A multilayer model for inferring dry deposition using standard meteorological measurements

Abstract

Abstract. In this paper, we describe the latest version of the dry deposition inferential model, which is used to estimate the deposition velocities (V a) for SO2, 03, HNO3, and particles with diameters less than 2 •m. The dry deposition networks operated by the National Oceanic and Atmospheric Administration (NOAA) and the Environmental Protection Agency (EPA) use this model to estimate dry deposition on a weekly basis. This model uses a multilayer approach, discretizing the vegetated canopy into 20 layers. The use of canopy radiative transfer and simple wind profile models allows for estimates of stomatal (rs) and leaf boundary layer (%) resistances to be determined at each layer in the plant canopy for both sunlit and shaded leaves. The effect of temperature, water stress, and vapor pressure deficits on the stomatal resistance (rs) have been included. This paper describes the multilayer modeling approach for estimating the dry deposition of SO2, HNO3, and 03 that is currently implemented in the NOAA and EPA national networks. The model is evaluated against 30 min average direct flux measurements recently obtained over corn near Bondville, Illinois, over soybeans near Nashville, Tennessee, and over grass near Sand Mountain, Alabama. 22,645

Dry nitrogen deposition estimates over a forest experiencing free air CO2 enrichment

“…The first scenario takes the measured Candor CASTNet concentration as a proxy for Duke Forest and calculates HNO 3 fluxes using a resistance-based multilayer model (MLM; Meyers et al, 1998) to produce weekly estimates of dry deposition as described by Clarke et al (1997). A comparison of concentration estimates using ADS during the CELTIC study at Duke Forest and filter packs from the Candor CASTNet site suggested a possible bias in the partitioning between HNO 3 and NO 3 À (Table 3) in the CASTNet data.…”

“…This is primarily due to the difficulty in achieving acceptable precision at short sampling times required by traditional micrometeorological flux measurement techniques. We have, therefore, estimated fluxes of NH 3 , NH 4 1 , HNO 3 , and NO 3 À using a combination of measurements and modeling, which is a common approach when only routine chemical and meteorological data are available (Meyers et al, 1998;US EPA, 2004). Only chemical and meteorological measurements taken above the canopy were used to estimate dry deposition fluxes from the model simulation.…”

“…For HNO 3 , R c is a function of the dynamic stomatal resistance (Monteith & Unsworth, 1990) and static cuticular (R w ) and ground (R g ) resistances. Based on the approaches of Brook et al (1999) and Meyers et al (1998), R w and R g are both set to a value of 30 s m À1 . Forests act as both sources and sinks of NH 3 , depending on the ambient NH 3 concentration, leaf and soil N status, and other environmental factors (Duyzer et al, 1992;Wyers & Erisman, 1998;Pryor et al, 2001).…”

Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest

“…Alternatively, if information about the vegetation morphology (e.g., canopy height (h c ), and LAI) is known, z 0 can be calculated following Meyers et al (1998): z 0 ¼ h c 0:215 À LAI 0:25 10 ;…”

“…Wesely, 1989;Meyers et al, 1998;Zhang et al, 2002Zhang et al, , 2003Niyogi et al, 2009;Wu et al, 2003) to estimate the dry deposition velocity (V d ) by commonly utilizing the resistance approach analogous to Ohm's law in electrical circuits. Accurately parameterizing the complex surfaceatmosphere exchange process remains challenging for V d modeling due to large variability in surface conditions (e.g., vegetation types, and soil contents) at model sub-grid scales.…”