scholarly journals Conceptual study on nucleation burst evolution in the convective boundary layer – Part IV: Comparison with previous observations

2005 ◽  
Vol 5 (6) ◽  
pp. 11557-11581
Author(s):  
O. Hellmuth
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Field Experiments ◽  
High Order ◽  
Convective Boundary ◽  
Vertical Fluxes ◽  
Physico Chemical ◽  
Modelling Studies ◽  
Conceptual Study

Abstract. In part I to III of the present paper a revised columnar high-order modelling approach to model gas-aerosol interactions in the convective boundary layer (CBL) was proposed, and simulation results of two nucleation scenarios (binary vs. ternary) on new particle formation (NPF) in the anthropogenically influenced CBL were presented. It was demonstrated that both scenarios strongly differ with respect to the amplitude and phase of the NPF burst detectable in the Prandtl layer, as well as with respect to the time-height evolution of turbulent vertical fluxes and double correlation terms of physico-chemical and aerosoldynamical variables. In the present part, an attempt is made to re-evaluate previous observations of NPF bursts in the CBL in view of the scenario simulations discussed in part III. Special attention is payed to the role of CBL turbulence in NPF burst evolution. At first, a compilation of empirical findings and hypothesis on NPF in the CBL derived from a number of field experiments, is performed. Secondly, it is demonstrated, that the binary scenario simulated in part III corresponds well to a number of NPF burst events observed in Hyytiälä (Finland) and Melpitz (Eastern Germany). Here, one of the key hypothesis on the role of turbulence in NPF is confirmed. Other NPF events, such as those observed at Hohenpeissenberg, a mountain site (Southern Germany), can not yet be conclusively explained. To note, that the results of previous box modelling studies to explain NPF events at Hohenpeissenberg are not unambiguous. Nonetheless, based on only two simulated scenarios it is demonstrated, that a columnar high-order model is a helpful tool to elucidate the genesis of NPF bursts frequently observed in the CBL. A comprehensive verification/validation study using observed high-order moments as well as further scenario simulations remain to be performed.

scholarly journals Conceptual study on nucleation burst evolution in the convective boundary layer – Part III: Physico-chemical characterization

2005 ◽  
Vol 5 (6) ◽  
pp. 11517-11555
Author(s):  
O. Hellmuth
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Chemical Characterization ◽  
High Order ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Convective Boundary ◽  
Aerosol Dynamics ◽  
Physico Chemical ◽  
Conceptual Study

Abstract. In part I of the present paper a revised columnar high-order model to investigate gas-aerosol interactions in the convective boundary layer (CBL) was proposed. In part II the model capability to predict first-, second-, and third-order moments of meteorological variables in the CBL was demonstrated using available observational data. In the present part, the high-order modelling concept is extented to sulfur and ammonia chemistry as well as to aerosol dynamics. Based on the previous CBL simulation, two conceptual scenarios of the evolution of ultrafine condensation nuclei (UCN) in an anthropogenically influenced CBL are investigated. The scenarios differ in the treatment of new particle formation, whereas homogeneous nucleation according to the classical nucleation theory is considered. The first scenario considers nucleation of a binary system consisting of water vapour and sulfuric acid vapour, the second one on nucleation of a ternary system additionally involving ammonia. Here, the two scenarios are discussed in detail, whereas special attention is payed to the role of turbulence in the formation of the typical UCN burst behaviour, that can often be observed in the Prandtl layer.

scholarly journals Columnar modelling of nucleation burst evolution in the convective boundary layer – first results from a feasibility study Part IV: A compilation of previous observations for valuation of simulation results from a columnar modelling study

2006 ◽  
Vol 6 (12) ◽  
pp. 4253-4274 ◽  
Author(s):  
O. Hellmuth
Keyword(s):  
Boundary Layer ◽  
Classical Theory ◽  
Nucleation Rate ◽  
Convective Boundary Layer ◽  
Particle Formation ◽  
High Order ◽  
Convective Boundary ◽  
Binary Nucleation ◽  
Simulation Results

Abstract. In the preceding Papers I, II and III a revised columnar high-order modelling approach to model gas-aerosol-turbulence interactions in the convective boundary layer (CBL) was proposed, and simulation results of two synthetic nucleation scenarios (binary vs. ternary) on new particle formation (NPF) in the anthropogenically influenced CBL were presented and discussed. The purpose of the present finishing Paper IV is twofold: Firstly, an attempt is made to compile previous observational findings on NPF bursts in the CBL, obtained from a number of field experiments. Secondly, the scenario simulations discussed in Paper III will be evaluated with respect to the role of CBL turbulence in NPF burst evolution. It was demonstrated, that completely different nucleation mechanisms can lead to the occurrence of NPF bursts in the surface layer, but the corresponding evolution patterns strongly differ with respect to the origin, amplitude and phase of the NPF burst as well as with respect to the time-height evolution of turbulent vertical fluxes and double correlation terms of physicochemical and aerosoldynamical variables. The large differences between the binary and ternary case scenario indicate, that ammonia (NH3) can not be considered as a time-independent tuning parameter in nucleation modelling. Its contribution to the evolution of the NPF burst pattern is much more complicated and reflects the influence of CBL turbulence as well as the strong non-linearity of the ternary nucleation rate. The impact of water (H2O) vapour on the nucleation rate is quite varying depending on the considered nucleation mechanism. According to the classical theory of binary nucleation involving H2O and sulphuric acid (H2SO4), H2O vapour favours NPF, according to the classical theory of ternary nuncleation involving H2O, H2SO4 and NH3 and according to organic nucleation via chemical reactions involving stabilised Criegee intermediates (SCIs), H2O vapour disfavours nucleation, and according to the parameterisation of the collision-controlled binary nucleation rate proposed by Weber et al. (1996), H2O vapour does not explicitly affect the particle formation. Since the H2SO4 concentration is overpredicted in the simulations presented in Paper III, the nucleation rates are too high compared to previous estimations. Therefore, the results are not directly comparable to measurements. Especially NPF events, where organics are suspected to play a key role, such as those observed at the boreal forest station in Hyytiälä (Southern Finland) or at Hohenpeissenberg (mountain site in Southern Germany), can not be explained by employing simple sulphur/ammonia chemistry. However, some valuable hints regarding the role of CBL turbulence in NPF can be obtained. In the literature a number of observations on the link between turbulence and NPF can be found, whose burst patterns support a strong contribution of CBL turbulence to the NPF burst evolution simulated here. Observations, that do not correspond to the scenarios are discussed with respect to possible reasons for the differences between model and observation. The model simulations support some state-of-the-art hypotheses on the contribution of CBL turbulence to NPF. Considering the application of box models, the present study shows, that CBL turbulence, not explicitly considered in such models, can strongly affect the spatio-temporal NPF burst evolution. The columnar high-order model presented here is a helpful tool to elucidate gas-aerosol-turbulence interactions, especially the genesis of NPF bursts in the CBL. An advanced description of the cluster formation and condensation growth is required as well as a comprehensive verification/validation study using observed high-order moments. Further scenario simulations remain to be performed.

scholarly journals Characterization of a boreal convective boundary layer and its impact on atmospheric chemistry during HUMPPA-COPEC-2010

2012 ◽  
Vol 12 (19) ◽  
pp. 9335-9353 ◽  
Author(s):  
H. G. Ouwersloot ◽  
J. Vilà-Guerau de Arellano ◽  
A. C. Nölscher ◽  
M. C. Krol ◽  
L. N. Ganzeveld ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Chemistry ◽  
Convective Boundary Layer ◽  
Large Scale ◽  
Spatial Scales ◽  
Potential Temperature ◽  
Chemical Species ◽  
Convective Boundary ◽  
The Impact

Abstract. We studied the atmospheric boundary layer (ABL) dynamics and the impact on atmospheric chemistry during the HUMPPA-COPEC-2010 campaign. We used vertical profiles of potential temperature and specific moisture, obtained from 132 radio soundings, to determine the main boundary layer characteristics during the campaign. We propose a classification according to several main ABL prototypes. Further, we performed a case study of a single day, focusing on the convective boundary layer, to analyse the influence of the dynamics on the chemical evolution of the ABL. We used a mixed layer model, initialized and constrained by observations. In particular, we investigated the role of large scale atmospheric dynamics (subsidence and advection) on the ABL development and the evolution of chemical species concentrations. We find that, if the large scale forcings are taken into account, the ABL dynamics are represented satisfactorily. Subsequently, we studied the impact of mixing with a residual layer aloft during the morning transition on atmospheric chemistry. The time evolution of NOx and O3 concentrations, including morning peaks, can be explained and accurately simulated by incorporating the transition of the ABL dynamics from night to day. We demonstrate the importance of the ABL height evolution for the representation of atmospheric chemistry. Our findings underscore the need to couple the dynamics and chemistry at different spatial scales (from turbulence to mesoscale) in chemistry-transport models and in the interpretation of observational data.

Estimating Methane Emissions in the Surat Basin, Australia, including turbulent vertical Fluxes

2020 ◽  
Author(s):  
Bruno Neininger ◽  
Jorg M. Hacker ◽  
Wolfgang Lieff
Keyword(s):  
Boundary Layer ◽  
Mass Balance ◽  
Convective Boundary Layer ◽  
Lower Layer ◽  
Lower Boundary ◽  
Turbulent Fluxes ◽  
Methane Emissions ◽  
Convective Boundary ◽  
Airborne Measurements ◽  
Vertical Fluxes

<p>Last year we described the campaign and the first results (Kelly et al., 2019; Neininger et al., 2019).</p><p>This year we will give an update on methods applied for estimating the regional methane emissions on a scale of about 10'000 km<sup>2</sup>, and sub-regions of about 2'500 km<sup>2</sup>.</p><p>Two approaches were applied:</p><ol><li>The classical mass balance, where the inflow and the outflow of an imaginary box was calculated, based on almost perfect Lagrangian cross-sections (following the air mass).</li> <li>A mass balance for the part of the boundary layer, where flight tracks were available (below 300 m above ground), supplemented by vertical turbulent fluxes to above this height.</li> </ol><p>In the best case, the two methods are leading to similar emission rates. The advantage of method (2) is, that the long flight legs can be limited to the lower boundary layer, which is especially useful when a convective boundary layer is reaching up to typically 2 km or higher above the surface.</p><p>The method worked quite well for water vapour, CO<sub>2</sub> and sensible heat, where fully resolved turbulent fluxes could be calculated based on 10 Hz measurements along the flight legs. Since CH<sub>4</sub> could only be measured with a temporal resolution of about two seconds (0.5 Hz), these a-priori results of the turbulent vertical fluxes are less consistent. However, by applying factors of turbulent versus advective fluxes from the other species, the agreement between the two methods was improved. The turbulent transport to above the 300-metre-layer during the convective conditions was about equal to the accumulation in this layer.</p><p>Since estimating the height of the convective boundary layer and the assumption that the mixing is perfect for approach (1) has many limitations, using method (2) has the advantage that less assumptions on homogeneity of the atmosphere above the densely observed layer has to be made. Even when the concentration profiles and the wind are known from vertical soundings (excursions to above the convective boundary layer), the horizontal inhomogeneity remains unknown. When using the vertical turbulent fluxes into this unknown volume above the lower layer, inhomogeneous mixing is not a problem.</p><p>The challenge of method (2) is to measure fast and precise enough for the quantification of the vertical fluxes. When concentrating on this, one could save time by omitting high soundings, improving the horizontal coverage, and therefore the statistics for the vertical fluxes.</p><p><strong>References</strong></p><p>Kelly et al.: Direct Measurement of Coal Seam Gas and Agricultural Methane Emissions in the Surat Basin, Australia. EGU 2019.</p><p>Neininger, B., J. M. Hacker and W. Lieff: Airborne Measurements for estimating Methane Emissions in the Surat Basin, Australia. EGU 2019.</p>

The role of thermals in the convective boundary layer

1980 ◽  
Vol 19 (4) ◽  
pp. 509-532 ◽  
Author(s):  
D. H. Lenschow ◽  
P. L. Stephens
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Convective Boundary

scholarly journals Conceptual study on nucleation burst evolution in the convective boundary layer – Part I: Modelling approach

2005 ◽  
Vol 5 (6) ◽  
pp. 11413-11487 ◽  
Author(s):  
O. Hellmuth
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Ultrafine Particle ◽  
Particle Formation ◽  
Convective Boundary ◽  
Aerosol Dynamics ◽  
Boundary Layer Turbulence ◽  
Model Setup ◽  
Conceptual Study ◽  
Modelling Approach

Abstract. A high-order modelling approach to interprete 'continental-type' particle formation bursts in the anthropogenically influenced convective boundary layer (CBL) is proposed. The model considers third-order closure for planetary boundary layer turbulence, sulfur and ammonia chemistry and aerosol dynamics. In part I of the present paper, previous observations of ultrafine particle evolution are reviewed, model equations are derived, the model setup for a conceptual study on binary and ternary homogeneous nucleation is defined, and shortcomings of process parameterization are discussed. In subsequent parts of the paper simulation results obtained within the framework of a conceptual study on the CBL evolution and new particle formation (NPF) will be presented and compared with observational findings.

scholarly journals Conceptual study on nucleation burst evolution in the convective boundary layer – Part II: Meteorological characterization

2005 ◽  
Vol 5 (6) ◽  
pp. 11489-11515
Author(s):  
O. Hellmuth
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Convective Boundary ◽  
Large Eddy ◽  
Previous Hypothesis ◽  
Lidar Measurements ◽  
Present Part ◽  
Model Setup ◽  
Conceptual Study

Abstract. While in part I of the present paper a revised columnar high-order modelling approach to investigate gas-aerosol interactions in the convective boundary layer (CBL) was deduced, in the present part the model capability to predict the evolution of meteorological CBL parameters is demonstrated. Based on a model setup to simulate typical CBL conditions, predicted first-, second- and third-order moments were shown to agree very well with those obtained from in situ and remote sensing turbulence measurements such as aircraft, SODAR and LIDAR measurements as well as with those derived from ensemble-averaged large-eddy simulations and wind tunnel experiments. The results show that the model is able to predict the meteorological CBL parameters, required to verify or falsify, respectively, previous hypothesis on the interaction between CBL turbulence and new particle formation.

scholarly journals Columnar modelling of nucleation burst evolution in the convective boundary layer – first results from a feasibility study Part I: Modelling approach

2006 ◽  
Vol 6 (12) ◽  
pp. 4175-4214 ◽  
Author(s):  
O. Hellmuth
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Ultrafine Particle ◽  
Particle Formation ◽  
Convective Boundary ◽  
Aerosol Dynamics ◽  
Boundary Layer Turbulence ◽  
First Results ◽  
Conceptual Study ◽  
Modelling Approach

Abstract. A high-order modelling approach to interpret "continental-type" particle formation bursts in the anthropogenically influenced convective boundary layer (CBL) is proposed. The model considers third-order closure for planetary boundary layer turbulence, sulphur and ammonia chemistry as well as aerosol dynamics. In Paper I of four papers, previous observations of ultrafine particle evolution are reviewed, model equations are derived, the model setup for a conceptual study on binary and ternary homogeneous nucleation is defined and shortcomings of process parameterisation are discussed. In the subsequent Papers II, III and IV simulation results, obtained within the framework of a conceptual study on the CBL evolution and new particle formation (NPF), will be presented and compared with observational findings.

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