Measurement of climate-relevant trace gases via infrared spectroscopy
This work introduces a new fully automated FTIR system for ground-based total column measurements of atmospheric greenhouse gases. It is part of the Total Carbon Column Observation Network (TCCON), which has the main role to provide data for calibration and validation of satellite based measurements of greenhouse gases. This work describes the development of the system in three parts: design and setup, calibration, and testing. Chapter 2 describes the principal components and the design concept of the system. The focus lies on reliability and low maintenance effort to facilitate operation at remote sites. This is realized through the interaction of independent subsystems that are kept as simple as possible. Critical components are redundant as much as possible. To monitor the instrument's stability, the instrumental line shape of the FTIR is determined from HCl cell measurements. These measurements show that during a period of six months this ILS changes only slightly. From these results one can expect that -once aligned- the instrument will be very stable over long time periods. During the installation phase at Jena, Germany, the instrument measured columnaveraged XCO2 , XCO and XCH4 . Compared to ground-based in-situ CO2 VMR measurements, the FTIR total column XCO2 show an expected offset in the morning which mostly disappeared with the breakup of the nighttime planetary boundary layer. This effect demonstrates the reduced sensitivity of XCO2 measurements to mixing processes in the planetary boundary layer and confirms results of model simulations. Otherwise, the XCO2 measurements show a distinct diurnal cycle...
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