Recent satellite-based trends of tropospheric nitrogen dioxide over large urban agglomerations worldwide

Abstract

Abstract. Trends in tropospheric nitrogen dioxide (NO2) concentrations over 66 large urban agglomerations worldwide have been computed using data from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument onboard the Envisat platform for the period August 2002 to March 2012. A seasonal model including a linear trend was fitted to the satellite-based time series over each site. The results indicate distinct spatial patterns in trends. While agglomerations in Europe, North America, and some locations in East Asia/Oceania show decreasing tropospheric NO2 levels on the order of −5 % yr−1, rapidly increasing levels of tropospheric NO2 are found for agglomerations in large parts of Asia, Africa, and South America. The site with the most rapidly increasing absolute levels of tropospheric NO2 was found to be Tianjin in China with a trend value of 3.04 (±0.47) × 1015 molecules cm−2 yr−1, whereas the site with the most rapidly increasing relative trend was Kabul in Afghanistan with 14.3 (±2.2) % yr−1. In total, 34 sites exhibited increasing trends of tropospheric NO2 throughout the study period, 24 of which were found to be statistically significant. A total of 32 sites showed decreasing levels of tropospheric NO2 during the study period, of which 20 sites did so at statistically significant magnitudes. Overall, going beyond the relatively small set of megacities investigated previously, this study provides the first consistent analysis of recent changes in tropospheric NO2 levels over most large urban agglomerations worldwide.

Analysis of Tropospheric Nitrogen Dioxide Using Satellite and Ground Based Data over Northern Thailand

“…However, strongly increasing trends of 5-10% per year were found over China, India, and the Middle East. Similar results were reported in Schneider et al [18] using SCIAMACHY to analyze the trends of tropospheric NO2 over 66 large urban agglomerations worldwide in 2002-2012. Chen et al [6] compared products from different satellites (GOME, OMI, SCIAMACHY, GOME-2A and GOME-B) across China for 1995-2015.…”

“…For SCIAMACHY [19,38], global coverage requires 6 days with a spatial resolution of 60×30 km 2 . The original satellite retrievals are regridded on a regular 0.125°×0.125° grid for OMI and on a regular 0.25°×0.25° grid for SCIAMACHY, GOME-2A, and GOME-2B by averaging the satellite observations weighted by the size of the overlapping surface area [18]. SCIAMACHY, GOME-2A, and GOME-2B have a satellite overpass local time (LT) in the morning of approximately 9:30 LT for SCIAMACHY and 10:30 LT for GOME-2A/B.…”

Linear and Non-Linear Trends for Seasonal NO2 and SO2 Concentrations in the Southern Hemisphere (2004−2016)

“…However, trends for tropospheric NO 2 concentrations were presented at major urban agglomerations in the SH [26]. According to Figure 6a the monotonic upward trends in Lima and SCL are in qualitative match with the results presented in [33] as they are in Jakarta and Sydney for a downward trend, whereas they do not match in Buenos Aires, Johannesburg, San Pablo and Rio de Janeiro, as the monotonic trends at these cities are not significant.…”

“…There have been an increasing number of studies related to NO x and SO x emissions in the last decade [10,13,[20][21][22][23][24][25]. However, few of them were devoted to analysing linear and non-linear trends in the Southern Hemisphere (SH), and those papers dealing with this particular topic only studied specific locations [26]. In order to fill this gap and to complement the existing studies, this paper presents a comprehensive analysis of NO 2 and SO 2 linear and non-linear trends in the entire SH within the 2004-2016 period using OMI data.…”

Typical meteorological conditions associated with extreme nitrogen dioxide (NO<sub>2</sub>) pollution events over Scandinavia

“…Natural sources of NO 2 are lightning and forest fires. Recent studies indicate increasing trends in NO 2 in developing countries and decreasing trends in developed countries as a result of environmental regulation policies Zhang et al, 2007;van der A et al, 2008;Schneider et al, 2015;Geddes et al, 2016). NO 2 is an oxidizing agent resulting in the corrosive nitric acid and plays an important role in aiding the formation of ozone.…”