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Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest
Abstract Hourly measurements of O3, NO, NO2, PAN, HNO3 and NOy concentrations, and eddy-covariance fluxes of O3 and NOy over a temperate deciduous forest from June to November, 2000 were used to evaluate the dry deposition velocities (V d) estimated by the WRF-Chem dry deposition module (WDDM), which adopted scheme for surface resistance (R c), and the Noah land surface model coupled with a photosynthesis-based Gas-exchange Evapotranspiration Model (Noah-GEM). Noah-GEM produced better V d(O3) variations due to its more realistically simulated stomatal resistance (R s) than WDDM. V d(O3) is very sensitive to the minimum canopy stomatal resistance (R i) which is specified for each seasonal category assigned in WDDM. Treating Sep-Oct as autumn in WDDM for this deciduous forest site caused a large underprediction of V d(O3) due to the leafless assumption in ‘autumn’ seasonal category for which an infinite R i was assigned. Reducing R i to a value of 70sm−1, the same as the default value for the summer season category, the modeled and measured V d(O3) agreed reasonably well. HNO3 was found to dominate the NOy flux during the measurement period; thus the modeled V d(NOy) was mainly controlled by the aerodynamic and quasi-laminar sublayer resistances (R a and R b), both being sensitive to the surface roughness length (z 0). Using an appropriate value for z 0 (10% of canopy height), WDDM and Noah-GEM agreed well with the observed daytime V d(NOy). The differences in V d(HNO3) between WDDM and Noah-GEM were small due to the small differences in the calculated R a and R b between the two models; however, the differences in R c of NO2 and PAN between the two models reached a factor of 1.1–1.5, which in turn caused a factor of 1.1–1.3 differences for V d. Combining the measured concentrations and modeled V d, NOx, PAN and HNO3 accounted for 19%, 4%, and 70% of the measured NOy fluxes, respectively.
Highlights ► The first study on evaluating V d(NOy) in the dry deposition models. ► Compared the performance of two models with different canopy treatments. ► Assessed the sensitivity of key parameters to simulate V d(O3) and V d(NOy). ► Improved the models by comparing with the field observations. ► Further developed the GEM model.
Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest
Abstract Hourly measurements of O3, NO, NO2, PAN, HNO3 and NOy concentrations, and eddy-covariance fluxes of O3 and NOy over a temperate deciduous forest from June to November, 2000 were used to evaluate the dry deposition velocities (V d) estimated by the WRF-Chem dry deposition module (WDDM), which adopted scheme for surface resistance (R c), and the Noah land surface model coupled with a photosynthesis-based Gas-exchange Evapotranspiration Model (Noah-GEM). Noah-GEM produced better V d(O3) variations due to its more realistically simulated stomatal resistance (R s) than WDDM. V d(O3) is very sensitive to the minimum canopy stomatal resistance (R i) which is specified for each seasonal category assigned in WDDM. Treating Sep-Oct as autumn in WDDM for this deciduous forest site caused a large underprediction of V d(O3) due to the leafless assumption in ‘autumn’ seasonal category for which an infinite R i was assigned. Reducing R i to a value of 70sm−1, the same as the default value for the summer season category, the modeled and measured V d(O3) agreed reasonably well. HNO3 was found to dominate the NOy flux during the measurement period; thus the modeled V d(NOy) was mainly controlled by the aerodynamic and quasi-laminar sublayer resistances (R a and R b), both being sensitive to the surface roughness length (z 0). Using an appropriate value for z 0 (10% of canopy height), WDDM and Noah-GEM agreed well with the observed daytime V d(NOy). The differences in V d(HNO3) between WDDM and Noah-GEM were small due to the small differences in the calculated R a and R b between the two models; however, the differences in R c of NO2 and PAN between the two models reached a factor of 1.1–1.5, which in turn caused a factor of 1.1–1.3 differences for V d. Combining the measured concentrations and modeled V d, NOx, PAN and HNO3 accounted for 19%, 4%, and 70% of the measured NOy fluxes, respectively.
Highlights ► The first study on evaluating V d(NOy) in the dry deposition models. ► Compared the performance of two models with different canopy treatments. ► Assessed the sensitivity of key parameters to simulate V d(O3) and V d(NOy). ► Improved the models by comparing with the field observations. ► Further developed the GEM model.
Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest
Wu, Zhiyong (author) / Wang, Xuemei (author) / Chen, Fei (author) / Turnipseed, Andrew A. (author) / Guenther, Alex B. (author) / Niyogi, Dev (author) / Charusombat, Umarporn (author) / Xia, Beicheng (author) / William Munger, J. (author) / Alapaty, Kiran (author)
Atmospheric Environment ; 45 ; 2663-2674
2011-02-25
12 pages
Article (Journal)
Electronic Resource
English
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