Long-term (2005–2015) trends analysis of OMI retrieved NO 2 columns in Taiwan

Chih Sheng Lee, Ken Hui Chang, Hyunook Kim

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In this study, the monthly data retrieved from the Ozone Monitoring Instrument (OMI) have been used to estimate long-term trends of NO 2 (2005–2015) in the entire Taiwan as well as in five representative city areas of Taiwan. The long-term NO 2 data have been used for trend analysis and evaluated to find the extent of the effects of NO x emission reduction and related environmental regulations on the NO 2 trend. Desirable policies and strategies for further reducing NO x emission have been also discussed. The corresponding reductions are 15–37% for the five city areas and 24% for the entire Taiwan over the 10-yr span. Clearly, the governmental policies/measures enacted during this 10-yr period are responsible for the reduction of tropospheric NO 2 column values. The OMI NO 2 column values of four cities (i.e., Taipei, Taichung, Kaohsiung, and Douliu) are relatively highly correlated (r = 0.70–0.95), indicating the cities have similar emission sources. Furthermore, the correlations between observed OMI NO 2 columns and their emission NO x are all significant in the three metropolitan cities and the entire Taiwan (r = 0.66–0.89). The correlation of OMI-based NO 2 VCDs and ground-based NO 2 levels is high in Kaohsiung (r = 0.82) and moderate in Taipei and Taichung (r = 0.60 and 0.59, respectively). The satellite retrieved OMI NO 2 data clearly indicate their usefulness in evaluating decreasing trend of the NO 2 , a precursor gas of PM 2.5 during the 10-yr span for the entire region of Taiwan and for the selected five cities.

Original languageEnglish
Pages (from-to)960-970
Number of pages11
JournalAtmospheric Pollution Research
Issue number3
StatePublished - May 2019


  • Ground-based NO
  • Long term trend analysis
  • NO emission
  • OMI satellite NO data
  • Taiwan air quality


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