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Aura Science

Signature of the Solar Rotational Cycle in Mesospheric Hydroxide and Water

Aura figure

Figure. 1 Comparison of the tropical mean daytime averaged and 20-35 day filtered MLS OH at ~78 km altitude (upper panel) and filtered (central panel) and unfiltered (lower panel) H2O at ~80 km altitude with SOLSTICE/SORCE Ly-_ line irradiance. The comparison is performed for the period from August 2004 to December 2006.

The AURA Microwave Limb Sounder (MLS) data reveal a strong OH and H2O response to the 27-day solar irradiance variability.

We show that the mesospheric Hydroxide (OH) and Water (H2O) correlate well with the solar irradiance. The OH variation correlates positively and the H2O variation correlates negatively with solar irradiance. Both species demonstrate a pronounced 27-day periodicity, which resembles the solar rotational cycle (Fig. 1). The 27-day harmonic in OH and H2O power spectra is strong during the period of high solar activity and negligible for the solar minimum conditions (Fig.2.) This proves that the 27-day variability in the OH and H2O data is caused by the solar rotational cycle.

Aura figure

Figure. 2 The normalized power spectra of the tropical mean unfiltered daytime OH (top panel) and H2O (bottom panel).

Shapiro, A. V., et al., (2012), Atmospheric Chemistry and Physics