Transport Processes in the Coastal Atmospheric Boundary Layer

2000 ◽  
Author(s):  
Michael Tjernstrom
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Transport Processes

scholarly journals The topography contribution to the influence of the atmospheric boundary layer at high altitude stations

2017 ◽  
Author(s):  
Martine Collaud Coen ◽  
Elisabeth Andrews ◽  
Diego Aliaga ◽  
Marcos Andrade ◽  
Hristo Angelov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
High Altitude ◽  
Geometric Mean ◽  
Convective Transport ◽  
Transport Processes ◽  
The Tibetan Plateau ◽  
Diurnal Cycles ◽  
Air Convection ◽  
Aerosol Parameters

Abstract. High altitude stations are often emphasized as free tropospheric measuring sites but they remain influenced by atmospheric boundary layer (ABL) air masses due to convective transport processes. The local and meso-scale topographical features around the station are involved in the convective boundary layer development and in the formation of thermally induced winds leading to ABL air lifting. The station altitude is not a sufficient parameter to characterize the ABL influence. Topography data from the global digital elevation model GTopo30 were used to calculate 5 parameters for 46 high altitude stations situated in five continents. The geometric mean of these 5 parameters determines a topography based index called ABL-TopoIndex which can be used to rank the high altitude stations as a function of the ABL influence. To construct the ABL-TopoIndex, we rely on the criteria that the ABL influence will be low if the station is one of the highest points in the mountainous massif, if there is a large altitude difference between the station and the valleys or plateaus, if the slopes around the station are steep, and finally if the drainage basin for air convection is small. All stations on volcanic islands exhibit a low ABL-TopoIndex whereas stations in the Himalaya and the Tibetan Plateau have high ABL-TopoIndex values. Spearman's rank correlation between aerosol optical properties and number concentration from 28 stations and the ABL-TopoIndex, the altitude and the latitude are used to validate this topographical approach. Statistically significant (s.s.) correlations are found between the 5 and 50 percentiles of all aerosol parameters and the ABL-TopoIndex whereas no s.s. correlation is found with the station altitude. The diurnal cycles of aerosol parameters seem to be best explained by the station latitude although a s.s. correlation is found between the amplitude of the diurnal cycles of the absorption coefficient and the ABL-TopoIndex. Finally, the main flow paths for air convection were calculated for various ABL heights.

scholarly journals Investigation of the atmospheric boundary layer dynamics during the ESCOMPTE campaign

2007 ◽  
Vol 25 (3) ◽  
pp. 597-622 ◽  
Author(s):  
F. Saïd ◽  
A. Brut ◽  
B. Campistron ◽  
F. Cousin
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Lower Layer ◽  
Lower Troposphere ◽  
Sea Breeze ◽  
Transport Processes ◽  
Topographic Effects ◽  
Pollution Transport ◽  
Data Set ◽  
Diurnal Variability

Abstract. This paper presents some results about the behavior of the atmospheric boundary layer observed during the ESCOMPTE experiment. This campaign, which took place in south-eastern France during summer 2001, was aimed at improving our understanding of pollution episodes in relation to the dynamics of the lower troposphere. Using a large data set, as well as a simulation from the mesoscale non-hydrostatic model Meso-NH, we describe and analyze the atmospheric boundary layer (ABL) development during two specific meteorological conditions of the second Intensive Observation Period (IOP). The first situation (IOP2a, from 22 June to 23 June) corresponds to moderate, dry and cold northerly winds (end of Mistral event), coupled with a sea-breeze in the lower layer, whereas sea-breeze events with weak southerly winds occurred during the second part of the period (IOP2b, from 24 June to 26 June). In this study, we first focus on the validation of the model outputs with a thorough comparison of the Meso-NH simulations with fields measurements on three days of the IOP: 22 June, 23 June and 25 June. We also investigate the structure of the boundary layer on IOP2a when the Mistral is superimposed on a sea breeze. Then, we describe the spatial and diurnal variability of the ABL depths over the ESCOMPTE domain during the whole IOP. This step is essential if one wants to know the depth of the layer where the pollutants can be diluted or accumulated. Eventually, this study intends to describe the ABL variability in relation to local or mesoscale dynamics and/or induced topographic effects, in order to explain pollution transport processes in the low troposphere.

scholarly journals The Vertical Variability of Black Carbon Observed in the Atmospheric Boundary Layer during DACCIWA

2019 ◽  
Author(s):  
Barbara Altstädter ◽  
Konrad Deetz ◽  
Bernhard Vogel ◽  
Karmen Babić ◽  
Cheikh Dione ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Black Carbon ◽  
West African Monsoon ◽  
Transport Processes ◽  
Small Scale ◽  
Scale Modelling ◽  
Research Aircraft ◽  
Reactive Trace Gases ◽  
Vertical Variability

Abstract. The vertical variability of the black carbon (BC) mass concentration in the atmospheric boundary layer (ABL) is analysed during the West-African Monsoon (WAM) season. BC was measured with a micro aethalometer (model AE51, AethLabs) integrated in the payload bay of the unmanned research aircraft ALADINA (Application of Light-weight Aircraft for Detecting IN situ Aerosol) as part of the field experiment of the DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) project. In total, 53 measurement flights were performed at the local airfield of Save, Benin, in the period of 2–16 July 2016. The mean results show a high variability of BC (1.79 to 2.42 ± 0.31 μg/m3) influenced by the stratification of the ABL during the WAM. The model COSMO-ART (Consortium for Small-scale Modelling–Aerosols and Reactive Trace gases) was applied for the field campaign period and used in order to investigate possible sources of the measured BC. The model output was compared with the BC data on two selected measurement days (14 and 15 July 2016). The modeled vertical profiles of BC show that the observed BC was already altered, as the size was mainly dominated by the accumulation mode. Further, the calculated vertical transects of wind speed and BC showed that the measured BC layer was transported from the south with maritime inflow, but was mixed vertically after to the onset of the nocturnal low-level jet (NLLJ) at the measurement site. The validations and the ground observations of gas concentrations NOx and CO confirm that primary emission could be excluded during the case study, in contrast to initially expected. The case underlines the important role of BC transport processes in the WAM area.

scholarly journals Current Challenges in Understanding and Predicting Transport and Exchange in the Atmosphere over Mountainous Terrain

Atmosphere ◽  
2018 ◽  
Vol 9 (7) ◽  
pp. 276 ◽  
Author(s):  
Manuela Lehner ◽  
Mathias Rotach
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Transport Processes ◽  
Mountainous Terrain ◽  
Moist Convection ◽  
Free Atmosphere ◽  
Spatial And Temporal Scales ◽  
Exchange Processes ◽  
Thermally Driven ◽  
Definition Of

Coupling of the earth’s surface with the atmosphere is achieved through an exchange of momentum, energy, and mass in the atmospheric boundary layer. In mountainous terrain, this exchange results from a combination of multiple transport processes, which act and interact on different spatial and temporal scales, including, for example, orographic gravity waves, thermally driven circulations, moist convection, and turbulent motions. Incorporating these exchange processes and previous studies, a new definition of the atmospheric boundary layer in mountainous terrain, a mountain boundary layer (MBL), is defined. This paper summarizes some of the major current challenges in measuring, understanding, and eventually parameterizing the relevant transport processes and the overall exchange between the MBL and the free atmosphere. Further details on many aspects of the exchange in the MBL are discussed in several other papers in this issue.

scholarly journals Modeling of the Coastal Boundary Layer and Pollutant Transport in New England

2006 ◽  
Vol 45 (1) ◽  
pp. 137-154 ◽  
Author(s):  
Wayne M. Angevine ◽  
Michael Tjernström ◽  
Mark Žagar
Keyword(s):  
Boundary Layer ◽  
New York ◽  
New England ◽  
Atmospheric Boundary Layer ◽  
Urban Areas ◽  
Large Scale ◽  
Cold Water ◽  
Mixed Boundary ◽  
Pollutant Transport ◽  
Transport Processes

Abstract Concentrations of ozone exceeding regulatory standards are regularly observed along the coasts of New Hampshire and Maine in summer. These events are primarily caused by the transport of pollutants from urban areas in Massachusetts and farther south and west. Pollutant transport is most efficient over the ocean. The coastline makes transport processes complex because it makes the structure of the atmospheric boundary layer complex. During pollution episodes, the air over land in daytime is warmer than the sea surface, so air transported from land over water becomes statically stable and the formerly well-mixed boundary layer separates into possibly several layers, each transported in a different direction. This study examines several of the atmospheric boundary layer processes involved in pollutant transport. A three-dimensional model [the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS)] run on grids of 2.5 and 7.5 km is used to examine the winds, thermodynamic structure, and structure of tracer plumes emitted from Boston, Massachusetts, and New York City, New York, in two different real cases—one dominated by large-scale transport (22–23 July 2002) and one with important mesoscale effects (11–14 August 2002). The model simulations are compared with measurements taken during the 2002 New England Air Quality Study. The model simulates the basic structure of the two different episodes well. The boundary layer stability over the cold water is weaker in the model than in reality. The tracer allows for easy visualization of the pollutant transport.

Analysis of physicochemical characteristics in the atmospheric boundary layer over the North Plain China based on large tethered balloon and Doppler wind lidar

2020 ◽  
Author(s):  
Haijiong Sun ◽  
Yu Shi ◽  
Fei Hu ◽  
Zhe Zhang ◽  
Weichen Ding
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Vertical Profile ◽  
Layer Structure ◽  
Physicochemical Characteristics ◽  
Transport Processes ◽  
Observation Data ◽  
Tethered Balloon ◽  
Wind Lidar ◽  
Doppler Wind Lidar

<p>Physicochemical characteristics of the atmospheric boundary layer over North Plain China during the comprehensive observation experiment from 10 to 21 December 2018 were investigated in this paper. The observation data are obtained from the large tethered balloon, Doppler wind lidar, ground-level instruments. The maximum concentration of PM<sub>2.5</sub> exceeded 200 µg m-3, and the ratio value of PM<sub>2.5</sub>/PM<sub>10</sub> was basically around 0.4 (maximum has reached approximately 0.8) during the whole observation period, indicating that explosive growth of fine ode dominant aerosols during the winter heating season. The peak solar irradiance was slightly larger on the clean day, compared with the value during the pollution process. The correlation coefficient between the concentration of PM<sub>2.5</sub> and CO was highest (0.725) among the gas pollutants, and the relationship between O<sub>3</sub> and PM<sub>2.5</sub> was basically negative correlated, not simple linear relationship. Three distinctly different vertical profile types of the PM<sub>2.5</sub> were categorized according to the vertical changes based on the total 33 vertical profiles obtained by the tethered balloon. Type 1 was mainly observed in the daytime, accounted for nearly 51.5%, the PM<sub>2.5</sub> concentration decreased nearly linearly as a function of height below approximate 600 m; Type 2 shows a sharp decreasing trend from the ground to about 200 m; Type 3 shows multi-layer structure of pollutants, some pollutants suspended aloft in upper air. The vertical profile of PM<sub>2.5</sub> was closely related to the atmospheric vertical structure such as the wind, temperature and turbulent kinetic energy, caused by the diurnal variation of the boundary layer. Small wind layer and the weak turbulence activities contributed to the accumulation of pollutants. Vertical patterns of the concentration of PM<sub>2.5</sub> were also greatly affected by the local ground emission sources and regional transport processes.</p>

Characteristics of the Night and Day Time Atmospheric Boundary Layer at Dome C, Antarctica

2007 ◽  
Vol 25 ◽  
pp. 49-55 ◽  
Author(s):  
S. Argentini ◽  
I. Pietroni ◽  
G. Mastrantonio ◽  
A. Viola ◽  
S. Zilitinchevich
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Night And Day
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