Ground-based millimeter-wave observation of stratospheric ClO over Atacama, Chile in the mid-latitude Southern Hemisphere

[摘要] We have performed ground-based measurements of stratospheric chlorinemonoxide (ClO) during the summer in 2009 over the Atacama highland, Chile, anew observing site in the mid-latitude region in the Southern Hemisphere, byusing a millimeter-wave spectroscopic radiometer. The radiometer, equippedwith a superconducting receiver and a digital Fourier spectrometer, wasdeveloped by Nagoya University, and the new observing system provides us highsensitivity and stable performance to measure the very weak ClO lines. Thereceiver noise temperature of the superconducting receiver is 170 K in DSB.To reveal the diurnal variation of ClO, we retrieved the vertical mixingratio profiles by the weighted-damped least-squares algorithm applied for thespectral data at 203 GHz obtained between 5 and 16 December 2009. The totalerror on the retrieval is estimated to be 20% to 30% in an altituderange from 40 km to 50 km. The amplitude of the diurnal variation isestimated as 33% of the daytime average at 40 km. The observed timevariation shows a pattern similar to that of the previous works observed inthe northern mid-latitude region.

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