Name: ____________________________ Date: _________________________ Mr. Lanik/Ms. Cooley/Mr. Liebowitz Chapter 20.1-20.2 Notes Meteorology – _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ Air Mass – _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _________________________________________ Front _________________________________________________ _________________________________________________ _________________________________________________ _________________________________________________ _________________________________________________ Cold Front ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ Warm Front – ____________________________________________________ ____________________________________________________ ____________________________________________________ ____________________________________________________ ____________________________________________________ ____________________________________________________ Occluded Front – ______________________________________________ ______________________________________________ ______________________________________________ ______________________________________________ ______________________________________________ ______________________________________________ ______________________________________________ Stationary Front – _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ I – Air Masses An (1) ___________________________ is a large body of air in the lower troposphere that has similar characteristics throughout. An air mass can be several thousand kilometers in diameter and several kilometers high. Two or three air masses can (2) ________________ the entire United States! Throughout an air mass, (3) _________________________ and (4) _______________________________ are nearly uniform (the same). The temperature and humidity of an air mass depends on where the mass (5) ________________________. In polar regions the lack of (6) ____________________ causes the ground to be very cold. If an air mass stays in a polar region for a long time, the air mass becomes cold as well. The opposite happens in tropical regions. The moisture of an air mass depends on the surface where it came from. If an air mass stays over land for a long period of time, it becomes (7) ______________, where an air mass over the ocean (8) _________________ water vapor and becomes (9) ___________________. When an air mass moves from one place to another, it takes the temperature and humidity of its place of origin with it. However, some of its characteristics may change as it moves across the country. When cold polar air moves south, it affects the (10) ______________________ of the area it enters, as well as slowly (11) ______________________ as it moves across a warmer (12) _________________________________. Earth’s topography also helps change the temperature and humidity of an air mass as it travels. II – Types of Air Masses There are (13) ________________ main air masses in North America: (14) _____________________________________________, (15) _____________________________________________, (16) _____________________________________________, (17) _____________________________________________, (18) _____________________________________________. Continental Arctic (cA) air masses originate in the arctic regions where the air is extremely cold. Because cold air is incapable of containing much (19) ________________________, cA air masses are very (20) ______________________. Continental Polar (cP) air masses start over Alaska and Canada and are somewhat warmer than the cA air masses. The differences in temperature and humidity between cA and cP air masses are usually (21) ______________________. When cP air passes over the Great Lakes region in the late fall when the water is still warm, the cold, dry air picks up moisture from the lakes, then dumps the precipitation as snow, causing (22) _______________________________. Maritime polar (mP) air masses form over the ocean in high latitudes. These air masses are both (23) ____________________ and (24) ______________________. mP air is not as cold as cP air because of the difference in temperatures between the land and the oceans. Occasionally mP air from the North Atlantic brings heavy snowstorms called (25) ______________________________ to the East Coast in the winter and cool, clear weather to the area in the summer. Maritime tropical (mT) air masses form over a warm tropical ocean and gain both warmth and moisture. In the summertime, mT air from the Bahamas and the Gulf of Mexico moves (26) __________________________ around the high pressure over the Atlantic Ocean, bringing heat and humidity to the Midwest and Eastern U.S. Since this air mass contains a lot of moisture, (27) ______________________________________ often develop. As the sun heats the ground, the moist mT air is heated from below and (28) _____________________, forming thunderclouds. When the sun sets, the clouds and thunderstorms leave as the surface cools. Continental tropical (cT) air masses originate over deserts and are hot and dry. Most of the time a cT air mass originates as a maritime air mass but becomes dry as it passes over mountains. cT air masses produce massive (29) ______________________________ in most of the United States. mT air usually produces temperatures no higher than 100 degrees Fahrenheit, but cT air is much (30) ______________________, with temperatures exceeding 100 degrees Fahrenheit. cT air is dry and does not bring cloud or thunderstorms, however if this type of air mass comes into a crop region, it can cause serious damage to them. III – Fronts Air masses of different types do not mix easily. The boundary that separates different air masses are called (31) ________________________. The width of a front can range from 200 meters to 200 kilometers. Fronts can also be as high 5 kilometers and as long as 2000 kilometers and can effect weather patterns in areas hundreds of kilometers wide. Fronts are most common at (32) ____________________________________, where southward moving polar air masses and northern moving tropical air masses often meet. At the front, the less-dense air mass is forced to (33) _________________________ over the denser air mass. Because of this the front is usually (34) ___________________________________. Fronts usually bring (35) ___________________________________. At the surface of the front the less-dense air rises into the troposphere where the air cools, and if humid enough, can create clouds and bring precipitation. IV – Types of Fronts The weather associated with a particular front depends on two things: (36) _______________________________________ (37) _______________________________________. A (38) ______________________________________ is the boundary between an advancing cold air mass and a warmer air mass. Since cold air is denser than warm air, the cold air slides underneath the warm air, forcing it upward. Cold fronts can create thunderstorms, or cause no greater change than a shift in wind direction. In the summer, some cold fronts cause a decrease in humidity, while in the winter a cold front can cause (39) _________________________________ (40) _________________________________. If warm air moves cold air, the boundary between the air masses is known as a (41) _____________________________________. The advancing warm air rises above the denser cold air, which moves away slowly. The first signs of a warm front are high cirrus clouds, which are followed by cirrostratus clouds and lower and thicker stratiform clouds. Such clouds form in the warm, stable air sliding up the front surface. These clouds may stretch 1500 kilometers ahead of the place where the warm front touches the ground; this cirrus clouds may warn of approaching (42) ___________________________________. Cold fronts usually move (43) _______________________ as fast as warm fronts. If a cold front “catches up” to a warm front, the result is an (44) ______________________________________________. The warm air that is caught between the two colder air masses is forced to rise. Once this warm air rises, it cools, often resulting in: (45) ______________________________ and (46) ______________________________. If a front is not moving forward, it is called a (47) ____________________________________. The warmer air rises over the denser, colder air, and clouds and precipitation may form.