Abstract
Abstract. The Canadian ACE (Atmospheric Chemistry Experiment) mission is dedicated to the retrieval of a large number of atmospheric trace gas species using the solar occultation technique in the infrared and UV/visible spectral domain. However, two additional solar disk imagers (at 525 nm and 1020 nm) were added for a number of reasons, including the retrieval of aerosol and cloud products. In this paper, we present first comparison results for these imager aerosol/cloud optical extinction coefficient profiles, with the ones derived from measurements performed by 3 solar occultation instruments (SAGE II, SAGE III, POAM III), one stellar occultation instrument (GOMOS) and one limb sounder (OSIRIS). The results indicate that the ACE imager profiles are of good quality in the upper troposphere/lower stratosphere, although the aerosol extinction for the visible channel at 525 nm contains a significant negative bias at higher altitudes, while the relative differences indicate that ACE profiles are almost always too high at 1020 nm. Both problems are probably related to ACE imager instrumental issues.
Highlights
The Canadian ACE instruments (Atmospheric Chemistry Experiment; see (Bernath et al, 2005)) on SCISAT-I are pri-marily intended to derive concentration profiles for a large number of trace gases, with the aim of studying chemical and physical processes that control ozone in the upper troposphere and lower stratosphere at mid- and high latitudes
The subject of this paper is the comparison of the aerosol and cloud extinction profiles that are derived from the two ACE imager measurements, with results from four satellite occultation instruments (SAGE II, Stratospheric Aerosol and Gas Experiment (SAGE) III, POAM III and GOMOS) and one limb sounder (OSIRIS)
The two imagers at 525 nm and 1020 nm onboard the ACE mission offer a promising and novel way to study aerosol and clouds in the Earth atmosphere, since it is in principle possible to derive 2-D aerosol extinction fields in a plane perpendicular to the line of sight
Summary
The Canadian ACE instruments (Atmospheric Chemistry Experiment; see (Bernath et al, 2005)) on SCISAT-I are pri-. The subject of this paper is the comparison of the aerosol and cloud extinction profiles that are derived from the two ACE imager measurements, with results from four satellite occultation instruments (SAGE II, SAGE III, POAM III and GOMOS) and one limb sounder (OSIRIS). 3 pixels centred on the co-registred ACE-FTS FOV are being analysed They all are located in the geometric centre of the high Sun image, where the solar limb. Considering the fact that the ACE FTS and the imagers are optically aligned and are viewing the same central part of the solar disk, the gas extinction contributions (O3, NO2, neutral density) can be obtained from the FTS gas retrieval data set. Since we are only considering instruments that have very good vertical resolution (looking sideways at the atmosphere with a small FOV; narrow averaging kernels), this effect will be minimal, and the usual convolution with averaging kernels is unnecessary
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