title: Measurements of tropospheric NO2 in Romania using a zenith-sky mobile DOAS system and comparisons with satellite observations.
abstract: 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 in the same area give a value of (3.4 ± 0.7) × 10(15) 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) × 10(15) molec./cm2 (GOME-2) and (3.2 ± 3.2) × 10(15) molec./cm2 (OMI), while average mobile measurements give (3.8 ± 0.8) × 10(15) molec./cm2. Average ground measurements over "clean areas", on 18 July 2011, give (2.5 ± 0.6) × 10(15) molec./cm2 while the satellite observes a value of (1.8 ± 1.3) × 10(15) molec./cm2.
authors.affiliation: Dunarea de Jos, University of Galati, Faculty of Sciences and Environment, European Center of Excellence for the Environment, Galati, Romania. daniel.costantin@ugal.ro
authors.forename: Daniel-Eduard
authors.initials: DE
authors.lastname: Constantin
authors.forename: Alexis
authors.initials: A
authors.lastname: Merlaud
authors.forename: Michel
authors.initials: M
authors.lastname: Van Roozendael
authors.forename: Mirela
authors.initials: M
authors.lastname: Voiculescu
authors.forename: Caroline
authors.initials: C
authors.lastname: Fayt
authors.forename: François
authors.initials: F
authors.lastname: Hendrick
authors.forename: Gaia
authors.initials: G
authors.lastname: Pinardi
authors.forename: Lucian
authors.initials: L
authors.lastname: Georgescu
mesh_terms: D000393:Air Pollutants; D004784:Environmental Monitoring; D006801:Humans; D009585:Nitrogen Dioxide / Q000302:isolation & purification*; D055096:Optical Devices; D010126:Ozone / Q000302:isolation & purification*; D012383:Romania; D017215:Satellite Communications
chemical_list: D000393:Air Pollutants; D010126:Ozone; D009585:Nitrogen Dioxide