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Surface O 3 over Beijing: Constraints from New Surface Observations

Surface O 3 over Beijing: Constraints from New Surface Observations. Yuxuan Wang, Mike B. McElroy, J. William Munger School of Engineering and Applied Sciences, Harvard University Jiming Hao, Hong Ma, Yaosheng Chen Tsinghua University, Beijing, China. GC 3 rd Users Meeting, April 15, 2007.

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Surface O 3 over Beijing: Constraints from New Surface Observations

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  1. Surface O3 over Beijing: Constraints from New Surface Observations Yuxuan Wang, Mike B. McElroy, J. William Munger School of Engineering and Applied Sciences, Harvard University Jiming Hao, Hong Ma, Yaosheng Chen Tsinghua University, Beijing, China GC 3rd Users Meeting, April 15, 2007

  2. Miyun Station Beijing http://www.fallingrain.com/world/CH/22/Miyun.html

  3. Overview of Miyun Station • Established by the China Project; started in Nov 2004, continuously to date • Miyun (40.3N, 116.8E): Location chosen to observe both clean continental air and pollution in the Beijng plume • Directly observe trace-gas covariances near the source; • Species measured: CO, O3, CO2 (NOx, NOy, SO2) • Data used here: 30-min averages prepared by J.W. Munger

  4. Sometimes It’s Clear Courtesy of Bill Munger

  5. Mean Flow Patterns at the surface Jan July East Asian Monsoon

  6. Seasonal variations of other factors Precipitation Beijing AOD (1984-1994) AOD obs model Qiu et al., Atmos. Environ., 2000 Model sulfate AOD peaks in July (0.5)

  7. variations in summer O3 observations: monthly statistics daytime O3 Legend daytime 80ppbv • distributions of O3 skewed toward high values in summer months • O3 peak in early summer and early fall • Summertime ozone pollution

  8. Seasonality of Ozone at Lin An obs: daytime mean (1999-2000) model Wang et al., 2002

  9. variations in summer CO observations : monthly statistics >3ppm CO! daytime CO Legend • small seasonality in CO • distributions of CO close to bimodal: clean continental air and local pollution

  10. GEOS-Chem Model Set-up • GEOS-4 global simulation; 2o x 2.5o resolution; version 7-04-09 • Updated Chinese emissions of CO and NOx with monthly variability • Simulation period: Nov 2004 – Dec 2006. Focus on 2006 • 1-hr model outputs sampled by observations.

  11. Chinese emissions of CO and NOx NOx (2004) CO (2001) Streets, et al., 2006 China total: 146 Tg/yr (up from 100) Zhang, Streets, et al., 2007 China total: 17.8 TgNO2 (up from 11.3 for TRACE-P)

  12. Monthly variations in Chinese emissions CO (1.5:1) heating and residential NOx (1.3: 1) Zhang, Streets, et al., 2007 Seasonality not yet in the standard model

  13. Soil NOx emissions a priori soil a posteriori soil Wang et al., 2007 • derived from 3-year GOME observations over east China • a posteriori 0.85 TgN/yr vs a priori 0.24 TgN/yr • peak in summer, significant in spring and fall

  14. model high bias in summer Simulated Seasonal Variations (O3) Afternoon model • model captures the overall seasonal patterns • model fails to simulate the decrease of O3 in July • model cannot reproduce very high ozone levels

  15. Simulated Seasonal Variations (CO) model • model tends to underestimate mean CO concentrations • model captures the overall seasonal patterns

  16. small correlation in July CO-O3 relationship Miyun Sable Island Parrish et al., 1998 • O3/CO ratio is much lower at Miyun • seasonal variability are generally consistent between the two sites

  17. not captured by model! Average diurnal pattern of summertime ozone obs June obs July Model July very low ozone in the afternoon! (< 20 ppb!)

  18. 9-10 1 6 rain or thunderstorm! 28 18 24-26 21 Low Ozone Events in July model obs

  19. Flow patterns between June and July June July

  20. <200ppb June July frequency distribution of CO 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 4000 June O3 levels as a function of CO O3 July 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 4000 R.H. as a function of CO July RH June 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 4000

  21. Sensitivity: increase cloud optical depth model July CO-O3 Relationship Impact of precipitation and cloudiness on local ozone production!

  22. Summary • Observations reveal seasonal variations in O3, CO, and their correlations in north China region • Model capture the general characteristics in observations of CO and O3 • Major discrepancies in the model: • Underestimate CO concentrations • Not able to represent small-scale dynamics (in transition seasons) • Not able to capture low-ozone events in July, likely due to underestimate of cloudiness • still work in progress…. • Need for a finer-resolution model -- nested-grid capability in GEOS-5

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