Radiative Impacts of Urban Aerosols in Seoul, Korea

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1 Radiative Impacts of Urban Aerosols in Seoul, Korea
IAIA2007 (June 3~8, 2007, COEX, Seoul, South Korea) Radiative Impacts of Urban Aerosols in Seoul, Korea 안녕하십니까? 저의 학위논문제목은 “아시아지역 …” 입니다. Jiyoung Kim and Byoung-Cheol Choi Applied Meteorology Research Team National Institute of Meteorological Research Korea Meteorological Administration

2 Introduction Radiative impacts of aerosol
Atmospheric Aerosols: A tiny particle suspended in the atmosphere (size range: ~nm to ~10 um) Adverse effect on human health Visibility impairments Impacts on urban climate and meteorology (heat island, heavy precipitation) Radiative impacts of aerosol => visible light scattering and absorption

3 Aerosol Sources in East Asia
NOx Terra/MODIS 0.55m (April 2000 ~ September 2005) NMVOC NH3 Anthropogenic Emission 한반도가 속한 동아시아 지역은 전세계적으로 볼 때 에어로솔의 배출량과 또한 그 종류가 매우 다양하게 분포하는 지역으로 알려져 있습니다. 아래의 그림은 테라/모디스 위성센서로 최근 6년간의 연평균 에어로솔 광학 깊이의 공간적 분포를 나타낸 그림입니다. 중국 동부 해안의 산업시성이 밀집된 지역과 황사의 발원지 부근에서 에어로솔 광학 깊이가 매우 크게 나타남을 알 수 있습니다. 또한, 동아시아 지역의 인근서 발생하는 대규모의 Biomass Burning 또한 동아시아 지역에 영향을 주는 것을 알 수 있습니다. 이러한 분포로 볼 때 동아시아 지역의 인위적 기후변화와 대기환경의 변화를 이해하기 위해서는 이 지역의 에어로솔에 대한 연구가 매우 중요함을 알 수 있습니다. Asian Dust Storm Biomass Burning

4 Various Adverse Impacts of Urban Aerosols
Urban Climate (UHI, Radiation budget) Urban Meteorology (cloud formation, precipitation process) Industrial Activity (agriculture, machine industry) 또한 에어로솔에 의한 흡습성은 에어로솔의 물리적 광학적 성질을 변화시킬 뿐만 아니라 에어러솔 화학, 구름 형성, 대기화학, 시정 등 대기환경적인 측면에서도 매우 중요한 것으로 알려져 있습니다. Urban Aerosols Urban Environment (urban air quality, visibility) Health Impacts (respiratory system, CVD) Acid Deposition (destruction of cultural monuments)

5 Objectives of This Study
To overview the importance of atmospheric aerosols in urban climate and environment issues To characterize optical properties of urban aerosol observed in Seoul, Korea To investigate the radiative impact of the urban aerosols

6 Data and Radiative Transfer Model
AERONET (Aerosol Robotic Network) : operated by NASA/GSFC Aerosol Optical Depth (AOD) at Seoul Site (Seoul National Univ.) - spectral 440, 675, 870, 1020 nm and water vapor (cm) - data period : November 2000 to February 2003 - level 2.0 (quality assured data) Fu & Liou RTM model was employed (Fu and Liou, JAS 1993) Surface albedo: IGBP 17-ocean type Time interval: 30 minutes; Meteorological profiles: Aerosol optical properties: OPAC data (Hess et al., BAMS 1998)

7 Aerosol Optical Depth at Seoul
Beijing Kim et al. (AE 2007) AOD maximum in June : - anticyclonic atmospheric circulation system in early summer (build-up of pollutants, prolonged dry or less rainy days, less scavenging) - hygroscopic growth of hydrophilic fine urban pollution aerosols - medium-range transported biomass burning aerosol from eastern China

8 Results of AOD Measurements at Seoul
Statistical Summary of AOD at Seoul - Spectral wavelength : 440 nm Average AOD : 0.50, S.D. of AOD : 0.37 Maximum : 2.58, Minimum : 0.12 - Spectral wavelength : 675 nm Average AOD : 0.29, S.D. of AOD : 0.23 Maximum : 1.57, Minimum : 0.06

9 Urban Aerosol Optical Properties (Hess et al., BAMS 1998)

10 OPAC (continued) Urban aerosol represents strong pollution in urban
areas. The mass density of soot is 7.8 ug m-3, and the mass densities of both water-soluble substance and insoluble substance are about twice those of the continental polluted aerosol as found in center areas of large cities.

11 What is Aerosol Radiative Forcing?
Radiative impacts of aerosols: Direct, Indirect(1st, 2nd), Semi-Direct Shortwave vs. Longwave/ Surface vs. TOA ∆F = Fnet - Fneto : Direct ARF (unit : W/m2) Fnet = F↓ - F↑= F↓-F↓ = (1-α)F↓ where Fnet = net flux (with aerosol) Fneto = net flux at pristine (without aerosol) Assume: no cloud, same atmospheric profile (T, P, H2O, CO2, O3, etc)

12 Diurnal Variation of ARF

13 Diurnal Variation of ARF

14 AOD Influences on URBAN ARF

15 Diurnal Variation of ARF

16 Conclusion and Discussion
Mean of aerosol optical depth at 440 nm obtained from AERONET measurements found to be 0.50 at Seoul, Korea. Radiative transfer model was employed to estimate direct aerosol radiative forcing due to urban aerosol. 24-hr and daylight averaged ARF at AOD of 550 nm found to be and W/m2, respectively. Direct and indirect impacts on urban meteorology and climate need to be carried out through both well-designed measurements and model studies.