Air Pollution

1
Chapter 13

• Air Pollution

2
Meteorology - Driving Processes

• Heat from the Sun
• Latitude/Orientation
• Rotation
• Heat transfer/conversion
• In Sum - induce expansion, compression, heat
  exchange and interaction of the atmosphere with
  the earths surface.

3
Pressure

• Differences in Pressure induce motion

4
Turbulence

• Mechanical Turbulence
• Random fluctuation in wind speed and direction
• Cause wind flowing past objects, 0 at surface,
  increases with elevation
• Higher speed ---- greater turbulence
• More turbulence -- more dispersion of pollutants
• Thermal turbulence
• Heating the ground --- heats air --- less dense
  air rises

5
Stability - Dry Adiabatic Lapse Rate

• Related to
• wind speed (we have not dealt with it in this
  course!)
• changes in air temperature with height
• Dry Adiabatic Lapse Rate (?)
• The rate of temperature decrease with elevation
  equals -1.00?C/100m
• Evaluate stability by comparing ambient lapse
  rate to ?

6
Neutral (Adiabatic) - Ambient ?

• Neutral stability - thermal structure doesnt
  affect mechanical turbulence

7
Unstable (Superadiabatic)- ambient gt ?

• Unstable air - mechanical turbulence enhanced by
  thermal structure - characterized by cyclones
  (low-pressure areas)

8
Stable (Subadiabatic)-ambient lt ?

• Stable air - mechanical turbulence inhibited by
  thermal structure -- characterized by
  anticyclones (high-pressure)

9
Special Subadiabatic Lapse Rates

• Isothermal - no change in temperature with
  elevation
• Inversion - temperature increases with elevation
• Condition often associated with pollution
  episodes due to restricted air volumes
• Radiative, advective, subsiding air

10
Terrain Effects on Stability

• Heat Islands (cities, large industrial sites)
• atmosphere less stable than over farm land
• Good news - ground level pollutants diluted
• Bad news - smoke stack emissions mix more and
  some may come to ground in city
• Land/sea breezes
• Land heats/cools more rapidly than water
• Night - offshore breeze
• Day - onshore breeze
• Valley breezes

11
Factors That Affect Pollutant Dispersion

• Emission point characteristics
• Nature of pollutants
• Meteorological conditions (wind, stability,
  temperature, precipitation, humidity..)
• Effects of terrain and structures

12
Chapter 15

• World Climates

13
Weather versus Climate

• Weather occurs in the troposphere from day to
  day and week to week. It is the state of the
  atmosphere at a particular location and moment
  in time.
• http//weathereye.kgan.com/cadet/climate/climate_
  vs.html
• http//apollo.lsc.vsc.edu/classes/met130/notes/ch
  apter1/wea_clim.html

14
Weather versus Climate

• Climate is the sum of weather trends over long
  periods of time (centuries or even thousands of
  years).
• http//calspace.ucsd.edu/virtualmuseum/climatecha
  nge1/07_1.shtml

15
What we are going to learn?

• We are going to learn the answers to the
  following questions
• What are the factors that regulate global
  climate?
• How climates are classified?
• What are the different types of climate?
• What are micro-, macro- and meso-climates?

16
Climate

• Climate Statistics of the day-to-day weather
  over a long duration
• Microclimate Small climatic region near or on
  the ground
• Mesoclimate Climate of a small area of the
  earths surface
• Macroclimate Climate of a much larger area
  (state or a country)
• Global Climate Climate extending over the entire
  earth
• Two important weather elements temperature
  precipitation
• Climate Controls are
• Intensity of sunshine and its latitudinal
  variations
• Ocean currents and thermohaline circulation
  systems
• Relative distribution of land and water
• Air masses
• Wind intensity and direction
• Position of high- and low-pressure areas
• Land surface including topography (e.g. Mountain
  barriers, Altitude)

17
Natural Climatic Forcing

• Natural climatic forcing refers to naturally
  occurring factors that affect global
  temperatures. These include, but are not limited
  to
• 1. Volcanic eruptions
• 2. Variations in the Suns output
• 3. Milankovitch Cycles
• 4. Natural variations in concentrations of CO2
  and other greenhouse gases

18
Volcanic Eruptions

• Volcanic eruptions may impact global climate.
• 1. Reduces the amount of short wave radiation
  reaching Earths surface
• 2. Reduces the temperature of the troposphere
• 3. Increases climatic variability
• http//www.cotf.edu/ete/modules/volcanoes/vclimat
  e.html
• http//earthobservatory.nasa.gov/Study/Volcano/

19
Variation in Solar Output

• Extremely accurate satellite measurements of the
  Suns energy output indicate that solar
  variability may be as much as 0.1 over an 18
  month period.
• A variation of 1 would cause the average global
  temperature to change by 1oC. This may be a cause
  of the current increase in hurricane activity.
• http//vathena.arc.nasa.gov/curric/space/solterr/
  output.html
• http//news.google.com/news?qsolaroutputhlen
  lrsaNtabnnoinewsr

20
Milankovitch Cycles

• Milankovitch identified three cyclical changes
  he believed relevant to climate change
• 1. Orbital eccentricity 100,000 year cycle
• 2. Axial Tilt 42,000 year cycle
• 3. Precession 19,000 - 23,000 year cycle
• http//deschutes.gso.uri.edu/rutherfo/milankovit
  ch.html
• http//www.homepage.montana.edu/geol445/hypergla
  c/time1/milankov.htm

21
Milankovitch Cycles

• To support his hypo-thesis, Milankovitch
  calculated the dates when these variations
  combined to minimize and maximize solar radiation
  over hun-dreds of thousands of years.
• The dates coincided with the ice ages.
• http//deschutes.gso.uri.edu/rutherfo/milankovit
  ch.html
• http//www.homepage.montana.edu/geol445/hypergla
  c/time1/milankov.htm

22
Natural Variationin Greenhouse Gases

• Natural variations in the concentration of
  greenhouse gases can and do occur.
• 1. CO2 is not the only greenhouse gas.
• 2. H2O is the major green- house gas.
• 3. High levels of CO2 are associated with
  global warming and low levels are associated
  with global cooling.
• http//www.agu.org/eos_elec/99148e.html
• http//yosemite.epa.gov/OAR/globalwarming.nsf/con
  tent/Emissions.html
• http//www.ghgonline.org/

23
Global Temperatures
24
Global temperatures (cont.)

• Isotherms are oriented East-West (same latitude
  locations receive same amount of solar energy)
• Bending of isotherms along the coastal margins is
  partly due to the unequal heating cooling of
  land water
• Variation in temperature between summer and
  winter will be far greater over continental
  interiors than along the west coastal margins of
  continents climates of interior continental
  regions will be more extreme (higher summer temp
  and lower winter temp) than their counterparts in
  the west coast west coast climates are typically
  quite mild for their latitude
• Highest mean temperatures do not occur in the
  tropics, but rather, in the subtropical deserts
  of the Northern Hemisphere

25
Global Temperatures (cont.)

• Lowest mean temperatures occur over large land
  masses at high latitudes coldest areas of the
  world is the Antarctic
• Snow and ice reflect 80 of the sunlight that
  reaches the surface much of the absorbed solar
  energy is used to transform the ice and snow into
  water vapor
• Southern hemisphere is cooler than Northern
  Hemisphere because
• Cold Antarctic
• Polar regions of the southern hemisphere reflect
  more incoming sunlight
• Less land area found in the tropical and
  subtropical areas

26
Global Precipitation

• Global distribution of precipitation is closely
  tied to the general circulation of the atmosphere
  and to the distribution of mountain ranges high
  plateaus
• Equatorial regions are typically wet, while the
  subtropics and the polar regions are relatively
  dry
• Precipitation is most abundant where the air
  rises least abundant where it sinks
• In tropical regions, the trade winds converge
  along the ITCZ producing rising air --- heavy
  precipitation all year long near 30 deg, the
  sinking air of the subtropical highs produces a
  dry belt around the globe presence of Sahara
  Desert of North Africa in this region

27
Annual global pattern of precipitation
28
Vertical cross section along a line running N-S
illustrating main global regions of rising and
sinking air
29
Global climate (cont.)

• Hottest places on earth generally occur in the
  subtropical deserts of the Northern Hemisphere,
  where clear skies and sinking air produce clear
  skies and scorching heat
• Coldest places on earth tend to occur in the
  interior of high-latitude land masses The
  coldest areas of the Northern Hemisphere are
  found in the interior of Siberia and Greenland
  coldest area of the world is Antarctic
• Wettest places in the world are located on the
  windward side of mountains where warm, humid air
  rises upslope
• Driest places in the world are located on the
  leeward (downwind) side of mountains where air
  parcels undergo drying and compressional heating
  rain shadow

30
Variations in annual precipitation for three
Northern Hemisphere cities
31
Effect of topography on average annual
precipitation along a line from the Pacific Ocean
through CA and western Nevada
32
Key to map of precipitation records thoughout the
world

• Key

33
Some precipitation records

• .

34
Köppen Classification System

• The Köppen Classification System is the most
  widely accepted system for classifying world
  climates.
• This system is based on certain plant
  assem-blages that correlate temperature with
  precipi-tation the major determinants of
  climate.
• The original system recognized five major climate
  types, labeled A through E, running in broad
  bands from equator to poles.
• http//geography.about.com/library/weekly/aa01170
  0a.htm
• http//www.squ1.com/index.php?http//www.squ1.com
  /climate/koppen.html
• http//www.geofictie.nl/ctkoppen.htm

35
Köppen Classification System
36
Major Climate Regions of the WorldKöppen System
37
The Köppen System (group A)

• Tropical Moist Climate (A) Monthly average temp
  above 18C no real winter season and year around
  warm temp. abundant rainfall (gt150 cm) extends
  from equator to 15-25 N or S
• Examples Amazon lowland of South America, the
  Congo River Basin of Africa, and the East Indies
  from Sumatra to New Guinea

38
Major Climate Regions of the WorldKöppen System
39
Group A (cont.)

• High temperature and abundant rainfall --- dense,
  broadleaf, evergreen forest tropical rain
  forest with vegetation abundant sunlight allows
  for the growth of tangled shrubs forming
  impenetrable jungle
• Major types are tropical wet (Af) and tropical
  monsoon (Am) and tropical wet and dry (Aw)
• Tropical wet climate seasonal temperature
  variations are lt 3 C greater variation in
  temperature between day night (diurnal, average
  high 32C average low 22C) than annual
  temperature variation
• towering cumulus clouds form every day to produce
  heavy, localized showers in the afternoon annual
  rainfall gt 150 cm (windward side can exceed 400
  cm/yr)
• high humidity cloud cover tend to keep maximum
  temp from reaching very high values

40
Temperature and Precipitation data for Peru
(latitude 4S tropical wet climate, Af)
41
Climate A Type (cont.)

• In Peru, monthly rainfall variations are more
  than the temperatures --- due to migrating
  position of the intertropical convergence zone
  (ITCZ) associated wind patterns
• Laterite A soil formed under tropical conditions
  where heavy rainfall leaches soluble minerals
  from the soils leaving soil hard and poor for
  growing crops
• Tropical Monsoon Climate When precipitation
  totals drop below 6 cm for perhaps one or two
  months a tropical climate with a brief dry
  period of perhaps one or two months examples
  coasts of southeast Asia, India, and in
  northeastern South America

42
Climate A Type (cont.)

• Tropical wet and dry climate (Aw) Distinct dry
  season prevails annual rainfall gt100 cm, but
  monthly rainfall for more than 2 months is lt6 cm
  --- rainforests cannot survive to this drought
  giving rise to coarse savanna grass, scattered
  with low, drought-resistant deciduous trees
• Examples of Aw climate are western Central
  America, north and south of the Amazon Basin
  (South America), southcentral Asia and northern
  Australia

43
Climate data for Timbo, Guinea (11N) tropical
wet-and-dry climate (Aw)
44
Dry Climates (Group B)

• Dry Climate Evaporation (E) Transpiration (T)
  gt Precipitation (P)
• Subtropical deserts extend from 15-30 (often
  surrounded by mountains)
• 26 of land area falls in this group
• Major types Arid (BW 12 of the land) and
  Semi-arid (BS 14 of the land)
• Arid region is divided as follows
• a) BWh or BSh Climate is hot dry with a mean
  annual T gt 18C
• b) BWk or BSk Climate is cold (in winter) and
  dry with mean annual T lt 18C
• Examples for Arid region West coast of South
  America, Africa and over much of the interior of
  Australia
• Most of the native plants are xerophytes (capable
  of surviving prolonged periods of drought)

45
Rain streamers (virga) in dry climates, as
falling rain evaporates into the drier air
beneath the cloud
46
Bushes and cactus found in the arid southwestern
American deserts (BWh)
47
Dry climate B (cont.)

• In low-latitude deserts (BWh),
• maximum daytime during the summer can gt50C
  (40-45C) are more common) RH in the middle of
  the day 5-25
• minimum T can drop below 25C
• Mid-latitude deserts (BWk)
• Summer maximum temp reaches 40C
• Winters are extremely cold with minimum temp
  below -35C
• Lie in the rain shadow of an extensive mountain
  chain (Sierra Nevada and Cascade mountains in
  North America), Himalayan mountains and Andes in
  South America
• Around the margins of the arid regions, where
  rainfall amounts are greater, the climate is
  gradually changes into semi-arid (BS)
• examples Most of the Great Plains, southern
  coastal sections of California, northern
  valleys of the Great Basin annual precipitation
  20-40 cm examples are Denver, Colorado

48
Arid (BWh) Climate Phoenix, AZ (33.5N)
49
Cumulus clouds in a semi-arid climate (BS) in
Western North America
50
Climatic data for Denver, CO (40N) a semi-arid
climate (BSk)
51
Moist subtropical mid-latitude climates (Group C)

• Humid with mild winters with the average temp of
  the coldest month -3C to 18C commonly found on
  the eastern and western regions of most
  continents, 25-40 latitude
• Major types Humid subtropical (Cfa), marine
  (Cfb) and dry-summer subtropical or Mediterranean
  (Cs)
• Humid subtropical climate (Cfa) Found
  principally along the east coasts of continents,
  25-40 latitude
• summer is hot and muggy summer dew-point temp
  and RH are high (exceeding 23C)
• In winters, frost, snow, and ice storms are more
  common, but heavy snowfalls are rare
• Rainfall 800-1650 mm/yr, fairly well distributed
  annually

52
Climatic data for Mobile, Alabama (30N) a
humid subtropical climate (Cfa)
53
Moist subtropical - Marine

• Marine (Cfb) Along western side of most
  continents from 40 to 60 winds from the oceans
  moderate the climate summers are quite cool
• Low annual temperature range in high latitude
  region oceans influence keeps daily temp
  ranges low
• Coastal Mediterranean Climate Precipitation
  300-900 mm/yr summer afternoon temperatures
  climb above 34C and occasionally above 40C

54
Climatic data for Port Hardy, Canada (51N)
marine climate
55
Comparison of a coastal Mediterranean climate
(Csb San Francisco) with an interior
Mediterranean climate (Csa) Sacromento
56
Moist Continental Climates (Group-D)

• Warm-to-cool summers and cold winters warmest
  month average temp gt10C coldest monthly
  average temp drops below -3C D climates are
  controlled by large land masses found only in
  the Northern hemisphere D climates extend across
  North America and Eurasia (40 - 70N)
• Major types
• Humid continental with hot summers (Dfa long and
  hot summer mid-day temp exceed 32C nights are
  usually warm humid),
• Humid continental with cool summers (Dfb less
  humid temp can exceed 35C) and subpolar (Dfe)

57
Comparison of a humid continental hot summer
climate, Dfa (Des Moines) with a humid
continental cool summer climate (Winnepeg)
58
Subpolar climate (Dfc) Fairbanks, AK (65N)
winters are severe, summers are short cool, 1-3
months exceed mean temp of 10C
59
Polar Climate Group E

• Year-round low temp (average temp of the warmest
  month lt 10C), but above freezing
• Two major types Polar tundra (ET) and Polar ice
  caps (EF)
• Polar tundra ground is permanently frozen
  (Permafrost)
• Annual precipitation lt 200 mm (in lower
  latitudes, would constitute desert, but in the
  cold polar regions, evaporation rates are very
  low and moisture is adequate)
• Polar ice cap Temp for every month is below
  freezing, plant growth is impossible the region
  is covered with snow and ice Greenland and
  Antarctica precipitation lt 100 mm/yr

60
Climate data for Barrow, Alaska (71N) polar
tundra climate (ET)
61
Climatic data for Eismitte, Greenland (71N)
polar ice cap climate 3000 m above MSL (EF)
62
Highland Climates (Group H)

• Varying climate with altitude 300 m elevation
  is equivalent to traveling 300 km northward (3N)
• Ascending on a mountain, one can travel through
  many climatic regions in a relatively short
  distance
• Elevation in the central Sierra Nevada
• Base of the mountain semi-arid conditions
• foothills Mediterranean and the vegetation
  changes
• higher elevations subpolar and vegetation
  changes
• near the summit, permanent patches of ice and
  snow, with some glaciers (in less than 4 km),
• the climate has changed from semi-arid to polar

63
Vertical view of changing vegetation and climate
due to elevation in the central Sierra Nevada