What is meteorology?? (and why should you care?).

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  • What is meteorology??(and why should you care?)

  • The American Meteorological Society defines a meteorologist as a person with specialized education "who uses scientific principles to explain, understand, observe, or forecast the earth's atmospheric phenomena and/or how the atmosphere affects the earth and life on the planet." meteorologyThe study of the physics, chemistry, and dynamics of the earth's atmosphere.

  • What do we mean by severe and unusual weather extremes?

  • Severe weather not only includes things like heavy thunderstorms, lightning, hail, flash floods, and tornadoes. . .

  • . . . but all kinds of hazardous weather

  • In addition to the day to day weather, some meteorologists study longer-term events like El Nio, the ozone hole, acid rain, and global warming

  • Some meteorologists study how dust from Africa can be deposited in Florida, or how changes on the Sun affect our atmosphere. Meteorologists study how destruction of rain forests or eruptions of volcanoes can change the composition of our atmosphere.

  • Europes main threats: flooding and heat

  • Extreme weather events are very costly. And have been increasing recently.

  • In other words, more than 98% of the atmosphere is nitrogen and oxygen

    **Water vapor, not displayed in this dry atmosphere chart, can occupy anywhere from 0 4 % volume, making it the most variable atmospheric constituentThe first thing we need to know is what the atmosphere is made of

    Percent composition of dry atmosphere, by volumeppmv: parts per million by volumeGasVolumeNitrogen (N2)78.084%Oxygen (O2)20.946%Argon (Ar)0.9340%Carbon dioxide (CO2)365 ppmv

  • Amount of carbon dioxide in the atmosphere has changed over timeCO2 acts as a greenhouse gasAs heat rises from earth surface, CO2 molecule absorbs it & prevents from escaping to spaceNet result: global warmingImpt. caveat: global warming is WAY more complicated than simply looking at chg of CO2 over timeAt Mauna Loa, CO2 increased in the last 40 yrs, coincident with avg. sfc. temp of earth increasing ~ 1C

  • *

  • The relative composition varies from place to place on the surface of the Earth. The reason for this variation is the presence of aerosols and water vapor - both of which vary widely in amount:

    Aerosols: either tiny liquid droplets, such as fog, or tiny solid particles, such as ice crystals, smoke, sea salt crystals, dust, and volcanic emissions, suspended in the air. Aerosols play very important roles in cloud formation more on that later!

  • Earths atmosphere probably had a very different composition when the planet first formed: the earliest atmosphere may have had a significant amount of hydrogen and helium these gases were probably lost to space early in Earth's history because Earth's gravity is not strong enough to hold lighter gases a secondary atmosphere probably formed from gases being emitted by volcanoes the gases produced were probably similar to those created by modern volcanoes (H2O, CO2, SO2, CO, N2, ) and NH3 (ammonia) and CH4 (methane) there was essentially no free O2 at this time (not found in volcanic gases)

  • The vast amounts of water vapor expelled by the volcanic earth resulted in the formation of clouds which, in turn, produced rain. Over a period of thousands of years, the rain accumulated as rivers and lake and ocean basins.

    The water reservoirs acted as sinks for the large amounts of carbon dioxide (as they do today) and through chemical and biological processes became locked up in sedimentary rocks as limestone.

    The nitrogen, which is not very chemically active continued to accumulate in the atmosphere.

  • While oxygen currently makes up about 21 percent of the atmosphere, there was only a trace in the air when life first appeared on the planet. Oxygen first appeared in the environment when early bacteria developed the ability to split water molecules apart by harnessing the energy of sunlight - a key part of photosynthesis. Photosynthesizing organisms produced the oxygen that accumulated over geologic time.

  • Next we need to know a little about the general structure of the atmosphere.

    Start with pressure.

  • Consider a column of air 1 inch2 in size extending from sea level to the top of the atmosphere:

    The weight (=mass X gravity) of the column of air will be about 14.7 lbs

    Hence, the pressure at sea level is = force/area = 14.7 lbs/inch2

    Sea-level pressure is also given in other units:14.7 lbs/inch2 1013.25 millibars 1013.25 hPa (hecto Pascals) 29.92 inches of Hg (mercury)

  • Atmospheric pressure decreases exponentially with height.

    50% of earths air lies in the lowest 6 kilometers (3.7 miles)

    Atmosphere officially extends up over 100 miles

  • Pressure is basically the weight of the air above a location so if youre location is sea level, you have the greatest atmospheric pressure. Pressure decreases exponentially with height (more air molecules are found in air at the surface than in the same volume of air aloft)

  • Short clip about meteorologists, weather men, hurricanes, and climate change

  • Atmosphere divided into different levels

    Meteorologists concern ourselves with the TROPOSPHERE


    Definition:TEMPERATURE INVERSION a layer of the atmosphere where the temperature increases with height

    Rule of thumb: the word pause indicates the top of a layer.

    Ozone is concentrated in the stratosphere

  • At the top of the troposphere is the tropopause, which marks the beginning of the temp. inversion of the stratosphereThus the tropopause acts as a good level for the top of buoyant clouds Note that thunderstorm clouds are tallest in the tropics

  • Interesting electromagnetic property of the atmosphere: at night ionosphere has different properties than during the day.

    Thus, short-wave radio waves (the AM frequency) can be reflected and travel long distances from America to Europe

  • We need to keep in mind a few simple rules:

    Warm air is less dense (lighter) than cold airHumid air is less dense than dry airLess dense air can be forced up over denser airAs air is forced upward, it cools and can form clouds and precipitation (if there is enough water vapor)The type of precipitation that falls will depend on the temperature of the air and the ground

  • In addition to forecasting the daily weather, some meteorologists study severe weather, and try to predict where it will occur

  • Meteorologists also study the past climate of our planet from the most recent ice age (about 12,000 years ago), to dinosaur extinction (65 million years ago), to a time when our planet might have been completely frozen (700 million years ago), and even back to the beginning of our planet

  • ORSome meteorologists also work to be able to better predict what our planet will be like in the future by studying the past

  • In short, meteorologists study the Earth system in an effort to help us better understand our planet, for both the short and long time-scales.

  • A few definitions we need to know:

    Temperature: measure of hotness or coolness of the air. Specifically a measure of the kinetic energy of an air molecule

    Pressure: the force of air above an area (remember, mass x gravity)

    Humidity: measure of amount of water vapor in the air