Chapter 1Introduction

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

What’s portrayed:

•Temperature

•Precipitation

•Cloud cover

•Air pressure (crudely only)

Also important:

•Wind

•Humidity

Weather is important

atmospheric conditions at

a point in time

Salt Lake City Temperatures Dec 07

Observed, Normals, Records

Temp. at one

place over time

(temp-erature “time

series”)

Salt Lake City Temperatures 2007 –Observed, Normals, Records

Temperature Measurement

Thermometer

Anemometers

Barometer

Thermometer

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

Where is the air?

• 50% below 6km altitude

• 90% below about 18km

• 0.00003% above 100km

Sealevel Pressure = 14.7 lb/in2 or 1013 mb or 29.9

inches (of mercury)Orem Pressure =12.5 lb/in2 or 855 mb

Composition of the Atmosphere Below ~ 80 km

altitude; Ionosphere exists higher

Nitrogen gas = N2

Oxygen gas = O2

= CO2

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

Examples include dust and air pollution

Aerosols are variable in concentration and location

Aerosols

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!

Troposphere

Stratosphere

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!)

Earth’s Four Spheres

Lithosphere

Atmosphere

Hydrosphere

Biosphere

The Earth System

Earth

Atmospheric Carbon Dioxide

Modern Atmospheric Greenhouse Gas Concentrations and Temperature

CH4

CO2

Temperature