Hicks B.B.,Metcorps |
Hunter C.H.,Savannah River National Laboratory |
Weber A.H.,Savannah River National Laboratory
Journal of the Air and Waste Management Association | Year: 2016
Data collected over a mixed conifer/deciduous forest at the U.S. Department of Energy’s Savannah River Site in South Carolina using sonic anemometry reveal that on-site and real-time measurements of the velocity component standard deviations, σv and σw, are preferred for dispersion modeling. Such data are now easily accessible, from the outputs of cost-effective and rugged sonic anemometers. The data streams from these devices allow improvements to conventional methodologies for dispersion modeling. In particular, extrapolation of basic input data from a nearby location to the site of the actual release can be facilitated. In this regard reliance on the velocity statistics σv and σw appears to be preferred to the conventional σθ and σϕ. In the forest situations addressed here, the uncertainties introduced by extrapolating initializing properties (u, θ, σθ, and σϕ, or alternatively, σv and σw) from some location of actual measurement to some nearby location where an actual release occurs are similar to those associated with the spread of the plume itself and must be considered in any prediction of the likelihood of downwind concentration (exposure) exceeding some critical value, i.e., a regulatory standard. Consideration of plume expansion factors related to meander will not necessarily cause predicted downwind maxima within a particular plume to be decreased; however, the probability of exposure to this maximum value at any particular location will be reduced. Three-component sonic anemometers are affordable and reliable, and are now becoming a standard for meteorological monitoring programs subject to regulatory oversight. The time has come for regulatory agencies and the applied dispersion community to replace the traditional discrete sets of dispersion coefficients based on Pasquill stability by the direct input of measured turbulence data. Implications: The continued endorsement of legacy Pasquill-Gifford stability schemes is presently under discussion among professional groups and regulatory agencies. The present paper is an attempt to introduce some rationality, for the case of a forested environment. © 2016 A&WMA.
Hicks B.B.,Metcorps |
Callahan W.J.,Earth Networks |
Pendergrass III W.R.,National Oceanic and Atmospheric Administration |
Dobosy R.J.,National Oceanic and Atmospheric Administration |
Novakovskaia E.,Earth Networks
Journal of Applied Meteorology and Climatology | Year: 2012
The utility of aggregating data from near-surface meteorological networks for initiating dispersion models is examined by using data from the "WeatherBug" network that is operated by Earth Networks, Inc. WeatherBug instruments are typically mounted 2-3 m above the eaves of buildings and thus are more representative of the immediate surroundings than of conditions over the broader area. This study focuses on subnetworks of WeatherBug sites that are within circles of varying radius about selected stations of the DCNet program. DCNet is aWashington, D.C., research program of the NOAA Air Resources Laboratory. The aggregation of data within varying-sized circles of 3-10-km radius yields average velocities and velocitycomponent standard deviations that are largely independent of the number of stations reporting-provided that number exceeds about 10. Given this finding, variances of wind components are aggregated from arrays of WeatherBug stations within a 5-km radius of selected central DCNet locations, with on average 11 WeatherBug stations per array. The total variance of wind components from the surface (WeatherBug) subnetworks is taken to be the sum of two parts: the temporal variance is the average of the conventional windcomponent variances at each site and the spatial variance is based on the velocity-component averages of the individual sites. These two variances (and the standard deviations derived from them) are found to be similar. Moreover, the total wind-component variance is comparable to that observed at the DCNet reference stations. The near-surface rooftop wind velocities are about 35% of the magnitudes of the DCNet measurements. Limited additional data indicate that these results can be extended to New York City. © 2012 American Meteorological Society.
Hicks B.B.,Metcorps |
Callahan W.J.,Milestone Technologies |
Hoekzema M.A.,Milestone Technologies
Boundary-Layer Meteorology | Year: 2010
Data collected in 2007 from a dense commercial network (operated by AWS Convergence Technologies, Inc.) of roof-mounted temperature sensors are used to explore the heat island characteristics of Washington, DC, and New York City, NY. Considerable spatial detail is revealed, but aggregating data in annuli centered on assumed central locations in the business districts of the two cities reveals that the heat islands extend out to more than 30 km, with the New York City island being somewhat larger. The results from both arrays reveal the influence of the surroundings, with large scatter of daytime results being characteristic of sites with the greatest local surface inhomogeneity. Nighttime data are more ordered, and suggest that surface air temperatures decrease by about 0.02°C km-1 for the Washington case, and 0.04°C km-1 for New York, with the winter behaviour being more pronounced than for other seasons. Scatter of the data in the daytime is a common feature for all seasons, but mainly for those with the strongest insolation. Comparison between working day and weekend temperatures provides convincing verification that the air responds quite slowly to changes in surface (radiometric) temperatures, with distance constants of the order of many tens of km. There appears to be a small wind speed effect, which is evident in the nighttime data but is largely obscured by scatter for the daytime. © Springer Science+Business Media B.V. 2010.
Hicks B.B.,MetCorps |
O'Dell D.L.,University of Tennessee at Knoxville |
Eash N.S.,University of Tennessee at Knoxville |
Sauer T.J.,Ames Laboratory
Agricultural and Forest Meteorology | Year: 2015
An exploratory study of CO2 concentrations and fluxes was conducted during 2013, at a site 12km North of Harare, Zimbabwe. CO2 measurements were made over four adjacent fields of differing surface vegetation. The data illustrate the role of atmospheric intermittency as a mechanism for transferring CO2 between the surface and the atmosphere. At night, limited atmospheric mixing permits CO2 concentrations to increase to levels well above those conventionally reported (exceeding a spatial average of 450ppm on some nights), but these high levels are moderated by a periodic intermittency that appears similar to that observed elsewhere and often associated with the presence of strong, synoptic-scale winds aloft (especially low-level jets). The availability of CO2 data with adequate time resolution facilitates investigation of the general behavior, which is suspected to be a common although rarely observed feature of the lower terrestrial atmosphere. If true, this means that the nocturnal vertical transfer of momentum, heat and mass is not solely through a constrained spectral continuum of turbulence as much as by intermittent bursts, propagating from above and penetrating the surface boundary layer. © 2014 The Authors.
Saylor R.D.,National Oceanic and Atmospheric Administration |
Wolfe G.M.,NASA |
Wolfe G.M.,University of Maryland Baltimore County |
Meyers T.P.,National Oceanic and Atmospheric Administration |
Atmospheric Environment | Year: 2014
The Multilayer Model (MLM) has been used for many years to infer dry deposition fluxes from measured trace species concentrations and standard meteorological measurements for national networks in the U.S., including the U.S. Environmental Protection Agency's Clean Air Status and Trends Network (CASTNet). MLM utilizes a resistance analogy to calculate deposition velocities appropriate for whole vegetative canopies, while employing a multilayer integration to account for vertically varying meteorology, canopy morphology and radiative transfer within the canopy. However, the MLM formulation, as it was originally presented and as it has been subsequently employed, contains a non-physical representation related to the leaf-level quasi-laminar boundary layer resistance that affects the calculation of the total canopy resistance. In this note, the non-physical representation of the canopy resistance as originally formulated in MLM is discussed and a revised, physically consistent, formulation is suggested as a replacement. The revised canopy resistance formulation reduces estimates of HNO3 deposition velocities by as much as 38% during mid-day as compared to values generated by the original formulation. Inferred deposition velocities for SO2 and O3 are not significantly altered by the change in formulation (<3%). Inferred deposition loadings of oxidized and total nitrogen from CASTNet data may be reduced by 10-20% and 5-10%, respectively, for the Eastern U. S. when employing the revised formulation of MLM as compared to the original formulation. © 2014.
Hicks B.B.,MetCorps |
Pendergrass W.R.,National Oceanic and Atmospheric Administration |
Vogel C.A.,National Oceanic and Atmospheric Administration |
Vogel C.A.,Oak Ridge Associated Universities |
And 2 more authors.
Boundary-Layer Meteorology | Year: 2014
Fast-response micrometeorological data obtained from an instrumented 32-m tower at an arid site near Ocotillo, Texas are used to examine the daily time evolution of the lower atmosphere. Correlation coefficients between turbulence properties (fast response wind-speed components and temperature) confirm that over this sparsely vegetated site the effects of convection are observed soon after sunrise, well ahead of the morning transition from stable to unstable stratification. Details of this kind are obscured when results are considered as functions of conventional stability parameters, since such standard analytical methods combine features of the morning and evening transitions into a single presentation. Partial correlation coefficients and semi-partials indicate that the local turbulent kinetic energy is mainly associated with local fluxes of heat and momentum near neutral and in most stable conditions, but decreases substantially during the times of strongest instability (possibly reflecting the scatter introduced by sampling infrequent convective episodes using a single tower). For many of the variables considered here, the standard deviations are about the same as the linear averages, indicating that the distributions are close to log-normal. The present data indicate that if the intent is to address some specific situation then ±10 % error bounds on turbulence quantities (e.g. fluxes) correspond to averaging over a distance scale of the order of 10 km and a time scale of about 3 h. As the distance and time scales become smaller, the uncertainties due to factors external to the local surface increase. © 2014, The Author(s).