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Weather in Troposphere SHORT TERM PRESSURE , TEMPERATURE, MOISTURE CONDITIONS IN THE ATMOSPHERE REGENTS EARTH SCIENCE WITH MS. CONNERY Weather and climate result from temperature, pressure, and moisture in Earth’s atmosphere The external energy source that drives Earth’s weather and climate is… INSOLATION INCOMING SOLAR RADIATION RADIATION is energy transfer by waves CONDUCTION – energy transfer by direct molecule to molecule interaction (contact). Conductors (metals) do this well but insulators (air) don’t! Less dense floats up and takes energy with it More dense sinks down and heats up again CONVECTION - Energy transfer by density circulation. MOST IMPORTANT in WEATHER and CLIMATE To understand weather & climate you need to know relations among: temperature (kinetic energy of air molecules) pressure (force related to air’s composition and density) moisture (humidity in the atmosphere) And their role in the water cycle locally and around the globe! WATER CYCLE results from convection in the atmosphere infiltration Long-term latitude based convection of water cycle cause climate zones on Earth Equator http://www.cid.harvard.edu/ciddata/geog/GISfiles/kgzones_lrg.jpg Warm and cold currents in ocean circulation occur because of convection and effect climate PHASE CHANGE REVIEW! GAS PHASE CHANGE REVIEW! GAS Temperature = average kinetic energy of the molecules Pressure = force exerted by the molecules over an area. Related to density and composition of air. The range in air pressure typically found on Earth is ~ 960-1040 mb Weather and climate result from temperature, pressure, and moisture in Earth’s atmosphere Relation between altitude, air pressure, density, and gravity Humidity measures moisture in the air. What’s in the atmosphere? (ESRT p1)? “Other” Water vapor Carbon dioxide Methane Nitrous oxide Water (H2O) as vapor is less dense than nitrogen gas (N2) or oxygen gas (O2) so moist air masses rise in atmosphere Humidity (moisture) changes the density and pressure of an air mass. What is the density relationship between moist air and dry air? Which one creates higher pressure if it is more dense? What’s in the atmosphere? (ESRT p1)? Stratosphere has ozone layer that protects us from harmful UV and other short wavelength radiation “Other” are greenhouse gases Water vapor Carbon dioxide Methane Nitrous oxide Greenhouse effect is a general long term warming of the planet due to heat trapping in the atmosphere What are greenhouse gases and the greenhouse effect? Stratosphere has ozone layer that protects us from harmful UV and other short wavelength radiation What’s the first thing you think of when someone says weather around here? Cirrus = wispy ice clouds Cumulus = fluffy clouds stratus clouds = extensive layers NIMBUS CLOUDS = PRECIPITATION OCCURRING Cirro = high clouds (>6 km high) Cirrocumulus Cirrostratus Altocumulus (ALTO = mid level of about 3-6 km high) Altocumulus Altostratus LOW CLOUDS <3 km HAVE NO PREFIX Cumulus Fog Fog Cumulonimbus = unstable storm clouds Contrails = ice from plane exhaust MAJOR CLOUD TYPES CLOUD HEIGHT PREFIXES CIRRUS CIRRO- CUMULUS ALTOSTRATUS NIMBUS NO PREFIX CLOUD OBSERVATIONS Why are clouds named this way? Real World - Why does the size of an air mass change as it rises? Clouds form when water vapor (gas) in air condenses to liquid. Clouds form when the air mass cools to the dew point temp! How do we measure moisture in the air? Sling psychrometer a tool to measure the relative humidity & dew point temperature of the air Dew Point and Relative Humidity Dry Bulb Temp (oC) Wet Bulb Temp (oC) Wet-bulb Depression (oC) Dew Point Temp (oC) Relative Humidity (%) 1 2 - outside classroom oC oC oC oC 3 4 5 20oC 4oC 28oC 12oC -1oC 19oC SLING PSYCHROMETER tool that measures atmospheric moisture (humidity) & dew point temp Dry bulb measures air temperature Wet bulb some wet cotton on a thermometer that measure temperature after evaporation occurs What happens to the temps when you swing it? Why? Steps to determine relative humidity and/or dew point temp 1. Wet the cotton on the wet bulb 2. Sling the psychrometer until the values stabilize over two readings 3. Record the air temperature (dry bulb) 4. Record the wet bulb temp 5. Subtract (dry – wet temp) to find the wet bulb depression 6. Use the proper ESRT tables to find dew point temp and relative humidity Evaporation cools the air because the wet bulb temperature got lower when the water evaporated from the wet cloth condensation heats up the air because the energy is released from the water vapor molecule into the air as the water molecule cools from gas to a liquid. Reaching the dew point temp at higher altitudes shows energy transfer by convection – the water cycle! CONVECTION in a room There would be no weather without convection The external energy source that drives Earth’s weather and climate is… INSOLATION INCOMING SOLAR RADIATION What can happen to light energy (insolation) from the sun? 1. Absorbed – molecular capture of light energy from the sun 2. Reflected – light energy bounces off 3. Reradiated – absorbed light energy is converted from light heat and returned back to atmosphere in its new form of infrared Reference Table page 14 HEAT (INFRARED) RERADIATED BACK TO ATMOSPHERE and SPACE LIGHT FROM SUN! Uneven heating and cooling of earth’s surface drives convection! Ways air masses lift to get convection started - air masses have characteristics based on where they form at Earth’s surface - air masses get forced up at fronts - air masses get forced over mountains Air masses take on the temperature and moisture characteristics of the places where they form at high or low latitudes (temp) over land or sea (moisture) We already know that the angle of insolation affects temperature daily, seasonally, and at each latitude) Fronts are the leading edge of air masses. Fronts are where air is forced over another air mass and cools as the it rises up in altitude. That’s why there’s usually precipitation at fronts! Symbols used to show fronts on weather maps Fronts are boundaries of air masses with different temperature and moisture conditions A cold front advance is fast and furious – Think instability & BIG STORMS like thunderstorms and supercells with Tornadoes Warm front moves over cold front Occluded fronts : warm air mass squished between cold air masses Occluded front What happens after a front passes through an area? Remember – the prevailing wind direction drives the air mass forward The new air mass controls conditions once it arrives Temperatures change to whatever that air mass characteristics are Clearer skies likely when high pressure Generally less wind when high pressure In this lab you will use temp, winds, & air pressure to find the front boundaries and predict weather. Break the Pressure code Mid latitude cyclone: counter-clockwise Prevailing winds move storms along a typical path Why do the radial storm arms rotate around the low pressure system in a cyclone pattern (counter-clockwise) in the northern hemisphere? Coriolis Effect (curves because of Earth’s rotation) It’s same reason that the prevailing winds curve to the right in northern hemisphere, too! Coriolis Effect LAB 26 – CLIMATE How the oceans, atmosphere, and land respond to sun’s energy and moisture is what drives our weather & climate patterns on earth. Equator http://www.cid.harvard.edu/ciddata/geog/GISfiles/kgzones_lrg.jpg Latitude based convection affects climate Prevailing wind direction affects climate Warm and cold currents ( ocean circulation) affect climate Mountains affect climate because they force air up and down Forcing it over a mountain! PROPERTIES of MATERIALS on EARTH affect climate because they handle energy in different ways SPECIFIC HEAT is the property of a material that determines its ability to absorb and reradiate energy LAND and SEA are a good place to start SPECIFIC HEAT Energy needed to raise temp of 1g of mass by 1oC Land or sea? Which changed temp rapidly? It took less energy for the land to change temperature. Land is a good absorber and reradiator of energy. It does not store energy well. That’s what low specific heat means. SPECIFIC HEAT Energy needed to raise temp of 1g of mass by 1oC Sea changed temp slowly. It took more energy for the sea to change temperature. Water is a poor absorber and reradiator of energy. It stores energy well. That’s what high specific heat means. What does this material difference in rate of heating and cooling cause? What happens at the beach during the day when the land absorbs energy faster than the water? What happens at the beach at night when the land reradiates heat faster than the water? LAB 26 – CLIMATE How the oceans, atmosphere, and land respond to sun’s energy and moisture is what drives our weather & climate patterns on earth.