2The AtmosphereThe atmosphere is the envelope of gases that surround our planetIt is a very thin layer compared to the radius of the Earth
3State of the Atmosphere We discuss and study the atmosphere in terms of the following variables:PressureTemperatureWindHumidityCloud coverPrecipitation type and amountVisibility (distance one can see horizontally)
4Weather vs. ClimateWeather is the state of the atmosphere at a particular time and a particular place.Climate is the long-term state of the atmosphere at a particular location.
5Atmospheric Composition Dry air (neglecting water vapor) is composed of the following gases:Nitrogen (N2) = 78%Oxygen (O2) = 21%Argon (Ar) = 1%Trace GasesDust, bacteria, and other particulates
6Atmospheric Composition Trace GasesGases that are only found by examining a million or billion air moleculesExamples include:Carbon Dioxide (CO2) = 340 ppmvNeon (Ne) = 18 ppmvHelium (He) = 5 ppmvMethane (CH4) = 2 ppmvHydrogen (H2) = 0.5 ppmv
7Composition of AirThere are many different types of gasses in the atmosphereThey include nitrogen, oxygen, argon, carbon dioxide and other noble gassesThe gas that is most abundant is nitrogen
8Vertical Layers of the Atmosphere The Earth’s atmosphere has 4 distinct layers that are identified by the way temperature changes with height. These layers are:- Troposphere- Stratosphere- Mesosphere- Thermosphere
9Vertical Layers of the Atmosphere (continued) Layers of the atmosphere are determined based on how temperature changes
11Troposphere This is the layer closest to the Earth’s surface Almost all the weather phenomenon we know of occurs in this layer.The depth of the troposphere varies by the season (deeper in summer)Temperature on average decreases with height.
13Stratosphere The next layer above the troposphere The boundary between the stratosphere and troposphere is called the tropopause.The ozone layer is found hereSome clouds can form here near the polesTemperature increases with heightVery little mixing occurs between the troposphere and stratosphere.
17ThermosphereThe thermosphere rests above the mesosphere, and no clouds exist.Temperature increases with height in the thermosphere.The highest temperatures for the atmosphere occur in the thermosphere, but it doesn’t feel hot because the atmosphere is so thin up there.
24Atmospheric DensityDensity and pressure in the atmosphere decrease exponentially with heightApproximately 75% of the total atmosphere is in the troposphereApproximately 99% of the atmosphere is the troposphere and stratosphere