Ozone (O3) concentration and flux (Fo) were measured using the eddy covariance technique over a wheat field in the Northwest-Shandong Plain of China. The O3-induced wheat yield loss was estimated by utilizing O3 exposure-response models. The results showed that: (1) During the growing season (7 March to 7 June, 2012), the minimum (16.1 ppbV) and maximum (53.3 ppbV) mean O3 concentrations occurred at approximately 6:30 and 16:00, respectively. The mean and maximum of all measured O3 concentrations were 31.3 and 128.4 ppbV, respectively. The variation of O3 concentration was mainly affected by solar radiation and temperature. (2) The mean diurnal variation of deposition velocity (Vd) can be divided into four phases, and the maximum occurred at noon (12:00). Averaged Vd during daytime (6:00-18:00) and nighttime (18:00-6:00) were 0.42 and 0.14 cm/sec, respectively. The maximum of measured Vd was about 1.5 cm/sec. The magnitude of Vd was influenced by the wheat growing stage, and its variation was significantly correlated with both global radiation and friction velocity. (3) The maximum mean Fo appeared at 14:00, and the maximum measured Fo was -33.5 nmol/(m(2)·sec). Averaged Fo during daytime and nighttime were -6.9 and -1.5 nmol/(m(2)·sec), respectively. (4) Using O3 exposure-response functions obtained from the USA, Europe, and China, the O3-induced wheat yield reduction in the district was estimated as 12.9% on average (5.5%-23.3%). Large uncertainties were related to the statistical methods and environmental conditions involved in deriving the exposure-response functions.

Ozone (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 fast-response 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 fast-response 03 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. (C) 2015 Elsevier B.V. All rights reserved

Monthly estimates of the global emissions of anthropogenic CO₂ are presented. Approximating the seasonal CO₂ emission cycle using a 2‐harmonic Fourier series with coefficients as a function of latitude, the annual fluxes are decomposed into monthly flux estimates based on data for the United States and applied globally. These monthly anthropogenic CO₂ flux estimates are then used to model atmospheric CO₂ concentrations using meteorological fields from the NASA GEOS‐4 data assimilation system. We find that the use of monthly resolved fluxes makes a significant difference in the seasonal cycle of atmospheric CO₂ in and near those regions where anthropogenic CO₂ is released to the atmosphere. Local variations of 2–6 ppmv CO₂ in the seasonal cycle amplitude are simulated; larger variations would be expected if smaller source‐receptor distances could be more precisely specified using a more refined spatial resolution. We also find that in the midlatitudes near the sources, synoptic scale atmospheric circulations are important in the winter and that boundary layer venting and diurnal rectifier effects are more important in the summer. These findings have implications for inverse‐modeling efforts that attempt to estimate surface source/sink regions especially when the surface sinks are colocated with regions of strong anthropogenic CO₂ emissions.