Friday, February 13, 2009

Then we went on to the “cloud in a bottle” experiment and what we observed is that only after adding in the smoke, when the bottle is squeezed, we don't see “clouds” however when we release it we see “clouds.” Yes, you guessed it, its all related to pressure and this is very much like how clouds are formed. But what is the link between pressure, smoke and clouds?

Well, since clouds do not appear in our homes, we can safely say that yes, pressure on earth is higher than that in our atmosphere. Lets say you have 100 units of heat for an ice cube(solid state). Now if I want to make this solid a liquid, I would have to force these molecules apart, as in the liquid state, molecules are further away from each other, this would eventually leave me with less units of heat as the molecules have absorbed the heat energy to move apart. Now think, if I were to make this liquid into a gas, I would have to again force the molecules apart, this time further than before and I am thus left with even less units of heat.

What does all this mean? Well, it is simply that releasing the pressure allows air to expand, and in doing so, the temperature of the air becomes cooler. Thus condensation occurs but clouds do not form because the water droplets are too small. So what happens? The water droplets collide instead of coalescing to form clouds. The air now is super saturated however, the water droplets would group together more easily if there are some solid particle in the air to act as a nucleus. This is where the smoke comes in, thus the cloud only forms when you add the smoke into the bottle. In the troposphere, the solid particles in the air may be in the form of pollution, smoke, dust or even tiny particles of dirt.

We now know how clouds are formed, but do you know how rain is formed? And did you know that there are 3 different types of rain? (well there may be more but we only covered 3 during lesson)

The three different kinds of rain are namely relief rain, frontal rain and convectional rain. Before I carry onto explain how each of these rain is formed I would like you to know what adiabatic cooling is. It is basically a process whereby air is forced to rise,expand and then condense to form water droplets.

1. Relief Rain:

The unique thing about this rain:

• only occurs where there is a really high mountain or a mountain range

• only rains on one side of the mountain (the leeward side). It doesn't rain at the rain shadow/windward side. Why? Well simply because there is little or no moisture here, the air then sinks and heats up.

• take a look at the Himalayan and Andes mountains, notice how there are deserts found there.

NOTE: warm air and cold air do meet but they do not mix, so what happens when they meet? Well, since cold air is denser than warm air, the cold air will sink, forcing the warm air to rise, we then get adiabatic cooling. After which clouds and rain form.

Unique thing about this rain:

• only found at temperate regions, because this is where the cold air from the polar regions meet the warm air from the tropical regions.

3) Convectional Rain

Note that for convectional rain, the sun does not heat up the air. What happens is, the sun heats up the ground (land) the land then heats up the air. The warm air then rises and once again we get adiabatic cooling, after which clouds and rain form.

Unique thing about this rain:

• found at tropical regions as it is sufficiently warm there.

  - normally occurs during the afternoon to evening, why? Well cause thats when the sun is up. It doesn't occur during the day time, as the ground isn't hot enough to heat up the land. But then why is it we experience rain in the daytime sometimes? Well thats monsoonal rain and I'm not about to get into that.

We'll that's basically it. Enjoy! Oh and for those guys who missed out on all the FUN during lesson, here;s a little video, though i don't think you can see much.