Abstract
We evaluated a new high-resolution solar reference spectrum for characterizing space-borne Ozone Monitoring Instrument (OMI) measurements as well as for retrieving ozone profile retrievals over the ultraviolet (UV) wavelength range from 270 to 330 nm. The SAO2010 solar reference has been a standard for use in atmospheric trace gas retrievals, which is a composite of ground-based and balloon-based solar measurements from the Kitt Peak National Observatory (KPNO) and Air Force Geophysics Laboratory (AFGL), respectively. The new reference spectrum, called the TSIS-1 Hybrid Solar Reference Spectrum (HSRS), spans 202–2730 nm at a 0.01 to ~0.001 nm spectral resolution. The TSIS-1 HSRS in the UV region of interest in this study is a composite of AFGL and ground-based solar measurements from the Quality Assurance of Spectral Ultraviolet Measurements In Europe (QASUME) campaign, with a radiometric calibration that used the lower resolution Spectral Irradiance Monitor (SIM) instrument on the space-based Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) mission. The TSIS-1 HSRS radiometric uncertainties were below 1% whereas those of SAO2010 ranged from 5% in the longer UV part to 15% in the shorter UV part. In deriving slit functions and wavelength shifts from OMI solar irradiances, the resulting fitting residuals showed significant improvements of 0.5–0.7% (relatively, 20–50%) due to switching from the SAO2010 to the TSIS-1 HSRS. Correspondingly, in performing ozone profile retrievals from OMI radiances, the fitting residuals showed relative improvements of up to ~5% in 312–330 nm with relative differences of 5–7% in the tropospheric layer column ozone; the impact on stratospheric ozone retrievals was negligible.
Highlights
The accurate knowledge of extraterrestrial solar radiation is required in many physical applications to study the natural influence of the sun on the radiative forcing of the climate and photochemistry of the earth as well as its oceanic and atmospheric circulation
The spectral resolution stands for the full-width at half-maximum (FWHM) of the slit functions or instrument spectral response function (ISRF). a The spectral resolution of the Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) Hybrid Solar Reference Spectrum (HSRS) ranges from 0.001 nm to ~0.01 nm and variants of the dataset are provided for lower, fixed spectral resolutions
To reduce the impact of different spectral resolutions on the comparison, the high-resolution spectra were commonly smoothed with the measured TSIS-1 Spectral Irradiance Monitor (SIM) wavelength-dependent instrument line shapes (ILS) whose FWHMs increase from 0.2 nm at 200 nm to 2.4 nm at 360 nm [11]
Summary
The accurate knowledge of extraterrestrial solar radiation is required in many physical applications to study the natural influence of the sun on the radiative forcing of the climate and photochemistry of the earth as well as its oceanic and atmospheric circulation. Ground-based observations of the sun at high-altitude sites have been applied to derive the high-resolution solar reference spectra in the UV, both visible and near-infrared These spectra have the advantages of broadband coverage with a single instrument as well as a high-resolution capability but lack an absolute radiometric accuracy due to strong interference from atmospheric absorption and scattering. To extend the spectral range to the shorter UV spectrum, a high-altitude stratospheric balloon spectrum by Hall and Anderson [13] has typically been employed to avoid the strong absorption of the ozone layer and aerosol/cloud loading It has a lower spectral resolution and narrower spectral coverage than ground-based measurements due to constraints on the size and weight of the instruments the atmospheric interferences above the balloon altitude can still be significant.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
