Ground-based tunable diode laser measurements of formaldehyde: Improvements in system performance & recent field campaigns

Formaldehyde (HCHO) is an important reactive intermediate in atmospheric studies. Accurate measurements of HCHO are required to constrain and validate photochemical models. Despite this importance, there is still considerable uncertainty in present ambient measurements of this gas as well as in measurement-model relationships. The present paper discusses the long-term effort at NCAR to develop, employ, and validate a highly sensitive tunable diode laser absorption spectrometer (TDLAS) for ambient measurements of HCHO. A detailed analysis of measurement precision will be presented and performance improvements using rapid background subtraction, FFT filtering, and scan-by-scan demeaning will be discussed. This paper will conclude with a brief discussion of recent photochemistry and intercomparison field campaigns employing the TDLAS.