Initial Results and Diurnal Variations Measured by a New Microwave Stratospheric ClO Instrument at Mauna Kea

Abstract

AbstractWe present the first year of ClO and O3 measurements from a new 278 GHz Chlorine monOxide Experiment (ChlOE) microwave instrument on Mauna Kea. We make use of comparisons with the Aura Microwave Limb Sounder (MLS) O3 measurements to recalibrate the ground‐based instrument and find that the recalibrated ground‐based O3 retrievals remain stable relative to MLS throughout the year. The MLS measurements provide daily daytime (~1330 local solar time) and nighttime (~0200 local solar time) ClO retrievals, and we find that the monthly ChlOE ClO retrievals show mixing ratios slightly smaller than those from MLS in the vicinity of Mauna Kea, with daytime values near the peak ~6–8% lower at 30–45 km for the average of the 12 months in this study. The nighttime monthly ClO values are almost all within ±0.03 ppbv over most of this altitude range, with very little overall bias. We have also made detailed hourly diurnal O3 comparisons with a multiyear analysis of previous retrievals from the much stronger 110 GHz O3 emission line being measured by our instrument at Mauna Loa and find that the hour‐to‐hour differences are within ±2% at 40 km, which indicates that the overall calibration of the ChlOE instrument is stable relative to time of day. We show hourly diurnal variations of ClO and compare these to 2010 measurements from the Submillimeter‐Wave Limb‐Emission Sounder and to a model.