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Weather Study Guide Heat transfer: When heat is transferred from one piece of matter to another Conduction: transfer of heat between substances that are in direct contact with each other, the better the conductor, the more rapidly heat will transfer Convection: the up and down movement of gases and liquids caused by heat transfer – due to density Radiation: electromagnetic waves travel through space, it is called radiation. When the waves come in contact with an object, the waves transfer the heat to that object Light: form of electromagnetic energy made up tiny bundles of energy Light travels in waves Electromagnetic Spectrum Different wavelengths = different kinds of waves Longer wavelengths are less harmful Visible light: light we can see Form of radiation Reflection: bouncing of a wave after striking a barrier Refraction: bending of a wave as it moves from one medium to another Water gains energy when it is getting hotter Water loses energy when it is getting colder Energy is gained or lost when water changes phases Transpiration: evaporation of water from the stems or leaves of plants Reminder: Water vapor Liquid: Condensation Liquid Water Vapor: Evaporation Liquid Ice: Freezing Ice Liquid: Melting Specific heat: amount of energy needed to raise 1 gram of a substance one degree (highest specific heat is liquid water so water doesn’t heat up easily or cool down easily) Humidity and Dew Point Humidity: water vapor in the atmosphere Controlled by how much water The Atmosphere Troposphere: lowest layer; what we breathe; weather happens here Stratosphere: second layer; airplanes travel here; contains the ozone layer Mesosphere: third layer Thermosphere: fourth layer Exosphere: last layer, mostly empty space In between the layers… Tropopause: Division between troposphere and stratosphere Stratopause: Division between stratosphere and mesosphere Mesopause: Division between mesophere and thermosphere Air Masses and Fronts Air mass: large body of air, in it temperature and moisture levels are similar is evaporating The hotter the temperature, the more water evaporates, so the humidity is higher When the rate of condensation and evaporation is equal, the air is saturated When the air is “full” – meaning no more water can evaporate into the air Dew: if the air is saturated, water vapor comes out of the air as dew (it’s the water you find on leaves/grass in the morning – without it raining) Dew point: the temperature where condensation and evaporation are equal (the air is completely saturated) At temperatures below the dew point, condensation (liquid water droplets) form Relative humidity: the ratio of the amount of water vapor in the air to the amount of water vapor needed to reach saturation at a given temperature (how close the air is to dew point or saturation) Psychrometer: tool used to measure humidity, has two thermometer bulbs One bulb is dry, one is wet Use the difference to calculate the relative humidity Wet bulb temperature is always lower Atmospheric pressure: the pressure exerted (put) on the surface by the atmosphere (the gas in the atmosphere), exerted equally in all directions (up, down, and sideways) Atmospheric pressure decreases as altitudes increases Air pressure changes with differences in temperature and the amount of water vapor in air As temperature increases, pressure at sea level decreases As the amount of water vapor increases, pressure at sea level decreases Pressure measured with barometers Unit = mb (millibars) o Air masses take the properties of the area of the Earth they are over Air masses over land are continental (c) o Dry, form over large landmasses Air masses over oceans are maritime (m) o Moist, formed over large bodies of water Air masses formed over warm areas (closer to equator) are tropical (T) Air masses formed over cold regions are polar (P) Four main kinds of air masses: cP, cT, mP, mT There is also an arctic air mass that covers the poles Cold front: cold air mass overtakes a warm air mass, lifts warm mass, often creates short but violent storms Warm front: when a cold air mass retreats (leaves) from an area, less dense air rises over it, generally causes precipitation and sometimes violent weather Stationary front: when the meeting air masses move very slowly or not at all Occluded front: forms when a cold air mass overtakes a warm air mass and lifts the warm air mass off the ground and over another mass (involves three masses) Pressure differences in the atmosphere cause the movement of air worldwide – air moves from high pressure regions to low pressure regions High pressure regions: where cold air sinks towards the surface, wind (or air) moves outwards, clockwise and outward Low pressure regions: where warm air rises away from the surface, wind moves inward and counterclockwise Wind always moves from areas of high to low pressure The bigger the difference in pressure, the stronger the wind Thunderstorm: a usually brief, heavy storm, that consists of rain, strong winds, lightning, and thunder Hurricane: a severe storm that develops over tropical oceans and whose strong winds of more than 120 km/h spiral in towards the intensely lowpressure storm center (the eye) Tornado: a destructive, rotating column of air that has very high wind speeds and that maybe visible as a funnel shaped cloud Ways to prepare for a hurricane Have food prepared Have a place to hide/evacuation route Have emergency supplies ready: water, flashlights etc Clouds form when small water droplets or ice crystals suspended in the air gather around pieces of dust or salt or ice; formed by condensation Stratus cloud: flat uniform base, form at low altitudes Cumulus: look like cotton balls, fluffy, low level Cirrus: feathery cloud made of ice crystals that has the highest altitude Fog: condensation formed at low altitudes (similar to really low clouds) Station model: states weather conditions in a specific location, can be recorded on a weather map Weather map: shows weather conditions using symbols, colors, and isobars (isobar = line of equal AIR PRESSURE) When isobars are close together, the wind is stronger (the map of air pressure that looks like a contour map) Wind direction is measured with a wind vane Wind speed is measured with an anemometer 3 zones, or wind systems in each hemisphere; direction describes where the wind comes from Polar easterlies Prevailing westerlies Trade winds Coriolis effect: the Earth rotating causes the wind to curve Jet stream: small band/stream of fast wind Adiabatic cooling: the process by which the temperature of an air mass decreases as the air mass rises and expands As air rises and goes over a mountain it expands and cools down Global Warming CO2 and methane contribute to global warming There has been an increase in CO2 due to human activity, started 100 years ago with the Industrial Revolution What could happen if global warming increases the temperature? The ice caps would melt and the sea level would rise What can we do? Decrease our use of fossil fuels – save electricity! Use renewable sources of energy like solar energy Ocean Currents Also follow convection! (warmer ocean water rises, cooler sinks) Follows the same patterns as global wind patterns