Solar UV irradiance variations from the UARS SUSIM and SOLSTICE instruments
Abstract
Accurate knowledge of long-term changes in solar ultraviolet (UV) irradiance is crucial for assessing the impact of solar variability on climate change. The UARS SUSIM and SOLSTICE instruments provide the first long-term solar UV irradiance data sets with complete in-flight calibration of instrument behavior. The current data sets from both instruments cover the full range of solar activity levels, from the end of the maximum of solar cycle 22 through solar minimum and the rise of solar cycle 23. In this paper, selected 5 nm bands are averaged to characterize broader spectral regions in the middle and near UV. We use the Singular Spectrum Analysis (SSA) technique to separate the irradiance time series into multiple components, representing short -term and long-term variations. Similar analysis is performed on both versions of the Mg II core -t o-wing ratio index, a common proxy for solar UV activity, derived from the corresponding irradiance data from each instrument. We find that the first two reconstructed components of each time series typically capture the long-term behavior (both solar-cycle-related changes and instrumental degradation effects), while intermediate-term and short-term variations are represented by progressively higher components. Comparisons of the relative importance of different components between the irradiance data and proxy data will be shown.
- Publication:
-
34th COSPAR Scientific Assembly
- Pub Date:
- 2002
- Bibcode:
- 2002cosp...34E1089D