24.11.2014: FB1-Seminar

11:00 h, Hörsaal, Düsternbrooker Weg 20

Abstract:

Solar ultraviolet (UV) radiation absorbed by ozone is the main source of heating in the stratosphere and affects the chemistry, temperature and dynamics of the atmosphere. Here I will present recent revisions to the SATIRE-S solar spectral and total irradiance model, in the context of other models and observations, and discuss the limits in our knowledge of how SSI may vary over the solar cycle (SC) using stratospheric ozone observations and Bayesian inference. The new SATIRE-S SSI dataset spans 1974 to 2013. I will on compare SATIRE-S with the NRLSSI model and SORCE observations. SATIRE-S and NRLSSI show similar SC changes below 250 nm. However, SATIRE-S show almost double the change in flux as NRLSSI between 250 and 310 nm, but less than half that of SOLSTICE, one of the instruments on SORCE. UV changes from each of these SSI datasets would lead to different ozone responses in the stratosphere. Instead of simply comparing the ozone response to different SSI datasets with ozone observations, can the observed SC change in stratospheric ozone be used to constrain the allowed range of solar UV changes? To answer this, I first show that the response of equatorial stratospheric ozone to SC changes in UV can be estimated using a simple linear approximation. From this, a Bayesian formalism can be used to show that one cannot distinguish between different SSI datasets using current estimates of ozone changes. This Bayesian approach could be developed to investigate other datasets and provide a better understanding of both variations in SSI and the atmospheric response to it.

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