CCMVal recommendations

Variations in the total solar irradiance (TSI), the so-called "solar constant", over a solar cycle are small (0.08%, e.g., Fröhlich, 2000). However, variations in the ultraviolet (UV) part of the solar spectrum, which is important for ozone production and middle atmosphere heating, range from 8% at 200nm to about 5% from 220nm to 260nm, 0.5% around 300nm, and 0.1% above 400nm (e.g., Lean et al., 1997; Woods and Rottman, 2002). Much larger variations are observed at shorter wavelengths (over 50% at 120nm, 10-15% from 140-200nm), which are mainly absorbed in the higher atmosphere (mesosphere and thermosphere).

To account for the highly variable and wavelength-dependent changes in solar irradiance, daily spectrally resolved solar irradiance data from 1 Jan 1950 to 31 Dec 2006 (in mW/m2/nm) are provided by Judith Lean for different time periods, different time resolution (daily or monthly) and different wavelength regions. The data were derived with the method described in Lean et al. (1997), Lean (2001), and Lean et al. (2005). A short description of how the data were (re)constructed can be found here.

Each modelling group is asked to integrate these data over the individual wavelength intervals in their radiation scheme (to adjust the shortwave heating rates) and chemistry scheme (to adjust the photolysis rates). It is recommended to use the provided solar flux data directly (integrated over the respective intervals in the radiation and chemistry schemes), rather than a parameterization with the F10.7cm radio flux previously used.

The data files are in ascii format and zipped. Each of the ascii files is organized as follows:

header
wavelength grid centers...
wavelength bands width (1 nm bins from 0 to 750 nm, 5 nm bins from 750 to 5000 nm, 10 nm bins from 5000 to 10000 nm, 50 nm bins from 10000 to 100000 nm)
Spectral irradiance (mW/m2/nm) daily for years indicated in the file name
YEAR MONTH DAY TSI in W/m2
solar flux data...
YEAR MONTH DAY+1 TSI in W/m2

Daily Solar Flux Data (CCMVal: REF1, SCN2d)

The following NEW data set is recommended for use in the new CCMVal reference runs as well as any other solar cycle studies. Note that the solar irradiance is the energy incident at 1 AU - so the variations in distance of the earth's orbit around the sun have been removed - this is true for all irradiance data. You have to account for the distance in your model. For Lyman-alpha irradiance it is recommended to use the respective values at 121.5nm.

Data REF1

SCN2d

We recommend using the daily solar flux data from REF1. To extend the limited observations it is proposed to repeat the period 1962-2004 (roughly solar cycles 20 to 23) and therefore neglect the extreme solar cycle 19 (peaking in 1957/58).

Average Solar Cycle Data (CCMVal: REF0, CTL0, REF2)

A short description of how the average solar cycle data were constructed can be found here. The following reference data sets are provided.

Monthly Solar Flux Data (for Historical Simulations)

Daily Spectral Irradiance from WACCM from first REF1 simulation round as comparison to other models

A whole solar spectrum data set covering 1950 to 2004 is available below (data provided by Dan Marsh, marsh AT ucar.edu).