WHY STUDY THE ATMOSPHERE? The atmosphere is a major component of the Earth System, because it a. helps distribute energy over the Earth (moving air masses,major circulation patterns, origin of climatic deserts) b. is where weather is made (predict what weather will be tomorrow, next week, etc.; What should we wear?) c. controls how our homes and other buildings must be built (air conditioning, heating, insulation, etc.) CHANGES IN THE ATMOSPHERE CAN BE BENEFICIAL OR DEADLY. 2. Changing atmospheric conditions can cause major modifications in both weather and climate, affecting how and where humans can produce food. 3. Our atmosphere is unique in the solar system. Earth is the only planet on which we can survive without a space suit—we have evolved to function in our atmosphere, not on Mars or Venus.

Commonly Accepted Definitions Weather refers to the current atmospheric conditions (including temperature, precipitation, wind, humidity, barometric pressure) at a particular time and place. Climate refers to the general weather patterns expected in a given area (sometimes based on the 30 year average weather). Climate may also be applied more generally to large-scale weather patterns in time or space (e.g., an Ice Age climate or a tropical climate). Or, in the words of a middle school student… ……."climate tells you what clothes to buy, but weather tells you what clothes to wear."

Weather is made in the Troposphere

Pressure Density Altitude (km) Pressure (mb) 90 80 70 60 50 40 30 20 10 Pressure Density Altitude (km) 1 10 100` 1000 0.1 0.01 0.001 Pressure (mb) 10 1 0.1 .01 .001 .0001 .00001 Density (Kg/m3)

ORIGIN AND EVOLUTION OF THE ATMOSPHERE ● Early atmosphere [H, He, Ammonia (NH3) and Methane (CH4)] was driven away by solar radiation and lost by their low atomic masses ● Primordial Earth melted completely and gases bubbled out or erupted from early volcanoes. Result was a N-rich atmosphere ● Evolution of blue-green algae changed everything! Photosynthesis by these algae absorbed CO2 from the atmosphere and released O2 ● Most of that oxygen was dissolved in the oceans where it combined with iron and precipitated until about 2.5 billion years ago (2.5 Ga) to form iron oxides in banded iron formation ● At about 2.5 Ga, oceans were saturated with oxygen and free oxygen was added to the atmosphere. Resulting surface oxidation produced first redbeds on the continents. ●At about 1 Ga, reservoirs of oxidizable rock at the surface were saturated and oxygen began to build up in the atmosphere ● Ultraviolet light split O2 molecules forming ozone (O3) that shielded the surface from intense solar radiation. At that point, life could emerge from the ocean and colonize the continents.

EVOLUTION OF ATMOSPHERE OXYGEN CONTENT Billions of years before present Today 1.0 2.0 3.0 4.0 Cumulative oxygen production Rise of atmospheric O2 Little atmospheric O2 20 40 60 80 100 Redbeds Banded Iron formation

EVIDENCE FOR ATMOSPHERIC EVOLUTION COMES FROM THE GEOLOGIC RECORD Banded iron formation (3 Ga) Continental redbeds Until about 2.5—2.0Ga, there was not enough oxygen in the atmosphere to oxidize iron minerals. Oxygen dissolved in the oceans oxidized iron to produce marine banded iron formation. At 2.5—2.0 Ga, enough oxygen accumulated in the atmosphere to oxidize iron on the continents and the first redbeds formed.

Atmosphere Protocols Cloud type and cover Contrails Precipitation Precipitation pH Digital Max/Min/Current Air & Soil Temperature Surface Temperature Surface Ozone Aerosols Water Vapor Relative Humidity Barometric pressure Cloud Protocols also includes contrails. Precipitation Protocols includes both liquid and solid precipitation. Optional protocols include Automated Weather Station, Barometric Pressure, Automated Soil and Air Temperature Monitoring, and AWS Weathernet. These protocols are available on the GLOBE Web site (www.globe.gov).

Atmosphere Measurements The atmosphere measurements are components of each atmosphere protocol. For example, Cloud Protocols include cloud type, contrail type, percentage of cloud cover, and percentage of contrail cover. The atmosphere study site is usually located on school grounds within easy walking distance of your classroom so that students can take data in a minimum of time. The atmosphere study site must be defined prior to entering your atmosphere data. If you are taking measurements that require instruments, an instrument shelter will need to be set up. Where? Atmosphere Study Site