The Earth’s Atmosphere Ch 10-11: An Overview

Overview of the Earth’s Atmosphere The atmosphere is a delicate life-giving blanket of air surrounding the Earth. Without the atmosphere the Earth would not have lakes or oceans. Radiant energy from the sun energizes the atmosphere driving day to day weather.

The Earth’s Atmosphere Composition 99% of the atmosphere is within 30km of the Earth’s surface. N2 78% and O2 21%, H2O vapors, etc. The percentages represent a constant amount of gas but cycles of destruction and production are constantly maintaining this amount.

Composition %

The Earth’s Atmosphere Composition Water is a variable gas following the hydrologic (H2O) cycle. Carbon dioxide has risen in recent years and is an important greenhouse gas. Other greenhouse gases exist beyond carbon dioxide. Ozone – surface, upper, large hole above Antarctica Aerosols (which damage ozone)

Ozone Layer

Vertical Structure of the Atmosphere Layers of the Atmosphere Troposphere: decrease in temperature, day to day weather, tropopause Stratosphere: increase in temperature, ozone, stratopause Mesosphere: decrease in temperature, mesopause Thermosphere: increase in temperature, suns strongest radiation

Weather and Climate Weather: short term air temperature, air pressure, humidity, clouds, precipitation, visibility, and wind Climate: long term patterns and average weather; not just magnitude but also frequency

Weather and Climate Meteorology Study of the atmosphere and its phenomena Aristotle 340 B.C. Meterologica, meteoros: high in air 1843 telegraph 1920s air masses 1940s upper air 1950s radar and computers 1960s satellite

Meteorologists Special Topic: Any person with a college degree in meteorology or atmospheric science; not just the TV weather person Half of 9000 meteorologists employed by the US National Weather Service Researchers and operational meteorologists

Weather and Climate Weather and Climate in Our Lives Two general reasons for studying how weather and climate impacts our lives: economic efficiency and public safety. Clothing Crops Utilities Extreme cold and heat Tornados and hurricanes

Weather & Climate A Look at the Weather Map Wind Wind direction Wind speed Front

Types of Weather Storms of All Sizes Middle-latitude cyclone Hurricane Thunderstorms Tornadoes

Local Temperature Variations Southern exposure: warmer, drier locations facing south. Implications for Vegetation Viniculture Ski slopes Landscaping Architecture

Why the Earth Has Seasons Earth revolves in elliptical path around the sun every 365.25 days. Earth rotates counterclockwise or eastward every 24 hours. Earth closest to Sun (147 million km) in January, farthest from Sun (152 million lm) in July Distance not the only factor impacting seasons

Why the Earth Has Seasons Seasons in the Northern Hemisphere Summer solstice: June 21, Sun directly above Tropic of Cancer, Northern Hemisphere days greater than 12 hours Winter solstice: December 21, Sun directly above Tropic of Capricorn, Northern Hemisphere days less than 12 hours Autumnal and Spring Equinox: September 22, Marc 20, Sun directly above Equator, all locations have a 12 hour day

Why the Earth Has Seasons Seasons in the Southern Hemisphere Opposite timing of Northern Hemisphere Closer to sun in summer but not significant difference from north due to: Greater amount of water absorbing heat Shorter season

Why the Earth Has Seasons Special Topic: First day of winter December 21 is the astronomical first day of winter, sun passes over the Tropic of Capricorn; not based on temperature