Effect Of Atmospheric Stability Research Articles

Impacts of oasis on the atmospheric hydrological cycle over the nearby desert

Using the data of “A field experiment on landatmosphere interaction over arid region in Northwest China” carried out in Dunhuang of Gansu Province from May to June 2000; Characteristics of the atmospheric humidity over desert and Gobi near oasis in the Northwest China Arid Region are analyzed. According to the difference of the characteristics in different wind directions, the impacts of oasis on atmospheric hydrological cycle over desert and Gobi near it are revealed. The relation of atmosphere inverse humidity and negative water vapor flux to wind direction and atmospheric stability is studied. It shows that distribution of the atmosphere inverse humidity is inconsistent with that of the negative water vapor flux; sometimes 1-hour-average value demonstrates the characteristic of counter-gradient transfer. And the diurnal variation of distribution of the counter-gradient transfer and the effect of atmospheric stability on the counter-gradient transfer are also given.

The effects of atmospheric stability intensity on the movement of windblown sand

Using a model that couples wind flow with the motion of sand particles under different atmospheric stability intensities, this paper studied the effects of atmospheric stability on the trajectory and velocity of sand particles in the saltation layer, and the duration before a steady state was achieved. The vertical velocity, horizontal distance, and the maximum height of saltating sand particles increased with increasingly negative stability intensity under unstable conditions. The wind–sand flow reached equilibrium more quickly with increasingly negative stability intensity under unstable conditions, but reached equilibrium more slowly with increasing stability intensity under stable conditions.

Optimal facility layout under toxic release in process facilities: A stochastic approach

This paper presents a new approach for the optimal facility siting considering the uncertainty of toxic release in one of the installed facilities. The proposed formulation incorporates the effect of wind speed, wind direction and atmospheric stability to calculate the risk of death via probit functions and Monte Carlo simulation. The overall problem is initially modeled as a disjunctive program where the Cartesian coordinates of each new facility for siting and cost-related variables are the main unknowns to determine. Then, the convex hull approach is used to reformulate the problem as a mixed integer nonlinear program (MINLP). The numerical difficulties are shown in a case study where multiple optimal layouts have been found. In general, the numerical results demonstrate the potential of this approach to improve the process layout design activity.

MTBE concentration profiles near MTBE manufacturing plant: Modeling approach and modeling uncertainty

The methyl tert-butyl ether (MTBE) concentration profiles near a MTBE manufacturing plant were monitored on two occasions. The US EPA’s atmospheric dispersion model (industrial source complex short-term) was used to model the ambient MTBE levels with the input of local meteorological data as well as MTBE emissions from the plant. The measured ambient MTBE concentrations range from 6 to 76 μg m −3 with the average value about 33 μg m −3. These values are similar to those values reported in ambient air in the vicinity of service stations of 4–12 μg m −3 and tollbooths at a highway of 10–22 μg m −3, but lower than those values reported in ambient air near gas stations of 50–690 μg m −3, and higher than those values reported in atmospheric of 0.9–3.0 μg m −3. Since the model has not been validated for the simulated MTBE profiles, there exist differences between the observed and mode-predicted data. The sensitivity and uncertainty of model parameters were then analyzed. The effects of wind direction, wind velocity and atmospheric stability are discussed in terms of their impact on model sensitivity/uncertainty.

Effect of varied atmospheric stability on sea surface drag in shallow seas and its impact on wind-wave growth

This work reports an efficient bulk formulation of sea surface drag that incorporates effect of dynamic stability under varied atmospheric forcing. The proposed formulation exhibits a polynomial dependence of wind speed on air-sea temperature dif- ference based on statistical analysis. Quality checked meteorological and oceanographic data from four shallow water buoys located off Korean seas having measurements at an interval of every 1 h were used for this study. The analyses of in situ records for this region suggest stability ranging from highly stable to very unstable conditions. Importance of this proposed formulation is better reflected during unstable condition where other popular bulk formulations fail. In addition, importance and impact of such a study on wind-wave growth using the state-of-art wave model was also investigated. Finally, we advocate a new drag formulation, which accounts for varied atmospheric stability and suggest that this should be considered as an essential pre-requisite for ocean modeling studies.

제주도 풍력자원 데이터베이스 구축을 위한 기상통계분석

In order to support the development of wind farms in Jejudo, a wind resource database for Jejudo has been established using a meteor-statistical analysis of KIER(Korea Institute of Energy Research) met-mast measurements and KMA(Korea Meteorological Administration) weather data. The analysis included wind statistics, tower shading, an exposure category classification using satellite images, the effect of atmospheric stability on the wind profile exponent, and a correlation matrix of wind speed to gain an understanding of the meteorological correlation between long-term weather observation stations and short-term met-mast measurements. The wind resource database for Jejudo, is to be provided as an add-on to Google <TEX>$Earth^{TM}$</TEX>, which is expected to be utilized as a guideline for the selection of an appropriate reference site for long-term correction in the next wind farm development project.

Effects of different eddy covariance correction schemes on energy balance closure and comparisons with the modified Bowen ratio system

Eddy covariance (EC) and modified Bowen ratio (MBR) systems have been shown to yield subtly different estimates of sensible heat ( H), latent heat (LE), and CO 2 fluxes (Fc). Our study analyzed the discrepancies between these two systems by first considering the role of the data processing algorithm used to estimate fluxes using EC and later examining the effects of atmospheric stability on discrepancies between EC and MBR. We found that EC correction algorithms disproportionately increase the magnitude of LE and Fc, and consequently have a strong effect on the Bowen ratio measured by EC. Two corrections not universally employed were each found to account for up to 20% of LE and Fc: the correction for signal asynchrony by adjusting the lag between the IRGA and the sonic anemometer, and the frequency domain correction for path-length averaging in both instruments. Comparison of fluxes between two EC systems 10 m apart showed that LE and Fc are inherently more variable than H, highlighting the role of field heterogeneity in determining canopy gas exchange at very small spatial scales. When all relevant corrections were applied, there was no bias for H and LE between EC and MBR. An examination of discrepancies between EC and MBR showed that the discrepancies were highest during neutral periods when shear drove vertical mixing much more than buoyancy. During these neutral periods, the correlation between T, H 2O, and CO 2 was much lower on average, which violates the similarity assumption exploited in the MBR technique. The largest discrepancies in Fc in both systems were clearly visible when plotted against a light–response curve, which creates the possibility of using a screening technique to exclude data that depart markedly from other recently collected data. The EC system tended to have the largest departures from the expected value at low light and during the night, while the MBR system tended to show occasionally spikes of high photosynthetic uptake.

愛媛県における大気エアロゾル中多環芳香族炭化水素類（ＰＡＨｓ）の濃度レベル，変動の特徴とその起源

Concentrations of particulate polycyclic aromatic hydrocarbons(PAHs) in ambient air were investigated every month during the period Apr. 2004 to Mar. 2006 at two sampling sites in Ehime Prefecture; Site-N in Niihama city industrial area and Site-U in Uwajima city nonindustrial area. The sampling was carried out by high volume air sampler on quarts filters, extracted with dichloromethane and analyzed by HPLC with programmable fluorescence detection. Heavy metals and water soluble ios in particulate samples and benzene in air samples were also analyzed in this study. Annual average of total PAHs concentrations ranged from 4.5 to 4.7 ng/m3 at Site-N, higher than in Site-U (2.0∼3.4 ng/m3). Estimated risks of each PAHs based on unit risk were in the order of 10-7∼10-5, but overall risk was higher than objective criteria suggested by Central Environmental Council, Japan. B[a]P contributed above 50 % followed by DB[a,h]A. To have a complete knowledge on PAHs in atmosphere, their levels in the gaseous phase should also be monitored. Major source of PAHs would be vehicles especially diesel cars because of their diagnostic ratios of B[ghi]P/IP, IP/(IP+B[ghi]P) and (B[b]F+B[k]F)/B[ghi]P ranged within values reported for diesel exhausts so far. This view can be substantiated by the observed high correlation of PAHs with benzene and carbon oxide. Indexes of sources were selected by hierarchical cluster analysis on datasets of PAHs, metals and ions at Site-U which has no significant sources from industries. Then temporal variations of them and back trajectories at points in time were analyzed. It appears that high concentrations of anthropogenic metals and NH4SO4 are observed when the air mass was originated and passed through low-altitudes on industrial regions of China. Although PAHs showed significant correlation with these metals, they would be increased mainly by the effect of atmospheric stability.

The dependency of sand transport rate by wind on the atmospheric stability: A numerical simulation

A theoretical model of the process for wind–sand flow is developed through consideration of the coupling between wind flow and the motion of sand particles under different atmospheric stability conditions. Using this model, we studied the effects of atmospheric stability on the sand transport rate, the number of sand particles per unit area and time, and the duration before a steady state is achieved in detail. The results show that atmospheric stability has a strong effect on the movement of the wind–sand flow, and produces results with different characteristics from those previously reported in the literature which apply only to conditions of neutral stability. Under unstable conditions, the wind–sand flow reached equilibrium more quickly, with a higher total sand flux and sand flux at all heights than under neutral or stable conditions.

Observations of the Effects of Atmospheric Stability on Turbulence Statistics Deep within an Urban Street Canyon

Abstract Data obtained in downtown Oklahoma City, Oklahoma, during the Joint Urban 2003 atmospheric dispersion study have been analyzed to investigate the effects of upstream atmospheric stability on turbulence statistics in an urban core. The data presented include turbulent heat and momentum fluxes at various vertical and horizontal locations in the lower 30% of the street canyon. These data have been segregated into three broad stability classification regimes: stable (z/L &amp;gt; 0.2), neutral (−0.2 &amp;lt; z/L &amp;lt; 0.2), and unstable (z/L &amp;lt; −0.2) based on upstream measurements of the Monin–Obukhov length scale L. Most of the momentum-related turbulence statistics were insensitive to upstream atmospheric stability, while the energy-related statistics (potential temperatures and kinematic heat fluxes) were more sensitive. In particular, the local turbulence intensity inside the street canyon varied little with atmospheric stability but always had large magnitudes. Measurements of turbulent momentum fluxes indicate the existence of regions of upward transport of high horizontal momentum fluid near the ground that is associated with low-level jet structures for all stabilities. The turbulent kinetic energy normalized by a local shear stress velocity collapses the data well and shows a clear repeatable pattern that appears to be stability invariant. The magnitude of the normalized turbulent kinetic energy increases rapidly as the ground is approached. This behavior is a result of a much more rapid drop in the correlation between the horizontal and vertical velocities than in the velocity variances. This lack of correlation in the turbulent momentum fluxes is consistent with previous work in the literature. It was also observed that the mean potential temperatures almost always decrease with increasing height in the street canyon and that the vertical heat fluxes are always positive regardless of upstream atmospheric stability. In addition, mean potential temperature profiles are slightly more unstable during the unstable periods than during the neutral or stable periods. The magnitudes of all three components of the heat flux and the variability of the heat fluxes decrease with increasing atmospheric stability. In addition, the cross-canyon and along-canyon heat fluxes are as large as the vertical component of the heat fluxes in the lower portion of the canyon.

Urban Dispersion Modeling: Comparison with Single-Building Measurements

Abstract Two models have been developed to predict airflow and dispersion in urban environments. The first model, the Realistic Urban Spread and Transport of Intrusive Contaminants (RUSTIC) model, is a fast-running urban airflow code that rapidly converges to a numerical solution of a modified set of the compressible Navier–Stokes equations. RUSTIC uses the k–ω turbulence model with a buoyancy production term to handle atmospheric stability effects. The second model, “MESO,” is a Lagrangian particle transport and dispersion code that predicts concentrations of a released chemical or biological agent in urban or rural areas. As a preliminary validation of the models, concentrations simulated by MESO are compared with experimental data from wind-tunnel testing of dispersion around both a multistory rectangular building and a single-story L-shaped building. For the rectangular building, trace gas is forced out at the base of the downwind side, whereas for the L-shaped building, trace gas is forced out of a side door in the inner corner of the “L.” The MESO–RUSTIC combination is set up with the initial conditions of the wind-tunnel experiment, and the steady-state concentrations simulated by the models are compared with the wind-tunnel data. For the multistory building, a dense set of detector locations was available downwind at ground level. For the L-shaped building, concentration data were available at three heights in a lateral plane at a distance of one building height downwind of the lee side. A favorable comparison between model simulations and test data is shown for both buildings.

Effects of Atmospheric Stability on Wave and Energy Propagation in the Troposphere

Abstract The very high frequency (VHF) middle and upper atmosphere radar radio acoustic sounding system (MU-RASS) in Shigaraki, Japan, is able to provide tropospheric virtual temperature data with high temporal resolution on the order of a few minutes. The objective of this paper is to test the usefulness of MU-RASS as a tool for examining high-frequency changes in atmospheric stability and its effects on wave and energy propagation. For this study, temperature and wind data below 8-km altitude during a 2-day campaign period in October 2001 were used. A long-lasting inversion layer at 3.5-km altitude dominated the observation period. Large vertical wind perturbations with periods of less than 30 min were observed inside this inversion layer. Wavelet analysis was used to identify the dominant wave period for calculating the wind and temperature variances. The temperature variance characteristics exhibited a combination of the horizontal and vertical wind variance characteristics. In conclusion, the high temporal resolution of the MU-RASS enabled the study of short time-scale wind and temperature perturbations. These perturbations were related to the atmospheric stability, wave propagation, and energy in the troposphere, demonstrating the usefulness of the MU-RASS for this kind of study.

A note on the top-down and bottom-up gradient functions over a forested site

The dimensionless bottom-up and top-down gradient functions in the convective boundary layer (CBL) are evaluated utilizing long-term well-calibrated carbon dioxide mixing ratio and flux measurements from multiple levels of a 447-m tall tower over a forested area in northern Wisconsin, USA. The estimated bottom- up and top-down functions are qualitatively consistent with those from large-eddy simulation (LES) results and theoretical expectations. Newly fitted gradient functions are proposed based on observations for this forested site. The integrated bottom-up function over the lowest 4% of the CBL depth estimated from the tower data is about five times larger than that from LES results for a 'with-canopy' case, and is smaller than that from LES results for a 'no-canopy' case by a factor of 0.7. We discuss the uncertainty in the evaluated gradient functions due to stability, wind direction, and uncertainty in the entrainment flux and show that while all of these have a significant impact on the gradient functions, none can explain the differences between the mod- elled and observed functions. The effects of canopy features and atmospheric stability may need to be considered in the gradient function relations.

Exposure of traffic police to Polycyclic aromatic hydrocarbons in Beijing, China

Exposure of on-duty traffic police in Beijing to polycyclic aromatic hydrocarbons (PAHs) was investigated during the summer, 2004 using a personal sampling technique in measuring both particulate and gaseous phase PAHs. The results were then compared with those from two control sites away from the street. Exposure levels to gaseous and particulate PAHs for the traffic police were found to be 1525 ± 759 ng m −3 and 148 ± 118 ng m −3, respectively, representing 2–2.5 times higher levels than those at the control sites. The daily inhalation exposure of the police was estimated to be 277 ng kg −1 d −1. Most of the PAHs exposure came from the vapor phase, particularly NAP, FLO and PHE. Based on calculated PAH diagnostic ratios, the major source of PAHs exposure was from vehicle exhaust. The effects of temperature, humidity and atmospheric stability on exposure levels are also discussed.

Effects of boundary-layer stability on urban heat island-induced circulation

The effects of atmospheric boundary-layer stability on urban heat island-induced circulation are numerically and theoretically investigated using a nonlinear numerical model (ARPS) and a two-layer linear analytical model. Numerical model simulations show that as the boundary layer becomes less stable, a downwind updraft cell induced by the urban heat island strengthens. It is also shown that as the boundary layer becomes less stable, both the height of the maximum updraft velocity and the vertical extent of the downwind updraft cell increase. Hence, in the daytime with a nearly neutral or less stable boundary layer the urban heat island-induced circulation can become strong, even though the urban heat island is weak. It is suggested that these findings can be a mechanism for urban-induced thunderstorms observed in the late afternoon or evening with a nearly neutral or less stable boundary layer. The boundary-layer stability affects the spatial distribution of scalar concentration through its influencing urban heat island-induced circulation. Analytical results from a two-layer model with different boundary-layer stabilities in the lower and upper layers are in general qualitatively consistent with the numerical simulation results, although the low-level maximum vertical velocity does not change monotonically with lower-layer stability.

Impact of an unstressed canopy conductance on the Bouchet‐Morton complementary relationship

Indirect methods of quantifying evapotranspiration (λEa) are sought since regional estimations of λEa require prohibitive instrumentation or highly parameterized and data‐intensive land surface models (e.g., involving temporally and spatially varying soil moisture, soil hydraulic properties, and vegetation properties). Complementary relationship (CR) models, based on Bouchet's hypothesis, are one such method of estimating λEa from routinely measured meteorological variables. Bouchet's CR states that given a change in regional surface moisture availability (MA), changes in λEa are reflected in changes in potential evapotranspiration (λEp), such that λEa + λEp = 2λE0, where λE0 is an assumed equilibrium condition at which λEa = λEp = λE0 given sufficiently large MA. Whereas λEp conceptually includes a transpiration component, the treatment of vegetation in existing CR applications varies from neglecting it to indirectly accounting for it through recalibration of Penman's empirical wind function. We utilize the First International Land Surface Climatology Field Experiment (FIFE) data set to demonstrate that inclusion of a maximum (i.e., unstressed) canopy conductance (gc,max) in a Penman equation with stability‐corrected atmospheric conductance (i.e., replacing the Penman equation with an unstressed Penman–Monteith equation) significantly improves both CR convergence and symmetry. Inclusion of gc,max results in more accurate λEa estimates than are found with the Penman equation (using either Monin–Obukhov atmospheric conductance or using empirical wind functions in the literature). The proposed method also performs better than the 1992 advection‐aridity CR method, modified to include atmospheric stability effects, which attributes noncomplementarity to horizontal advection and corrects for it by adjusting λE0 by the magnitude of the potential sensible heat flux (∣Hp∣), found from the surface energy balance of the λEp calculation. In the proposed method a similar energy balance adjustment occurs naturally because the finite canopy conductance causes an increase of surface temperature and sensible heat flux in the λEp energy balance calculation. The proposed method is consistent with CR explanations that rely on feedbacks with the boundary layer vapor pressure deficit since the impact of such changes on both λEp and λEa would be modulated by stomatal conductance.

Meteorological Effects on Deposition and Drift of Aerially Applied Sprays

Drift from aerial application of crop protection materials is influenced by many factors such as ambient winds, temperature, relative humidity, and atmospheric stability. The applicator is responsible for making all possible efforts to reduce the potential for drift. Atmospheric conditions and stability must be considered and adjusted for on the basis of real-time observations and past experience. The objective of this research was to document the effects of atmospheric conditions and stability on the deposition and drift of aerially applied sprays. Two treatments, a fine spray and a medium spray, were used. Ground deposition and airborne concentrations of spray were sampled at multiple downwind locations using Mylar cards and monofilament line, respectively. Results indicated increased downwind ground deposition resulting from increased wind speed, and increased airborne concentrations resulting from smaller droplet sprays and increased wind speed. Airborne concentration data demonstrated that increased atmospheric stability increased the time that smaller droplets remained suspended in the air, which could lead to increased downwind transport. However, these stable conditions are generally characterized by low wind speeds, which could potentially offset the increased suspension time. Overall, the results indicated that wind speed was the most dominant meteorological factor in the transport and fate of aerially applied sprays.

The Beat is Getting Stronger: The Effect of Atmospheric Stability on Low Frequency Modulated Sound of Wind Turbines

The Beat is Getting Stronger: The Effect of Atmospheric Stability on Low Frequency Modulated Sound of Wind Turbines

Evaluation of Novel Techniques for Measurement of Air−Water Exchange of Persistent Bioaccumulative Toxicants in Lake Superior

We report initial measurements of concentrations and net air-water exchange fluxes of target persistent bioaccumulative toxicants (PBTs) in Lake Superior utilizing techniques not previously applied for this purpose. Gaseous PBTs are collected in diffusion denuders containing sections of commercial chromatography columns and subsequently thermally extracted into the cooled injection inlet of a high-resolution gas chromatograph. The PBT sampling/analytical methods enable accurate determination of gas-phase PBT concentration and micrometeorological measurement of fluxes to be carried out. PBT fluxes are measured by the modified Bowen ratio technique in which sensible heat flux is related to PBT flux, with the assumption of identical transfer velocities of heat and PBTs between two heights in the atmospheric surface layer. Micrometeorological measurement of flux accounts for all sources of resistance to mass transfer, including atmospheric stability effects, surface films, waves, sea spray, and bubbles. The sensible heatflux, PBT concentration, and PBT flux measurements carried out in 14 2- or 3-h periods during seven sampling events in Lake Superior in summer and fall 2002 and spring 2003 demonstrate advantages under the constraints of the techniques. The uncertainty of the flux measurements was typically in the range from 1% to 160%. Gaseous concentrations of a-hexachlorocyclohexane (alpha-HCH) and hexachlorobenzene (HCB) over Lake Superior were in the range from 6 to 170 and 12-95 pg/m3, respectively. Fluxes out of Lake Superior were measurable in 75% of the cases in which a concentration gradient was measured, and were in the range from -0.17 to +0.064 ng/m2 x h for alpha-HCH and from -0.60 to -0.093 ng/m2 x h for HCB.

입력변수의 조건에 따른 대기확산모델의 민감도 분석

In order to how well predict ISCST3(lndustrial Source Complex Short Term version 3) model dispersion of air pollutant at point source, sensitivity was analysed necessary parameters change. ISCST3 model is Gaussian plume model. Model calculation was performed with change of the wind speed, atmospheric stability and mixing height while the wind direction and ambient temperature are fixed. Fixed factors are wind direction as the south wind(l80") and temperature as 298 K(25 "C). Model's sensitivity is analyzed as wind speed, atmospheric stability and mixing height change. Data of stack are input by inner diameter of 2m, stack height of 30m, emission temperature of 40 "C, outlet velocity of 10m/s. On the whole, main factor which affects in atmospheric dispersion is wind speed and atmospheric stability at ISCST3 model. However it is effect of atmospheric stability rather than effect of distance downwind. Factor that exert big influence in determining point of maximum concentration is wind speed. Meanwhile, influence of mixing height is a little or almost not.