EQ: Let’s cook up some weather. What happens when we add water to air and then the sun-warmed ground heats them up?

Cumulus Stratus

Cumulonimbus

Cirrus

We get CLOUDS!What are their

Names?

ClassroomUnsquared

Let’s look at a box of air where we can see the tiny invisible molecules. They have kinetic energy, or motion energy. The higher the temperature of the air, the faster they are moving. The water molecules in the air are called humidity. The more water molecules, the higher the humidity.Now let’s take out the nitrogen and oxygen molecules so

we only look at the humidity.

Sometimes the more energetic molecules in the droplets will break free.

Moving water molecules will often collide and stick together on tiny dust or salt particles in the air. So, humidity will be in the form of invisible water molecules and micro-droplets.

If we make the micro-droplet grow in size, we call that process condensation. If millions of these micro-droplets get big enough to see, we now have a cloud! If the cloud droplets get big enough for gravity to pull them down, now we have rain, or precipitation!

So what makes cloud droplets grow?1. High humidity makes droplets grow.2. Colder air also makes droplets grow.

Either one or both. The temperature that air must drop below for condensation to occur is called the dew point. Clouds grow bigger and taller into thunderstorms when air is forced to rise quickly!

On this sunny day, the ground gets hot and heats the air above it.

Hot air expands, becomes lighter, and it rises.As it rises, the air cools and reaches the dew point, and guess what, condensation forms a cloud! On a low humidity day, the clouds are cumulus clouds.

Pixabay.com

HOT

Dew Point

So what are the ways that air can be forced to rise to form clouds and possibly rain?

1. Ground heating, mostly during the summer, can form cumulus clouds or cumulonimbus (thunderstorm) clouds.2. In low pressure centers, air comes together and is forced to rise over a large area. This process generally forms blanket-like clouds called stratus clouds.

3. Surface winds that hit a mountain range are forced to rise forming clouds on the windward side. This process forms mostly stratus clouds.

4. When air masses converge, the colder air mass is heavier than the warmer one, and the cold air plows under the warm, forcing the warm to rise. This boundary area is called a front. Fronts can form cumulonimbus, stratus, and cirrus clouds.

Here you can see a wind from right to left, rising on the right side of the mountains forming clouds and rain, then drier wind passing over the mountains, sinking and warming on the leeward side and no clouds.

http://en.wikipedia.org/wiki/Rain_shadow

A Low Pressure center forces air to circulate. A cold dry air mass from Canada flows south to collide with warm moist air from the Gulf of Mexico. This makes a cold front and often severe weather. Warm air flows north to collide with cooler air to make a warm front and rain.

Fronts move slowly around the Low and 15-35 mph (25 avg.) west to east with the low pressure center.

Water vapor in the atmosphere condenses, it rains or snows, water eventually runs off the land surface or in the underground causing erosion, partly evaporating on its way to the ocean, then more evaporation returns water to the atmosphere, and the same water recycles again.

The Earth makes 1 complete orbit around the Sun in one year. The Earth rotates on a tilted axis like a spinning top as it revolves on a flat plane in a counterclockwise direction.

23.50

If the axis was not tilted, we would only have 1 season, hottest at the Equator.

So where do the 4 United States seasons occur in the orbit and why?

SummerSolstice

WinterSolstice

Spring Equinox

Fall Equinox