Meteorology Notes.ppt

Meteorology Notes General Information Weather Weather is the condition in the atmosphere at a given place and time. It includes temperature, atmospheric pressure, precipitation, cloudiness, humidity, and wind. Climate Climate is the average weather conditions that occur in a place over a period...

Meteorology Notes General Information Weather Weather is the condition in the atmosphere at a given place and time. It includes temperature, atmospheric pressure, precipitation, cloudiness, humidity, and wind. Climate Climate is the average weather conditions that occur in a place over a period of years. The two most important factors are temperature and precipitation. Composition of the Atmosphere Components – Oxygen 21%, Nitrogen 78% Layers – troposphere, stratosphere, mesosphere, thermosphere, exosphere (extends from 310 miles to interplanetary space) Composition of the Atmosphere (cont.) Primary Pollutants – methane, ozone, dust particles, microorganisms, and chlorofluorocarbons (CFC’s) Causes of Primary Pollutants – factories, cars, wind and soil, volcanoes, forest fires, pollen, decaying plants, salt particles from the sea, and refrigerants. Seasons The Earth’s 23.5 degree incline on its axis remains the same as it travels around the sun. As the earth spins around the sun the seasons change. Heat Transfer Conduction Warm air holds more moisture than cold air. During conduction, heat & moisture from the ocean or land moves into the atmosphere. Ex. cold air moving over warm water (like a lake), forming steam fog. Heat Transfer Convection This causes rising air currents and leads to cloud formation. It takes heat from the lower atmosphere to the higher atmosphere where pressure is less, causing air to expand, which in turn cools the air. The air cannot hold as much moisture because it is cooler, so clouds form (condensation). Heat Transfer Radiation Radiation drives weather. Heat from the sun warms the earth, which radiates the heat back into the atmosphere. Solar Radiation Scattering As the sun hits the earth, molecules are scattered into the air. This changes the direction of the heat coming in. Some are scattered back to space, but others are absorbed. Scattering is what makes the sky blue. Solar Radiation Albedo The proportional reflectance of the Earth’s surface. Ex, glaciers and ice sheets have a high albedo and reflect 80-90% of the sunlight hitting them, but asphalt and buildings have low albedos and reflect 1015%, and oceans and forests reflect only about 5%. Solar Radiation Absorption 70% of the solar radiation that falls on Earth is absorbed and runs the water cycle, drives winds and ocean currents, powers photosynthesis, and warms the planet. Solar Radiation Control of Temperature When there isn’t a lot of moisture in the atmosphere & it’s a clear night, we have a large temperature drop (like in the desert), but when there is a blanket of clouds, the temperature stay uniform. Solar Radiation Isotherms “Iso” means equal; this is a line drawn on a weather map of equal temperatures. Water Vapor in the Atmosphere Importance Life! It also makes weather possible. Earth would be like Mars if there was no water vapor. Humidity Specific (absolute) The amount of water vapor found in a certain mass of air, and is expressed as grams of water per kilogram of air. Relative Humidity The amount of water vapor in a certain mass of air, expressed as a % of the maximum amount it could hold at that temperature. Humidity Measurement A relative humidity of 60% at 80°F means that each kilogram of air contain 60% of the maximum amount of water it could hold at that temperature. Humidity Dew Point The temperature at which condensation occurs. Cloud Formation Methods Results from a cooling of water vapor. Types of Clouds Cirrus These are high clouds, appearing from about 20,000 feet on up. They are so cold that cirrus clouds are composed of ice crystals rather than water droplets. Types of Clouds Stratus Stratus clouds come in layers or broad sheets, and are more or less uniform in contour and color. Types of Clouds Cumulus (cauliflower clouds) These build up vertically. The tops are usually domeshaped, with billows, and their bottoms are flat. Precipitation Rain/Drizzle Rain and drizzle consist of water condensed in the atmosphere. Snow Precipitation Snow is solid precipitation in the form of soft, white, crystalline flakes, formed by the freezing of water vapor in the atmosphere. Sleet Precipitation This is precipitation consisting of ice pellets, smaller than hail, formed by the freezing or partial freezing of rain. Hail Precipitation This is small, usually round pieces of layered ice that fall in a shower, especially during thunderstorms. Rime Precipitation Rime is frost, as on grass or trees. Air Pressure Definition Air pressure is pressure exerted by the weight of Earth’s atmosphere. At sea level it is equal to 14.69 pounds per square inch. Air Pressure Measurement A barometer is used to measure atmospheric pressure. Air Pressure Isobars These are the lines of equal pressure on a map. It makes it possible to understand wind patterns and many other aspects of weather. Air Pressure Pressure Gradient This changes from high to low. On a map there is an arrow to show this. A higher pressure gradient means stronger winds (the isobars on a weather map would be drawn closer together). Cause Wind Wind is caused by the pressure gradient force. High pressure means more air, and low pressure means less air. The air moves from high to low, causing wind. Wind The Coriolis Effect Forces in the atmosphere, created by the rotation of the Earth on its axis, that deflect winds to the right in the N. Hemisphere and to the left in the S.Hemisphere. Friction Wind This is a combination of the pressure gradient force and the coriolis effect. Friction at the Earth’s surface causes winds to turn a little. Friction runs parallel to the isobar. Wind Upper Level Flow There is little friction up in the upper troposphere, driving surface features. Ex. during big thunderstorms, the wind in the upper level will tell which way the thunderstorm will move. Cyclones Wind (called hurricanes in the Atlantic and typhoons in the Pacific) Violent storms that form over warm ocean waters and can pass over coastal land. Giant, rotating storms with winds of at least 74 mph. The most powerful ones have wind velocities greater than 155 mph. Wind Anticyclones An extensive system of winds spiraling outward from a high-pressure center, circling clockwise in the N. Hemisphere and counter-clockwise in the S. Hemisphere. Circulation Patterns Hadley Cells Wind that rises at the equator. As air rises, it spreads out north & south, then cools and sinks at 30 degrees. This is why most of the world’s deserts are found at 30 degrees. These are called the horse latitudes because early settlers would get stuck here in their boats & couldn’t move. They would finally throw their horses overboard to lighten the load & get moving again. Circulation Patterns Convection Cells Ocean water transfers heat to the atmosphere, especially near the hot equator. This creates convection cells that transport heat and water from one area to another. The resulting convection cells circulate air, heat, and moisture both vertically and from place-to-place in the troposphere, leading to different climates & patterns of vegetation. Circulation Patterns Polar Cells Air rises at about 60 degrees, floats south, and sinks at around 30 degrees, both north and south. Sea Breeze These are ocean-to-land breezes that occur during the day. Land Breeze These are land-to-ocean breezes that occur at night. Valley Breeze As the wind blows from the plains into a valley between two mountains, the wind must divert into a smaller area. This causes high winds to form through the valleys. Mountain Breeze Cool air coming from the top of the mountain sinks down on the eastern slope, causing increased winds on the mountain. Chinook A moist, warm wind that blows from the sea to the coast. Air Masses and Storms Polar vs. Tropical The atmosphere has three prevailing winds. Prevailing winds that blow from the northeast near the North Pole or from the southeast near the South Pole are called polar easterlies. Tropical winds that blow from the northeast in the N. Hemisphere or from the southeast in the S. Hemisphere are called trade winds. Air Masses and Storms Continental vs. Maritime Continental fronts are generally cool and dry, whereas maritime (ocean) fronts are generally warm and moist. When these two air masses converge, the result is usually rain. Warm Front Weather The boundary between an advancing warm air mass and the cooler one it is replacing. Because warm air is less dense than cool air, an advancing warm front will rise up over a mass of cool air. Cool Front The leading edge of an advancing air mass of cold air. Because cool air is more dense than warm air, an advancing cold front stays close to the ground and wedges underneath less dense, warmer air. A cold front produces rapidly moving, towering clouds called thunderheads. Stationary Front A stationary front is a transitional zone between two nearly stationary air masses of different density. Occluded Front An occluded front is the air front established when a cold front occludes (prevents the passage of) a warm front. Storms Thunderstorms Characteristics Thunderstorms have high, cumulonimbus clouds that can reach 50,000 feet. An updraft of warm air causes cold air to rush downwards. This is why you feel a sudden cold breeze right before a thunderstorm. Lightening causes the ozone smell. Problems •Problems include rain, flooding, hail, lightening, high winds, and loss of life can occur. Tornadoes Characteristics Tornadoes are a powerful, rotating funnel of air associated with severe thunderstorms. Tornadoes form when a mass of cool, dry air collides with warm, humid air, producing a strong updraft of spinning air on the underside of a cloud. It is a tornado if the spinning air descends and touches the ground. Tornadoes Problems They can destroy buildings, bridges, and freight trains, and even blow the water out of a river or small lake, leaving it empty. Tornadoes also kill people; more than 10,000 people in the U.S. died in tornadoes in the 20th century. They are most common in the Great Plains and Midwestern states (especially Texas, Oklahoma, and Kansas), as well as states along the Gulf of Mexico. Hurricanes Characteristics Hurricanes are giant, rotating tropical storms with winds of at least 74 miles per hour, with some reaching 155 miles per hour. They form as strong winds pick up moisture over warm surface waters of the tropical ocean and start to spin as a result of the rotation of the Earth. The spinning causes an upward spiral of massive clouds as air is pulled upward. Hurricanes Problems These are destructive when they hit land, not so much from strong winds as from resultant storm surges, but waves that rise as much as 25 feet above the ocean surface. These can damage property and result in loss of life. Climate Types Wet Tropics This is near the equator, with hot, moisture rich air that rises and dumps its moisture. Warm annual temperatures, high humidity and heavy, almost daily rainfall. Climate Types Tropical Wet an Dry (Ex. Hawaii) This is where one side of the island is very wet and the other side is dry. Climate Types Low Latitude Desert and Steppes (grassland) Ex. Calahari desert, a desert in Chili where you get little rain. Climate Types Mid-Latitude Desert and Steppes Ex. Pampas in South America, where there is still little rain. Climate Types Humid Subtropical Ex. Gulf Coast, where there is much rain, Climate Types Marine West Coast Ex. California, where it is warm, and moist air comes from the ocean. Climate Types Dry-summer Subtropics Ex. Northwestern Australia or Central Mexico’s lowlands. They have long, hot, dry summers. Climate Types Humid Continental Ex. England, where is is humid nearly year-round and very green. Climate Types Subarctic This area has long, cold winters, like in Northern Canada, Alaska, and Scandinavia. Climate Types Polar (tundra and ice cap) Ex. Iceland, which has long, cold winters. Climate Types Highland Climates This area has mountain tops.