The Atmosphere Chapter 11 Atmospheric basics Atmospheric composition

The Atmosphere Chapter 11

Atmospheric basics § Atmospheric composition – Permanent gases § 99% Nitrogen and Oxygen § 1% CO 2 Argon and H 2 O – Variable gases § Water vapor and Ozone vary place to place – Atmospheric particles § Dust, salt and ice

Atmospheric Layers § Troposphere – Closest to Earth – Where weather is found – Temp and altitude are inversely related § Stratosphere – Temp and altitude are directly related – Contains the ozone layer § Source of heat § Absorbs UV radiation

§ Mesosphere – Temp and altitude are inversely related – Little UV is absorbed here § Thermosphere – Temp and altitude are directly related § Due to lack of density of particles – Contains the ionosphere § Exosphere – Outermost layer – No definitive outer layer

Energy Transfer in the Atmosphere § Radiation – Transfer of thermal energy by electromagnetic waves – Touching does NOT happen § Conduction – Transfer of thermal energy when particles collide – Touch is REQUIRED § Convection – Transfer of thermal energy as heated fluids move – Has to be in a FLUID

Properties of the Atmosphere § Temperature – Measured in Celsius or Fahrenheit here in US § Air pressure – This is the downward force of the air molecules above you in the atmosphere – Measured in millibars (. 8 mm. Hg or. 03 in Hg) § Density – The amount of molecules in the air per unit of volume – Measured in kg/m 3

§ Pressure-temperature-density relationships – Pressure and temperature § At the same density, The greater the temperature, the greater the pressure – Pressure and density § At the same temperature, the greater the pressure the greater the density – Temperature and density § At the same pressure, the greater the temperature, the less the density

§ Temperature inversion – This is an increase in temperature with elevation in the troposphere – 1 possibility is rapid cooling of surface temperature – cold, clear, still winter night § This can negate the radiation of heat from the surface leaving the surface colder than the air above it. – Can lead to a hazy or dense foggy conditions – Pollutants can be trapped in this situation because it can’t escape the cold air

§ Wind – Pressure difference is the primary factor in wind movement § Wind moves from areas of higher pressure to areas of lower pressure § Temperature affects the density of the air and hence the pressure – Wind speed changes in the upper atmosphere § It speeds up because of lack of friction

§ Humidity – Saturation occurs when the amount of water vapor in the air is “maxed out” – Relative humidity is how much water is in the air vs. how much it can hold – Dew point is the temperature air must be cooled to reach saturation – Latent heat is the extra energy water vapor has that liquid water doesn’t have – change of state

Clouds and precipitation § Cloud formation – – – Clouds form when rising air carrying water vapor cools a condensation nucleus is required for the cloud to form. When there are enough droplets formed around the nucleus to be visible… a cloud is formed § Stable Air – Air is stable when it rises based on its thermal energy, then settles back into a position – This determines the type of cloud formation present § Unstable Air – Air that is surrounded by a cooler air – this forms thunder storm clouds

§ Atmospheric lifting – Orographic lifting occure when clouds lift over topography – a mountain – Convergence § This is where clouds approach from opposite directions. § Uplift occurs based on the temperatures of the air masses

§ Types of Clouds – Low clouds § Cumulus § Stratus – Middle clouds § Altocumulus § Altostratus – High clouds § Cirrus – Unstable air gives clouds a vertical build

§ Precipitation – Any water that falls from the sky § Water droplets must increase in size significantly in order to fall § Coalescence is one way this happens