A Comparative Assessment of Solar Irradiance Observations and Models at the Dawn of TSIS
Journal Article
Overview
abstract
A wide variety of research applications require knowledge of total solar; irradiance (TSI) and solar spectral irradiance (SSI) on time scales from; minutes to centuries. The current satellite data record of TSI and; ultraviolet SSI is 40 years long while observations of solar irradiance; at visible wavelengths through the near-infrared span 15 years. In late; 2017, the NASA Total and Spectral Solar Irradiance Sensor-1 (TSIS-1); mission was deployed on the International Space Station (ISS); these new; TSI and SSI datasets are now extending the observational solar; irradiance record with a planned 5-year mission. Recognizing the need; for ongoing specification of solar irradiance, the National Centers for; Environmental Information established the Solar Irradiance Climate Data; Record (CDR) in 2014. The CDR includes a composite record of TSI; observations and estimates of solar total and spectral irradiance; variations during, and prior, to the space-based record based on the; Naval Research Laboratory (NRL) models. Utilizing as inputs proxies of; sunspot darkening and facular brightening, the models specify TSI and; SSI annually since 1610 and daily since 1882. Both the observational; composite and the model specifications are updated regularly and will; eventually utilize the new TSIS-1 observations, both to extend the; observational composite and to validate and improve the models. With the; goal of establishing the utility of the NRL models in specifying the; time and wavelength dependence of solar variability for the Solar; Irradiance CDR, we compare the latest NRLTSI2 and NRLSSI2 modeled; irradiances with observations, including composite records, and with; independent models of solar irradiance variability. Our assessments; quantify current understanding of solar irradiance variability on; multiple timescales and identify areas where TSIS-1 observations are; expected to provide improved understanding of solar irradiance; variability. We use the following datasets in our comparisons: TSIS-1,; Solar Radiation and Climate Experiment (SORCE), Ozone Monitoring; Instrument (OMI), Solar Irradiance Data Exploitation (SOLID), Spectral; and Total Irradiance Reconstructions for the Satellite Era (SATIRE-S), a; three-dimensional extension of the SATIRE-S model (SATIRE-3D), and; Empirical Irradiance Reconstruction (EMPIRE).
