Lecture 2Outline of Last Lecture I. AtmosphereII. AerosolsIII. History of MeteorologyIV. WeatherV. ClimateVI. Observing WeatherVII. Wind DirectionOutline of Current Lecture VIII. MoleculesIX. Atmospheric PressureX. How much does air weigh?XI. Pressure and HeightXII. Air DensityXIII. Surface Weather MapXIV. Atmospheric TemperatureXV. TroposphereXVI. TropopauseXVII. StratosphereXVIII. MesosphereXIX. ThermosphereCurrent LectureXX. Moleculesa. molecules are in everythingi. you, me, the chairs, everythingATMS 100 1st Editionb. the more volume of air, the more molecules there are, thus the more it weighsXXI. Atmospheric pressurea. at the bottom of a column of air, there are the most moleculesi. greatest weightii. greatest pressureb. as you go up the column of air there are less and less molecules above you, so the weight of that pressure decreasesc. **atmospheric pressure decreases as we go up**XXII. How much does air weigh?a. depends on how many air molecules are in the air column b. pressurei. weight/areaii. force/areaiii. independent of the area of the columniv. **columns of air above lower elevations always weigh more than columns above higher elevations**XXIII. Pressure and Heighta. pressure change with altitude: 1 mb per 10 m (near surface)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. lower the pressure in the center, the stronger the stormi. go up about 850 m and average pressure is the same as in the eye of Hurricane Katrina at landfall1. because less pressure is above you c. pressure difference due to weather:i. varies day to day, but typically 30 mb or so across the USd. pressure difference due to elevation:i. roughly constant with time, about 300 mb between sea level and tops of highest mountainsXXIV. Air Densitya. gravity pulls most air molecules closest to surfaceb. density always decreases with heightc. density= mass/volume (kg/m^3)XXV. How do we measure pressure?a. barometersb. unitsi. millibars (mb)ii. pounds per square inchiii. inches of mercury (inHg)c. Mean sea-level pressurei. 1013.25ii. 29.92 in Hgiii. 14.7 lb/in^2XXVI. Surface Weather Mapsa. lower pressure generally means a stronger stormb. more molecules above highsc. fewer molecules above lowsd. on weather maps, pressures typically around 1000 mbe. pressure is typically between 950-1050XXVII. Atmospheric Temperaturea. we use temperature to divide the atmosphere into vertical layersb. lapse ratei. the rate at which the temperature decreases with heightc. inversioni. layer in which the temperature increases with heightXXVIII. Tropospherea. lowest layer (8-12 km deep) of the atmosphereb. contains all of the earth’s weatherc. temperature usually (but not always) decreases with heighti. sun heats ground, ground heats airXXIX. Tropopausea. marks the top of the troposphereb. about 8-12 km above surfacec. acts as lid on weatheri. inversion very stabled. level of jet streamsXXX. Stratospherea. temperature increases with height (inversion layer)b. ozone layeri. ozone absorbs UV radiation, warming stratospherec. if you looked up, you’d see black spaced. no well-defined “top of atmosphere”i. slowly fades to spaceXXXI. Mesospherea. name means “middle atmosphere”b. temperature decreases with heighti. lack of ozonec. air very thin < .1% of surface pressured. mesopause marks top of mesophereXXXII. Thermospherea. temperature increases with heighti. oxygen absorbs gamma rays and cosmic raysb. air is very thini. molecules can travel 1 km without running into eachotherii. you will