2 Layers of the Atmosphere Troposphere (lowest layer)TropopauseStratosphereStratopauseMesosphereMesopauseThermosphere (highest km)
3 Composition of the troposphere Less than 2%H2O vapor (.01%-4%)Argon gas (1%)CO2 (0.04%)Trace gases
4 Structure & Temp of Atmosphere Look at Fig and Table 20-1Troposphere = lowest layer; tropics 10 miles (16km); higher altitudes 5 miles (8km)Water vapor & cloudsGreenhouse gasesColder w/ altitude (generally)Pollutants reach top w/in a few days
5 Structure & Temp of Atmosphere cont. Tropopause ---- separate Troposphere from stratosphereStratosphere- temp increases w/ altitude 40 miles- contains the ozone shield- Ozone absorbs UV radiation from the sun &filters the rays- No precipitation
6 Global warmingThe greenhouse effect is natural and important to keep the earth warm enough for life to existGlobal warming occurs when humans contribute too much of these greenhouse gases leading to a small (1-3 degree C) but significant rise in the global average temperature.Analogy – Car on a sunny day
12 Ozone (O3) Tropospheric ozone is BAD If we breath it, it causes lung damageIt is also a greenhouse gasStratospheric ozone is GOODIt shields us from the harmful UVB rays of the sun.Ozone depletion is the thinning of the stratospheric ozone shield (mostly over the South Pole)Analogy – Stratospheric O3 is like sunscreen for the earth.
13 The Making of Ozone O2 + UVB (280 – 320 nm more energetic) O + O The free O bonds to existing O2 (O + O2)Ozone is made (O3)O2 + UVB O + O ; O + O2 O3
15 The Destruction of Ozone CFC – chlorofluorocarbonsCl – FC (UV rays breaks bond)The free Cl “attacks ozone”O3 + Cl O2 + (Cl – O)Cl – O is unstable so the bond will break and the Cl will “attack” another ozone molecule