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Diurnal cycle of the relevant chemical families and their partitioning ratio on day 5 of the solar average simulation. Chemical families are shown in units of volume mixing ratio. Vertical yellow dashed lines show the sunrise and sunset times, 06:00 a.m. and 06:00 p.m., respectively.
Source publication
The photochemical response of the stratosphere to short-term solar
variability is investigated using a photochemistry column model with
interactive photolysis calculation. The solar variability is here simply
represented using the Lean (1997) solar minimum and maximum spectra. In
order to isolate the photochemistry effect, simulations are devoid of...
Contexts in source publication
Context 1
... . To place in context the response of chemical families to solar variability, it is use- ful to first briefly map the chemical state for average solar irradiance (SI) conditions. This is represented in Fig. 2 by the diurnal cycle of day 5 of the simulation using average SI. The variation in the pattern of this diurnal cycle through the ten days of the simulation is minor and its diurnal average change is provided in Table 2. Note that these diurnal cycles are consistent with Brasseur et al. (1990) and Dessler (2000), for instance. Figure 3 ...
Context 2
... with an adjusted coefficient of determination larger than 0.8 at all al- titudes (not shown). Figure 4 shows that the adjusted coefficient of determina- tion for the 2-predictor model is larger than 0.97 through- out the column, demonstrating that the 2-predictor linear model provides a reasonable representation of the response. Consistently with Fig. 2, the intercept term (from the non- normalised regression) shows that the peak daily average mixing ratio of O x in solar average conditions occurs around 32 km (∼ 9 ppmv). The standardised regression coefficients shows that the current day's SI is dominant in the upper stratosphere (above 40 km) where the UV irradiance is in- tense and ...
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Citations
We present a model for the reconstruction of spectral solar irradiance between 200 and 400 nm. This model is an extension of the total solar irradiance (TSI) model of Crouch et al. (Astrophys. J.
677, 723, 2008) which is based on a data-driven Monte Carlo simulation of sunspot emergence, fragmentation, and erosion. The resulting time-evolving daily area distribution of magnetic structures of all sizes is used as input to a four-component irradiance model including contributions from the quiet Sun, sunspots, faculae, and network. In extending the model to spectral irradiance in the near- and mid-ultraviolet, the quiet Sun and sunspot emissivities are calculated from synthetic spectra at T
eff=5750 K and 5250 K, respectively. Facular emissivities are calculated using a simple synthesis procedure proposed by Solanki and Unruh (Astron. Astrophys.
329, 747, 1998). The resulting time series of ultraviolet flux is calibrated against the data from the SOLSTICE instrument on the Upper Atmospheric Research Satellite (UARS). Using a genetic algorithm, we invert quiet Sun corrections, profile of facular temperature variations with height, and network model parameters which yield the best fit to these data. The resulting best-fit time series reproduces quite well the solar-cycle timescale variations of UARS ultraviolet observations, as well as the short-timescale fluctuations about the 81 day running mean. We synthesize full spectra between 200 and 400 nm, and validate these against the spectra obtained by the ATLAS-1 and ATLAS-3 missions, finding good agreement, to better than 3 % at most wavelengths. We also compare the UV variability predicted by our reconstructions in the descending phase of sunspot cycle 23 to SORCE/SIM data as well as to other reconstructions. Finally, we use the model to reconstruct the time series of spectral irradiance starting in 1874, and investigate temporal correlations between pairs of wavelengths in the bands of interest for stratospheric chemistry and dynamics.
