Urban Climate

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Climate
October 22, 2012
Lecture learning objectives:
You should be able to:
• Describe the difference between climate and
weather
• Describe major climate factors
–
-radiation, albedo, energy budgets, wind and
atmospheric circulation, temperature, and moisture.
• Explain the differences between urban and forest
microclimates and what drives those differences.
• Identify indicators of climate change
Micro, meso, macro and megaclimate
Scale
Length
Area
Locale
Micro
1 m - 1 km
1m² - 1 km²
local
Meso
1 - 100 km
1 - 100 km²
regional
Macro
100 - 10 000 km
100 - 10 000 km² continental
Mega
>10 000 km
>10 000 km²
global
What is the difference between
weather and climate?
• Climate is what you expect
• Weather is what you get
Climate factors
• Radiation and albedo
• Energy budgets
• Wind – global circulation, high and low pressure
systems
• Temperature – effects of latitude and elevation,
greenhouse effect
• Moisture – types of precipitation, seasonal
distribution, latitudinal distribution, orographic
precipitation
Ecosystems use solar energy to
drive processes
• < 2 % of solar energy is used for photosynthesis
• Most goes into evaporating water.
• Heat balance, hydrologic cycle and climate are
strongly linked.
• Forests have 70% of leaf area on the Earth.
Radiation and albedo
• Forms of radiation
Ultraviolet, visible, infrared (heat)
short wave
long wave
http://serc.carleton.edu/images/eslabs
/weather/balance_diagram_simple.jpg
www.windows.ucar.edu/earth/Atmosphere/images/...
Albedo
Proportion of shortwave radiation that is
reflected (0-1 scale)
Albedos of different surfaces
Vegetation type
Albedo
Temperate forest
(summer)
0.12
(winter)
0.25
Tropical forest
0.07
Savanna
0.16
Field, grassland
0.16 (summer)
Desert
0.35
Ocean ice
0.5-0.7
Asphalt
0.04-.12
Color of the surface is important – white surfaces have the
highest albedos – dark surfaces (black) have the lowest
albedos
Species have different leaf strategies
with respect to radiation
• Species adjust leaf areas to capture light or handle heat loads.
• western hemlock (shade tolerant) has greater leaf area (m2
leaf/m2 of surface) than Douglas-fir (shade intolerant).
• Species like Noble fir have sun and shade needles.
• Eucalyptus leaves are vertical to reduce
heat load in a hot environment.
http://www.nps.gov/neri/naturescience/images/web_HWA_01.jpg
http://t1.gstatic.com/images?q=tbn:ANd9GcRcUJDJPOFyMWtGLbA-DNCe0QgQX7IC4Hw-mnLvdigIDHtZDFCUAxYAyNafZQ
http://www.cirrusimage.com/Trees/Eucalyptus_leaves.jpg
Global wind and
circulation patterns
Broadly predicts global to
continental climate
Nasa.gov
Local winds
Santa Ana Winds
USA Today
Mountain valley winds
http://t3.gstatic.com/images?q=tbn:ANd9GcTRZqSuMV9Rkd9MIIk-FqKXpexuhgPVn8Fiy0O1arw0od_gmz2rP778sCCH
Urban canyons (valleys)
Urban structure also
affects winds, albedo
and radiation
http://en.wikipedia.org/wiki/File:42nd_st_canyon.jpg
TEMPERATURE
INVERSIONS
Ag.arizona.edu
http://www.stuffintheair.com/images/Inversion_Smoke.jpg
apollo.lsc.vsc.edu
Temperature
Global temperatures are highest in tropics and
lowest at the poles
Lowest at highest elevation
Temperature at noon on field trip Oct 13, 2012
46 F
Stampede Pass
3965 feet
58 F
Seattle
100 feet
64 F
Ellensburg
1764 feet
Moisture – humidity and precipitation
Precipitation tends to be highest in tropics and lowest at the poles
Modified by mountain ranges that produce orographic
rainfall on the windward side of mountains and
rain shadows on the lee side of mountains
http://www.whymap.org/whymap/EN/Downloads/Additional_global_maps/precipitation_g.jpg?__blob=normal&v=3
3. Urban and Forest Microclimates
• Forest and urban trees modify the climate because of albedo and
energy budgets.
• Trees cool the environment (low albedo, high evapotranspiration,
low sensible heat)
• Concrete and dark asphalt surfaces heat the environment (high
albedo, no transpiration, low evaporation, high sensible heat.
The urban heat island effect
Clearcuts are hotter and colder than forests.
South slopes, particularly SW slopes are hotter and drier
than north slopes.
Steeper slopes are hotter.
www.arch.hku.hk
Mitigation of Urban Heat Islands
• Increase vegetative cover
• Use porous concrete surfaces
• Change the albedo of surfaces
PNW weather and climate are
dominated by two elements:
Pacific Ocean to the west
Mountain ranges that block and deflect
24
Average Rain Per Year
• Seattle: 37”
• New York City: 47”
• Miami: 56”
Number of Cloudy Days Per Year
Seattle: 228 (61%)
Houston: 166
Miami: 117 (31%)
25
East vs West Cascades
• Annual temperature range
– East side: varies by 60ºF between Jan-July
– West side: varies by 30ºF
• Precipitation range
– I-84 along Columbia River gorge: Rain forest near
Cascade Locks (80”/year) to arid environment
near The Dalles (13”/year) in just 45 miles
26
27
Most temperate forests are dominated by
broad-leaved deciduous trees
• If enough water to
support trees vs grasses
• Dormant during winter
• New leaves in spring
• Photosynthesis in wet
summer
28
PNW Ecosystems
Why do conifers dominate here?
• Short, cool summers
• Mild winters
• Precipitation mostly in
winter (75% between OctMar)
• Dry summers
29
Photosynthesis and Water Conservation are
opposites.
The Photosynthesis-Transpiration
Compromise: must open stomata to bring in
CO2 but in so doing, the plant loses water vapor
30
The PNW west-side Challenge
•
•
•
•
Optimum photosynthesis: warm and bright
PNW is warm and bright mid-July to mid-Sept
* These are the driest months *
Regulate stomatal opening to reduce water loss during
drought conditions
• Lose best opportunity for photosynthesis
31
Solution? Retain leaves and do
photosynthesis whenever possible
32
West  East
• Precipitation
drops off
rapidly east of
the passes
• Droughttolerant pines
and junipers
• Grassland and
desert
33
34
Global Climate Change
• Thin layer of atmosphere traps some of the
Sun’s energy and heat
• Problem = Thickening layer (“Greenhouse
gases”)
• Average global temperatures are rising
Instrument Data (thermometer records)
Global mean surface temperature anomaly 1850 to 2006 relative to 1961–1990
Hotter than normal
globally
• Hottest years on record in USA:
1934, 1998, and 2006
• Red=warmer than average
• 1934: hot in some areas; 1998 &
2006: globally hotter
Departure from normal temperatures
Image credit: U.S. Global Change Research Program (www.globalchange.gov).
Past warming trends
• From 1000-2000: 3 little blips (3 between
1000-1400 A.D.) before current trend
• Shorter duration and smaller magnitude
Indications of Global Climate Change
1. Glaciers are melting
2. Heat waves
3. Ocean temperature is rising
4. More powerful storms
5. Increased flooding
6. Drought (relocalization of precipitation)
7. Melting ice caps
8. Melting tundra
9. Tropical plants moving north
10. Insect infestations
11. Sea level is rising
And more
1. Glaciers are melting
1928
2004
Upsala Glacier in South American Andes in Argentina
- Retreating 180 feet per year
• The total
surface area
of glaciers
worldwide
has
decreased
by 50%
since the
end of the
19th century
What controls glacier changes?
Accumulation (snowfall, rainfall)
Temperature (summer/winter)
Dr. Michelle Koutnik (UW PhD ‘07)
2. Heat waves
• Heat wave in Europe 2003- killed 35,000
• Record-breaking heat in 2005 in many
American cities
– Hottest and longest duration above 100F
• Of the 21 hottest years on record (global), 20
within last 25 years
3. Ocean temperature is rising
• Cannot get the long
history of temperature
data
• Warming trend
• Since 1960’s, more
warm temperature
anomalies
4. More powerful storms
• Increased frequency
– 2004: Japan’s typhoons (10)
– U.S. severe hurricanes (Katrina)
– 2005: First time World Meteorological Society ran
out of names (27)
4. More powerful storms (cont.)
• Unusual places
– 2004: first hurricane in Brazil
• Previously thought impossible in South
Atlantic
Power of
hurricanes
correlates with
sea surface
temperature
5. Increased flooding
350
Number of Major Flood Events
300
250
200
Europe
Americas
Asia
150
100
50
0
19501959
19601969
19701979
Source: Millennium Ecosystem Assessment
19801989
19902000
6. Relocalization of precipitation
• Global precipitation increased by 20% in last
century
• But not evenly distributed
• Severe droughts
Changes in precipitation
• Amount, intensity, frequency, and type
• More in E North America, S South America, N
Europe
• Less in Mediterranean, Africa, and S Asia
• More rain and less snow in mountains
7. Melting ice caps
• Antarctica- frozen desert
• Losing land ice at rate of 31 billion tons of
water per year
• Ice shelves are breaking up
• Emperor penguin population declined 70% in
last 50 years
– Depends on stable sea ice
8. Melting Tundra
• Western Siberia is thawing
for the first time in 11,000
years
• Size of France + Germany
• Started to thaw only
recently
• Western Siberia temp
increasing faster than
anywhere else
9. Subtropical plants moving North
• Overwintering plants that normally don’t
survive
• Subtropical camellias in Pennsylvania
• Kudzu (fast-growing vine) moving north
• State Flowers of 28 states soon can’t grow
there
9. Plant zones are changing (cont.)
• Gardening maps are changing
– Many areas are a full zone warmer
– Some are two zones warmer than in 1990
10. Insects
• Beetles wiping out
forests in Canada
– Pine beetles kept in
check by cold
– 14 million acres of
bark beetle-infested
spruce trees
11. Sea level is rising
•
•
•
•
2000 years of little change
Rose 8” in last 100 years
Water expands as it warms
Melting glaciers and ice sheets
http://climate.noaa.gov/warmingworld/docs/WarmingWorldInteractive-04062012.ppt
Figure from NASA.gov
Climate Change in the PNW?
• Local simulations:
– largest warming on lower and middle mountain
slopes
– More cloudiness in spring in west side
– More rain and less snow
Impacts of these changes?
64
The 2007 IPCC report
Conclusions
• “Warming of the climate system is unequivocal, as is
now evident from observations of increases in global
average air and ocean temperatures, widespread
melting of snow and ice, and rising global average
sea level.”
• Eleven of the last 12 years (1995-2006) rank among
the 12 warmest years in the instrumental record
since 1850.
West Olym pic Coastal Division, Washington Tem perature(C)
Climate Division (01), 12 month period ending in December
12 month
period
11
Tem perature (C)
10 year
running mean
10
average
+sigma
9
-sigma
8
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Ending Year of Period
Cascade Mountains West Division, Washington Tem perature (C)
Climate Division (05), 12 month period ending in December
12 month period
Temperature (C)
10
9
10 year running
mean
8
average
7
6
-sigma
5
+sigma
4
1890
1900
1910
1920
1930
1940
1950
1960
Ending Year of Period
1970
1980
1990
2000
Temperature trends – WA, ID
WA
ID
Modeled predicted species changes
• Ponderosa pine will expand, Douglas-fir and
lodgepole pine will increase range
• Tree line in mountains will be much higher –
shrinking alpine zone. Engelmann spruce, Mt.
hemlock and Pacific silver ranges will be
reduced.
• Some desert species will expand
Lecture learning objectives:
You should be able to:
• Describe the difference between climate and
weather
• Describe major climate factors
–
-radiation, albedo, energy budgets, wind and
atmospheric circulation, temperature, and moisture.
• Explain the differences between urban and forest
microclimates and what drives those differences.
• Identify indicators of climate change
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