Sensitivity of tropical stratospheric ozone to rotational UV variations estimated from UARS and Aura MLS observations during the declining phases of solar cycles 22 and 23

Abstract

of tropical stratospheric ozone to rotational UV variations estimated from UARS and Aura MLS observations during the declining phases of solar cycles 22 and 23. Journal of Atmospheric and Solar-Terrestrial Physics, Elsevier, 2015, 130-131, pp.96-111. <10.1016/j.jastp.2015 AbstractThe correlation between tropical stratospheric ozone and UV radiation on solar rotational time scales is investigated using daily satellite ozone observations and reconstructed solar spectra.We consider two 3-year periods falling within the descending phases of two 11-year solar cycles 22 (1991-1994) and 23 (2004-2007). The UV rotational cycle is highly irregular and even disappears for half a year during cycle 23. For the 1991-1994 period, ozone and 205 nm UV flux are found to be correlated between about 10 and 1 hPa with a maximum of 0.29 at ~5 2 hPa; ozone sensitivity (percentage change in ozone for 1 percent change in UV) peaks at ~0.4.Correlation during cycle 23 is weaker with a peak ozone sensitivity of 0.2. The correlation is found to vary widely, not only with altitude, but also from one year to the next with a rotational signal in ozone appearing almost intermittent. Unexpectedly, the correlation is not found to bear any relation with the solar rotational forcing. For instance, solar rotational fluctuations are by far the strongest during 1991-1992 whereas the correlation peaks at the end of 1993, a rotationally quiescent period. When calculated over sliding intervals of 1-year, the sensitivity is found to vary very strongly within both 3-year periods; it is almost negligible over the entire vertical profile during some 1-year intervals or reaches close to 1 around 2-5 mb for other intervals. Other sources of variability, presumably of dynamical origin, operate on the rotational spectral range and determine to a large extent the estimated solar rotational signal. Even considering 3 years of observations (corresponding to about 40 solar cycles), the extraction of the rotational solar signal does not appear to be robust during declining phases of 11-year solar cycles. As observational studies cover at best three 11-year solar cycles, it must be challenging to produce a reliable estimation of the 11-year solar cycle signal in stratospheric ozone, especially in the presence of decadal climate variability.Ozone -stratosphere -solar variability -27-days -photochemistry

Reply to reviewer #3

“…Furthermore, the overall variation of the time lag with altitude shown in Fig. 6 is similar to that found in previous studies (Hood, 1986;Brasseur et al, 1987;Brasseur, 1993;Hood and Zhou, 1998) with a negative lag above 3-4 hPa (ozone "leading" the solar flux) and a positive lag below (ozone lagging the solar flux). As mentioned in the Introduction, the negative lag in the upper stratosphere results of the influence of the temperature feedback on the ozone response through the temperature dependent chemical reactions.…”

“…However, they noticed that including the solar induced temperature changes alone was not sufficient to adequately reproduce the observed magnitude and phase lag of the ozone response and suggested that atmospheric dynamical variability -which is not simulated in 1-D models -may also have a sizeable influence (Hood, 1986;Brasseur et al, 1987). The latter issue has later been addressed with two-dimensional models which revealed better agreement with observations (Brasseur, 1993;Fleming et al, 1995;Chen et al, 1997). Fleming et al (1995) further stressed the increasing importance with height of the solar-modulated HO x chemistry on the ozone response above 45 km.…”

Evaluation of the inter-annual variability of stratospheric chemical composition in chemistry-climate models using ground-based multi species time series

“…A statistically significant solar signature is found in tropics in both CCMs and observations but the solar signature is generally underestimated in CCMs. Note that the solar component results are found to be strongly dependent on the length of the data series (Bossay et al, 2015). For both observations and CCMs, the amount of variance explained by the aerosol forcing is very variable and strongly depends on the period covered by the time series, whether it is background (nonvolcanic) or volcanically active periods.…”

“…It is likely that only MLR analysis on time series of at least several decades can provide robust and reliable estimates of ozone column sensitivities to solar variations for monthly mean data, especially at high latitudes (see Figure 14). If daily data have been considered, a solar signal could have been extracted from much shorter time series because of an important periodicity in the solar activity, the 27-day solar rotational cycle (Rozanov et al, 2006;Fioletov, 2009;Bossay et al, 2015).…”

Nighttime Mesospheric/Lower Thermospheric Tropical Ozone Response to the 27‐Day Solar Rotational Cycle: ENVISAT‐GOMOS Satellite Observations Versus HAMMONIA Idealized Chemistry‐Climate Model Simulations

“…It is already well established that a substantial component of stratospheric ozone variability originates from short-term and long-term quasi-periodic fluctuations in solar activity, notably the 11-year solar magnetic activity cycle (also called the Schwabe cycle) and the 27-day solar rotational cycle (also called the Carrington cycle). Numerous observational (Bossay et al, 2015;Chandra & McPeters, 1994;Dikty et al, 2010;Fioletov, 2009;Hood, 1986;Hood & Zhou, 1998;Ruzmaikin et al, 2007;Zhou et al, 1997;Zhou et al, 2000) and modeling (Austin et al, 2007;Brasseur, 1993;Gruzdev et al, 2009;Merkel et al, 2011;Rozanov et al, 2006;Sukhodolov et al, 2017;Thiéblemont et al, 2017;Williams et al, 2001) studies have demonstrated the influence of the 27-day solar rotational cycle on stratospheric ozone. The main process responsible for the stratospheric ozone response to solar variability is the solar UV-driven photolysis of molecular oxygen (O 2 ) that is the source of O 3 in the stratosphere.…”