Observing downwind structures of urban HCHO plumes from space:
Implications to non-methane volatile organic compound emissions
Abstract
Non-methane volatile organic compounds (NMVOCs) have a significant
impact on air quality in urban areas. Detecting NMVOCs emission with its
proxy HCHO on urban scales from space, however, has been limited by the
lack of discernible enhancement. Here we show clear urban HCHO plumes
from 11 cities over the globe by rotating TROPOspheric Monitoring
Instrument (TROPOMI) HCHO pixels according to wind directions. We fit
the downwind structure of the plumes with the exponentially modified
Gaussian (EMG) approach to quantify urban HCHO effective production
rates between 22.7 mol s-1 and 115.8 mol s-1. Our results are in line
with estimations using the EDGAR inventory (r = 0.81). Our work offers a
new way of constraining NMVOC emissions from urban areas and highlights
the potential of satellite HCHO data to provide new information for
monitoring urban air quality.