1. OMI Tropospheric NO2 in China
Dasa Gu
EAS 6410

2. NO2 in Troposphere
Nitrogen dioxide is an important chemical species in both the stratosphere, where it plays a key role in ozone chemistry, and in the troposphere, where it is a precursor to ozone production. In the troposphere, it is produced in various combustion processes and in lightning.
(From SHODOR)

3. Motivation
Normally, understanding of NOx sources has been developed largely using the “bottom-up” approach, meanwhile, the tropospheric NO2 distributions measured by several satellite instruments in last decade provide very important information to constrain the “bottom-up” inventories.
Richter et al. [2005] presented the tropospheric column amounts of NO2 retrieved from two satellite instruments GOME and SCIAMACHY over the years They found a highly significant increase of about 50% over east China.
Zhang et al. [2007] estimated bottom-up NOx emissions and its trend. Compared with the satellite observations, the growth rate from the bottom-up inventory is lower.
Therefore:
1. China is a hot area being concerned.
2. There is a new satellite observation – OMI, started from 2004 and haven’t been used for trop-NO2 analysis in papers.
3. There is inconsistence between bottom-up inventory and satellite observations.

4. Aura OMI NO2 Observation
The OMI NO2 data product, OMNO2, contains the observed slant column NO2 (total amount along the optical path from the sun into the atmosphere, and then toward the satellite), the total vertical column NO2 (cm−2), and the estimated tropospheric portion of the total column NO2 (cm-2).
(From NASA)

5. Trop-OMI NO2 in China North China Plain (NCP) 112E – 120E, 34N – 40N
Yangtze River Delta (YRD)
Pearl River Delta (PRD)
112E – 120E, 34N – 40N
118E – 122E, 20N – 32.5N
112.5E – 114E, 22N N

6. Trop-NO2 Concentration Variations

7. Concentration Trend

8. Conclusions
OMI Troposheric NO2 shows there are three significant high value areas in China: North China Plain, Yangtze River Delta and Pearl River Delta.
Compared between three areas, PRD NO2 concentration was higher than both NCP and YRD.
NO2 concentrations increased from Sep to Nov at each 3 areas in every individual years.
In NCP and YRD, NO2 concentration increased from 2004 to 2007, while the value had a decreasing trend in PRD.

9. Future Plans More months, cover the whole years. Sensitivity analysis.
Compared with bottom-up inventory. ……