Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Video: Urban Heat Island Effect (UHI)Video: Urban Rainfall EffectVideoSlide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65METR112- Global Climate Change:Urban Climate SystemProfessor Menglin JinSan Jose State UniversityOutline:Urban observationsUrban heat island effectUrban aerosolUrban rainfallThrough this lecture, you need to know:Urban Heat Island Urban aerosol effect on rainfall and snowfall,Spatial temperatures in the same regionUrban aerosol suppress fainSF, 2008Urban Heat Island Effect (UHI): Urban surface is hotter than that of surrounding non-urban regionsSurface temperatureWe need to understand why and what are UHI effectsVideo: Urban Heat Island Effect (UHI)http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/urban%20system/Urban Heat Island.mp4reasons for UHI how to reduce UHIVideo: Urban Rainfall Effecthttp://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/urban%20system /Urban Rainfall Effect.mp4Video•Observe urban system effecthttp://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 lifeWhy do we need to Study Urban regions?Related PublicationsJin, 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 1551-1565Jin, 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 Agriculture1. Satellite remote sensing on urban regionsMODIS land coverRed color means urban built-upNight Light of TokyoNight Light of Parispictures made by U.S. Defense Meteorological Satellites Program (DMSP)Satellite observations retrieve urban system: Land surface properties: surface temperature, surface albedo, emissivity, soil moisture, vegetation coverAtmosphere conditions: aerosol, clouds, and rainfallurbanization significantly changes weather and climateIt shows thatUrban 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 rainfallUrban Heat Island Effect (UHI): Urban surface is hotter than that of surrounding non-urban regionsSurface temperatureWe need to understand why and what are UHI effectsDr. Menglin Jin San Jose State University (1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0Urbanization EffectsLand Surface Energy Budget:Dr. Menglin Jin San Jose State University (1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0Urbanization EffectsLand Surface Energy Budget:Urbanization changes:Albedo (black surface)Vegetation ocverage (EP, roughness length)Sd, LWd (by aerosols, clouds)Tskin, SH/LE/GEOS 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 temperature10°C !!!Urbanization changes surface albedo (MODIS)Urban surface albedo has a 4-6% decrease -> more solar radiation will be absorbed at surface\increase surface temperatureUrbanization 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 increasesWhat 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 PavementsCool 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 TemperatureVideo•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.mp4July 2005NASA MODIS observed Aerosol DistributionUrban Pollution SourcesTrafficIndustryIndoor warmingAerosols are solid/liquid particles pending in atmosphereSize -0.01-100μmResidence time – hours-daysIndirect Effect: serve as CCNCloud dropRain dropIce crystalIce precipitationAerosol Direct Effect: Scattering Absorb0oCsurfaceBlack carbon heats atmosphere and surfaceMost aerosols cool surfaceMore aerosol ->small cloud effective radius->high cloud albedo->cooling