2Heating the Earth Weather is the daily conditions of the atmosphere The factors that interact to cause weather are heat energy, air pressure, winds, and moisture
3Moisture in the AirWater vapor or moisture in the air is called humidityHumidity can vary from place to place and time to timeLatent heat is the amount of energy that is absorbed or released during a phase change.
4Absolute humidityThe mass of humidity contained in a certain amount of airabsolute humidity = mass of water vapor (g)volume of air m³
5Relative HumidityThe actual amount of water vapor in the air relative to the amount of water vapor needed to reach saturationrelative hum = amt. of H2O vapor in air X 100amt. of H2O vapor to saturationIf the temperature does not change and more moisture enters the air, RH goes up. If the temperature decreases RH goes up. If temperature goes down RH decreases.
6Dew PointWhen the air temperature and the dew point is the same 100% humidity occurs. This causes dew on cool objects. When the temperature is below freezing frost occurs.
7Measuring Relative Humidity Psychrometer has two thermometers, one dry and one wet. The difference in the temperature of the two will determinethe humidity using the table.
8Water Drop FormationWater needs to condense on a condensation nuclei
24PrecipitationWhen water vapor in the clouds becomes too heavy, it can fall as rain, sleet, snow, or hailCloud droplets must first increase in size until gravity pulls them downIf they pass through extremely cold layers of air, they can freeze and produce sleetSnow is formed when water vapor changes directly into a solidHail is formed when water droplets hit ice pellets
28Causes of Precipitation Coalescence is the formation of a large droplet by the combination of smaller droplets
29Measuring Rainfall A rain gauge is used to measure precipitation Snow usually is measured as 10” of snow = 1” of rain
30Doppler RadarThe intensity of precipitation can be measured using Doppler Radar which is the bouncing of radio waves off rain or snow.
31Weather Patterns: Air Masses Changes in the weather are caused by very large areas of air with specific temperature and humidity called air massesThere are four main air masses that affect the weather in the United StatesThey are named for the regions they originate in
33Maritime massesMaritime tropical air mass originates near the equator over the ocean, it brings warm moist air onto the continentMaritime polar air mass forms over the Pacific Ocean in both winter and summer, it forms over the North Atlantic and brings cold winter weather in the winter and cooler temperatures during the summer to the east coast
34Continental massesThe continental tropical forms over land in the Southwestern US it brings dry hot airThe continental polar mass forms over the land in Canada and brings very cold dry air into the US
35FrontsFronts form when large air masses meet that have different temperatures and humidityThe weather at a front is can be very unstable and stormyThere are four different types of fronts: cold front, warm front, occluded front, and stationary front
36Cold FrontA cold front forms when a mass of cold air pushes over a mass of warm airThe cold air pushes its way below the warm airViolent storms, even tornadoes can be associated with these frontFair, cooler, and drier air usually follows
44High PressureSome high pressure systems are associated with cold air systems that move in and change the weatherSubtropical high pressure systems are slow moving, usually bring very warm conditions
45Low Pressure SystemsLow pressure systems are associated with precipitation and a change to the weather for an extended timeLow pressure systems can bring rain or snowLow pressure systems can bring a sudden dramatic drop in temperatures
46Measuring Air Pressure A barometer measures the pressure of the airMercury BarometerAneroid Barometer
47WindsBoth local winds and global winds are caused by differences in air pressure due to unequal heating of the atmosphereIsobars that are closer together indicate stronger windsWinds travel from areas of high pressure to areas of low pressure
48Measuring WindWind is measured by an anemometer for speed and a weather vane for direction
49Storms A storm is a violent disturbance in the atmosphere It is marked by a sudden drop in pressureSome may cover a very large area
50Rainstorms and Snowstorms Caused when two different fronts collideWhen a warm front overrides a cold frontRain or snow occursDuring the winter, if the rain freezes it can cause an ice storm
55Cyclones and Anticyclones Areas of low pressure that contain rising warm air are cyclonesWinds spin in a counterclockwise inward movement with rain and stormsAreas of high pressure, cool and dry winds are anticyclonesWinds spin in a clockwise movement from the center outward
58Hurricanes Powerful cyclone Warm moist air begins to rise rapidly Cooler air moves in and the air begins to spinThe pressure in the center drops and more air rushes in causing the winds to spin fasterAir forms a doughnut shape wall of strong winds with a calm centerThese storms are accompanied with strong winds and a high storm surgeThese are the most powerful storms on Earth
62Tornadoes Whirling funnel shaped cloud Develops in heavy cumulonimbus cloudsAir pressure at the bottom is low so the funnel acts like a vacuum cleaningOccur in the spring and summer in the area called Tornado Alley
65Forecasting the Weather Just think the endis near!!!!
66Predicting the Weather Meteorologist is a person who studies and predicts the weatherThey interpret weather information from local weather observers, balloons, satellites, and weather stations around the world
67Weather MapsData from stations around the country is gathered and put on weather mapsThis includes temperature, air pressure, precipitation, and the wind speed and directionInformation about cloud cover, air masses, and fronts may be includedThe information is recorded by a number of symbols and numbers
71Controlling the Weather At the present time, weather control is limited to seeding of cloudsThis is done by placing dry ice or silver iodine crystals into the super cooled layers of the stratosphereThese cause large ice crystals to form that eventually fall as rain
72I know how you feel!!!!Nothing is wrongwith your eyes!!