1. New developments for SKYNET Chiba/Japan & Phimai/Thailand sites by utilizing the MAX-DOAS technique
Hitoshi Irie
Center for Environmental Remote Sensing (CEReS)
Chiba University, Japan
1T. Takamura, 1P. Khatri, 1T. Muto, 1T. Kato, and 2S. Itahashi
1Chiba University, 2Central Research Institute of Electric Power Industry

2. SKYNET In recent years, Chiba Univ. is reinforcing
An observation network dedicated for aerosol-cloud-radiation interaction researches.
(e.g., Takamura et al., 2004; Nakajima et al., 2007)
Initiated under the WCRP/GAME project and expanded focusing on East Asia as ADEOS/GLI validation activity.
A growing network linking more than 100 sites (as of 2015) all over the world. Still expanding with one main focus on satellite validations.
　(GCOM-C, EarthCARE, GOSAT, GOSAT-2, Himawari-8, GEMS, ...).
Chiba Univ. is playing the leading role in SKYNET.
Sky radiometer
(AOD, SSA, COD, O3, H2O, ...)
MAX-DOAS
(AOD, NO2, SO2, H2O, O3, HCHO, ...)
In recent years, Chiba Univ. is reinforcing
the capability of SKYNET as the leading institute.

3. Air quality research under SKYNET
The idea to reinforce the capability of SKYNET
SKYNET International Network
Atmospheric chemistry
Atmospheric physics
trace gases
(inorganic/organic)
aerosols
clouds
radiation
We have a further uniqueness with our observations as follows...

4. Explored the potential for multi-component observations by MAX-DOAS (Irie et al., 2011, 2015)
Aerosols
Inorganic
Organic
JM2
Irie et al. (2011,2015)
Lower-tropospheric vertical profile information for 8 quantities:
Aerosols at 357 & 476 nm
NO2(UV&vis), SO2, O3, H2O
HCHO, CHOCHO

5. The two sites equipped with MAX-DOAS as part of growing network SKYNET
Chiba
Phimai

6. SKYNET/Chiba site & 4AZ-MAXDOAS
Chiba site: 35.63ºN, ºE, 21 m a.s.l.
Located in Chiba University
Sky radiometer
Lidar
Pyranometer
Directo solar rad obs
Pyrgeometer
Microwave radiometer
Cloud camera
Met obs.
4AZ-MAXDOAS
Chiba
Chiba
Earth’s city lights
To understand spatial inhomogeneity of trace gases and aerosols in an urban environment, the 4AZ-MAXDOAS system has been in operation since November 7, 2014.

7. Differences in AOD by a factor of 6!
According to the sky radiometer obs.,
AOD was slowly changing in daytime.
factor 6!
4AZ-MAXDOAS
Large deviations (by a factor of 6) were observed with the north-looking MAX-DOAS.

8. The large deviations were due to high spatial inhomogeneity produced by the transport of polluted airs from Tokyo!
GOME-2 NO2
OMI NO2
MODIS AOD
Back trajectory
wind

9. Selected other interesting features seen from observations at Chiba site
NO2
H2O
factor 4!
For NO2 VCD, very high spatial inhomogeneity with a difference by a factor of 4 was observed.
For H2O, spatial inhomogeneity was not high. Temporal variations was well captured by CMAQ (27-km resolution).
→ This gives a hint to explain large deviations often seen from validation comparison between satellite and MAX-DOAS at urban sites.
→ This gives some confidence with our MAX-DOAS observations.

10. The two sites equipped with MAX-DOAS as part of growing network SKYNET
Chiba
Phimai

11. SKYNET/Phimai site
Phimai site: 15.18ºN, ºE, 212 m a.s.l.
In Bureau of Royal Rainmaking and Agricultural Aviation (BRRAA), Phimai, Thailand. Supported by Chulalongkorn Univ.
Sky radiometer
Lidar
Pyranometer
Directo solar rad obs
Pyrgeometer
Microwave radiometer
Cloud camera
Met obs.
MAX-DOAS
Satellite-retrieved HCHO VCD (1015 molec. cm-2)
(De Smedt et al., 2010)
We started continuous observations by MAX-DOAS at Phimai on Sep. 18, 2014.

12. Diurnal variations (the first 3 days)
Rapid diurnal variation in NO2 and SO2 VMRs.
→　can models reproduce these diurnal variations?
HCHO VMR is much higher than NO2 VMR.
→　significant biogenic contributions

13. Evaluation of MAX-DOAS retrievals
Apr.14
Apr.22
Aerosols
H2O
Late wet season
Dry season
MODIS fire maps (Tsuruta et al., 2008)
LIDAR attenuated backscatter coefficient
Cloud-free conditions
Aerosol below ~2 km

14. Seasonal variations (Oct.2014 – Feb.2015)
Aerosols
NO2 O3
SO2
From the late wet season through the dry season,
aerosols, NO2, SO2, and O3 were enhanced.

15. Seasonal variations for HCHO&CHOCHO
Jan. 31-Feb. 9, 2008
Dry season
MODIS fire maps (Tsuruta et al., 2008)
RGF = [CHOCHO]/[HCHO]
HCHO and CHOCHO VMRs were also enhanced.
RGF was at a moderate level of 0.03.
→ mixed contributions from BVOC and BB emissions

16. Summary
As an option for AQ study, the 4AZ-MAXDOAS and MAX-DOAS have been in operation at SKYNET/Chiba and SKYNET/Phimai sites, respectively, since last autumn.
At Chiba site, the 4AZ-MAXDOAS detected spatial inhomogeneity with differences in AOD (NO2 VCD) by a factor of 6 (4).
At Phimai site, the MAX-DOAS showed that aerosols, NO2, SO2, O3, HCHO, and CHOCHO VMRs were all enhanced from the late wet season through the dry season.
RGF was at a moderate level of 0.03, suggesting mixed contributions from BVOC and BB emissions in the dry season.
As a next step, it is interesting to evaluate if these are reproduced by a model quantitatively.

18. The large deviations were caused by spatial inhomogeneity!
Ground-based surface PM2.5 data
Back trajectory
wind
Satellite data
MODIS AOD
GOME-2 NO2
OMI NO2

19. Spatial inhomogeneity increased due to the transport from Tokyo
Nov. 13, 2014
Back trajectory
wind
MODIS AOD
Nov. 13, 2014
On Nov. 13, strong winds blew from west, bringing polluted air originated from Tokyo to around northern region of Chiba.
For precise validation, spatial inhomogeneity needs to be carefully considered in detail.

20. Principle of MAX-DOAS observations (Multi-AXis Differential Optical Absorption Spectroscopy)
■ High sensitivity to trace gases in the boundary layer
■ Long-term operation
■ Easy to handle
■ Inexpensive
■ Low power consumption
UV/Vis. spectrum
~10-20 km

21. MAX-DOAS instrument Outdoor unit (telescope, etc.）
Indoor unit（spectrometer, etc.）
10-m fiber optic cable
movable mirror
・Maya2000Pro (Ocean Optics)
・FWHM: about 0.3 nm
・Wavelength: nm
・Temperature kept at 40℃
・Integ. time constant throughout the day
・Field of view < 1 deg
・Elevation angles = 2, 3, 4, 6, 8, 70 deg