Ground-based millimetre-wave measurements of middle-atmospheric carbon monoxide above Ny-Ålesund (78.9° N, 11.9° E)

oleh: N. J. Ryan, M. Palm, C. G. Hoffmann, J. Goliasch, J. Notholt

Format: Article
Diterbitkan: Copernicus Publications 2019-07-01

Deskripsi

<p>We present a new ground-based system for measurements of middle-atmospheric carbon monoxide (CO) at Ny-Ålesund, Svalbard, and the altitude profiles of CO volume mixing ratios (VMRs) measured during the 2017/2018 winter. The Carbon Monoxide Radiometer for Atmospheric Measurements (CORAM) records spectra from CO spectral emissions in the middle atmosphere with the aid of a low-noise amplifier designed for the 230&thinsp;<span class="inline-formula">GHz</span> spectral region. Altitude profiles of CO VMRs are retrieved from the measured spectra using an optimal estimation inversion technique. The profiles in the current dataset have an average altitude range of 47–87&thinsp;<span class="inline-formula">km</span>, with special consideration to be given to data at <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>&gt;</mo><mo>∼</mo><mn mathvariant="normal">70</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="2d97819add5fc2addad59b768a1c18b8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-12-4077-2019-ie00001.svg" width="32pt" height="10pt" src="amt-12-4077-2019-ie00001.png"/></svg:svg></span></span>&thinsp;<span class="inline-formula">km</span> altitude. The estimated uncertainty in the CO profile peaks at <span class="inline-formula">∼12</span>&thinsp;% of the a priori data used in the inversion. The CORAM profiles are compared to co-located CO measurements from the Microwave Limb Sounder (MLS) aboard the Aura satellite and show a difference of 7.4–16.1&thinsp;%, with a maximum absolute difference of 2.5&thinsp;ppmv at 86&thinsp;<span class="inline-formula">km</span> altitude. CO profiles are currently available at 1&thinsp;<span class="inline-formula">h</span> resolution between November 2017 and January 2018. The instrument measures during Arctic winter because summer time CO concentrations are so low as to be undetectable by CORAM.</p>