Abstract
Abstract. Nitrogen dioxide (NO2) profile retrievals were performed by ship-borne Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) using a compact/low-power spectrometer on the Japanese research vessel Kaiyo during two ocean cruises around Japan and Japan–Bali (Indonesia)–Indian Ocean. DOAS analysis using a 425–450 nm fitting window revealed a clear land–ocean contrast in NO2 differential slant column densities (DSCDs) but poor fitting results and negative values, especially at low elevation angles at low latitudes (
Highlights
Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a recently developed remote sensing technique designed for atmospheric aerosol and gas profile measurements using scattered solar radiation at several elevation angles (e.g. Honninger et al, 2004; Wagner et al, 2004; Wittrock et al, 2004; Sinreich et al, 2005; Frieß et al, 2006)
We investigated other relationships and found a negative correlation between H2O differential slant column densities (DSCDs) and the Ring effect, suggesting that the Ring effect contributed to the poor fitting (Fig. 6c)
The telescope was mounted on an active gimbal to ensure it was kept horizontal; it was successfully kept within ±0.2◦ of the target elevation angle for ∼ 60 % of the time
Summary
Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a recently developed remote sensing technique designed for atmospheric aerosol and gas profile measurements using scattered solar radiation at several elevation angles (e.g. Honninger et al, 2004; Wagner et al, 2004; Wittrock et al, 2004; Sinreich et al, 2005; Frieß et al, 2006). We report on the development of a MAX-DOAS instrument for use on ocean vessels, using an active-type gimbal to keep the telescope horizontal. Aerosol and gas measurements by MAX-DOAS were continuously conducted during two ocean cruises on the Japanese R/V Kaiyo of JAMSTEC. For the first cruise (KY08-05), a miniaturized UV/visible spectrometer (USB4000, Ocean Optics) was installed inside the telescope unit, and the spectra data were recorded by a laptop located indoors on the vessel. For comparison with in situ measurements, we use MAX-DOAS data obtained at Yokosuka, Japan (35.32◦ N, 139.65◦ E), which have been measured continuously since April 2007 using basically the same instrument as that used at Okinawa (Takashima et al, 2009), employing a USB4000 spectrometer and 5-m fiber optics.
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