Impacts of Meteorological Conditions Modified by Urban Expansion on Surface Ozone over Yangtz River Delta and Pearl River Delta region, China Xuemei Wang, Ziwei Chai Dept. of Environmental Sciences, Sun Yat-Sen University, China Fei Chen, Christine Wiedinmyer, Alex Guenther, Mukul Tewari National Center for Atmospheric Research, Boulder, CO, USA 6th Annual CMAS Conference October 1st,2007

Outline Regional Air Quality IssuesRegional Air Quality Issues Meteorological conditions modified by urban expansion Impacts of urban expansion on surface ozoneImpacts of urban expansion on surface ozone Summary

Satellite View Alerts China to Soaring Pollution (GOME and SCIAMACHY) (Richter et al., Nature, Sept 1, 2005) NO 2 (vertical column)  NO 2 ( ) Yangtze River Delta/ Shanghai Region (YRD) Pearl River Delta Region (PRD)

Spring Summer Autumn Winter Atmospheric Opitcal Depth(AOD)

Rapid Urban Expansion in PRD and YRD, China PRD Area = km 2, Population: 1986~20million, 2005 > 45 million YRD Area= km 2, Population: 1986~30million, 2005 > 60 million

:57am Consequences of rapid urbanization more pronounced urban heat islands (UHI) more surface emission in PRD

Impacts of Meteorological Conditions Urban heat islands reduce the strength of nocturnal land-breeze (return flow from land to sea), so air pollutants tend to accumulate over land. Lo, J.C.F., A.K.H. Lau, F. Chen,J.C.H. Fung, and K.K.M. Leung, 2007 (J. Appli. Meteorol. And Climate)

WRF-Chem 12-km Simulation and Configuration WRF-CHEM model configuration WSM 5-class microphysics Kain-Fritsch cumulus Dudhia scheme short wave RRTM longwave radiation Yonsei University (YSU) (PBL) Noah land surface scheme Urban Canopy model (UCM) Fast-J radiation scheme RADM2/SORGAM (gas+ aerosol) Initial and Boundary conditions 1-degree FNL for meteorology 6-min resolution emission inventory TRACE-P observation data for chemistry Simulation March 2001 Topographical height (m)

Evaluation of WRF-Chem Met. Simulation Compared with NCEP analysis data, WRF monthly averaged 2-m temperature and wind direction have the same pattern, but with higher wind speed in YRD

Evaluation of WRF-Chem Simulated Concentration Simulations from two WRF-Chem packages have similar trend

Urbanization Increases both Day- and Night-time 2-m Temperature Simulation Urban - Simulation PRE-Urban averaged for March 2001 PRD has smaller increase of 2-m temperature than YRD YRD PRD

Urbanization Decreases both Day- and Night-time 10-m Wind Speed PRD has larger decrease of 10-m wind speed than YRD, and daytime reduction in wind speed is larger than that for nighttime

Urbanization Decreases both Day- and Night-time 2-m Water Mixing Ratio PRD has larger decrease of 2-m water mixing ratio than YRD, and daytime reduction in Q2 is larger than that for nighttime

Urbanization Increases both Day- and Night-time Boundary Layer Depth PRD has smaller increase in PBL depth than YRD

Urbanization Increases Surface Ozone Concentration Urbanization increases surface ozone (more for nighttime) PRD has larger increase than YRD

Differences in 10-m wind and O 3 between Urban and Pre-urban Urbanization enhances the convergence, especially in the PRD. Daytime convergence is weaker than that for nighttime Relative O 3 change (ppbv) and relative 10-m wind difference DaytimeNighttime

Summary Impacts of urban expansion can modify surface and PBL structures: –increase temperature and decrease wind speed –PBL depth increase more in the day time than that in the night time. Comparing PRD and YRD (cities clusters with different urban distribution and located in different climate regimes), PRD has –smaller increase of 2-m temperature than YRD –larger decrease of 10-m wind speed than YRD –smaller increase of PBL depth than YRD –larger increase of surface ozone than YRD. –larger decrease of 2-m water mixing ratio than YRD Dynamic and thermal effects of urbanization all have impacts on surface ozone.

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