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Background CO2 levels and error analysis from ground-based solar absorption IR measurements in central Mexico

Baylon, Jorge L.; Stremme, Wolfgang; Grutter, Michel; Hase, Frank; Blumenstock, Thomas

Abstract (englisch):
In this investigation we analyze two common optical configurations to retrieve CO2 total column amounts from solar absorption infrared spectra. The noise errors using either a KBr or a CaF2 beam splitter, a main component of a Fourier transform infrared spectrometer (FTIR), are quantified in order to assess the relative precisions of the measurements. The configuration using a CaF2 beam splitter, as deployed by the instruments which contribute to the Total Carbon Column Observing Network (TCCON), shows a slightly better precision. However, we show that the precisions in XCO2 ( =  0.2095  ⋅  Total Column CO2Total Column O2) retrieved from  >  96 % of the spectra measured with a KBr beam splitter fall well below 0.2 %. A bias in XCO2 (KBr − CaF2) of +0.56 ± 0.25 ppm was found when using an independent data set as reference. This value, which corresponds to +0.14 ± 0.064 %, is slightly larger than the mean precisions obtained. A 3-year XCO2 time series from FTIR measurements at the high-altitude site of Altzomoni in central Mexico presents clear annual and diurnal cycles, and a trend of +2.2 ppm yr−1 could be determined.

Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung - Atmosphärische Spurenstoffe und Fernerkundung (IMK-ASF)
Publikationstyp Zeitschriftenaufsatz
Jahr 2017
Sprache Englisch
Identifikator DOI: 10.5194/amt-10-2425-2017
ISSN: 1867-8548, 1867-1381
KITopen ID: 1000071696
HGF-Programm 12.03.01; LK 01
Erschienen in Atmospheric measurement techniques
Band 10
Heft 7
Seiten 2425–2434
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