SH32A-07
First Evidence of Middle Atmospheric HO2 Response to UV variability during 27-day Solar Cycles From Satellite Observations

Wednesday, 16 December 2015: 12:04
2011 (Moscone West)
Shuhui Wang1, Qiong Zhang2, Luis F Millan Valle1, King-Fai Li3, Yuk L Yung2, Stanley P Sander1, Nathaniel J Livesey1 and Michelle L Santee1, (1)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (2)California Institute of Technology, Pasadena, CA, United States, (3)University of Washington, Department of Applied Mathematics, Seattle, WA, United States
Abstract:
HO2 and OH, also known as odd oxygen HOx, play an important role in middle atmospheric chemistry, in particular O3 destruction through catalytic HOx reaction cycles. Due to their photochemical production and short chemical lifetimes, HOx species are expected to show rapid responses to solar irradiance changes, resulting in variability in the corresponding O3 chemistry. While the OH response to solar cycles has been investigated, HO2 studies have been limited by the lack of reliable observations. The recently developed “offline” HO2 data product from the Aura Microwave Limb Sounder (MLS) makes it possible, for the first time, to investigate HO2 variability and the behavior of OH/HO2 partitioning, which plays an important role in O3-destroying HOx cycles. Here we present the first evidence of global mean HO2 variability during solar 27-day cycles by investigating the new MLS HO2 data. We focus on the most recent data from 2012 - 2015, when solar irradiance variability is strong near the peak of Solar Cycle 24. The features of mesospheric HO2 variability are found to correlate well with those of solar Lyman-α variability. The strongest HO2 solar cycle signals occur in the pressure range 0.01 – 0.068 hPa. When continuous MLS OH observations are not available, the new HO2 data could be a promising alternative for investigating HOx variability and the corresponding impacts on O3 and the climate.