scholarly journals 100 Years of Progress in Mesoscale Planetary Boundary Layer Meteorological Research

2019 ◽  
Vol 59 ◽  
pp. 19.1-19.41 ◽  
Author(s):  
David A. R. Kristovich ◽  
Eugene Takle ◽  
George S. Young ◽  
Ashish Sharma
Keyword(s):  
Boundary Layer ◽  
Future Research ◽  
Sea Breezes ◽  
Atmospheric Circulations ◽  
American Meteorological Society ◽  
Urban Land Cover ◽  
Scientific Organizations ◽  
Lake Effect ◽  
Thermally Driven ◽  
Hydrological Fields

Abstract This chapter outlines the development of our understanding of several examples of mesoscale atmospheric circulations that are tied directly to surface forcings, starting from thermally driven variations over the ocean and progressing inland to man-made variations in temperature and roughness, and ending with forced boundary layer circulations. Examples include atmospheric responses to 1) overocean temperature variations, 2) coastlines (sea breezes), 3) mesoscale regions of inland water (lake-effect storms), and 4) variations in land-based surface usage (urban land cover). This chapter provides brief summaries of the historical evolution of, and tools for, understanding such mesoscale atmospheric circulations and their importance to the field, as well as physical processes responsible for initiating and determining their evolution. Some avenues of future research we see as critical are provided. The American Meteorological Society (AMS) has played a direct and important role in fostering the development of understanding mesoscale surface-forced circulations. The significance of AMS journal publications and conferences on this and interrelated atmospheric, oceanic, and hydrological fields, as well as those by sister scientific organizations, are demonstrated through extensive relevant citations.

Surface-layer scaling for thermally-driven up-slope flows

2020 ◽  
Author(s):  
Dino Zardi
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Complex Terrain ◽  
Scaling Laws ◽  
Field Experiments ◽  
Layer Structure ◽  
Transport Processes ◽  
Future Research ◽  
Comprehensive Overview ◽  
Thermally Driven

<p>Sloping terrain of any inclination favour the development, under daytime heating, of thermally-driven organised flows, displaying peculiar boundary layer structures, and eventually triggering the development of atmospheric convection.</p><p>The ubiquitous occurrence of variously tilted surfaces - from gently sloping plains top steep cliffs, or valley sidewalls – makes the understanding of such flows of utmost importance in view of the appropriate forecasting of the associated boundary layer transport processes. These may display quite a different structure from those, much better known, occurring over horizontal plain surfaces [1]. Also, they display a highly conceptual relevance, as the simplest, prototypal situations for many other thermally driven-flows over complex terrain [2]. Finally, with the increasing resolution of operational model runs, a more accurate parameterisation of these processes is required for a realistic simulation of their development in space and time.   </p><p>However, up-slope flows have received so far much less attention than downslope flows originating from cooling, which have been extensively investigated by means of theoretically analysis, field experiments and numerical simulations. Even the theoretical analysis on their onset and structure are rather limited (e.g. to gentle slopes: [3]). Analytical solutions, such as Prandtl’s [4], rely on severely restrictive assumptions (parallel flow, constant or slowly varying eddy viscosity and diffusivity, along-slope invariance of the ambient factors). Extensions of such solutions relaxing those restrictions are still limited [5]. Even extensive high-resolution numerical simulations are rare, and not much progress has been made after Schumann’s [6]. Further insight, especially on the conditions for flow separation, have been gained through laboratory-scale simulations [7], which however are limited to moderate flow situations.</p><p>The proposed presentation offers a comprehensive overview of our present understanding of these phenomena, ideas for scaling laws appropriate for these winds, and challenging open questions for future research.</p><p><strong>References</strong></p><ol><li>Rotach, M. W., and D. Zardi, 2007: On the boundary layer structure over complex terrain: Key findings from MAP. Quart. J. Roy. Meteor. Soc., 133, 937-948.</li> <li>Zardi, D. and C. D. Whiteman, 2013: Diurnal Mountain Wind Systems, Chapter 2 in “Mountain weather research and forecasting – Recent progress and current challenges” (Chow, F. K., S. F. J. De Wekker, and B. Snyder Editors), Springer Atmospheric Sciences, Springer, Berlin.</li> <li>Hunt, J. C. R., H. J. S. Fernando, and M. Princevac, 2003: Unsteady thermally driven flows on gentle slopes. J. Atmos. Sci., <strong>60</strong>, 2169-2182.</li> <li>Prandtl L. 1942. Führer durch die strömungslehre, ch. V. Vieweg und Sohn [English translation: Prandtl, L., 1952: Mountain and Valley Winds in Stratified Air, in Essentials of Fluid Dynamics, Hafner Publishing Company, pp.422-425].</li> <li>Zammett, R. J., and A. C. Fowler, 2007: Katabatic winds on ice sheets: A refinement of the Prandtl model. J. Atmos. Sci., <strong>64</strong>, 2707–2716.</li> <li>Schumann U. 1990. Large-eddy simulation of the up-slope boundary layer. Quart. J. Roy. Meteor. Soc. <strong>116</strong>, 637–670.</li> <li>Hilel Goldshmid, R.; Bardoel, S.L.; Hocut, C.M.; Zhong, Q.; Liberzon, D.; Fernando, H.J.S. Separation of Upslope Flow over a Plateau. Atmosphere 2018, <strong>9</strong>, 165.</li> </ol>

Boundary Layer Flashback Model for Hydrogen Flames in Confined Geometries Including the Effect of Adverse Pressure Gradient

2020 ◽  
Author(s):  
Ólafur H. Björnsson ◽  
Sikke A. Klein ◽  
Joeri Tober
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Flow Separation ◽  
Gradient Flow ◽  
Lewis Number ◽  
Adverse Pressure Gradient ◽  
Future Research ◽  
Diffuser Flow ◽  
Combustion Properties ◽  
Quenching Distance

Abstract The combustion properties of hydrogen make premixed hydrogen-air flames very prone to boundary layer flashback. This paper describes the improvement and extension of a boundary layer flashback model from Hoferichter [1] for flames confined in burner ducts. The original model did not perform well at higher preheat temperatures and overpredicted the backpressure of the flame at flashback by 4–5x. By simplifying the Lewis number dependent flame speed computation and by applying a generalized version of Stratford’s flow separation criterion [2], the prediction accuracy is improved significantly. The effect of adverse pressure gradient flow on the flashback limits in 2° and 4° diffusers is also captured adequately by coupling the model to flow simulations and taking into account the increased flow separation tendency in diffuser flow. Future research will focus on further experimental validation and direct numerical simulations to gain better insight into the role of the quenching distance and turbulence statistics.

scholarly journals Homotopy pertubation method analysis to MHD flow of a radiative nanofluid with viscous dissipation and ohmic heating over a stretching porous plate

2018 ◽  
Vol 22 (1 Part B) ◽  
pp. 413-422 ◽  
Author(s):  
Hitesh Kumar
Keyword(s):  
Boundary Layer ◽  
Viscous Dissipation ◽  
Reverse Flow ◽  
Ohmic Heating ◽  
Complete Solution ◽  
Porous Plate ◽  
Flow Characteristics ◽  
Mhd Flow ◽  
Future Research ◽  
Layer Flow

An analytical study is performed to explore the flow and heat transfer characteristics of nanofluid (Al2O3-water and TiO3-water) over a linearly stretching porous sheet in the presence of radiation, ohmic heating, and viscous dissipation. Homotopy perturbed method is used and complete solution is presented, the results for the nanofluids velocity and temperature are obtained. The effects of various thermophysical parameters on the boundary-layer flow characteristics are displayed graphically and discussed quantitatively. The effect of viscous dissipation on the thermal boundary-layer is seen to be reverse after a fixed distance from the wall, which is very strange in nature and is the result of a reverse flow. The finding of this paper is unique and may be useful for future research on nanofluid.

scholarly journals Inorganic bromine in the marine boundary layer: a critical review

2003 ◽  
Vol 3 (3) ◽  
pp. 2963-3050 ◽  
Author(s):  
R. Sander ◽  
W. C. Keene ◽  
A. A. P. Pszenny ◽  
R. Arimoto ◽  
G. P. Ayers ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Gas Phase ◽  
Marine Boundary Layer ◽  
Sea Water ◽  
Ocean Surface ◽  
Sea Salt ◽  
Future Research ◽  
Laboratory Studies ◽  
Model Calculations ◽  
Sea Salt Aerosol

Abstract. The cycling of inorganic bromine in the marine boundary layer (mbl) has received increased attention in recent years. Bromide, a constituent of sea water, is injected into the atmosphere in association with sea-salt aerosol by breaking waves on the ocean surface. Measurements reveal that supermicrometer sea-salt aerosol is depleted in bromine by about 50% relative to conservative tracers, whereas marine submicrometer aerosol is often enriched in bromine. Model calculations, laboratory studies, and field observations strongly suggest that these depletions reflect the chemical transformation of particulate bromide to reactive inorganic gases that influence the processing of ozone and other important constituents of marine air. However, currently available techniques cannot reliably quantify many \\chem{Br}-containing compounds at ambient concentrations and, consequently, our understanding of inorganic Br cycling over the oceans and its global significance are uncertain. To provide a more coherent framework for future research, we have reviewed measurements in marine aerosol, the gas phase, and in rain. We also summarize sources and sinks, as well as model and laboratory studies of chemical transformations. The focus is on inorganic bromine over the open oceans, excluding the polar regions. The generation of sea-salt aerosol at the ocean surface is the major tropospheric source producing about 6.2 Tg/a of bromide. The transport of  Br from continents (as mineral aerosol, and as products from biomass-burning and fossil-fuel combustion) can be of local importance. Transport of degradation products of long-lived Br-containing compounds from the stratosphere and other sources contribute lesser amounts. Available evidence suggests that, following aerosol acidification, sea-salt bromide reacts to form Br2 and BrCl that volatilize to the gas phase and photolyze in daylight to produce atomic Br and Cl. Subsequent transformations can destroy tropospheric ozone, oxidize dimethylsulfide (DMS) and hydrocarbons in the gas phase and S(IV) in aerosol solutions, and thereby potentially influence climate. The diurnal cycle of gas-phase \\Br and the corresponding particulate Br deficits are correlated. Higher values of Br in the gas phase during daytime are consistent with expectations based on photochemistry. Mechanisms that explain the widely reported accumulation of particulate Br in submicrometer aerosols are not yet understood. We expect that the importance of inorganic Br cycling will vary in the future as a function of both increasing acidification of the atmosphere (through anthropogenic emissions) and climate changes. The latter affects bromine cycling via meteorological factors including global wind fields (and the associated production of sea-salt aerosol), temperature, and relative humidity.

scholarly journals Unmanned Aerial Systems for Investigating the Polar Atmospheric Boundary Layer—Technical Challenges and Examples of Applications

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 416 ◽  
Author(s):  
Astrid Lampert ◽  
Barbara Altstädter ◽  
Konrad Bärfuss ◽  
Lutz Bretschneider ◽  
Jesper Sandgaard ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Low Temperatures ◽  
Open Water ◽  
Future Research ◽  
Small Scale ◽  
Unmanned Aerial Systems ◽  
Research Activities ◽  
Aerial Systems ◽  
The Impact

Unmanned aerial systems (UAS) fill a gap in high-resolution observations of meteorological parameters on small scales in the atmospheric boundary layer (ABL). Especially in the remote polar areas, there is a strong need for such detailed observations with different research foci. In this study, three systems are presented which have been adapted to the particular needs for operating in harsh polar environments: The fixed-wing aircraft M 2 AV with a mass of 6 kg, the quadrocopter ALICE with a mass of 19 kg, and the fixed-wing aircraft ALADINA with a mass of almost 25 kg. For all three systems, their particular modifications for polar operations are documented, in particular the insulation and heating requirements for low temperatures. Each system has completed meteorological observations under challenging conditions, including take-off and landing on the ice surface, low temperatures (down to −28 ∘ C), icing, and, for the quadrocopter, under the impact of the rotor downwash. The influence on the measured parameters is addressed here in the form of numerical simulations and spectral data analysis. Furthermore, results from several case studies are discussed: With the M 2 AV, low-level flights above leads in Antarctic sea ice were performed to study the impact of areas of open water within ice surfaces on the ABL, and a comparison with simulations was performed. ALICE was used to study the small-scale structure and short-term variability of the ABL during a cruise of RV Polarstern to the 79 ∘ N glacier in Greenland. With ALADINA, aerosol measurements of different size classes were performed in Ny-Ålesund, Svalbard, in highly complex terrain. In particular, very small, freshly formed particles are difficult to monitor and require the active control of temperature inside the instruments. The main aim of the article is to demonstrate the potential of UAS for ABL studies in polar environments, and to provide practical advice for future research activities with similar systems.

Characterizing and Constraining Uncertainty Associated with Surface and Boundary Layer Turbulent Fluxes in Simulations of Lake-Effect Snowfall

2019 ◽  
Vol 35 (2) ◽  
pp. 467-488 ◽  
Author(s):  
Justin R. Minder ◽  
W. Massey Bartolini ◽  
Christopher Spence ◽  
Newell R. Hedstrom ◽  
Peter D. Blanken ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Friction Velocity ◽  
Surface Fluxes ◽  
Weather Research And Forecasting ◽  
Neutral Stability ◽  
Turbulent Prandtl Number ◽  
Lake Effect ◽  
Simulated Precipitation ◽  
Pbl Parameterization ◽  
Heat And Moisture

Abstract Lake-effect snow (LeS) storms are driven by strong turbulent surface layer (SL) and planetary boundary layer (PBL) fluxes of heat and moisture caused by the flow of cold air over relatively warm water. To investigate the sensitivity of simulated LeS to the parameterization of SL and PBL turbulence, high-resolution simulations of two major storms, downwind of Lakes Superior and Ontario, are conducted using the Weather Research and Forecasting Model. Multischeme and parameter sensitivity experiments are conducted. Measurements of overlake fluxes and downwind snowfall are used to evaluate the simulations. Consistent with previous studies, LeS is found to be strongly sensitive to SL and PBL parameterization choices. Simulated precipitation accumulations differ by up to a factor of 2 depending on the schemes used. Differences between SL schemes are the dominant source of this sensitivity. Parameterized surface fluxes of sensible and latent heat can each vary by over 100 W m−2 between SL schemes. The magnitude of these fluxes is correlated with the amount of downwind precipitation. Differences between PBL schemes play a secondary role, but have notable impacts on storm morphology. Many schemes produce credible simulations of overlake fluxes and downwind snowfall. However, the schemes that produce the largest surface fluxes produce fluxes and precipitation accumulations that are biased high relative to observations. For two SL schemes studied in detail, unrealistically large fluxes can be attributed to parameter choices: the neutral stability turbulent Prandtl number and the threshold friction velocity used for defining regimes in the overwater surface roughness calculation.

scholarly journals Current Understanding of the Driving Mechanisms for Spatiotemporal Variations of Atmospheric Speciated Mercury: A Critical Review

2016 ◽  
Author(s):  
Huiting Mao ◽  
Irene Cheng ◽  
Leiming Zhang
Keyword(s):  
Boundary Layer ◽  
Northern Hemisphere ◽  
Seasonal Variations ◽  
Seasonal Pattern ◽  
High Elevation ◽  
Future Research ◽  
Free Troposphere ◽  
Spatiotemporal Variations ◽  
Driving Mechanisms ◽  
Diurnal Patterns

Abstract. Understanding of spatial and temporal variations of atmospheric speciated mercury can advance our knowledge of mercury cycling in various environments. This review summarized spatiotemporal variations of total gaseous mercury or gaseous elemental mercury (TGM/GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM) in various environments including oceans, continents, high elevation, the free troposphere, and low to high latitudes. In the marine boundary layer (MBL), the oxidation of GEM was generally thought to drive the diurnal and seasonal variations of TGM/GEM and GOM in most oceanic regions, leading to lower GEM and higher GOM from noon to afternoon and higher GEM during winter and higher GOM during spring-summer. At continental sites, the driving mechanisms of TGM/GEM diurnal patterns included surface and local emissions, boundary layer dynamics, GEM oxidation, and mountain-valley winds at high elevation sites. Oxidation of GEM and entrainment of GOM from the free troposphere influenced the diurnal patterns of GOM at continental sites. No pronounced diurnal variation was found for Tekran measured PBM at MBL and continental sites. Seasonal variations in TGM/GEM at continental sites were attributed to increased winter combustion, increased surface emissions during summer, and monsoons in Asia. GEM oxidation, free tropospheric transport, anthropogenic emissions, and wet deposition appeared to affect the seasonal pattern of GOM at continental sites. Since measurements were predominantly in the northern hemisphere (NH), increased PBM at continental sites during winter was primarily due to local/regional coal combustion and wood burning emissions. Long-term TGM measurements from the MBL and continental sites indicated an overall declining trend consistent with those of anthropogenic and natural emissions and potentially redox chemistry. The latitudinal gradient in TGM/GEM showed an increase from the southern to northern hemisphere due largely to the vast majority of Hg emissions in the NH. This gradient was insignificant during summer probably as a result of weaker meridional mixing. Aircraft measurements indicated no significant GEM gradient with altitude over the field campaign regions; however depletion of GEM was observed in air masses under stratospheric influence. Remaining questions and issues related to factors potentially contributing to the observed spatiotemporal variations were identified, and recommendations for future research needs were provided.

Thermally-driven linear vortex

1971 ◽  
Vol 48 (4) ◽  
pp. 801-814 ◽  
Author(s):  
S. Blumsack ◽  
A. Barcilon
Keyword(s):  
Boundary Layer ◽  
Layer Structure ◽  
Bottom Surface ◽  
Rossby Number ◽  
Heat Sources ◽  
Axially Symmetric ◽  
Ekman Number ◽  
The Core ◽  
Thermally Driven ◽  
Axial Heat

We investigate steady axially symmetric small Rossby number flows in which the driving consists of prescribed axial heat sources. By letting the velocity be proportional to the shear at the bottom surface we study the effects of that boundary condition on the resulting flows.A multi-boundary-layer structure is found in the core, surrounding the heat sources. That structure depends on the relative magnitudes of the aspect ratio, stratification parameter and Ekman number.

Tropospheric layering of ozone in regions of urbanized complex and/or coastal terrain: a review

2000 ◽  
Vol 24 (3) ◽  
pp. 329-354 ◽  
Author(s):  
I. G. McKendry ◽  
J. Lundgren
Keyword(s):  
Boundary Layer ◽  
Global Climate ◽  
Research Priorities ◽  
Lower Troposphere ◽  
Ground Level ◽  
Tropospheric Chemistry ◽  
Future Research ◽  
Data Set ◽  
Rich Data ◽  
The Impact

Exchange of pollutants between the atmospheric boundary layer and free troposphere is an important (yet often neglected) process that tends to produce distinct layers of pollution in the lower troposphere. These layers represent a potential sink for pollutants from the boundary layer, have the potential to be mixed to ground and likely influence tropospheric chemistry and the global climate system. Factors influencing the vertical distribution of ozone in the troposphere are outlined as a prelude to a more specific discussion of elevated layers and myriad meteorological processes responsible for their development. Evidence from a range of geographical settings suggests that these phenomena are ubiquitous. A rich data set from the Lower Fraser Valley, British Columbia, is used to provide an inventory of layer structures and to highlight their diverse origins and histories. Approaches used to assess the impact of down-mixing of pollutants from elevated layers on ground-level concentrations of ozone are outlined and future research priorities recommended.

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