metr112- global climate change: urban climate system
DESCRIPTION
METR112- Global Climate Change: Urban Climate System. Professor Menglin Jin San Jose State University. Outline: Urban observations Urban heat island effect Urban aerosol Urban rainfall. SF, 2008. Video: Urban Rainfall Effect. - PowerPoint PPT PresentationTRANSCRIPT
METR112- Global Climate Change:Urban Climate System
Professor Menglin JinSan Jose State University
Outline:
Urban observationsUrban heat island effectUrban aerosolUrban rainfall
Video: Urban Rainfall Effect
http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/urban%20system/
Urban Rainfall Effect.mp4
Video
• Observe urban system effect
http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/urban%20system/
Animation of Atlanta Tornado
•Urban is an extreme case of human-change natural land cover.
•Urban regions has strong pollution, greenhouse emission.
•60% people in USA live in cities
•Urban has unique water and heat cycles what directly affect human life
Why do we need to Study Urban regions?
Related Publications
Jin, M., J. M. Shepherd, M. D. King, 2005: Urban aerosols and their interaction with clouds and rainfall: A case study for New York and Houston. J. Geophysical Research, 110, D10S20, doi:10.1029/2004JD005081.
Jin, M, R. E. Dickinson, and D-L. Zhang, 2005: The footprint of urban areas on global climate as characterized by
MODIS. Journal of Climate, vol. 18, No. 10, pages 1551-1565
Jin, M. and J. M. Shepherd, 2005: On including urban landscape in land surface model – How can satellite data help? Bull. AMS, vol 86, No. 5, 681-689.
Jin, M. J. M. Shepherd, and Christa Peters-Lidard, 2007: Development of A Parameterization For Simulating the Urban Temperature Hazard Using Satellite Observations In Climate Model in press by Natural Hazards.
Jin, M. and M. J. Shepherd, 2007: Aerosol effects on clouds and rainfall: urban vs. ocean. Revised for JGR
% of Land Area Built-up3 - 6%
43% of Land Area Dominated by Agriculture
% of Land Area Built-up3 - 6%
43% of Land Area Dominated by Agriculture
1. Satellite remote sensing on urban regions
MODIS land coverRed color means urban built-up
Night Light of Tokyo
Night Light of Paris
pictures made by U.S. Defense Meteorological Satellites Program (DMSP)
The Afternoon SatellitesThe Afternoon Satellites“A-Train” of Earth Observing System “A-Train” of Earth Observing System
(EOS)(EOS)
The Afternoon constellation consists of 7 U.S. and international Earth Science satellites that fly within approximately 30 minutes of each other to enable coordinated science
The joint measurements provide an unprecedented sensor system for Earth observations Courtesy of M. King
Aura
Launched July 15, 2004 Is the stratospheric ozone layer recovering? What are the processes controlling air quality? How is the Earth’s climate changing?
HIRDLS
TES
MLS
OMI
Satellite measurements show unique features of
Land cover – urbanization coverageSurface Temperature – Urban Heat Island EffectVegetation coverageEmissivityAlbedo
CloudsRainfallAerosol
•Urban Surface
•Atmosphere
Satellite observations retrieve urban system: Land surface properties: surface temperature, surface albedo, emissivity, soil moisture, vegetation cover
Atmosphere conditions: aerosol, clouds, and rainfall
urbanization significantly changes weather and climate
It shows that
Urban Heat Island Effect (UHI)
This phenomenon describes urban and suburban temperatures that are 2 to 10°F (1 to 6°C) hotter than nearby rural areas.
UHI impacts:
Elevated temperatures can impact communities by increasing peak energy demand, air conditioning costs, air pollution levels, and heat-related illness and mortality
High temperature also enhances surface convection, and causes more clouds and rainfall
Urban Heat Island Effect (UHI): Urban surface is hotter than that of surrounding non-urban regions
Surface temperature
We need to understand why and what are UHI effects
Dr. Menglin Jin San Jose State University
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
Urbanization Effects
Land Surface Energy Budget:
EOS MODIS observed monthly mean daytime shows evident urban heat island effect (Copied from Jin et al, 2005a). The red areas show the dense building regions of Beijing.
Urbanization impacts on skin temperature
10°C !!!
50km
Local Urbanization changes surface temperature
Urban heat island effectDaytime Nighttime
50km 50km
MODIS
Jin et al. 2005 J. of Climate
MODIS Observed Global urban heat island effect
Comparison of skin temperaturefor urban and nearby forests
MODIS
Cities have higher Tskin
than forests
Urbanization changes surface albedo (MODIS)
Urban surface albedo has a 4-6% decrease -> more solar radiation will be absorbed at surface\increase surface temperature
Urbanization reduces surface emissivity (MODIS)
(Jin et al. 2005, J. of Climate)
Urban reduces surface emissivity ->Less longwave radiation emitted from surface More heat is kept at surfaceSurface temperature increases
MODIS15_A2 Leaf Area Index (LAI) over Houston regions
Often times, urban regions reduce surface vegetation cover
Existing Coupled Land-Atmosphere Models:Coarse Resolution, Biogeophysics Focus
BARE SOIL: 15%
10%
GRASSLAND:50%
SHRUBS:
NEEDLELEAFTREES: 25%
e.g., CLM: (NCAR, DAO) NOAH: (NCEP)
Turbulence production
Urban thermal properties
Radiation trapping
Radiation attenuation
Canopy heating & cooling
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
Simulate Urbanization to Examine Its Effects
Land Surface Energy Budget:
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
2. How to Simulate Urban?
Urbanization Modifies Surface Energy Budget:
Urban add new physical processes
What Can be Done ?to reduce negative Urban heat island effects?
Education : a key component of many heat island reduction effort
Cool Roofs: Over 90% of the roofs in the United States are dark-colored. These low-reflectance surfaces reach temperatures of 150 to 190°F (66 to 88°C)
Trees and Vegetation
Cool Pavements
Cool Roofs
Cool roof systems with high reflectance and emittance stay up to 70°F (39°C) cooler than traditional materials during peak summer weather.
The Utah Olympic Oval uses cool roof technology.
What Is a "Cool Roof"?
Cool roof materials have two important surface properties: •a high solar reflectance – or albedo
•a high thermal emittance
Solar reflectance is the percentage of solar energy that is reflected by a surface. Thermal emittance is defined as the percentage of energy a material can radiate away after it is absorbed.
3. Urban Aerosols and Their Direct Effects on Clouds, Surface Insolation, and Surface Temperature
Video
• Urban aerosol effect on rainfall
http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/urban%20system/
Summer Precip w-Pollution.mp4
Winter Precip w-Pollution.mp4
July 2005
NASA MODIS observed Aerosol Distribution
Urban Pollution Sources
Traffic
Industry
Indoor warming
Aerosols are solid/liquid particles pending in atmosphere
Size -0.01-100μm
Residence time – hours-days
Indirect Effect: serve as CCN
Cloud dropRain dropIce crystalIce precipitation
Aerosol Direct Effect: Scattering Absorb
0oC
surface
Black carbon heats atmosphere and surfaceMost aerosols cool surface
More aerosol ->small cloud effective radius->high cloud albedo->cooling (Kaufmann and Koren 2006)
More aerosol->reduce rainfall (Rosenfeld 2000)
Aerosol Dynamic Effect: Reduce Wind and Precipitation
surface
“aerosolized particles created from vehicle exhaust and other contaminants can accumulate in the atmosphere and reduce the speed of winds closer to the Earth's surface, which results in less wind power available for wind-turbine electricity and also in reduced precipitation…”
(Jacobson and Kaufmann 2006)
wind
3.2. Remote Sensing of Aerosol Properties
3.2. Remote Sensing of Aerosol Properties
• International satellite sensors enabling remote sensing of tropospheric aerosols– AVHRR, TOMS, ATSR-2, OCTS,
POLDER, SeaWiFS, MISR, MODIS, AATSR, MERIS, GLI, and OMI
Michael King, NASA GSFC
Aerosol-Cloud Relation
AOD vs. water cloud effective radius
More aerosols lead to smaller cloud droplets!
Total solar radiation decreased by aerosol= 20Wm-2
(Jin, Shepherd, and King, 2005, JGR)
Aerosol decreases surface insolation
Based on NASA GMAO radiative transfer model
par AOT
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 1 2 3 4 5 6 7
month
Beijing
New York
6-year averaged AERONET measurements
6-year daily averaged aerosol optical thickness (AOT) show •significant differences between Beijing and New York City•seasonal variation of urban aerosol
Beijing
New York City
New York Ftotal
-70
-60
-50
-40
-30
-20
-10
0
0 1 2 3 4 5 6 7
month
ch
an
ge
in
flu
x
6am/6pm
7am/5pm
8am/4pm
9am/3pm
10am/2pm
11am/1pm
12pm
Reduction on surface insolation, New York City
Beijing Ftotal
-160
-140
-120
-100
-80
-60
-40
-20
0
0 1 2 3 4 5 6 7
month
ch
an
ge
in
flu
x
6am/6pm
7am/5pm
8am/4pm
9am/3pm
10am/2pm
11am/1pm
12pm
Reduction of surface insolation, Beijing
MM5-Urban Model Study: Extreme case (Solar radiation reduced by -100wm-2)
How cold can the surface become due to the surface insolation decrease, in an urban environment?For Beijing, aerosols cold the surface by more than 5°C in daytime.
Beijing
Urban model simulation over New York City For June 15-16, 2006
For NYC, aerosol colds the surface by 1°C in daytime.
Urban Effects on Climate: An Analogue
Urban Effects on Radiative Forcing Known, but Effects on Water Cycle Processes (e.g. Precipitation Variability) Less Understood (IPCC, 2007)
Human Activities In Arid Urban Environments Can Affect Rainfall And Water Cycle
http://www.sciencedaily.com/releases/2006/06/060619222554.htm
Professor Marshall Shepherd of The University of Georgia found:
a 12-14 percent increase (which scientists call an anomaly) in rainfall in the northeast suburbs of Phoenix from the pre-urban (1895-1949) to post-urban (1950-2003) periods.
A case for Shang Hai, China
ShangHai city
Rural regions
Daytime, monthly skin temperature of Shanghai is higher than surrounding cropland
ShangHai
cropland
Menglin Jin, San Jose State University
UHI
UHI Is observed for nighttime for all months in year
Menglin Jin, San Jose State University
Class participation:
Climate Game!
City A
City B
City C
City D
City E
City F
City G
Climate Game Climate Game NamesNames
Match the city with the corresponding climatology by indicating Match the city with the corresponding climatology by indicating the appropriate letterthe appropriate letter
Sacramento, California (38°°N) _____________Phoenix, Arizona (33°N)Phoenix, Arizona (33°N) __________________________Denver, Colorado (40°N)Denver, Colorado (40°N) __________________________Iquitos, Peru (4°S)Iquitos, Peru (4°S) __________________________Mobile, Alabama (30°°N) _____________Winnipeg, Canada (50°°N) _____________Fairbanks, Alaska (65°°N) _____________