The effects of different calibration and frequency response correction methods on eddy covariance ozone flux measured with a dry chemiluminescence analyzer

Abstract

a b s t r a c tOzone (O 3 ) flux (F o ) was measured over a wheat field in Yucheng, China, using the eddy covariance technique. A dry chemiluminescence fast-response O 3 analyzer and a UV-absorption based slow-response O 3 analyzer were used for measuring fast O 3 concentration fluctuations and absolute concentrations, respectively. The main objective of this study was to determine a group of suitable methods for calculating F o based on the performance of the two O 3 analyzers in the field. We evaluated the effects of three calibration methods on F o . These calibration methods include the ratio method (RM, it assumes that the fast-response analyzer's signal-output is directly proportional to absolute ambient O 3 concentration within a 30-min interval), the ratio offset method (ROM, it is based on the ratio method with analyzer's offset modification), and the ratio variation method (RVM, it is based on the ratio method with the fastresponse analyzer's gain factor variation within a 30-min interval). Three frequency response corrections (analytic, revised analytic, and in-situ) for the estimation of F o were also evaluated. Our results show that: (1) Compared to the O 3 flux with the commonly-used method (RM), on average, the fluxes with ROM and RVM were decreased by about 9% and 7%, respectively. (2) Based on the spectral analysis, the fastresponse O 3 analyzer's noise could cause random errors, but did not result in a systematic error in F o . Tubing attenuation in O 3 concentration fluctuations can cause up to 20% loss in F o . (3) Frequency response corrections for F o with the original analytic method, the in-situ method, and the revised analytic method were 34.6%, 23.8% and 25.4% on average, respectively.

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

“…While there is a method to correct ozone fluxes measured with an ultraviolet (UV) photometric ozone analyzer, the empirical correction is large, and random uncertainty in the daytime ozone flux is 60% (Wohlfahrt, Hörtnagl, et al, ). Reported frequency response corrections from fast ozone analyzers typically range from 5% to 30% (Bauer et al, ; Keronen et al, ; Horváth et al, ; Munger et al, ; Plake, Stella, et al, ; Zhu et al, ).…”

“…A second ozone analyzer, which can be a commonly used UV absorbance instrument, is always necessary in dry chemiluminescence setups to account for the changing disc sensitivity. Different techniques to calculate an absolute signal can lead to substantially different ozone fluxes, as shown by measurements at Easter Bush (Muller et al, ) and a Chinese wheat field (Zhu et al, ).…”

Effects of Environmental Factors on Ozone Flux over a Wheat Field Modeled with an Artificial Neural Network

“…Since the fast-response O 3 analyzer's sensitivity is not constant [14], the sensitivity must be calibrated by a slow-response O 3 concentration analyzer. However, it has been shown that the sensitivity can be treated as constant when using a 30 min averaging interval [32].…”

“…O 3 flux loss caused by time delay was corrected by the maximum covariance method [35]. Only the effect of density variation caused by water vapor on O 3 flux was considered [14,36]. e more detailed description of observations, calculations, and corrections can be found in Zhu et al [14].…”

“…F o is usually measured by micrometeorological methods, and the eddy covariance (EC) method is considered the most direct fluxmeasuring method [8,[10][11][12]. However, due to a lack of high performance fast-response O 3 analyzers (e.g., it needs to change O 3 -sensitive dye often and its sensitivity is unstable), EC-measured O 3 flux has many temporal gaps in the associated datasets [8,13,14]. is leads to difficulties in calculating the value of a O 3 stomatal flux-based index using the EC O 3 flux since the effect of O 3 on crop yields results from the accumulation of O 3 damage.…”