Elements of Weather

1. Elements of Weather Changes in the atmosphere Physical Geography Part II

2. The atmosphere

3. Climate vs. Weather Understand the DIFFERENCE BETWEEN CLIMATE AND WEATHER… • Weather can be defined as the atmospheric conditions at a given time and place • Climate can be defined as the average weather conditions over a long period of time at a given place.

6. atmospheric Pressure

7. Atmospheric pressure High pressure Low pressure • Air pressure is measured on a barometer using units called millibars in a graduated tube. • Pressure is higher at the surface of the earth • Cold air falls and creates higher air pressure • Air pressure is measured on a barometer sometimes using inches of mercury in a graduated tube. • Pressure is lower in the upper atmosphere than at the surface • Warm air rises and creates lower air pressure

9. Temperature • Temperature is probably the most obvious element of weather to most people because regardless of the other elements, you always feel and are aware of temperature. • Temperature (for people) is simply how hot or cold it feels. Obviously, you can get more complex definitions in a science classroom

10. Temperature fahrenheit celsius • Temperature can be measured on the Fahrenheit scale and is good for human use because it is based upon how hot or cold it feels to people • Freezing = 32o • Boiling = 212o • Temperature can be measured on the Celsius scale and is good for scientific use because it is based upon how hot or cold it “feels” to water • Freezing = 0o • Boiling = 100o

11. Temperature • There is also a kelvin scale that is used to measure the temperature of light or very hot things. • Its scale is the same as the Celsius scale, but it begins at absolute zero, the temperature at which molecules stop moving = -273.16o • this is just for information, and we will not be using the kelvin scale in class

12. Temperature & latitude • Temperatures are warmer at the low latitudes close to the equator where there is more direct rays from the sun. • Temperatures are colder at the high latitudes close to the poles where the angles of sunlight are greater.

13. Temperature & bodies of water • Large bodies of water like oceans and large lakes moderate temperatures. • Water warms up and cools off slower than land and does not get as hot as land. • Land away from large bodies of water have more extreme temperatures

14. Temperature & elevation • Changes in elevation can also affect elevation. Moving to higher altitudes results in thinner air and lower temperatures. • In some regions, land is identified by its elevation which also affects its vegetation.

15. -wind= Simply put, wind is the movement of air from one place to another. But what causes it to move?

16. -wind= • Wind is often caused by a heat transfer from the sun to the crust to the air called convection (just like in the asthenosphere). • Air is warmed by the crust or water and rises. Cooler air rushes in to take its place.

17. -wind= Wind can also be caused by the rotation of the Earth. As the Earth rotates at roughly1040 mph., the air above the surface is bent and moved. This is known as the coriolis effect.

18. Coriolis effect • Note in the previous slide how the air is rising at the equator (tropics) because of the heat. The rising air is then bent or pushed by the rotation of the earth. Since it is happening on both sides of the equator, the winds exchange or trade; hence they are called “trade winds.” • Right at the equator, air is rising and pushing away. This means that at the surface there is little or no wind. This is called the doldrums. • Farther north is another area where winds are separating and there is little wind at the surface. This is called the horse latitudes….this is because they sometimes threw dead horses overboard from ships. Because of the lack of wind, other ships would often encounter dead horses in the water in these regions. • Notice that winds are named for the direction from which they blow.

19. -wind= • Sometimes wind can also be caused by tides or by storms. We will look at storms separately.

20. humidity • We said earlier that the atmosphere was 1% gasses other than nitrogen & oxygen. There is also h2o. • Humidity is the water in the air. This varies from one location to another.

21. humidity • Absolute humidity is the weight of the water in the air. • Dew point is the temperature at which the water vapor in a given body of air will condense • Relative humidity is the ration between absolute humidity and dew point.

22. humidity • It is important to note that all air has moisture to some degree, but warm air can hold more moisture than cold air. • That does not mean all warm air has a lot of moisture.

24. humidity • The air on top of a tall mountain will often be cold and, therefore, dry. • The air beside a mountain is often also dry but hot • Which body of air has the potential to hold the most moisture? The desert air

25. precipitation • Precipitation is the extraction of water from a body of air. This happens when the amount of water in the air becomes too great to remain suspended between air molecules. • Please beware and note: in mr.adams’ class, there is a big difference between “types” of precipitation and “forms” of precipitation!!

26. precipitation Types of precipitation Forms of precipitation • When mr.adams refers to “types” of precipitation, he is talking about what causes the water to come out of the air. • Types of precipitation will include • Convectional • Orographic (mountain) • When mr.adams refers to “FORMS” of precipitation, he is talking about what form the water takes when it comes out of the air. • forms of precipitation will include • rain • Sleet • Snow • hail • WE MAY ALSO INCLUDE: • VIRGA

27. Forms of precipitation snow sleet • Snow occurs high in the clouds when it is very cold, and the water vapor freezes. If the temperature is below freezing all the way to the surface, snowing precipitation has occurred. • Sleet starts off as snow. In some cases, the snow begins to melt on the way down. If conditions are right, the melted snow may refreeze before it hits the surface. These tiny ice pellets are called sleet.

28. Forms of precipitation rain hail • Rain is the most common form of precipitation in comanche. • Rain is simply condensed water falling from a cloud. • Water will condense onto a tiny dust particle when it becomes cooled. • Hail is unique. Hail starts off as a drop of rain or perhaps even snow. It occurs when a violent storm blows the drop up high enough to freeze. As it comes down, it gets blown up again, collecting moisture and freezing again. The more times it gets blown up into the clouds, the larger the hail becomes.

29. Types of precipitation • Convectionalprecipitation is the most common type of precipitation in comanche. • It is caused by the heating of the crust and then the air by the sun. Warm air rises. As it rises, it cools and moisture condenses. When the water becomes too heavy and air is saturated, precipitation occurs.

30. Types of precipitation • Orographic precipitation occurs when moist air is forced upward by a very large obstruction like a mountain. • As the air moves up, it cools and condenses. As with convectional precipitation, it then begins to fall when the air becomes saturated. DOES OROGRAPHIC PRECIPITATION OCCUR IN COMANCHE, TEXAS?

31. YIPPER DO! Surprise! • Though you cannot really see it, a cold front can be as tall as a mountain, and the warm, moist air can be forced up the wall of a cold front in the same way. • Like the rain shadow effect created by a mountain, it is often dry (and cool) on the back side of a cold front.

32. ADIABATIC RATES • As air rises due to convection or due to an obstruction, it cools off at a known rate. • We will keep it simple for our class. • Air with moisture cools at 3.5o for every 1000 feet (rise) of elevation. • This is the wet adiabatic rate • So if the air temp at the surface is 80o, and the air rises 2000 feet, the new temperature of the air is 73o • Because 2 (units of 1000) times 3.5 equals 7 • Subtract that product 7, from the original 80 degrees • As air moves down an obstruction like a mountain, it warms up at a known rate. • Keeping it simple…. • Air, now dry because it has lost its moisture on the windward side of a mountain warms at 5.5o for every 1000 feet (decline) of elevation. • This is the dry adiabatic rate

33. ADIABATIC RATES So air that is dry warms faster than it cooled when it had moisture. The air on the leeward side of a mountain is often dry and hot. The side from which the wind blows is called the Windward side. The opposite side is called the Leeward side.

34. storms • Thunderstorms are common in comanche during the spring. • Typical thunderstorms are caused by convection that can create an unstable atmosphere near the surface. • These can result in high winds, hail, heavy rains, and lightning.

35. storms

36. storms • Tornadoes occur all over the world but are most common in the central u.s. • They are caused by clashes of warm and cool air. • The cooler air rolls along the ground and can sometimes be turned upward. THE DEADLIEST THING ABOUT TORNADOES IS OBJECTS FLYING THROUGH THE AIR.

37. storms • Hurricanes (typhoons) are the largest storms on earth. They are created by warm air currents that move over water that is heated by the sun. • Hurricanes may be hundreds of miles across and can spawn tornadoes and heavy rain. THE DEADLIEST PART OF A HURRICANE IS THE STORM SURGE (WATER).

38. WORLD CLIMATE TYPES YOU NEED TO LEARN THE FOLLOWING CLIMATE TYPES AND IDENTIFY THEM BY THEIR DESCRIPTION

39. Tropical rainforest This climate experiences year around hot weather and abundant precipitation. The soil is leached of nutrients that are replaced with decaying matter from lush vegetation.

40. Tropical savanna Characterized by grasses and often occurring in the low latitudes, this climate type experiences year around warm weather and a definite dry season.

41. Humid subtropical A mid latitude climate, this type will experience long, hot summers and short, cool winters. Rainfall is usually between 40 and 60 inches per year. Some grasses, mixed forests, and tropical growth are present.

42. Humid continental This climate has deciduous and coniferous forests and experiences a dramatic range of temperatures throughout the year. Grasses also grow well. This is usually found in the mid latitudes.

43. mediterranean Long, hot summers and short, cool winters typify this mid latitude climate that usually appears close to water even though it is relatively dry. Palm trees and chaparral are common.

44. steppe A very hot and dry climate, one may experience a variety of grasses, deciduous trees, scrub brush, and cactus. Precipitation is between 10 and 20 inches per annually.

45. desert Common to this climate are very hot and dry conditions, although temperatures may be quite cold. Some scrub brush and cactus are common in these regions receiving less than 10 inches of precipitation annually.

46. Marine west coast A very wet climate, this type experiences relatively mild temperatures all year. Next to large bodies of water, it may have deciduous and coniferous trees.

47. taiga A mid latitude climate, this type experiences extremely cold and long winters. It is commonly recognized by its abundance of coniferous forests.

48. tundra This climate has very little vegetation due to extremely cold temperatures. The soil is frozen, and only mosses and lichen are likely to grow in this high latitude climate.

49. Ice cap This climate type is extremely cold. It is in the very high latitudes near the poles and has no vegetation because of the harsh temperatures. As implied by the name, this climate is typified by ice and snow with little or no habitation. MR. ADAMS LIKES POLAR BEARS!

50. Study this powerpoint! Tons of test information here