Abstract
Abstract. This article introduces a new fully automated FTIR system that is part of the Total Carbon Column Observing Network (TCCON). It will provide continuous ground-based measurements of column-averaged volume mixing ratio for CO2, CH4 and several other greenhouse gases in the tropics. Housed in a 20-foot shipping container it was developed as a transportable system that could be deployed almost anywhere in the world. We describe the automation concept which relies on three autonomous subsystems and their interaction. Crucial components like a sturdy and reliable solar tracker dome are described in detail. The automation software employs a new approach relying on multiple processes, database logging and web-based remote control. First results of total column measurements at Jena, Germany show that the instrument works well and can provide parts of the diurnal as well as seasonal cycle for CO2. Instrument line shape measurements with an HCl cell suggest that the instrument stays well-aligned over several months. After a short test campaign for side by side intercomaprison with an existing TCCON instrument in Australia, the system will be transported to its final destination Ascension Island.
Highlights
Surface flux estimations of CO2 on regional to global scales have so far been derived by a combination of data from a global network of surface sites (GLOBALVIEW-CO2) and the results of global transport models (Gurney et al, 2002; Rayner et al, 1999; Tans et al, 1990)
In case of a power failure the Programmable Logic Controller (PLC) ensures that all components are properly shut down and the dome is closed before the UPS battery runs out
The operating system is a minimal Debian Linux which emulates a FreeDOS environment for the original solar tracker software. This way, the solar tracker software can be controlled over the network and the clock can be synchronized through network time protocol (NTP)
Summary
Surface flux estimations of CO2 on regional to global scales have so far been derived by a combination of data from a global network of surface sites (GLOBALVIEW-CO2) and the results of global transport models (Gurney et al, 2002; Rayner et al, 1999; Tans et al, 1990). The column integral of the CO2 VMR profile is less sensitive to diurnal variations in atmospheric boundary layer height and details of vertical transport in general (Gerbig et al, 2008) It exhibits less spatial and temporal variability than near-surface in situ data, while retaining information about surface fluxes (Gloor et al, 2000). The instrument will be part of the Total Carbon Column Observation Network (TCCON) (Wunch et al, 2010; Toon et al, 2009) that provides ground-truth data for satellite validation It will be installed on Ascension Island, a British oversea territory in the South Atlantic. This article provides a technical overview of the system and shows first results obtained during this initial phase
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