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Dry deposition velocities (Vd) for peroxyacetyl nitrate (PAN) calculated using two community dry deposition models with different treatments of both stomatal and nonstomatal uptakes were evaluated using measurements of PAN eddy covariance fluxes over a Loblolly pine forest in July 2003. The observed daytime maximum of Vd(PAN) was ∼1.0 cm s-1 on average, while the estimates by the WRF-Chem dry deposition module (WDDM) and the Noah land surface model coupled with a photosynthesis-based Gas Exchange Model (Noah-GEM) were only 0.2 cm s-1 and 0.6 cm s-1, respectively. The observations also showed considerable PAN deposition at night with typical Vd values of 0.2-0.6 cm s-1, while the estimated values from both models were less than 0.1 cm s-1. Noah-GEM modeled more realistic stomatal resistance (Rs) than WDDM, as compared with observations of water vapor exchange fluxes. The poor performance of WDDM for stomatal uptake is mainly due to its lack of dependence on leaf area index. Thermal decomposition was found to be relatively unimportant for measured PAN fluxes as shown by the lack of a relationship between measured total surface conductance and temperature. Thus, a large part of the underprediction in Vd from both models should be caused by the underestimation of nonstomatal uptake, in particular, the cuticle uptake. Sensitivity tests on both stomatal and nonstomatal resistances terms were conducted and some recommendations were provided. Copyright 2012 by the American Geophysical Union.

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 (Vd) estimated by the WRF-Chem dry deposition module (WDDM), which adopted Wesely (1989) scheme for surface resistance (Rc), and the Noah land surface model coupled with a photosynthesis-based Gas-exchange Evapotranspiration Model (Noah-GEM). Noah-GEM produced better Vd(O3) variations due to its more realistically simulated stomatal resistance (Rs) than WDDM. Vd(O3) is very sensitive to the minimum canopy stomatal resistance (Ri) 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 Vd(O3) due to the leafless assumption in 'autumn' seasonal category for which an infinite Ri was assigned. Reducing Ri to a value of 70sm-1, the same as the default value for the summer season category, the modeled and measured Vd(O3) agreed reasonably well. HNO3 was found to dominate the NOy flux during the measurement period; thus the modeled Vd(NOy) was mainly controlled by the aerodynamic and quasi-laminar sublayer resistances (Ra and Rb), both being sensitive to the surface roughness length (z0). Using an appropriate value for z0 (10% of canopy height), WDDM and Noah-GEM agreed well with the observed daytime Vd(NOy). The differences in Vd(HNO3) between WDDM and Noah-GEM were small due to the small differences in the calculated Ra and Rb between the two models; however, the differences in Rc 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 Vd. Combining the measured concentrations and modeled Vd, NOx, PAN and HNO3 accounted for 19%, 4%, and 70% of the measured NOy fluxes, respectively. © 2011 Elsevier Ltd.

This study intended to provide 4-km gridded, hourly, year-long, regional estimates of terpenoid emissions in the Pearl River Delta (PRD), China. It combined Thematic Mapper images and local-survey data to characterize plant functional types, and used observed emission potential of biogenic volatile organic compounds (BVOC) from local plant species and high-resolution meteorological outputs from the MM5 model to constrain the MEGAN BVOC-emission model. The estimated annual emissions for isoprene, monoterpene and sesquiterpene are 95.55 × 106 kg C, 117.35 × 106 kg C and 9.77 × 106 kg C, respectively. The results show strong variabilities of terpenoid emissions spanning diurnal and seasonal time scales, which are mainly distributed in the remote areas (with more vegetation and less economic development) in PRD. Using MODIS PFTs data reduced terpenoid emissions by 27% in remote areas. Using MEGAN-model default emission factors led to a 24% increase in BVOC emission. The model errors of temperature and radiation in MM5 output were used to assess impacts of uncertainties in meteorological forcing on emissions: increasing (decreasing) temperature and downward shortwave radiation produces more (less) terpenoid emissions for July and January. Strong temporal variability of terpenoid emissions leads to enhanced ozone formation during midday in rural areas where the anthropogenic VOC emissions are limited. ©2011 The Authors Tellus B©2011 John Wiley & Sons A/S.

The effectiveness and feasibility of urban planning are significantly influenced by the supply capacity and net value of ecosystem services offered by blue–green–grey infrastructure. This study used a cost–benefit analysis (CBA) to ascertain and contrast the ecological net present value (NPV) of the blue–green–grey infrastructure in three distinct functional areas (a park, a square, and a residential district) under 12 scenarios during the period characterized by representative summer temperature, which we refer to as "warm periods". Our findings suggest varied optimal scenarios for the three functional areas. For the park, the most beneficial scenario involved an integrated approach with a 5% increase in grey infrastructure and a 5% replacement of green infrastructure with grey. This scenario yielded an NPV of 7.31 USD/m2 in a short-term life span (25 years) and 11.59 USD/m2 in a long-term life span (150 years). In the case of the square, the introduction of an additional 5% of blue infrastructure led to the highest NPV of ecological benefits, resulting in gains of 1.49 USD/m2 for a short-term life span and 2.18 USD/m2 for a long-term life span. For the residential district, the scenario where 5% of green infrastructure was replaced with blue infrastructure resulted in the highest NPV across all scenarios, with values of 8.02 USD/m2 and 10.65 USD/m2 for a short- and long-term life span, respectively. Generally, the most beneficial scenario yielded greater benefits over the long term compared with short-term projects. By quantifying the ecological benefits of different blue–green–grey infrastructure combinations, our research provides theoretical support for optimizing both the ecological and economic value of urban infrastructures. This study could benefit academics, practitioners, and policymakers in urban planning in optimizing the allocation of the blue–green–grey infrastructure. [ABSTRACT FROM AUTHOR]