Transcript Weather
Weather & climate Chapter 16 & 17 Weather Factors H.W. pg. 461 1-4 Weather refers to the state of the atmosphere at a specific time and place One weather factor is air temperature. Temperature is a measure of the average amount of motion of molecules When the temperature is high, molecules in the air move faster and they feel warmer. Weather factors Wind- air moving in a specific direction is called wind. Wind results because air moves from high pressure systems (cold air) to low pressure systems (warm air). Wind is measured using a wind vane Dew point- temperature at which air is saturated and condensation forms is the dew point. This changes the amount of water vapor in the air. Weather factors Humidity- the amount of water vapor in the air is called humidity, and is evaporated water molecules. In cooler temperatures, water molecules stick together to form rain. In warmer weather, they move so fast, that they don’t get a chance to stick together. Relative humidity is the amount of water vapor present in the air compared to the amount needed for saturation at a specific temperature Cloud Formation Clouds are classified by shape and height. Stratus clouds- form layers or sheets of clouds in the sky at low altitudes. Fog is an example of a stratus cloud. Cumulus clouds- massive, puffy, white clouds with flat bases. They have great altitudes. Cirrus clouds- they appear fibrous or curly. They are thin, white and made of ice crystals and they can indicate an approaching storm. Nimbus clouds- these are clouds associated with snow. These clouds go up to 18km high. Stratus Cloud Cumulus Cloud Cirrus Cloud Weather Patterns Changes in weather are due to movements of air masses, which are large bodies of air that contain properties of the surface they developed over. Air masses over desserts will have less moisture than an air mass that forms over water. The boundary between two air masses of different moisture, temperature is called a front. A cold front is shown with a blue line with triangles. The cold air wedges under warmer air like a plow. That warm air is cooled, and the water vapor forms clouds. Weather Patterns Warm fronts are shown with a red line with semicircles. They form when lighter, warm air goes over colder air. Thunderstorms or hail occur in warm moist air masses, when warm air is forced upward by cool air. When the cold air lifts up the warm air, it causes parts of a cloud to become oppositely charged creating lightning. Thunder is the rapid heating of air around a bolt of lightning. Severe Weather Tornado- a violent rotating column of air in contact with the ground. They are due to severe storms that cause strong winds to blow in different directions. These winds cause the column to form. Hurricanes- large swirling, low pressure system that forms over warm Atlantic and Pacific Ocean water. A hurricane must have winds of at least 119km-hr. H.W. pg 478, 1-15 Katrina Weather Forecasts Meteorologist- a person who studies weather. They use a map called a station model. This model shows weather conditions over specific locations on Earths surface. Weather maps have isotherms, which are lines that connect points of equal temperature and isobars which connect points of equal atmospheric pressure. Isobars can also indicate wind speed and the movement of high and low pressure systems. H.W. pg 480, 1-20 Climate Climate is a pattern of weather that occurs in an area over many years(30). It helps determine plant and animal types that live in a certain area. The tropics is the region between latitude 23.5N and 23.5S. They receive the most solar radiation because the sun shines directly over them. That’s why the tropics have such hot temperatures. The polar zones extend from 66.5 N and 66.5 S latitude. Between the tropics and polar zones are temperature zones that have moderate temps. Climate changes The seasons are short periods of climatic change caused by changes in the amount of solar radiation an area receives. Throughout the year, Earth receives different amounts of radiation because the Earth is tilted. Tropic areas do not have much seasonal temperature change but do have dry and rainy seasons. Temperature zones have warm summers, cool winters, and mild spring and falls. Climate Change Climates can change due to atmospheric solids and liquids, like soil particles, automobile exhausts, and smoke stack emissions. These particles block solar radiation and cool the planet. Earths movements also affect climate. About every 41,000 years, the tilt of the earth changes +- 3 degrees. This can make summers hotter in some places and winters cooler in other places because it changes the amount of radiation absorbed in certain areas. Climate Changes Plate movement of the crust causes changes by affecting the transfer of heat on Earth which affects wind and precipitation patterns. The Greenhouse Effect is a natural heating process that occurs when certain gases in Earth’s atmosphere trap heat. This keeps the Earth warmer than what it otherwise would be. The gases include water vapor, CO2 and methane gas. Without them, life would not be possible on Earth. Global Warming Global warming is the increase in average global surface temperature. Over the past hundred years, the average global surface temperature has increased 0.6 degrees Celsius. This increase could cause glaciers to melt and sea levels to rise. Global warming also increases the CO2 levels in our air which could increase the average surface temperature of the Earth. H.W. pg 508, ques. 1-15.