . . There needs to be a “seed” (CONDENSATION NUCLEI) like dust, dirt, pollen, etc. Water vapor molecules need to gather close together and clump on the nuclei ( COALESCE ) It needs to be cold enough for water to turn from gas form to a liquid form, and become droplets (CONDENSATION) Heat energy from the water vapor needs to be released for this to happen (LATENT HEAT)

What is “dew” ? Water droplets that are formed overnight because the air got cold enough for CONDENSATION to occur . . . The temperature when that happens is called DEW POINT.

3) FRONTS. Clouds form when air masses of different temperatures collide. The warm air is forced up and cools underneath, causing water vapor to condense… clouds form.

Why do you only see clouds mostly in the troposphere? CLOUDS NEED: A source of rising warm air A place for that air to cool down Dirt Water vapor

Other easy cloud patterns to spot: . . “ANVIL” – thundercloud formation “STREAKS” – rain off in the distance

The water cycle is showing the movement of water on earth from energy being absorbed or released