High School Earth Science/Changing Weather - Wikibooks, open books for an open world
23 What happens with a warm front? Warm air mass advances and replaces cold air mass Warm air is less dense than cold Warm air rides above the colder air. But what happens when two different air masses meet? That's our focus today! Think of oil and water as two separate air masses. Since the surface of contact between the two masses is quite steep and ascent is rapid, the The passage of a warm front is marked by a rise in the temperatures, Here, the tropical warm and humid air and the cold dry polar air meet, and of a front can provoke variations and deformations of various types, that can lead.
Thunderstorms or tornadoes may form in spring and summer, when the air is unstable. In the spring, the temperature gradient can be very high, causing strong winds to blow at the front. In the summer, thunderstorms may be severe and may also include hailstorms. In the autumn, strong rains fall over a large area. If the front moves slowly, enough rain may fall to cause flooding.
Cold fronts in winter may bring frigid temperatures and heavy snows. The cold air mass is likely to have formed in the frigid arctic.
When the temperature gradient across a cold front is low, a cold front has little effect on the weather. This may occur at some locations in the summer. Along the western United States, the Pacific Ocean warms and moistens cold air masses so that the temperature gradient across a cold front is small.
Warm Fronts[ edit ] A warm front is found where warm air mass slides over a cold air mass Figure Since the warmer, less dense air is moving over the colder, denser air, the atmosphere is relatively stable. Warm fronts travel much more slowly than cold fronts because the leading cold air mass is dense and sluggish. Warm air moves forward to take over the position of colder air. Imagine that you are on the ground in the wintertime under a cold winter air mass with a warm front approaching.
The transition between the cold air and the warm air takes place over a long distance. This means that the first signs of changing weather appear long before the front is actually over you. In fact, weather changes may appear hundreds of kilometers ahead of the front. Initially, the air is cold: High cirrus clouds mark the transition from one air mass to the other. Illustration of a warm front. Over time, cirrus clouds become thicker and cirrostratus clouds form. As the front approaches, altocumulus and altostratus clouds appear and the sky turns gray.
Since it is winter, snowflakes fall.What happens when two different air masses meet
Soon the clouds thicken and nimbostratus clouds form. Winds grow stronger as the low pressure approaches. As the front gets closer, the cold air mass is just above you but the warm air mass is not too far above that.
As the warm air mass approaches, temperatures rise and snow turns to sleet and freezing rain. Warm and cold air mix at the front, leading to the formation of stratus clouds and fog Figure As the front passes over you, the temperature and dew point rise and the rain likely ends.
What Happens When a Cold Front Meets a Warm Front? | Sciencing
The transition is not nearly as dramatic as when a cold front passes over, since there is more mixing of the two air masses occurring in a warm front. The Pacific Ocean also plays a role in modifying the warm fronts that reach the west coast of the United States. These storms are so broad that it is very difficult to spot exactly where the warm front is! Occluded Fronts[ edit ] An occluded front or occlusion usually forms around a low pressure system Figure The occlusion starts when a cold front catches up to a warm front.
The air masses, in order from front to back, are cold, warm, and then cold again. The boundary line, where the two fronts meet, curves towards the pole because of the Coriolis effect. If the air mass that arrives third is colder than either of the first two air masses, that air mass will slip beneath the other two air masses.
This is called a cold occlusion. If the air mass that arrives third is warm, that air mass will ride over the other air mass. This is called a warm occlusion. An occluded front with a warm front being advanced on by a cold front. The order of air masses from front to rear is cold, warm, and then cold.
High School Earth Science/Changing Weather
Occluded fronts can cause drying or storms. Precipitation and shifting winds are typical. The weather is especially fierce right at the occlusion. The Pacific coast has frequent occluded fronts. All of these fronts are part of the mid-latitude cyclone. These weather systems will be discussed in the next lesson. Lesson Summary[ edit ] An air mass takes on the temperature and humidity characteristics of the location where it originates. Air masses meet at a front. Stationary fronts become trapped in place and the weather they bring may last for many days.
At a cold front, a cold air mass takes the place of a warm air mass and forces the warm air upwards.
The opposite occurs at a warm front, except that the warm air slips above the cold air mass. In an occluded front, a warm front is overtaken by a cold front, which creates variable weather. Review Questions[ edit ] What type of air mass will be created if a batch of air sits over the equatorial Pacific Ocean for a few days? What is the symbol for this type of air mass? In a cold front, the opposite occurs.
In a stationary front, neither air mass advances.
Think of it as two fronts bumping into each other by accident. In an occluded front, a cold front overtakes a moving warm front, like an army swarming over a fleeing enemy. When two air masses of the same temperature collide and neither is willing to go back down, the only way to go is up.
As the name implies, the two winds converge and rise together in an updraft that often leads to cloud formation. Remember the city example? This phenomenon employs the exact same principle, except on a smaller scale. Unequal heating on the Earth's surface can cause a pocket of air to heat faster than the surrounding air.
When a cooler air mass pushes away a warmer one called a cold front heavier rain or snow may result. Cold fronts often produce thunderstorms, which can sometimes be severe. A dry air mass pushing into a moist one called a dry linethunderstorms often develop. And advancing dry line is the type of front most likely to produce an outbreak of tornadoes. When 2 air masses meet it creates fronts -Warm air Rises. Why do air masses have different temperatures?
Air masses have unequal or different temperatures because of the kind of material that compose the Earth's surface, angle of sun's rays, which is due to the shape of the Earth…, and the length of daytime, which is due to the tilting of the earth's axis as it revolves around the sun.