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

Why do we need to Study Urban regions? 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

Satellite Measurements show unique features of Land cover – urbanization coverage Surface Temperature – Urban Heat Island Effect Vegetation coverage Emissivity Albedo Clouds Rainfall Aerosol Urban Surface Atmosphere

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: /2004JD 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 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, 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-up 3 - 6% 43% of Land Area Dominated by Agriculture

% of Land Area Built-up 3 - 6% 43% of Land Area Dominated by Agriculture

1. Satellite remote sensing on urban regions MODIS land cover Red color means urban built-up

Night Light of Tokyo

Night Light of Paris

pictures made by U.S. Defense Meteorological Satellites Program (DMSP)

SF, 2008

The Afternoon Satellites “A-Train” of Earth Observing System (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 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 Surface temperature

Dr. Menglin Jin San Jose State University (1-α)S d +LW d -εσT skin 4 +SH+LE + G= 0 Simulate Urbanization to Examine Its 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 effect Daytime Nighttime 50km MODIS

Jin et al J. of Climate MODIS Observed Global urban heat island effect

Comparison of skin temperature for urban and nearby forests MODIS Cities have higher T skin 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 surface  Surface 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 e.g., CLM: (NCAR, DAO) NOAH: (NCEP) Turbulence production Urban thermal properties Radiation trapping Radiation attenuation Canopy heating & cooling

(1-α)S d +LW d -εσT skin 4 +SH+LE + G= 0 Simulate Urbanization to Examine Its Effects Land Surface Energy Budget:

(1-α)S d +LW d -εσT skin 4 +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

July 2005 NASA MODIS observed Aerosol Distribution

Urban Pollution Sources Traffic Industry Indoor warming Aerosols are solid/liquid particles pending in atmosphere Size μm Residence time – hours-days

Indirect Effect: serve as CCN Cloud drop Rain drop Ice crystal Ice precipitation Aerosol Direct Effect: Scattering Absorb surface Black carbon heats atmosphere and surface Most 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 Ground-based remote sensing of aerosol optical properties –Optical thickness, size distribution, single scattering albedo –AERONET’s worldwide network International satellite sensors enabling remote sensing of tropospheric aerosols –AVHRR, TOMS, ATSR-2, OCTS, POLDER, SeaWiFS, MISR, MODIS, AATSR, MERIS, GLI, and OMI Instrument characteristics –Spacecraft, spatial resolution, swath width, sensor characteristics, and unique characteristics Michael King, NASA GSFC

Aerosol-Cloud Relation AOD vs. water cloud effective radius

Less clear signal is seen on AOD vs ice cloud effective radius Aerosol-Cloud Relation

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

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

Reduction on surface insolation, New York City

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? Beijing

Urban model simulation over New York City For June 15-16, 2006

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 Professor Marshall Shepherd of The University of Georgia found: a percent increase (which scientists call an anomaly) in rainfall in the northeast suburbs of Phoenix from the pre-urban ( ) to post-urban ( ) 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

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 Names Match the city with the corresponding climatology by indicating the appropriate letter ° Sacramento, California (38°N) _____________ Phoenix, Arizona (33°N)_____________ Denver, Colorado (40°N)_____________ Iquitos, Peru (4°S)_____________ ° Mobile, Alabama (30°N)_____________ ° Winnipeg, Canada (50°N)_____________ ° Fairbanks, Alaska (65°N)_____________