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Measurements of Tropospheric NO2 in Romania Using a Zenith-Sky Mobile DOAS System and Comparisons with Satellite Observations

Domenii publicaţii > Ştiinţele pământului şi planetare + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: D. E.Constantin, A. Merlaud, M. Van Roozendael, M. Voiculescu, C. Fayt, F. Hendrick, G. Pinardi and L.Georgescu

Editorial: Sensors, 13, p.3922-3940, 2013.


In this paper we present a new method for retrieving tropospheric NO2 Vertical
Column Density (VCD) from zenith-sky Differential Optical Absorption Spectroscopy
(DOAS) measurements using mobile observations. This method was used during three
days in the summer of 2011 in Romania, being to our knowledge the first mobile DOAS
measurements peformed in this country. The measurements were carried out over large and
different areas using a mobile DOAS system installed in a car. We present here a
step-by-step retrieval of tropospheric VCD using complementary observations from ground
and space which take into account the stratospheric contribution, which is a step forward
compared to other similar studies. The detailed error budget indicates that the typical
uncertainty on the retrieved NO2tropospheric VCD is less than 25%. The resulting
ground-based data set is compared to satellite measurements from the Ozone Monitoring
Instrument (OMI) and the Global Ozone Monitoring Experiment-2 (GOME-2). For instance,
on 18 July 2011, in an industrial area located at 47.03°N, 22.45°E, GOME-2 observes a
tropospheric VCD value of (3.4 ± 1.9) × 1015 molec./cm2, while average mobile measurements
Sensors 2013, 13 3923
in the same area give a value of (3.4 ± 0.7) × 1015 molec./cm2. On 22 August 2011, around
Ploiesti city (44.99°N, 26.1°E), the tropospheric VCD observed by satellites is
(3.3 ± 1.9) × 1015 molec./cm2 (GOME-2) and (3.2 ± 3.2) × 1015 molec./cm2 (OMI), while
average mobile measurements give (3.8 ± 0.8) × 1015 molec./cm2. Average ground
measurements over “clean areas”, on 18 July 2011, give (2.5 ± 0.6) × 1015 molec./cm2 while
the satellite observes a value of (1.8 ± 1.3) × 1015 molec./cm2.

Cuvinte cheie: DOAS; spectrophotometer; nitrogen dioxide; mobile measurements