METR202- Study Urban Climate System Using Satellite Remote Sensing and Climate Model

Professor Menglin JinSan Jose State University

Outline:Key Urban FeaturesSatellite ApproachModel ApproachFuture Directions

We studied:

Urban Heat Island EffectUrban aerosol effect on clouds and rainfall

•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 PublicationsJin, M, 2012; Development of UHI index. J. of ClimateJin, 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

SF, 2008

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

Traditional Way to Measure Urban Surface Temperature

UHI is function of city size, location, geographic conditions, population

Video: Urban Heat Island Effect (UHI)

http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/urban%20system/

Urban Heat Island.mp4

reasons for UHI

how to reduce UHI

Video: Urban Rainfall Effect

http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/urban%20system /

Urban Rainfall Effect.mp4

% of Land Area Built-up3 - 6%

43% of Land Area Dominated by Agriculture

Our Research Approach

• Using Satellite Remote Sensing to detect features of urban system

• Using Climate Model (land surface model) to simulate UHI and aerosol effects

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

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)

Dr. Menglin Jin San Jose State University

(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0

Urbanization Effects

Land Surface Energy Budget:

Dr. Menglin Jin San Jose State University

(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0

Urbanization Effects

Land Surface Energy Budget:

Urbanization changes:Albedo (black surface)Vegetation ocverage (EP, roughness length)Sd, LWd (by aerosols, clouds)Tskin, SH/LE/G

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 !!!

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

3. Urban Aerosols and Their Direct Effects on Clouds, Surface Insolation, and Surface Temperature

Urban Pollution Sources

Traffic

Industry

Indoor warming

Aerosols are solid/liquid particles pending in atmosphere

Size -0.01-100μm

Residence time – hours-days

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

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)

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

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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

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Beijing Ftotal

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Reduction of surface insolation, Beijing

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)

Urban Heat Island Effect (UHI)

Is it a

• day time phenomenon only

• night time phenomenon only

• both day+night phenomenon

How to deal with UHI?

http://www.youtube.com/watch?feature=endscreen&NR=1&v=t-sXHl3l-rMWatch video:

A case for San Jose-SF Bay Area, China

3 Km5/9/2011, 8 PM

WRF 1km 5/5/20115 PM

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