WEATHER AND CLIMATE

WEATHER

• Refers to the conditions in the atmosphere at a given place and time

• Changes from hour to hour and day to day– Temperature– Atmospheric (barometric)

pressure– Precipitation– Wind– Humidity– Cloudiness

WEATHER• Results from interactions

between leading edges of moving warm and cold air masses called fronts

• Warm front—warm air replacing cooler air– Less dense air rising over

cold. Acts as a moisture condenser forming clouds

– Clouds thicken, descend, then rain

• Cold front—cold replacing warm– Stays close to ground

producing rapidly moving towering clouds (thunderheads)

WEATHER• Also affected by changes in

atmospheric pressure• Greater at surface• High pressure—cool dense

air descends becoming warmer. Generally, clear cool weather

• Low pressure—low density, air rises warmer air expands and cools causing condensation forming clouds. Generally, cloudy stormy weather

WEATHER

• Relative humidity—amt. of water vapor in the air compared to the max. amt the air can hold at a specific temp.

• Dew point—temp. at which water vapor saturates from an air mass into liquid or solid. Occurs at 100% humidity

CLIMATE• Average weather conditions

that occur over a period of years

• Changes slowly over hundreds or thousands of years– Temperature—average and

extremes– Precipitation—averages,

seasonal, distribution– Also includes wind, humidity,

fog, cloud cover—seasonal and yearly variations

CLIMATE• Wladimir Köppen developed system for classifying

climates– Divided into 6 zones—humid equatorial, humid temperate,

humid cold, dry, cold polar, and highland climate

CLIMATE CHANGE

• Measurements showed CO2 levels went from 315 ppm in 1958 to 383 ppm in 2006

• Every May levels drop slightly as plant growth occurs but rises again in the winter

CLIMATE CHANGE

• Surface temp increased by .6⁰C over past cent w/ most in past 2 decades

• Greenhouse gases have increased– CO2 by 31%

– CH4 by 151%

– N2O by 17%

AIR POLLUTION

• Not counting CO2 and soil• Americans release 147

metric tons of air pollution/yr. Worldwide 2 billion tons

• Air quality has improved over past 20 yrs

• 1990 regulation of most hazardous materials began reducing emissions by 1 million tons/yr

AIR POLLUTION

• Conventional pollutants—7 major pollutants– SO2, CO, particulates,

NOx, ozone (O3), lead, volatile organic compounds (VOC’s)

– Ozone—released from by combustion. Interacts with UV radiation. Affects lung function

SOURCES & PROBLEMS

• SO2—colorless corrosive gas. Damages plants and animals.

• NOx—highly reactive gases formed by combustion. Gives smog its color part of acid rain

• CO—colorless and odorless, highly toxic. Inhibits respiration

SOURCES & PROBLEMS• Particulates—dust, ash, soot,

lint, smoke, pollen. Leaves residue damaging tissues

• VOC’s—organic gases from plants, bogs, termites. Forms photochemical oxidants and makes ozone

• Lead &other toxic elements—lead, mercury, arsenic. Highly reactive damaging nervous system

EFFECTS OF AIR POLLUTION• Breathing polluted air

increases heart attacks, respiratory disease and lung cancer

• A 5-10 yr decrease in life expectancy if you live in highly polluted areas (LA & Baltimore)

• Bronchitis & Emphysema common conditions– Accts for 50,000 deaths

EFFECTS OF AIR POLLUTION

• Plants are extremely sensitive

• SO2 & sulfuric acid destroys tissues

• Cell membranes damaged

• Chlorophyll destroyed• Metabolism, growth &

development disrupted

EFFECTS OF AIR POLLUTION

• Smog & haze reduces visibility– Without visibility would

reach 150 km (90 mi) instead of the 15 km (9mi) we are used to

• Acid Rain damages plants, lowers pH, destroys buildings & monuments