FLIIMP - a community software for the processing, calibration, and reporting of liquid water isotope measurements on cavity-ring down spectrometers.

Precise and accurate measurements of the stable isotope composition from precipitation, land ice, runoff, and oceans provide critical information on Earth's water cycle. The analysis, post-processing, and calibration of raw analytical signals from laser spectrometers during sample analysis involves a number of critical procedures to counteract instrumental drift, inter-sample memory effects, and the quantification of total uncertainty. We present a new software tool for the post-processing and calibration named FLIIMP (FARLAB Liquid Water Isotope Measurement Processor). FLIIMP facilitates sample processing by (1) a graphical user interface that guides the user along the processing steps from corrections for memory effects, drift, and mixing ratio to calibration, and (2) allows to monitor long-term measurement system behaviour, currently for Picarro-brand water isotope analysers. Final data files are accompanied by a detailed calibration report. Being an open-source software for the major operating systems, users can adapt FLIIMP to their laboratory environment, and the community can contribute the software development. •FLIIMP facilitates post-processing, calibration and reporting for stable water isotope liquid sample analysis.•The stepwise, interactive graphical user interface reduces possibility of errors and shortens processing time.•Open source software enables future development of FLIIMP by the user community.