Atmosphere Weather and Climate

Atmosphere Weather and Climate

Weather and Climate Weather Atmospheric conditions at a particular time and place Climate Long-term average of weather conditions Often over decades or centuries

Coastal winds Caused by: Solar heating Different heat capacities of land and water Sea breeze (on- shore) Land breeze (off-shore) Fig. 6.13

Relative Humidity The amount of water vapor in a parcel of air, relative to the total amount of water vapor that the parcel of air could contain. Expressed as a percent. The dew point temperature is the temperature at 100% relative humidity.

Dew Point The temperature at which water vapor condenses into water droplets. When the relative humidity is 100%, the air is saturated with water vapor. Cooling will lead to condensation Heating will lead to lower RH

Adiabatic Lapse Rate As a parcel of air rises, it expands. The parcel s heat is distributed over a larger volume, so the temperature drops. General rule = 3.5 F per 1,000 feet

Relationships How do the lapse rate, relative humidity, and dew point interact with one another? What causes a parcel of air to rise?

Lows and Highs A low pressure area develops where warm moist air rises. As it rises, it cools Water vapor condenses Storms can develop. A high pressure area develops where cool dry air descends. As it descends, it warms Able to evaporate more water, lower RH Associated with fair weather

Cyclones and Anticyclones Northern hemisphere winds move counterclockwise (cyclonic) around a low pressure region Clockwise around a high pressure region Southern hemisphere winds move clockwise (anticyclonic)) around a low pressure region Counterclockwise around a high pressure region

Fronts and storms Air masses meet at fronts Storms typically develop at fronts Fig. 6.14

Fig. 6.15

Basic Cloud Types Cumulus - Latin for 'heap', to describe a puffy cloud Cirrus - Latin for 'curl of hair', to describe a wispy cloud Stratus - Latin for 'layer', to describe a sheet-like cloud Nimbus - Latin for 'violent rain', to describe a rain cloud.

Lightning

Basic Lightning Facts Around 100 strikes per second on Earth Can heat air up to 54,000 F Kills up to 2,000 people a year, about 50 in the U.S. Only 10% of those struck are killed.

Lightning

Photo by Roch Hart Albuquerque, NM

Tropical cyclones (hurricanes) Large rotating masses of low pressure Strong winds, torrential rain Classified by maximum sustained wind speed Fig. 6.16

Hurricane morphology and movement Northern Hemisphere Fig. 6.17

Damage from Hurricanes Fast winds (>74 mph) Flooding from torrential rains Spawned tornadoes Storm surge (most damaging force)

Fig. 6.18

Polar oceans and sea ice Sea ice or masses of frozen seawater form in high latitude oceans small needle-like like crystals >>>> Slush >>>> thin sheets >>>> pancake ice >>>> ice floes Rate of formation depends on temperature Salt nearly completely excluded during freezing

Polar oceans and sea ice How does this affect albedo? Fig. 6.21

Polar oceans and icebergs Icebergs fragments of glaciers or shelf ice Fig. 6-23

Greenhouse effect Fig. 6.24 Ultraviolet light from Sun passes through atmosphere (and glass) Surfaces convert UV radiation to infrared radiation (heat) Infrared can not pass through some gases (or glass)

Fig. 6.25 Earth s heat budget

Main greenhouse gases that trap infrared radiation: Water vapor Carbon dioxide (CO 2 ) Other trace gases: methane, nitrous oxide, ozone, and chlorofluorocarbons Fig. 6.26

Global warming over last 100 years Average global temperature has increased Part of warming due to anthropogenic greenhouse (heat-trapping) trapping) gases Climate models can not recreate observed changes when anthropogenic factors are excluded. That is, natural factors alone can not account for the observed changes.

Fig. 6.28 Fig. 6.29

Possible consequences of global warming Melting glaciers Shift in species distribution Warmer oceans More frequent and more intense storms Changes in deep ocean circulation Shifts in areas of rain/drought Rising sea level

Ocean s role in reducing CO 2 Oceans absorbs CO 2 from atmosphere CO 2 incorporated in organisms and carbonate shells (tests) Stored as biogenous calcareous sediments and fossil fuels Ocean becomes a repository or sink for CO

Impact of Excess CO 2 As CO 2 is dissolved in sea water, some is consumed by organisms and sediments. Excess CO 2 stays dissolved in sea water, causing a change in ph level it becomes less basic. Carbonates are not as readily available for organisms, and can lead to shell loss, making them more vulnerable.

Reducing greenhouse gases Greater fuel efficiency Alternative fuels Re-forestation Eliminate chlorofluorocarbons, other gases Reduce CO 2 emissions Add iron to tropical oceans to fertilize oceans (increase biologic productivity) Reduce, reuse, recycle

Costs of reducing greenhouse gases More expensive fuels (energy and transportation) More expensive products and services Is it even possible to reverse the trend if necessary steps are taken now?