Water vapor density and turbulent fluxes from three generations of infrared gas analyzers

Abstract. Fast-response infrared gas analyzers (IRGAs) have been widely used over 3 decades in many ecosystems for long-term monitoring of water vapor fluxes the surface layer atmosphere. While some early IRGA sensors are still these national and/or regional eco-flux networks, optically improved newly employed same networks. The purpose this study was to evaluate performance density and flux data from three generations IRGAs – LI-7500, LI-7500A, LI-7500RS (LI-COR Bioscience, Inc., Nebraska, USA) course a growing season Bushland, Texas, USA, an irrigated maize canopy 90 d. Water measurements were generally good agreement, but temporal drift occurred different directions magnitudes. Means exhibited mostly shift changes that did not impact magnitudes, while their variances fluctuations occasionally poor especially following rainfall events. LI-7500 cospectra largest compared under unstable neutral static stability. Agreement among best typical irrigation-cooled boundary layer, with 14 % interinstrument coefficient variability advective conditions. Generally, smallest LI-7500RS, high-frequency spectral corrections larger measurements, resulting similar between LI-7500A LI-7500RS. Fluxes representative ET based on world-class lysimeter reference measurement, using energy balance ratio as estimate systematic bias corrected most differences measured fluxes.