I. Introduction

I. Introduction

A. weather
day-to-day changes in precipitation, temperature, cloudiness, and solar radiation

B. climate

weather of a locality averaged over 30 years plus extremes in weather behavior observed during the same period

II. Atmosphere

A. Composition - may vary from place to place and time to time
1. Pure dry air

a. 78% N₂ - space filler, nitrogen cycle, N2 - fixing bacteria

b. 21% O₂ - chemically very active - balance between intake by animals and release by plants

photosynthesis would provide enough for 2000 yrs even if all other sources ceased

c. 0.9% Ar

d. CO₂ - expect another 18% increase by 2000

50% absorbed by oceans

2. Water vapor - second major component

a. meteorologically most significant

b. 0% in desert & polar regions

c. 4 % in warm wet tropics

C. Dust particles and microscopic particles

D. water droplets or ice particles

E. Ozone (Dr. Kingston will cover this in detail later)

III. Density and Pressure

IV. Temperature

Environmental temperature lapse rate - 3.5° C/ 305 m

V. Structure

B. Layers and characteristics

1. troposphere
* thickness - 16 km in tropics, 9 km in polar region

* region of mixing air

* temperature decreases with altitude

* contains 75% of all gases

* clouds and precipitation

* storms

2. stratosphere - (9 km - 46 km)

* dry, thin air

* almost no air movement

* few clouds: nacreous (ice crystals)

* ozone layer

3. mesosphere (46 - 80 km)

* decrease in temperature - environmental temperature lapse rate: -100šC

* last layer with any significant density

4. thermosphere (80 km - 200 km)

* very thin air

* temperature rises - absorption of solar energy by oxygen and nitrogen: 1000šC

* electrically charged layer

* nitrogen and oxygen are ionized as they react with high-energy solar energy

* aurora borealis - result of solar flares - electrons generated by interaction between the solar wind and the magnetosphere generates ions that collide with atoms and molecules in the atmosphere - emit radiation: nitrogen - pink or magenta & oxygen - green

* magnetic storms

* reflects radio wave back to the Earth's surface

* end of atmosphere of gas

VI. Global Air Circulation

Factors Determining Patterns

1. long-term variation in amount of incoming solar energy
a. wobbling of Earth on its axis
b. shape of the orbit

2. differences in amount of solar radiation striking Earth's surface

3. pressure gradient

4. rotation of the Earth on its axis

PREVAILING WIND PATTERNS

VII. Ocean Circulation

1. drag of prevailing winds

2. land masses

a. act as barriers
upwellings

b. deflect currents and form clockwise gyres

3. Coriolis effect
a. deflect currents to right in northern hemisphere and to left in southern hemisphere

b. 0 deflection at equator

c. maximum at poles

Ocean Currents

VIII. Climate Influences

amount of solar radiation a point on the Earth's surface receives

B. Distribution of continents and ocean basins

1. atmospheric temperature over water is more uniform than over land
a. fewer temperature extremes

b. oceans tend to stabilize a climate

2. N. hemisphere vs S. hemisphere
a. northern hemisphere
1.) polar seas surrounded by continents

2.) 39% land and 61% ocean

b. southern hemisphere
1.) continent surrounded by ocean

2.) 19% land and 81% ocean

1. warmer currents increase temperature of air which passes over them

2. cold currents reduce temperature of air

environmental temperature lapse rate

e.g.: Mexico City - 2300 m: ave. temp. 16°C

e.g.: El Paso, Texas - lower elevation, 1600 km north 17°C

1. orographic precipitation

2. mountains channel path of air masses and storms

e.g.: Rocky Mountains, Himalaya Mountains

1. water surplus vs deficit (diagram of atmospheric circulation)

2. evaporation vs precipitation

IX. Climate Classification

classification according to vegetation communities and temperature and precipitation

B. Trewartha & Horn - 1980

1. 5 based on temperature

2. 1 based on precipitation

3. 1 applies to mountains

1. Tropical - not over 2 dry months, not < 18 °C

2. Dry - evaporation exceeds precipitation

a. encompasses a larger land area than any other single climate grouping - 30% of Earth's land surface

b. may be a latitudinal situation or rain shadow effect

3. Sub-tropical - 8 months > 10 °C, cool months, dry or humid

4. Temperate - 4 - 8 months > 10°C, greatest variation in seasons, temperature, and precipitation

5. Boreal - up to 3 months > 10°C, found only in northern hemisphere

summers are short and cool, and winters are long and bitterly cold

6. Polar - all months are < 10°C

precipitation mostly in form of snow, < 25 cm melts

7. Highland (mountain)

a. encompass a wide variety

b. factors are altitude, latitude, and exposure

c. every 300 m of elevation corresponds to a poleward advance of 500 km

X. Land Biomes

by precipitation, temperature, latitude, and altitude

B. Specific plant biomes

1. desert

2. grasslands

a. drought and fires prevent growth of forests

b. tropical

c. temperate - large, interior continental areas

pampas, prairies, veld (Africa), steppes (Europe)

d. polar - tundra

< 1% of world's vegetation because of permafrost

3. forests

a. tropical rainforests

b. temperate rainforests

c. temperate deciduous forests

d. boreal forests

The world's major terrestrial ecosystems.

freshwater lakes and reservoirs

Notes Table of Contents

Introduction to Environmental Science Home Page

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Revised 8/12/98