The Solar Irradiance Climate Data Record

Because solar irradiance is the source of more than 99.999% of Earth's energy, an accurate understanding of its magnitude and variability is essential for understanding and forecasting global and atmospheric climate variability change. Scientific researchers and user communities alike require reliable knowledge of both the total (spectrally integrated) and spectral solar irradiance over short and long-time scales for a broad range of applications that include, for example, remote sensing, regional and global climate modeling, and renewable energy, and solar cell technology.

A solar irradiance climate data record (CDR) is being developed as part of NOAA's Climate Data Record Program (CDRP) to provide effective, technically robust information that is available operationally through NOAA's National Climatic Data Center (NCDC) and the Laboratory for Atmospheric and Space Physics (LASP) Interactive Solar Irradiance Data Center (LISIRD). We discuss the statistical models, and observations upon which they are based, that we use to construct total solar irradiance (TSI) and solar spectral irradiance (SSI) variability through the net effect of opposing influences by sunspot darkening and faculae brightening. In the “next-generation” version of the statistical models, state-of-the-art measurements by the SOlar Radiation and Climate Experiments (SORCE) Total Irradiance Monitor (TIM) and Spectral Irradiance Monitor (SIM) from 120 to 2400 nm that extend from 2003 to the present are utilized to compute the model regression coefficients using regression analysis.

The quality assurance of the modeled solar irradiance depends on the accuracy and stability of the measured irradiance data, as well as the quality of the sunspot and facular proxy input data. We discuss the validation of the measured solar irradiance and proxy data against other measurements and models, as well as the approach where future measurements of solar irradiance will be incorporated into the generation of the solar irradiance CDR following the launch of the Total and Spectral Solar Irradiance Sensor (TSIS). In addition, we present future plans to monitor the variability in the proxy data in order to provide first-time uncertainty estimates in the modeled solar irradiance.