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High concentration ground-level ozone (O-3) has adverse effects on plant growth and photosynthesis. Compared to the O-3 concentration-based index, the O-3 flux-based (especially stomatal O-3 uptake) index has been considered the better criterion for assessing the impact of ozone on vegetation and ecosystems. This paper reports on a study of O-3 flux using the eddy covariance technique over a corn field in the Northwestern Shandong Plain of China. Diurnal variation of atmospheric O-3 concentration, deposition velocity and flux, and their relationships to environmental factors are analyzed. The results show that: (1) During the observation period (9 August-28 September, 2011), there was a strong diurnal variation of O-3 concentration, with low (16.5 nL L-1) and high (60.1 nL L-1) O-3 mean concentrations observed around 6:30 and 16:00, respectively. Mean O-3 concentrations during daytime (6:00-18:00) and nighttime (18:00-6:00) were 39.8 +/- 23.1 and 20.7 +/- 14.1 nL L-1 (mean +/- std), respectively. The maximum observed concentration was 97.5 nL L-1. The concentration was mainly affected by solar radiation and air temperature. (2) Whether daytime or nighttime, ground-level O-3 flux is always downward. The diurnal course of mean deposition velocity was divided into 4 phases: a low and stable process during nighttime, fast increasing in early morning, relatively large and steady changes around noon, and quickly decreasing in later afternoon. Daytime and nighttime mean deposition velocities were 0.29 and 0.09 cm s(-1), respectively. The maximum deposition velocity was 0.81 cm s(-1). The magnitude of deposition velocity was influenced by the corn growth period, and its diurnal variation was significantly correlated with global radiation and relative humidity. (3) O-3 flux was affected by variations of both O-3 concentration and deposition velocity, with mean O-3 fluxes -317.7 and -70.2 ng m(-2) s(-1) during daytime and nighttime, respectively. There was strong correlation between O-3 flux and CO2 flux or latent heat flux. By comparing the deposition velocities of daytime and nighttime, we infer that stomatal uptake was probably the main sink of ground-level O-3
High concentration ground-level ozone (O-3) has adverse effects on plant growth and photosynthesis. Compared to the O-3 concentration-based index, the O-3 flux-based (especially stomatal O-3 uptake) index has been considered the better criterion for assessing the impact of ozone on vegetation and ecosystems. This paper reports on a study of O-3 flux using the eddy covariance technique over a corn field in the Northwestern Shandong Plain of China. Diurnal variation of atmospheric O-3 concentration, deposition velocity and flux, and their relationships to environmental factors are analyzed. The results show that: (1) During the observation period (9 August-28 September, 2011), there was a strong diurnal variation of O-3 concentration, with low (16.5 nL L-1) and high (60.1 nL L-1) O-3 mean concentrations observed around 6:30 and 16:00, respectively. Mean O-3 concentrations during daytime (6:00-18:00) and nighttime (18:00-6:00) were 39.8 +/- 23.1 and 20.7 +/- 14.1 nL L-1 (mean +/- std), respectively. The maximum observed concentration was 97.5 nL L-1. The concentration was mainly affected by solar radiation and air temperature. (2) Whether daytime or nighttime, ground-level O-3 flux is always downward. The diurnal course of mean deposition velocity was divided into 4 phases: a low and stable process during nighttime, fast increasing in early morning, relatively large and steady changes around noon, and quickly decreasing in later afternoon. Daytime and nighttime mean deposition velocities were 0.29 and 0.09 cm s(-1), respectively. The maximum deposition velocity was 0.81 cm s(-1). The magnitude of deposition velocity was influenced by the corn growth period, and its diurnal variation was significantly correlated with global radiation and relative humidity. (3) O-3 flux was affected by variations of both O-3 concentration and deposition velocity, with mean O-3 fluxes -317.7 and -70.2 ng m(-2) s(-1) during daytime and nighttime, respectively. There was strong correlation between O-3 flux and CO2 flux or latent heat flux. By comparing the deposition velocities of daytime and nighttime, we infer that stomatal uptake was probably the main sink of ground-level O-3
Due to the complex and variable nature of the atmospheric conditions, traditional multi-wavelength differential absorption lidar (DIAL) methods often suffer from significant errors when inverting ozone concentrations. As the detection range increases, there is a higher demand for Signal to Noise Ratio (SNR) in lidar signals. Based on this, the paper discusses the impact of different atmospheric factors on the accuracy of ozone concentration inversion. It also compares the advantages and disadvantages of the two-wavelength differential method and the three-wavelength dual-differential method under both noisy and noise-free conditions. Firstly, the errors caused by air molecular extinction, aerosol extinction, and backscatter terms in the inversion using the two-wavelength differential method were simulated. Secondly, the corrected inversion errors were obtained through direct correction and the introduction of a three-wavelength dual differential correction. Finally, addressing the issue of insufficient SNR in practical inversions, the inversion errors of the two correction methods were simulated by constructing lidar parameters and incorporating appropriate noise. The results indicate that the traditional two-wavelength differential algorithm is significantly affected by aerosols, making it more sensitive to aerosol concentration and structural changes. On the other hand, the three-wavelength dual differential algorithm requires a higher SNR in lidar signals. Therefore, we propose a novel strategy for inverting atmospheric ozone concentration, which prioritizes the use of the three-wavelength dual-differential method in regions with high SNR and high aerosol concentration. Conversely, the direct correction method utilizing the two-wavelength differential approach is used. This approach holds the potential for high-precision ozone concentration profile inversion under different atmospheric conditions.
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