Chapter 1 Introduction Elements of Weather & Climate Composition of the Atmosphere Thermal Structure of the Atmosphere

Basic Elements of Weather & Climate Temperature Humidity Clouds Precipitation Air Pressure Wind

Hypothetical Winter Weather

Weather is important atmospheric conditions at a point in time What’s portrayed: Temperature Precipitation Cloud cover Air pressure (crudely only) Also important: Wind Humidity

Temp. at one place over time (temp-erature “time series”) Salt Lake City Temperatures Dec 07 Observed, Normals, Records

Salt Lake City Temperatures 2007 –Observed, Normals, Records

Temperature Measurement Thermometer

Anemometers

Thermometer Barometer

Tipping Bucket Rain Gauge

Thickness, Composition & Thermal Structure of the Atmosphere Thickness = pressure and density of air decrease with elevation Chemical composition = elements (gasses) that make up air and remain nearly constant (so ignoring water, aerosols [very fine dust], pollution) Thermal Structure = How temperature changes with elevation in the atmosphere

Atmosphere Thickness and Pressure Pressure is caused by weight of air above, so pressure decreases with altitude Pressure compresses air, so air becomes less dense or ‘thinner’ with altitude Atmosphere has no distinct top; it just becomes less and less dense until for practical purposes there is no air, above ~ 100 km Note: 1 km = 0.62 miles

Atmosphere Thickness and Pressure Sealevel Pressure = 14.7 lb/in2 or 1013 mb or 29.9 inches (of mercury) Orem Pressure = 12.5 lb/in2 or 855 mb Where is the air? 50% below 6km altitude 90% below about 18km 0.00003% above 100km

Composition of the Atmosphere Below ~ 80 km altitude; Ionosphere exists higher Oxygen gas = O2 Nitrogen gas = N2

Gasses in Dry Air N2 (‘Nitrogen’) – 78% O2 (‘Oxygen’) – 21% Ar (Argon)– 1% CO2 (Carbon dioxide) – 0.37% Ne (Neon), He (Helium), CH4 (Methane), Kr (Krypton), H2 (Hydrogen) – < 0.002%

Other, Variable Components of Air Water Vapor (H20) – 0 to 4% Aerosols (dust) Ozone (03) All are important!

Water on Earth

Aerosols Examples include dust and air pollution Aerosols are variable in concentration and location

Ionosphere Exists above ~ 80 km Radiation from Sun knocks electrons off gas molecules & atoms, ionizing them Ionosphere protects lower atmosphere from radiation by absorbing the energy (meaning we need it!)

Thermal Structure of the Atmosphere Temperature changes with altitude create 4 distinct layers to the atmosphere: Thermosphere – Above stratos.; T increase w/ height Mesosphere – Above stratosphere to ~ 90 km; T decreases w/ height Stratosphere – Above troposphere to ~ 50 km; T increases w/ height Troposphere – Ground to 10 – 15 km altitude; T decreases w/ height. Weather happens in this layer!

Temperature in Troposphere and lower Stratosphere

The Atmosphere Interacts With the Whole Earth

Weather affects many of our activities Weather events can be very expensive (droughts!) Weather can be deadly (droughts!)

Lithosphere Atmosphere Hydrosphere Biosphere Earth’s Four Spheres Lithosphere Atmosphere Hydrosphere Biosphere

The Earth System Earth

Atmospheric Carbon Dioxide

Modern Atmospheric Greenhouse Gas Concentrations and Temperature CH4 CO2 Modern Atmospheric Greenhouse Gas Concentrations and Temperature