What is the relationship between air masses, fronts, and pressure systems?

Answer 1

The two main air masses are high pressure, and low pressure. In the northern hemisphere, the winds are clock-wise around, high pressure; counter clock-wise around low pressure.

High pressure is more dense forcing air towards the earth's surface This action tends to dry the air. Low pressure is less dense, and tends to lift air, in general causing moisture to form.

Warm and cold fronts, are self descriptive. The air flow on the south (warm) side of the front travel upwards, in a general northerly direction.

The cold side of a front, generally flow in a downward, southerly direction.

Again, this applies in the northern hemisphere.

Hope this helps

Answer 2

Air mass:-
When a mass of air of substantialy the same nature and characteristics(involving temperature and humidity) covers a large area,it is called an air mass.
Based on temperatures,two main classifications can be made.(1) Tropical air mass and(2) Polar air mass.
Based on humidity two classifications can be made.(1) Continental air mass and (2) Maritime air mass.
Fronts:-
When contrasting air masses lie side by side,the narrow zone of discontinuity,separating the two air masses is called a front.Cold front,warm front and polar front are examples.
Pressure systems:-
All weather systems which develop due to the difference in pressure between various places are called pressure systems.Low and high pressure areas,trough of low pressure,ridge of high pressure,col region,secondary low all are called pressure systems only
The rising of warm air mass produces low pressure areas and the sinking of cold air mass results in high pressure areas.

Answer 3

This will be a bit long and likely a little more than what you are asking for, but I think it is more complete and I will try to make this simple to understand. First, why do we have differences in air masses. Then why fronts and pressure systems exists with an example of what can result from two different air masses.

The Earth gets energy from the sun. Because the Earth is round and spins on its axis, some parts of the earth gets more energy than other. You can see this by using a flash light in a dark room. Point the flash light toward a basketaball that is sitting on a table. You will noticed that only part of the surface of the basketball is better lit by the light from the flash light. Some parts of the surface of the basketballl gets no light at all. If the basketball was the Earth and the flash light was sun, you can see that the energy in the form of light from the sun is not balance. In other words, different parts of the earth may get heat from the direct rays of the sun, while other parts gets no energy from the sun and will be cool. This is why some air masses are warmer while others are colder.

But there are also other differences, like some air masses have more moisture or others they are relatively drier. The Earth's surface are made up of large land masses and large bodies of water. If an air masses stays over a large body of unfrozen water for a period of time, water will evaporate and help moisten up the airmass above it. If it stays over land, it will be become drier with time when compared to the air mass over the water.

So, in general, you have the following air masses near the surface of the Earth. If the airmass is from the...

1. Over water with little or no sunlight...it will be cold and moist.
2. Over water with many hours of direct sunlight...it will be warm and moist.
3. Over land with little or no sunlight...it will be cold and dry.
4. Over land and with many hours of direct sunlight, it will be warm and dry.

Now, in science we know that nature does not like it when energy is not in balance. So the Earth tries to move around the different air masses in a constant effort to balance out the energy it gets from the sun.

So, this attempt to balance of the energy is why we get weather on Earth. Weather is the result of all the reaction we get as two or more different air masses come together in an attempt to blend together. But this blending is usually not smooth as things can become violently unstable when they meet. The worse areas are at or near the border of where the strongest difference between the two air masses meet. This border or boundary between the different air masses is known as a "Front".

Because the earth is spinning, it causes things to be complicated as air that is trying to move to a certain area will not be able to do it because because the ground keeps moving. It like trying to play tag, but somebody keeps pulling and tugging the rug from under your feet. This causes the air to fall and rise as it moves and change direction. The large scale sinking and rising motion in combinaton with the strength of the airmasses are what gives you the pressure differences. Pressure differences with a given distance distance or the pressure gradient are usually the result of strong differences of potential energy between one air mass and the air masses around it. When you increase the diffences in energy strength and /or decrease the distance between the two different air masses, you will increase the pressure between the two system. You you will find things can get interesting near the front as air starts to rushes in and converges near the surface front.

When air converges near the surface front, it has no place to go but upwards, and that what you want to have happen if you want to get some good precipitation if enough moisture is availabe. If the atmosphere remains unstable as the air goes upward higher in altitude, you may get some more stronger weather like thunderstorms or severe weather too.

Once the air masses blend and become more like each other, the front will weaken and the pressure differences will relax and the fair weather will return until the next cycle begins.