Spaceborne evidence for significant anthropogenic VOC trends in Asian cities over 2005–2019

Abstract

Trends of formaldehyde (HCHO) linked to anthropogenic activity over large cities located in the Asian continent are calculated for the period 2005–2019 using the Quality Assurance for Essential Climate Variables (QA4ECV) dataset from the Ozone Monitoring Instrument (OMI) aboard the Aura satellite. Contributions due to anthropogenic emissions are isolated by applying a correction based on near-surface temperature in order to account for interference from local biogenic emissions. Strong positive trends are derived over the Middle East and the Indian subcontinent (up to 3.6% yr-1 and 2.4% yr-1 respectively) where regulations of anthropogenic non-methane volatile organic compound (NMVOC) emissions are currently limited. Weaker trends are observed over cities located in China, where the air pollution action plan (2013) may have mitigated NMVOC trends early on, but targeted legislature concerning VOC emissions was only recently introduced. HCHO trends for cities located in South and Equatorial Asia are mostly not significant or very uncertain. Cities located in Taiwan and Japan (regions in Asia where legislation has been in place since the early 2000s) display mostly negative trends.

Why is ozone in South Korea and the Seoul Metropolitan Area so high and increasing?

“…Using satellite and surface observations of NO2, Seo et al (2021) found that NOx emissions declined in Seoul by 30% during the 2015-2019 period, and Bae et al (2021) found a 18% decrease for the 2015-2018 period. On the other hand, Bauwens et al (2022) found an increase in satellite-observed HCHO columns over South Korea by 1-60 2% a -1 for the 2005-2019 period, which does not support a decrease in VOC emissions.…”

Disentangling temperature and water stress contributions to trends in isoprene emissions using satellite observations of formaldehyde, 2005–2016

“…the Copernicus Atmosphere Monitoring Service (CAMS-GLOB-ANT, Granier et al, 2019;Elguindi et al, 2020) or the Community Emissions Data System (CEDS; Hoesly et al, 2019). Note, however, that the estimated trends in bottom-up inventories have large uncertainties, especially in regions undergoing fast population and/or policy changes and where accurate information is either absent or limited (Bauwens et al, 2022). In the future, the availability of high resolution HCHO columns (De Smedt et al, 2021) and next-generation machine learning isoprene retrievals (Wells et al, 2022), together with longer time-series of soil moisture data from different datasets (e.g., the NASA Soil Moisture Active Passive instrument and the European Space Agency Soil Moisture and Ocean Salinity mission) will provide new opportunities to improve our understanding of the role of water availability in the isoprene production and emission.…”

Impact of Drought on Isoprene Fluxes Assessed Using Field Data, Satellite-Based GLEAM Soil Moisture and HCHO Observations from OMI

“…BVOCs, among which isoprene is largely dominant, are the major precursors of HCHO over vegetated areas (e.g., [41][42][43]), and therefore, satellite HCHO is an excellent proxy for the emissions of BVOCs. The anthropogenic signal of HCHO is low and only detectable in highly polluted regions [44,45], and does not play a role in the isoprene-dominated MOFLUX site area. The contribution of fires to the HCHO abundances is generally important in the vicinity of fires or downwind, but only small agricultural fires occurred during the summers of 2011 and 2012 over Missouri.…”