Open AccessComparison of OMI and ground‐based in situ and MAX‐DOAS measurements of tropospheric nitrogen dioxide in an urban area
Author(s) -
Kramer Louisa J.,
Leigh Roland J.,
Remedios John J.,
Monks Paul S.
Publication year - 2008
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007jd009168
Subject(s) - troposphere , ozone monitoring instrument , environmental science , differential optical absorption spectroscopy , nitrogen dioxide , atmospheric sciences , tropospheric ozone , remote sensing , meteorology , climatology , absorption (acoustics) , geography , physics , optics , geology
In this paper we compare retrieved tropospheric vertical column densities (VCDs) of nitrogen dioxide (NO 2 ) from the Ozone Monitoring Instrument (OMI) to coincident tropospheric columns retrieved from the Concurrent Multiaxis Differential Optical Absorption Spectroscopy (CMAX‐DOAS) instrument, installed at the University of Leicester (52.38°N, 1.08°W), and in situ near‐surface measurements from chemiluminescence detectors. The results show that tropospheric NO 2 columns retrieved from CMAX‐DOAS and OMI correlate well ( r = 0.64) when cloud clearing has been applied, and only those pixels that sample at least 90% of the Leicester area were included in the analyses. The correlation of OMI tropospheric VCDs with near‐surface measurements for cloud‐free days in 2005 and 2006 initially showed a strong positive bias in the near‐surface NO 2 measurements and scattered points. This was interpreted as being due to the satellite footprint of OMI sampling the NO 2 sources from the surrounding area of Leicester as well as emissions from the city. A field‐of‐view (FOV) weighted estimate for the OMI‐equivalent urban NO 2 was calculated for each coincidence by including background concentrations from a nearby in situ monitor, situated in a rural area. The subsequent agreement between the OMI tropospheric VCDs and FOV weighted near‐surface measurements is very good for spring ( r = 0.83) and summer ( r = 0.64) months. Finally, seasonal and weekly cycles of NO 2 are produced which show that OMI may be underestimating the amount of NO 2 during the winter months. However, all sets of data show expected weekly cycles, with lower values on a Sunday.