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In radiation therapy, investigating of the effects of the surface flux reaching on the tissue is important in planning the treatment and this requires a precise evaluation of the absorbed dose distribution throughout the irradiated tissue. Therefore, by Monte Carlo simulation with MCNP code, a point source with the size of E with a spectrum width of 0.6 µm with a single energy transfer of 6 MeV to the breast tumor tissue with a size of 2 x 4 x 4 cm and also a density (Kg/m^3) of 11.34 at a fixed depth of 3 cm. It is radiated from a standard phantom (VIP MAN) made of tissue. The results show the highest surface flux that received on the tumor is around 9.97 × 〖10〗^(-6) and is located almost in the center of the tumor in dimensions (-0.75 cm - 1.3 cm) and the less surface flux around the tumor is caused by the rate of the dose which is distributed. Also, the template phenomenon in the creation of electrons is based on the Compton effect, while in the creation of photons, the Compton effect did not occur.

The main objective of this study was to examine the implications of watershed management (WSM) on hydrological parameters in the Aba Gerima watershed in the Upper Blue Nile Basin. The Hydrus 1D model simulations were conducted in control sites and sites under WSM to estimate various components of the hydrologic cycle, using different soil physical & hydrological data under each category of experimental sites. Results were calibrated with measured soil moisture data through inverse solutions. Thus, Hydrus 1D model was found to be effective in predicting results, with R2 values of 0.73 to 0.853 and RMSE values ranging from 0.015 to 0.04. The cumulative evaporation estimated for 365 days for control sites was 37.6% higher than that of sites under WSM. Surface and bottom fluxes in the sites under WSM were 4.6% and 12.5%, respectively, higher than the control sites. This could be attributed to the increased soil water availability resulting from the implemented WSM practices in Aba Gerima, and the results of this study can be used as empirical evidence of the positive implications of WSM on water availability. Finally, WSM should be strengthened by concerned bodies and development partners in all watersheds, especially where water availability is affected by severe land degradation. [ABSTRACT FROM AUTHOR]

Land surface model is a powerful tool for estimating continuous soil water content (SWC) and surface fluxes. However, simulation error tends to accumulate in the process of model simulation due to the inevitable uncertainties of forcing data and the intrinsic model errors. Data assimilation techniques consider the uncertainty of the model, update model states during the simulation period, and therefore improve the accuracy of SWC and surface fluxes estimation. In this study, an Ensemble Kalman Filter (EnKF) technique was coupled to a Hydrologically Enhanced Land Process (HELP) model to update model states, including SWC and surface temperature (Ts). The remotely sensed latent heat flux (LE) estimated by Surface Energy Balance System (SEBS) was used as the observation value in the data assimilation system to update the model states such as SWC and Ts, etc. The model was validated by the observation data in 2006 at the Weishan flux station, where the open-loop estimation without state updating was treated as the benchmark run. Results showed that the root mean square error (RMSE) of SWC was reduced by 30%~50% compared to the benchmark run. Meanwhile, the surface fluxes also had significant improvement to different extents, among which the RMSE of LE estimation from the wheat season and maize season reduced by 33% and 44%, respectively. The application of the data assimilation technique can substantially improve the estimation of surface fluxes and SWC states. It is suggested that the data assimilation system has great potential to be used in the application of land surface models in agriculture and water management. [ABSTRACT FROM AUTHOR]

The state of Qatar has been experiencing rapid urbanization with around 85% of its population residing in Doha. The country faces notable challenges related to the Urban Heat Island (UHI) effect, which is exacerbated by its hot and humid desert climate. This study focuses on analyzing the UHI phenomenon in Doha, utilizing observed meteorological data and the Weather Research and Forecasting model (WRF v4.5). Two land use and land cover (LULC) datasets from 2001 and 2018 are employed, with simulations conducted using different urban canopy models. The 2018 LULC data includes 100 m resolution information that categorizes urban areas into 11 local climate zones. Results indicate significant UHI intensity during both winter and summer periods (up to 6.5 °C), with notable differences observed between daytime and nighttime temperatures. In agreement with observations, the model predicts not only a strong UHI effect during nighttime, but also a significant Urban Cool Island effect in Doha (up to −5.8 °C during daytime in summer). The impact of various urban parameterization schemes on simulation accuracy is highlighted. The building energy model demonstrates superior performance in predicting temperature and relative humidity during the summer period. The spatial distribution of heat index illustrates the intensified warming in the city. • The region's first numerical study of UHI with a recent urban classification. • Introduction of Local Climatic Zones (LCZ)with the BEM urban parameterization improves predictions. • Significant UHI intensity during both winter and summer periods (up to 6.5 °C). • Simulations show extreme heat index values posing potential risks to human health. [ABSTRACT FROM AUTHOR]

Inverse problems of recovering surface fluxes on the boundary of a domain from pointwise observations are considered. Sharp conditions on the data ensuring existence and uniqueness of solutions in Sobolev classes are exposed. They are smoothness conditions on the data, geometric conditions on the location of measurement points, and the boundary of a domain. The proof relies on asymptotics of fundamental solutions to the corresponding elliptic problems and the Laplace transform. The inverse problem is reduced to a linear algebraic system with a nondegerate matrix. [ABSTRACT FROM AUTHOR]

The main objective of this study was to examine the implications of watershed management (WSM) on hydrological parameters in the Aba Gerima watershed in the Upper Blue Nile Basin. The Hydrus 1D model simulations were conducted in control sites and sites under WSM to estimate various components of the hydrologic cycle, using different soil physical & hydrological data under each category of experimental sites. Results were calibrated with measured soil moisture data through inverse solutions. Thus, Hydrus 1D model was found to be effective in predicting results, with R2 values of 0.73 to 0.853 and RMSE values ranging from 0.015 to 0.04. The cumulative evaporation estimated for 365 days for control sites was 37.6% higher than that of sites under WSM. Surface and bottom fluxes in the sites under WSM were 4.6% and 12.5%, respectively, higher than the control sites. This could be attributed to the increased soil water availability resulting from the implemented WSM practices in Aba Gerima, and the results of this study can be used as empirical evidence of the positive implications of WSM on water availability. Finally, WSM should be strengthened by concerned bodies and development partners in all watersheds, especially where water availability is affected by severe land degradation.

Copyright of Journal of Remote Sensing is the property of Editorial Office of Journal of Remote Sensing & Science Publishing Co. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Land surface model is a powerful tool for estimating continuous soil water content (SWC) and surface fluxes. However, simulation error tends to accumulate in the process of model simulation due to the inevitable uncertainties of forcing data and the intrinsic model errors. Data assimilation techniques consider the uncertainty of the model, update model states during the simulation period, and therefore improve the accuracy of SWC and surface fluxes estimation. In this study, an Ensemble Kalman Filter (EnKF) technique was coupled to a Hydrologically Enhanced Land Process (HELP) model to update model states, including SWC and surface temperature (Ts). The remotely sensed latent heat flux (LE) estimated by Surface Energy Balance System (SEBS) was used as the observation value in the data assimilation system to update the model states such as SWC and Ts, etc. The model was validated by the observation data in 2006 at the Weishan flux station, where the open-loop estimation without state updating was treated as the benchmark run. Results showed that the root mean square error (RMSE) of SWC was reduced by 30%~50% compared to the benchmark run. Meanwhile, the surface fluxes also had significant improvement to different extents, among which the RMSE of LE estimation from the wheat season and maize season reduced by 33% and 44%, respectively. The application of the data assimilation technique can substantially improve the estimation of surface fluxes and SWC states. It is suggested that the data assimilation system has great potential to be used in the application of land surface models in agriculture and water management.

To study the spatial variability of water surface fluxes, turbulence measurements on a moving platform are useful. However, such measurements have only been carried out with large research vessels over the ocean. We tested the feasibility of flux measurements with a small excursion ship over Lake Kasumigaura, the second largest lake in Japan. After the formal application of coordinate rotations to account for the ship's movements, we derived mean wind velocities as well as latent and sensible heat fluxes. They were compared with spatially interpolated wind velocities from meteorological stations and with fluxes estimated from the bulk method. Equally good agreements were found with those reported in previous studies over the ocean, indicating the feasibility of ship measurements in a lake. Possible error sources were identified for the improvement of the accuracy of flux estimation. [ABSTRACT FROM AUTHOR]

Inverse problems of recovering surface fluxes on the boundary of a domain from pointwise observations are considered. Sharp conditions on the data ensuring existence and uniqueness of solutions in Sobolev classes are exposed. They are smoothness conditions on the data, geometric conditions on the location of measurement points, and the boundary of a domain. The proof relies on asymptotics of fundamental solutions to the corresponding elliptic problems and the Laplace transform. The inverse problem is reduced to a linear algebraic system with a nondegerate matrix.

Abstract Cold pools influence convective initiation and organization, dust lofting, and boundary layer properties, but little is known about their interactions with the land surface, particularly in dry continental environments. In this study, two‐way cold pool‐land surface interactions are investigated using high‐resolution idealized simulations of an isolated, transient cold pool evolving in a dry convective boundary layer. Results using a fully interactive land surface demonstrate that sensible heat fluxes are suppressed at the center of the cold pool but enhanced at the edge due to the spatial patterns of land surface cooling and the air temperature and wind speed perturbations. This leads to cold pool dissipation from the edge inward. Latent heat fluxes are primarily suppressed within the cold pool, and the magnitude of this suppression is controlled by competition between atmospheric and land surface effects. By comparing the fully interactive land surface simulation to a simulation with imposed surface fluxes, the land surface‐cold pool feedbacks are shown to reduce the cold pool lifetime, extent, and intensity by up to 50% and influence the pattern of boundary layer turbulent kinetic energy recovery, which have significant implications for cold pool‐induced convective initiation.

Aims: Soils are known to be significant sources of atmospheric nitric oxide (NO), a key compound in atmospheric chemistry. NO is a key regulating substance for inter- and intra-species signalling and competition and affects plant growth and soil microbial metabolisms. However, little is known about NO concentration in soils and production of NO in the soil profile. Methods: Here we report on soil NO concentrations down to 65 cm soil depth and soil surface flux measurements over a 15 months period in subdaily resolution. This is supplemented by information on aerobic and anaerobic NO production in various soil layers of a spruce stand in SW Germany. Results: NO concentrations showed a clear seasonality with highest concentrations of up to 800 nmol mol−1 (or part per billion in volume mixing ratio; ppbv) at the interface between the organic Of-Oh sub-layers in the summer. NO concentrations in the mineral subsoil (−65 cm) were approx. One order of magnitude lower than in the organic layer. Dynamic changes of soil NO concentrations were closely correlated with soil surface NO fluxes. Differences in soil NO concentrations across the soil profile reflected differences in aerobic and anaerobic NO production potential. Conclusion: The importance of such high NO concentrations for soil microbial and plant physiological processes remains unclear, but should be addressed in future research in order to improve our understanding of microbe-microbe and plant-microbe interactions. [ABSTRACT FROM AUTHOR]

Collection of landfill gas by horizontal perforated wells is studied. The problem combines flow through porous media in the landfill and unobstructed pipe flow in the well. Respective analytical solutions to flow equations are used in an iterative numerical procedure to solve the coupled system. Realistic landfill input parameters confirm the feasibility of estimates obtained with the model. The study identifies flow control parameters and furnishes tools to evaluate surface flux and radius of influence for this type of well. [ABSTRACT FROM AUTHOR]

Understanding links between the disturbance regime and regional climate in boreal regions requires observations of the surface energy budget from ecosystems in various stages of secondary succession. While several studies have characterized fire-induced differences in surface energy fluxes from boreal ecosystems during summer months, much less is known about these differences over the full annual cycle. Here we measured components of the surface energy budget (including both radiative and turbulent fluxes) at three sites from a fire chronosequence in interior Alaska for a 1-year period. Our sites consisted of large burn scars resulting from fires in 1999, 1987, and ∼1920 (hereinafter referred to as the 3-, 15-, and 80-year sites, respectively). Vegetation cover consisted primarily of bunch grasses at the 3-year site, aspen and willow at the 15-year site, and black spruce at the 80-year site. Annual net radiation declined by 31% (17 W m−2) for both the 3- and the 15-year sites as compared with the 80-year site (which had an annual mean of 55 W m−2). Annual sensible heat fluxes were reduced by an even greater amount, by 55% at the 3-year site and by 52% at the 15-year site as compared with the 80-year site (which had an annual mean of 21 W m−2). Absolute differences between the postfire ecosystems and the mature black spruce forest for both net radiation and sensible heat fluxes were greatest during spring (because of differences in snow cover and surface albedo), substantial during summer and winter, and relatively small during fall. Fire-induced disturbance also initially reduced annual evapotranspiration (ET). Annual ET decreased by 33% (99 mm yr−1) at the 3-year site as compared with the 80-year site (which had an annual flux of 301 mm yr−1). Annual ET at the 15-year site (283 mm yr−1) was approximately the same as that from the 80-year site, even though the 15-year site had substantially higher ET during July. Our study suggests that differences in annual ET between deciduous and conifer stands may be smaller than that inferred solely from summer observations. This study provides a direct means to validate land surface processes in global climate models attempting to capture vegetation-climate feedbacks in northern terrestrial regions.

Abstract Numerical error by an odd order difference approximation in the advection term dissipates energy in the resolved motion. We propose a method to estimate the energy dissipation rate derived from the numerical error to clarify its effect on the energy budget. The energy dissipation rate in Large‐Eddy Simulations for an ideal unstable boundary layer is analysed. The proposed method reveals that the imbalance of the energy budget can be ascribed to the non‐conservative property with respect to kinetic energy of the discretised advection terms, while the net energy dissipation in the resolved field is almost insensitive to the origins of the energy dissipation. However, the magnitude of the momentum and temperature fluxes is sensitive to the difference scheme; the numerical error in the advection term reduces these fluxes in the resolved part. A subgrid scheme should be designed so as to compensate decrease of the resolved flux when an odd order difference is applied to the advection term.

This paper is concerned with approximations and related discretization error estimates for the normal derivatives of solutions of linear elliptic partial differential equations. In order to illustrate the ideas, we consider the Poisson equation with homogeneous Dirichlet boundary conditions and use standard linear finite elements for its discretization. The underlying domain is assumed to be polygonal but not necessarily convex. Approximations of the normal derivatives are introduced in a standard way as well as in a variational sense. On general quasi-uniform meshes, one can show that these approximate normal derivatives possess a convergence rate close to one in L² as long as the singularities due to the corners are mild enough. Using boundary concentrated meshes, we show that the order of convergence can even be doubled in terms of the mesh parameter while increasing the complexity of the discrete problems only by a small factor. As an application, we use these results for the numerical analysis of Dirichlet boundary control problems, where the control variable corresponds to the normal derivative of some adjoint variable. [ABSTRACT FROM AUTHOR]

A dimethyl sulfide (DMS) vertical concentration profile and DMS surface emission flux were quantified in undisturbed acid sulfate soils (ASS) at Cudgen Lake on the north coast of New South Wales, Australia. A deuterated internal standard was used to account for soil adsorption characteristics. The DMS vertical concentration profile increased exponentially from 0.6 m depth to the surface layer. This profile reflected the adsorption properties of the ASS horizons present and the experimentally determined octanol/water partition coefficient for DMS of 1.36, suggesting that DMS would be mobilised in the soil water medium for upward translocation in time due to surface evaporation. The organic material in the oxidised ASS crustal layer had a chemically strong adsorption affinity for DMS, which appeared to restrain its emission from surface soil particles to the atmosphere. The seasonally averaged DMS surface flux estimate from the Cudgen Lake ASS was 9 ng S m−2 min−1, which is relatively low by comparison to DMS fluxes reported from other wetland soils such as salt-marshes and acidic peat bogs. The worldwide annual average DMS emission from ASS was estimated to be 1.14 × 10−3 Tg S, which is globally insignificant by comparison to DMS emission from the world's oceans. Image 1 • Dimethyl sulfide is most abundant in the oxidised organic crustal soil layer. • Soil-air surface flux of dimethyl sulfide is restrained by crustal adsorption. • Acid sulfate soils appear to be a globally insignificant source of dimethyl sulfide. [ABSTRACT FROM AUTHOR]

Copyright of Special Oil & Gas Reservoirs is the property of Special Oil & Gas Reservoirs Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There is no consensus on the physical mechanisms controlling the scale at which convective activity organizes near the Equator. Here, we introduce a diagnostic framework relating the evolution of the length‐scale of convective aggregation to the net radiative heating, the surface enthalpy flux, and horizontal energy transport. We evaluate these expansion tendencies of convective aggregation in 20 high‐resolution cloud‐permitting simulations of radiative‐convective equilibrium. While both radiative fluxes contribute to convective aggregation, the net long‐wave radiative flux operates at large scales (1,000–5,000 km) and stretches the size of moist and dry regions, while the net short‐wave flux operates at smaller scales (500–2,000 km) and shrinks it. The surface flux expansion tendency is dominated by convective gustiness, which acts to aggregate convective activity at smaller scales (500–3,000 km). [ABSTRACT FROM AUTHOR]

• Thermal infrared (TIR) camera as screening tool for landfill gas emission hotspots. • Temperature differences in the TIR images was limited to between 0.7 °C and 1.2 °C. • There is a lower limit for landfill gas emission to be detected by TIR camera. • Landfill gas emissions influenced by barometric pressure gradient. An unmanned aerial vehicle (UAV)-mounted thermal infrared (TIR) camera's ability to delineate landfill gas (LFG) emission hotspots was evaluated in a field test at two Danish landfills (Hedeland landfill and Audebo landfill). At both sites, a test area of 100 m2 was established and divided into about 100 measuring points. The relationship between LFG emissions and soil surface temperatures were investigated through four to five measuring campaigns, in order to cover different atmospheric conditions along with increasing, decreasing and stable barometric pressure. For each measuring campaign, a TIR image of the test area was obtained followed by the measurement of methane (CH 4) and carbon dioxide (CO 2) emissions at each measuring point, using a static flux chamber. At the same time, soil temperatures measured on the surface, at 5 cm and 10 cm depths, were registered. At the Hedeland landfill, no relationship was found between LFG emissions and surface temperatures. In addition, CH 4 emissions were very limited, on average 0.92–4.52 g CH 4 m−2 d−1, and only measureable on the two days with decreasing barometric pressure. TIR images from Hedeland did not show any significant temperature differences in the test area. At the Audebo landfill, an area with slightly higher surface temperatures was found in the TIR images, and the same pattern with slightly higher temperatures was found at a depth of 10 cm. The main LFG emissions were found in the area with the higher surface temperatures. LFG emissions at Audebo were influenced significantly by changes in barometric pressure, and the average CH 4 emissions varied between 111 g m−2 d−1 and 314 g m−2 d−1, depending on whether the barometric pressure gradient had increased or decreased, respectively. The temperature differences observed in the TIR images from both landfills were limited to between 0.7 °C and 1.2 °C. The minimum observable CH 4 emission for the TIR camera to identify an emission hotspot was 150 g CH 4 m−2 d−1 from an area of more than 1 m2. [ABSTRACT FROM AUTHOR]

A butterfly type of repeat track cruise was carried out in the South Eastern Arabian Sea (off Minicoy) onboard INS Sagardhwani during July 2016 to Aug 2016. We have also made use of the data from OMNI buoy, AD09, which is about 6 km close to the centre station of butterfly track. Air sea flux, the horizontal current data from AD09 and the time series data collected from the butterfly experiment were analysed to compute the mixed layer heat and salt budget. The short-term thermo-haline variability off Minicoy, relative contribution of heat/salt budget terms in MLD and its effects on acoustic propagation are addressed in this paper. In this study, most dominating term in the mixed layer heat budget estimation is net surface heat flux followed by the advective terms has been found. However the salinity in the mixed layer is dominated by the contribution of buoyancy mixing due to night time evaporative cooling. During the calm, sunny day, the so-called afternoon effect due to the diurnal heating restricts the sonar range. But during the windy day, the wind/wave mixing prevents the warming of the surface layer which in turn enhances the sonar range. Similarly, the night time cooling also enhance the acoustic propagation range. The presence of Arabian Sea High Salinity Watermass in the surface layer also enhances the acoustic propagation. [ABSTRACT FROM AUTHOR]

Surface fluxes of stratocumulus clouds over mid-latitude oceans have larger variability and bigger Bowen ratios than those over subtropical oceans. This study investigates how mid-latitude maritime stratocumulus clouds respond to surface fluxes and what the underlying mechanisms are. A closed-cellular stratocumulus cloud over mid-latitude North Pacific Ocean is simulated with large eddy simulation. A control case and a reduced-flux case (with surface fluxes 50% reduced) are compared. Liquid water path (LWP) and turbulent kinetic energy (TKE) decrease as surface fluxes are reduced. It is revealed that reducing surface fluxes leads to a cooler and drier boundary layer, which directly leads to a higher cloud base. The weaker turbulence near the cloud top leads to less entrainment, resulting in a lower cloud top. Therefore, the cloud is 21% thinner with a smaller LWP in the reduced-flux case. Quadrant analysis shows that TKE production processes including surface heating, in-cloud latent heating, and cloud-top evaporative cooling are all weaker in the reduced-flux case. Meanwhile, cloud-top entrainment heating and overshooting of air parcels into the inversion, as TKE consumption processes, are also weaker in the reduced-flux case. These TKE production and consumption processes counteract with each other, leading to quite different pictures of turbulence transport in the two cases. In the subcloud layer, the control case is dominated by surface heating (indicating a turbulent heating effect), while the reduced-flux case is dominated by evaporative cooling in the downdraft region (indicating a turbulent cooling effect). In the cloud layer, the difference of heat flux between the two cases is mainly due to the difference in latent heating. At cloud top, the two cases have similar heat flux. • When surface fluxes are reduced, liquid water path decreases due to higher cloud base and lower cloud top. • Turbulent kinetic energy decreases due to weaker turbulent kinetic energy production and consumption processes. • The dominant turbulence transport process in the subcloud layer changes from surface heating to cloud-top cooling. [ABSTRACT FROM AUTHOR]

Abstract: The Amazon forest plays an important role in the tropical circulation and global water and biogeochemical cycles. However, the common Amazon precipitation biases in global climate models undermine our ability to understand future changes in the Amazon and their global consequences. The Community Earth System Model exhibits a persistent wet season dry bias over the southwestern Amazon. The bias is also characterized by inaccurate diurnal timing and intensity of rainfall events. Analysis of a diverse set of simulations suggests that the bias originates from the land model and/or deep convection parameterization. A known land model bias in the partitioning of surface energy fluxes is found not to contribute significantly to the rainfall bias. Key model processes are identified to be the low‐level divergent circulation controlling horizontal moisture flow and the sensitivity of the modeled deep convection to the lower tropospheric moisture. The lower tropospheric moisture divergence dictates the spatiotemporal distributions of convective precipitation through parameterized entrainment mixing. While the entrainment effect improves the rainfall diurnal cycle, it suppresses convective precipitation under low‐level moisture divergence. Persistent moisture divergence is found over the southwestern Amazon and limits parameterized convective precipitation, particularly in the late afternoon, although uncertainty exists in the low‐level flow in the simulation and reanalyses. One way to sustain rainfall in the presence of low‐level divergence is a convective trigger based on both the moisture and temperature changes in the free troposphere, which is shown to help in reducing the dry bias. [ABSTRACT FROM AUTHOR]

Abstract: Cold pools influence convective initiation and organization, dust lofting, and boundary layer properties, but little is known about their interactions with the land surface, particularly in dry continental environments. In this study, two‐way cold pool‐land surface interactions are investigated using high‐resolution idealized simulations of an isolated, transient cold pool evolving in a dry convective boundary layer. Results using a fully interactive land surface demonstrate that sensible heat fluxes are suppressed at the center of the cold pool but enhanced at the edge due to the spatial patterns of land surface cooling and the air temperature and wind speed perturbations. This leads to cold pool dissipation from the edge inward. Latent heat fluxes are primarily suppressed within the cold pool, and the magnitude of this suppression is controlled by competition between atmospheric and land surface effects. By comparing the fully interactive land surface simulation to a simulation with imposed surface fluxes, the land surface‐cold pool feedbacks are shown to reduce the cold pool lifetime, extent, and intensity by up to 50% and influence the pattern of boundary layer turbulent kinetic energy recovery, which have significant implications for cold pool‐induced convective initiation. [ABSTRACT FROM AUTHOR]

We report on the continuous ambient measurements of total gaseous mercury (TGM) and several ancillary air quality parameters that were collected in Colorado Springs, CO. This urban area, which is located adjacent to the Front Range of the Rocky Mountains, is the second largest metropolitan area in Colorado and has a centrally located coal-fired power plant that installed mercury (Hg) emission controls the year prior to our study. There are few other Hg point sources within the city. Our results, which were obtained from a measurement site < 1 km from the power plant, show a distinct diel pattern in TGM, with peak concentrations occurring during the night (1.7 ± 0.3 ng m−3) and minimum concentrations mid-day (1.5 ± 0.2 ng m−3). The TGM concentrations were not correlated with wind originating from the direction of the plant or with sulfur dioxide (SO2) mixing ratios, and they were not elevated when the atmospheric mixing height was above the effective stack height. These findings suggest that the current Hg emissions from the CFPP did not significantly influence local TGM, and they are consistent with the facility’s relatively low reported annual emissions of 0.20 kg Hg per year. Instead, variability in the regional signal, diurnal meteorological conditions, and/or near-surface emission sources appears to more greatly influence TGM at this urban site.

Hyperresolution land surface modeling provides an unprecedented opportunity to simulate locally relevant water and energy cycle, but lateral surface and/or subsurface flows that are essential at fine scale are often neglected by most one-dimensional land surface models (LSMs). To analyze effects of lateral flows across scales, a Conjunctive Surface-Subsurface Process model, which considers soil moisture-surface flow interaction and quasi-three-dimensional subsurface flow, is implemented over a mountainous HyperHydro test bed in southwestern USA at different resolutions. Validation over more than 70 International Soil Moisture Network stations shows that there are significant improvements in soil moisture simulations from 30 km to 4 km as finer soil property and precipitation data are used, with correlation increased by 5%-16% and error decreased by 5%. Lateral surface flow has a significant influence on surface soil moisture and ground evaporation even at coarse resolution. Effect of lateral subsurface flow on soil moisture is nontrivial at 1 km or finer resolution especially over wet areas. At 100 m resolution, topography-induced lateral subsurface flow causes drier peaks and wetter valleys, decreases latent heat by 8% at peaks, while increases it by 12% at valleys. Furthermore, influences of lateral subsurface flow on ground evaporation and vegetation transpiration are more significant during dry season due to a stronger coupling between soil moisture and evapotranspiration. Therefore, it is worthy to incorporate lateral flow processes in hyperresolution LSMs to better represent water and energy heterogeneity even with limited hyperresolution meteorological and surface data. [ABSTRACT FROM AUTHOR]

To predict ice accretion on an aircraft, it is important to computationally track the path and concentration of water particles to the aerodynamic surface. The recently developed Lagrangian Parcel Volume (LPV) method allows for both zero-diffusion and comparatively small amounts of particles to track compared to other numerical methods. The LPV method uses Lagrangian particle trajectories to define a parcel's vertices and enclosed volume. As this parcel volume changes along its trajectory, this allows direct computation of changes in particle concentration. Previous unsteady one-dimensional investigations with the LPV method found that it provides accurate and efficient results when compared with other computational techniques. This study investigated key aspects of the two-dimensional (2-D) LPV method with respect to disperse phase particle concentration and impact efficiency predictions. These aspects included parcel shape definition, sensitivity to number of parcels and trajectory timesteps, as well as integration dynamics with a non-linear drag model and with polydisperse particle distributions. In general, the results indicate the 2-D LPV model as constructed herein was able to accurately predict impact efficiency on an aerodynamically relevant cylinder based on experimental data. In addition, a theoretical model was developed to accurately predict the impact Reynolds number on a cylinder. [ABSTRACT FROM AUTHOR]