About two years of MAXDOAS measurements of air pollutants

at SORPES in Nanjing, China

N. Hao1, M.Van Roozendael2, A.J. Ding3, F. Hendrick2, Steffen.Staedt 1, J. Ding4, Y.C. Shen3, Song Liu1, R. J. van der A 4 , P. Valks1

• Introductions The Station for Observing Regional Processes of the Earth system

(SORPES) • MAXDOAS measurements of air pollutants at SORPES

Aerosol optical properties including aerosol optical depth (AOD), Aerosol extinction vertical profile

NO2 vertical column density (VCD), NO2 volume mixing ratio (VMR) and NO2 vertical profile

HCHO and glyoxal VCD, HCHO VMR and vertical profile Comparison with satellite and in-situ measurements Applications

• Summary and future works

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Outline

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Ground-based measurements in SORPES-NJU • Station for Observing Regional Processes in the Earth

System of Nanjing University (SORPES-NJU) is a research and experiment platform developed by the Institute for Climate and Global Change Research (ICGCR) at Nanjing University (NJU) in collaboration with the University of Helsinki.

• Observation of atmospheric components including trace gases (O3, CO, SO2, NO-NOx-NOy and CO2) and aerosols (PM2.5 and PM10 ) since July, 2011

• Mini-MAXDOAS measurement since May, 2013

Location and Height: E118.9°, N32.1°,43 m

Ding et al., ACP, 2013

DOAS Retreival Setting for O4, NO2, HCHO and CHOCHO

Data source Fitting Intevals 338-370 nm (O4,

NO2) 407-430 nm

(NO2) 335-358 nm

(HCHO) 416-438 nm (CHOCHO)

O4 Hermans et al.(2003), 296K ×

O4 Greenblatt et al.(1990), 296K × × ×

NO2 Vandaele et al.(1998), 294K × × × ×

O3 Brion et al.(1998) , 218 K × × ×

O3 Brion et al. (1998) ,243 K × × × ×

BrO Fleischmann et al.(2004) 223K ×

×

HCHO Meller and Moorgat(2000), 293K ×

×

CHOCHO Volkamer (2005), 296K × ×

H2O HITRAN 2000 ×

Ring × × × ×

Polynomial Order 4 Order 3 Order 3 Order 3

Aerosol and trace gases profile retrieval

MAXDOAS spectra Radiative Transfer code LIDORT v3.3

Pressure and temperature profiles Surface albedo Trace gas: cross-sections, VMR profiles Aerosol: optical properties

O4 DSCDs

MAXDOAS measurement

O4 DSCDs

NO2 DSCDs

Aerosol extinction vertical profile E(z)

Optical Estimation NO2 DSCDs

Trace gas vertical profile Vertical Column Dentisity

Optical Estimation

DOAS Fitting

Clemer et al., AMT, 2010, Hendrick et al., ACP, 2014

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Aerosol optical properties-AOD at 360 nm

Fudan

Total AOD AERONET Taihu Level 1.5

BIRA algorithm (bePRO) for near real time retrieval of aerosol optical properites and trace gases vertical profile

Clemer et al., AMT, 2010, Hendrick et al., ACP, 2014, Wang et al., ACP, 2015

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Aerosol optical properties-AOD at 360 nm

Mean AOD: 0.58±0.09 High AOD appear in May, August and September. Smaller than the observation results at Gulou Station, Nanjing (Li et al., Atmos. Environ., 2015), but with similar seasonal variation.

Spring: Dust from the northwest of China and Mongolia can be transport to Nanjing, which results in the increase of coarse particles. Summer: High temperature and humidity is beneficial to the formation of the fine particles and hygroscopic growth of aerosols.

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Nanjing May, 2013 –Feb, 2015

* May13 * Jun13 * Jul13 ◊ Aug13 ◊ Sep13 ◊ Oct13 + Nov13 + Dec13 + Jan14 · ·* · ·Feb14 · · * · ·Mar14 · · * · ·Apr14 ..◊.. May14 ..◊.. Jun14 ..◊.. Jul14 ..+.. Aug14 ..+.. Sep14 ..+.. Oct14 ∆ Nov14 ∆ Dec14 ∆ Jan15 × Feb15

Aerosol Extinction Profile Monthly Mean

Most profiles peak at surface.

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◊ GOME-2A

* MAXDOAS

Satellite: 50 km radius

NO2 VCD-comparison with satellite

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◊ GOME-2B

* MAXDOAS

NO2 VCD-comparison with satellite

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Comparison with in-situ NO2 measurement

NO2 volume mixing ratio (surface 0-200 m)

AQI data from website

◊ MAXDOAS

* AQI

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An emission reduction of 10% during the Chinese Spring Festival based on DECSO(Daily Emission estimates Constrained by Satellite Observations) Air quality regulations taken by the Nanjing authorities in the year of Youth Olympic Game 2014 from May to August. NO2 VMR decrease about 30% NOx emissions show a reduction of at least 25% during the YOG period.

NO2 VMR –Monthly mean

Ding et al., ACPD, 2015

Chinese Spring Festival

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Nanjing May, 2013 – Feb., 2015 Monthly Mean

NO2 Profile Retrieval

* May13 * Jun13 * Jul13 ◊ Aug13 ◊ Sep13 ◊ Oct13 + Nov13 + Dec13 + Jan14 · ·* · ·Feb14 · · * · ·Mar14 · · * · ·Apr14 ..◊.. May14 ..◊.. Jun14 ..◊.. Jul14 ..+.. Aug14 ..+.. Sep14 ..+.. Oct14 ∆ Nov14 ∆ Dec14 ∆ Jan15 × Feb15

Most profiles peak at surface. Three layers can be distinguished: 0-200 m, 200-400m and above 400 m.

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HCHO VCD-comparison with satellite

◊ GOME-2B

* MAXDOAS

Seasonal variation

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HCHO and CHOCHO VCD

The ratio of CHOCHO to HCHO (RGF)was used to identify the sources of VOCs since CHOCHO and HCHO have different formation pathways. RGF in summer are higher than in other seasons. Summer: biomass burning Other season: anthropogenic

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HCHO VMR –Monthly mean

Air quality regulations taken by the Nanjing authorities in the year of Youth Olympic Game 2014 from May to August. HCHO VMR decrease about 18%

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Monthly Mean

HCHO Profile Retrieval

* May13 * Jun13 * Jul13 ◊ Aug13 ◊ Sep13 ◊ Oct13 + Nov13 + Dec13 + Jan14 · ·* · ·Feb14 · · * · ·Mar14 · · * · ·Apr14 ..◊.. May14 ..◊.. Jun14 ..◊.. Jul14 ..+.. Aug14 ..+.. Sep14 ..+.. Oct14 ∆ Nov14 ∆ Dec14 ∆ Jan15 × Feb15

Most profiles peak at surface.

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• About 2 years MAXDOAS measurements at SORPES have been analyzed

– Total AOD at 360 nm have been validated through comparison with AERONET – NO2 VCD and VMR have been compared with GOME-2 trop. NO2 product and in-situ

measurements respectively – HCHO VCD have been compared with GOME-2 HCHO product – The ratio of CHOCHO to HCHO has been studied.

• MAXDOAS measurements can be used to provide long-term time series of

aerosol optical properties and trace gases VCD, VMR and profiles.

• The effect of emission control during the Youth Olympic Games in 2014 on the reductions of air pollutants

• Future Work – Other trace gases (SO2 and HONO) – Verification and Validation

Summary and future work

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Thanks for your attention!