Abstract
Abstract. The mesospheric hydroxyl radical (OH) is mainly produced by the water vapor (H2O) photolysis and could be considered as a proxy for the influence of the solar irradiance variability on the mesosphere. We analyze the tropical mean response of the mesospheric OH and H2O data as observed by the Aura Microwave Limb Sounder (MLS) to 27-day solar variability. The analysis is performed for two time periods corresponding to the different phases of the 11-yr cycle: from December 2004 to December 2005 (the period of "high activity" with a pronounced 27-day solar cycle) and from August 2008 to August 2009 ("solar minimum" period with a vague 27-day solar cycle). We demonstrate, for the first time, that in the mesosphere the daily time series of OH concentrations correlate well with the solar irradiance (correlation coefficients up to 0.79) at zero time-lag. At the same time H2O anticorrelates (correlation coefficients up to −0.74) with the solar irradiance at non-zero time-lag. We found that the response of OH and H2O to the 27-day variability of the solar irradiance is strong for the period of the high solar activity and negligible for the solar minimum conditions. It allows us to suggest that the 27-day cycle in the solar irradiance and in OH and H2O are physically connected.
Highlights
It is well known that the solar radiation, which is the main energy source in the terrestrial atmosphere, is variable on different time scales
The Spectral Solar Irradiance (SSI) data used for this study were obtained by the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) instrument onboard the Solar Radiation and Climate Experiment (SORCE) satellite launched on 25 January 2003 (McClintock, 2005)
We analyzed the mesospheric response of the OH and H2O mixing ratios derived from AURA/Microwave Limb Sounder (MLS) data to the 27-day solar rotational cycle as measured by SOLSTICE/SORCE
Summary
It is well known that the solar radiation, which is the main energy source in the terrestrial atmosphere, is variable on different time scales (see e.g. Lean et al, 2005; Krivova and Solanki, 2008; Krivova et al, 2011; Shapiro et al, 2010, 2011b; and references therein). Egorova et al, 2004; Rozanov et al, 2004, 2008; Schmidt et al, 2006; Marsh et al, 2007; Austin et al, 2008) The results of these efforts revealed a noticeable disagreement among model results and high uncertainty of the observed solar signal in ozone and temperature obtained from the different satellite data. The recent studies of the solar rotation cycle effects with chemistry-climate models (Rozanov et al, 2006; Austin et al, 2007; Gruzdev et al, 2009; Chen et al, 1997; Kubin et al, 2011) showed that the ozone response to the short-term solar variability is more robust and is in a better agreement with available satellite data in the middle stratosphere in comparison with the decadal scale signal.
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