Validation of urban NO2 concentrations and their diurnal and seasonal variations observed from the SCIAMACHY and OMI sensors using in situ surface measurements in Israeli cities
Open Access
- 15 June 2009
- journal article
- Published by Copernicus GmbH in Atmospheric Chemistry and Physics
- Vol. 9 (12), 3867-3879
- https://doi.org/10.5194/acp-9-3867-2009
Abstract
We compare a full-year (2006) record of surface air NO2 concentrations measured in Israeli cities to coinciding retrievals of tropospheric NO2 columns from satellite sensors (SCIAMACHY aboard ENVISAT and OMI aboard Aura). This provides a large statistical data set for validation of NO2 satellite measurements in urban air, where validation is difficult yet crucial for using these measurements to infer NOx emissions by inverse modeling. Assuming that NO2 is well-mixed throughout the boundary layer (BL), and using observed average seasonal boundary layer heights, near-surface NO2 concentrations are converted into BL NO2 columns. The agreement between OMI and (13:45) BL NO2 columns (slope=0.93, n=542), and the comparable results at 10:00 h for SCIAMACHY, allow a validation of the seasonal, weekly, and diurnal cycles in satellite-derived NO2. OMI and BL NO2 columns show consistent seasonal cycles (winter NO2 1.6–2.7× higher than summer). BL and coinciding OMI columns both show a strong weekly cycle with 45–50% smaller NO2 columns on Saturday relative to the weekday mean, reflecting the reduced weekend activity, and validating the weekly cycle observed from space. The diurnal difference between SCIAMACHY (10:00) and OMI (13:45) NO2 is maximum in summer when SCIAMACHY is up to 40% higher than OMI, and minimum in winter when OMI slightly exceeds SCIAMACHY. A similar seasonal variation in the diurnal difference is found in the source region of Cairo. The surface measurements in Israel cities confirm this seasonal variation in the diurnal cycle. Using simulations from a global 3-D chemical transport model (GEOS-Chem), we show that this seasonal cycle can be explained by a much stronger photochemical loss of NO2 in summer than in winter.Keywords
This publication has 36 references indexed in Scilit:
- Comparison of tropospheric NO2 from in situ aircraft measurements with near‐real‐time and standard product data from OMIJournal of Geophysical Research: Atmospheres, 2008
- Intercomparison of SCIAMACHY and OMI tropospheric NO2 columns: Observing the diurnal evolution of chemistry and emissions from spaceJournal of Geophysical Research: Atmospheres, 2008
- Validation of Ozone Monitoring Instrument nitrogen dioxide columnsJournal of Geophysical Research: Atmospheres, 2008
- Intercomparison of SCIAMACHY nitrogen dioxide observations, in situ measurements and air quality modeling results over Western EuropeJournal of Geophysical Research: Atmospheres, 2007
- Near-real time retrieval of tropospheric NO2 from OMIAtmospheric Chemistry and Physics, 2007
- Cloud pressure retrieval using the O2‐O2 absorption band at 477 nmJournal of Geophysical Research: Atmospheres, 2004
- Error analysis for tropospheric NO2 retrieval from spaceJournal of Geophysical Research: Solid Earth, 2004
- Weekly cycle of NO2 by GOME measurements: a signature of anthropogenic sourcesAtmospheric Chemistry and Physics, 2003
- Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluationJournal of Geophysical Research: Solid Earth, 2001
- The reduced major axis of a bivariate sampleBiometrika, 1980