scholarly journals Nocturnal Boundary Layer Evolution and Its Impacts on the Vertical Distributions of Pollutant Particulate Matter

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 610
Author(s):  
Yu Shi ◽  
Lei Liu ◽  
Fei Hu ◽  
Guangqiang Fan ◽  
Juntao Huo
Keyword(s):  
Boundary Layer ◽  
Nitrate Concentration ◽  
Inversion Layer ◽  
Mixing Layer ◽  
Early Morning ◽  
Nocturnal Boundary Layer ◽  
Atmospheric Environment ◽  
Considerable Proportion ◽  
Surface Inversion ◽  
Vertical Distributions

To investigate the evolution of the nocturnal boundary layer (NBL) and its impacts on the vertical distributions of pollutant particulates, a combination of in situ observations from a large tethered balloon, remote sensing instruments (aerosol lidar and Doppler wind lidar) and an atmospheric environment-monitoring vehicle were utilized. The observation site was approximately 100 km southwest of Beijing, the capital of China. Results show that a considerable proportion of pollutant particulates were still suspended in the residual layer (RL) (e.g., the nitrate concentration reached 30 μg m−3) after sunset. The NBL height calculated by the aerosol lidar was closer to the top of the RL before midnight because of the pollutants stored aloft in the RL and the shallow surface inversion layer; after midnight, the NBL height was more consistent with the top of the surface inversion layer. As the convective mixing layer gradually became established after sunrise the following day, the pollutants stored in the nocturnal RL of the preceding night were entrained downward into the mixing layer. The early morning PM2.5 concentration near 700 m in the RL on 20 December decreased by 83% compared with the concentration at 13:34 on 20 December at the same height. The nitrate concentration also decreased significantly in the RL, and the mixing down of nitrate from the RL could contribute about 37% to the nitrate in the mixing layer. Turbulence activities still existed in the RL with the bulk Richardson number (Rb) below the threshold value. The corresponding increase in PM2.5 was likely to be correlated with the weak turbulence in the RL in the early morning.

The impacts of residual layer on the vertical distributions of pollutant particulate matter: combining large tethered balloon and remote sensing observations

2020 ◽  
Author(s):  
Shi Yu ◽  
Fei Hu ◽  
Haijiong Sun ◽  
Zhe Zhang ◽  
Weichen Ding
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Nitrate Concentration ◽  
Inversion Layer ◽  
Mixing Layer ◽  
Residual Layer ◽  
Considerable Proportion ◽  
Tethered Balloon ◽  
Surface Inversion ◽  
Vertical Distributions

<p>The combination of in situ observations from a large tethered balloon and remote sensing instruments (aerosol lidar and Doppler wind lidar) enabled the evolution of the residual layer (RL) to be observed during an intensive vertical detection experiment of the planetary boundary layer (PBL) conducted during December (Dec) 2018 in Wangdu County, China. This paper focused on the important role played by the RL in the variations of the vertical distributions of pollutant particulates. The results of the present analysis revealed the following. (1) A considerable proportion of pollutant particulates remained suspended in the RL (e.g., the nitrate concentration reached 30 µg m<sup>-3</sup>) in the nocturnal boundary layer (NBL). Multilayer pollutant structures appeared often, partly because of the existence of the RL. Because pollutants were still stored in the RL and the shallow surface inversion layer, the aerosol lidar-calculated PBL height was closer to the top of the RL before midnight in the NBL; after midnight, the PBL height was more consistent with the top of the surface inversion layer. (2) As the convective mixing layer gradually became established after sunrise the following day, the pollutants stored in the nocturnal RL of the preceding night were entrained downward into the mixing layer. The early morning PM<sub>2.5</sub> concentration near 700 m in the RL on Dec 20 decreased obviously compared with the concentration at 13:34 on Dec 20 at the same height (ranging from 30 µg m<sup>-3</sup> to 5 µg m<sup>-3</sup>). The nitrate concentration also decreased significantly in the RL, but its concentration increased to 12 µg m<sup>-3</sup> in the mixing layer. Near-surface PM<sub>2.5</sub> diffused upward more easily due to strong vertical mixing during the daytime, causing reductions in the surface concentration. The mixing layer heights in Wangdu County were estimated to be 600 m in the winter, and various emitted pollutant particulates eventually became well-mixed within the mixing layer. The daytime mixing layer heights were consistent with the PBL heights calculated by aerosol lidar representing the pollutant accumulation depth. (3) The RL was characterized by a Richardson number (Ri) below the threshold value of 0.25, revealing that turbulence still existed within the RL.</p>

scholarly journals A Review of Techniques for Diagnosing the Atmospheric Boundary Layer Height (ABLH) Using Aerosol Lidar Data

2019 ◽  
Vol 11 (13) ◽  
pp. 1590 ◽  
Author(s):  
Ruijun Dang ◽  
Yi Yang ◽  
Xiao-Ming Hu ◽  
Zhiting Wang ◽  
Shuwen Zhang
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Atmospheric Boundary Layer ◽  
Weather Prediction ◽  
Mixing Layer ◽  
Accurate Estimation ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Vertical Distributions ◽  
Multi Wavelength

The height of the atmospheric boundary layer (ABLH) or the mixing layer height (MLH) is a key parameter characterizing the planetary boundary layer, and the accurate estimation of that is critically important for boundary layer related studies, which include air quality forecasts and numerical weather prediction. Aerosol lidar is a powerful remote sensing instrument frequently used to retrieve the ABLH through detecting the vertical distributions of aerosol concentration. Presently available methods for ABLH determination from aerosol lidar are summarized in this review, including a lot of classical methodologies as well as some improved versions of them. Some new recently developed methods applying advanced techniques such as image edge detection, as well as some new methods based on multi-wavelength lidar systems, are also summarized. Although a lot of techniques have been proposed and have already given reasonable results in several studies, it is impossible to recommend a technique which is suitable in all atmospheric scenarios. More accurate instantaneous ABLH from robust techniques is required, which can be used to estimate or improve the boundary layer parameterization in the numerical model, or maybe possible to be assimilated into the weather and environment models to improve the simulation or forecast of weather and air quality in the future.

scholarly journals A Climatological Study of the Nocturnal Boundary Layer over a Complex-Terrain Station

2012 ◽  
Vol 51 (4) ◽  
pp. 813-825 ◽  
Author(s):  
M. Shravan Kumar ◽  
V. K. Anandan ◽  
T. Narayana Rao ◽  
P. Narasimha Reddy
Keyword(s):  
Boundary Layer ◽  
Seasonal Variation ◽  
Monsoon Season ◽  
Inversion Layer ◽  
Nocturnal Boundary Layer ◽  
Local Circulation ◽  
Sodar Data ◽  
Doppler Sodar

AbstractTwo years of Doppler sodar measurements are used to study the time–height structure of the nocturnal boundary layer (NBL), its seasonal variation, and the characteristics of different types of NBL. A total of 220 clear-sky nights during which the inversion layer is clearly visible on a sodar echogram are examined. The NBL depth estimated with sodar data using a wind maxima criterion matches reasonably well with radiosonde-based NBL depth estimates. The NBL exhibits clear seasonal variation with greater depths during the monsoon season. Shallow NBLs are generally observed in winter. The evolution of NBL height shows two distinctly different patterns (called type 1 and type 2), particularly in the second half of the night. Type 1 NBL depth is nearly constant and the wind speed in this type is generally weak and steady throughout the night, while type 2 is characterized by moderate to strong winds with considerable variations in NBL height. The local circulation generated by the complex topography is clearly seen in type 1 throughout the night, whereas it is seen only in the first half of the night in type 2. Type 1 NBLs seem to be more prevalent over Gadanki, India, with nearly 61% of total nights showing type 1 characteristics. Furthermore, type 1 NBL shows large seasonal variability with the majority of type 1 cases in winter. The type 2 cases are mostly observed in monsoon (~60%) followed by summer (39%). The surface meteorological parameters during type 1 and type 2 cases are examined. Differences between type 1 and type 2 NBL patterns are discussed in relation to the surface forcing.

scholarly journals The Morning NO<sub> x</sub> maximum in the forest atmosphere boundary layer

2011 ◽  
Vol 11 (10) ◽  
pp. 29251-29282 ◽  
Author(s):  
M. Alaghmand ◽  
P. B. Shepson ◽  
T. K. Starn ◽  
B. T. Jobson ◽  
H. W. Wallace ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Thermodynamic Stability ◽  
Rural Areas ◽  
Early Morning ◽  
Nocturnal Boundary Layer ◽  
Diurnal Pattern ◽  
Contributing Factors ◽  
Potential Sources ◽  
Soil Emissions

Abstract. During the 1998, 2000, 2001, 2008, and 2009 summer intensives of the Program for Research on Oxidants: PHotochemistry, Emissions and Transport (PROPHET), ambient measurement of nitrogen oxides (NO + NO2 = NOx) were conducted. NO and NOx mole fractions displayed a diurnal pattern with NOx frequently highest in early morning. This pattern has often been observed in other rural areas. In this paper, we discuss the potential sources and contributing factors of the frequently observed morning pulse of NOx. Of the possible potential contributing factors to the observed morning pulse of NO and NOx, we find that surface-layer transport and slow upward mixing from soil emissions, related to the thermodynamic stability in the nocturnal boundary layer (NBL) before its morning breakup are the largest contributors. The morning NOx peak can significantly impact boundary layer chemistry, e.g. through production of HONO on surfaces, and by increasing the importance of NO3 chemistry in the morning boundary layer.

scholarly journals Comparative Study of the West African Continental, Coastal, and Marine Atmospheric Profiles during the Summer of 2006

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Ibrahima Kalil Kante ◽  
Daouda Badiane ◽  
Saïdou Moustapha Sall ◽  
Abdoulaye Deme ◽  
Arona Diedhiou
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Comparative Study ◽  
Marine Boundary Layer ◽  
Inversion Layer ◽  
Mixing Layer ◽  
Vertical Gradient ◽  
Dew Point ◽  
Vertical Profiles ◽  
Rainy Period

We used sounding data of the Multidisciplinary Analysis of the African Monsoon experience in summer 2006 at continental and coastal sites of West Africa, respectively, to analyze the vertical profiles of relative humidity, temperature, dew point, and speed and wind direction for the JJAS rainy period. The vertical gradient method is applied to the profiles of some thermodynamic parameters estimated from sounding data to do a comparative study of the structure and thermal properties, moisture, and static stability of the atmospheric boundary layer of inland, coastal, and marine sites to show consistent differences related to geographic factors. In vertical profiles of relative humidity, the intensity is higher in Dakar than in Niamey particularly in the core of the season. There are dry intrusions in the low levels at the beginning and end of the season in Dakar, which do not exist in Niamey. The mixing layer on the continent during the day can reach a height greater than 1100 m, and the inversion layer height can exceed 1700 m. Therefore, the maximum thickness of the boundary layer is observed on the continent during the day, while at night the marine boundary layer is the thickest. The diurnal evolution shows that the mixing layer thickness decreases during the night over the continent but increases at the coast and at sea. In the night at the continental site there is a division of the mixing layer with a consistent residual mixing layer. Continental boundary layer is more unstable during the day, while at night it is the marine boundary layer that is more unstable than the coastal and inland ones.

scholarly journals Carbon dioxide measurements in the nocturnal boundary layer over Amazonian forest

1999 ◽  
Vol 3 (1) ◽  
pp. 39-53 ◽  
Author(s):  
A. D. Culf ◽  
G. Fisch ◽  
Y. Malhi ◽  
R. Carvalho Costa ◽  
A. D. Nobre ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Carbon Dioxide Concentration ◽  
Surface Flux ◽  
Co2 Concentration ◽  
Early Morning ◽  
Nocturnal Boundary Layer ◽  
Maximum Height ◽  
Carbon Dioxide Concentrations ◽  
The Difference

Abstract. Measurements of carbon dioxide concentration, temperature and windspeed were made in the nocturnal boundary layer over a tropical forest near Manaus, Brazil using a tethered balloon system. The measurements were made up to a maximum height of 300 m on ten consecutive nights in November 1995. Simultaneous surface flux and in-canopy concentration measurements were made at the surface close to the site. The observation period included several different types of conditions. Generally strong windshear and relatively weak temperature gradients prevented the formation of a strong capping inversion to the nocturnal boundary layer. On some nights, however, the inversion was sufficiently strong that the CO2 concentration at 100 m above the surface exceeded 400 ppm. The concentration within the canopy was largely controlled by the presence of an inversion very close to the canopy surface. The temperature and wind profiles are contrasted with conditions in Randônia, Brazil, where the windshear was found to be weaker and higher carbon dioxide concentrations were observed in the early morning. The difference in carbon dioxide concentrations in the nocturnal boundary layer between dusk and dawn is used to estimate the regional nighttime flux of carbon dioxide. The value obtained generally exceeds the measured surface flux and sometimes exceeds the sum of the surface flux and the in-canopy storage made at the tower site. The reasons for the discrepancy are not clear; either one of the methods is in error or the regional carbon dioxide budget differs significantly from the local budget measured at the tower site.

scholarly journals Coevolution of Down-Valley Flow and the Nocturnal Boundary Layer in Complex Terrain

2006 ◽  
Vol 45 (10) ◽  
pp. 1429-1449 ◽  
Author(s):  
J. O. Pinto ◽  
D. B. Parsons ◽  
W. O. J. Brown ◽  
S. Cohn ◽  
N. Chamberlain ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Complex Terrain ◽  
Salt Lake ◽  
Similarity Theory ◽  
Inversion Layer ◽  
Great Salt Lake ◽  
Nocturnal Boundary Layer ◽  
Vertical Transport ◽  
Low Level ◽  
Transport And Mixing

Abstract An enhanced National Center for Atmospheric Research (NCAR) integrated sounding system (ISS) was deployed as part of the Vertical Transport and Mixing (VTMX) field experiment, which took place in October of 2000. The enhanced ISS was set up at the southern terminus of the Great Salt Lake Valley just north of a gap in the Traverse Range (TR), which separates the Great Salt Lake and Utah Lake basins. This location was chosen to sample the dynamic and thermodynamic properties of the flow as it passes over the TR separating the two basins. The enhanced ISS allowed for near-continuous sampling of the nocturnal boundary layer (NBL) and low-level winds associated with drainage flow through the gap in the TR. Diurnally varying winds were observed at the NCAR site on days characterized by weak synoptic forcing and limited cloud cover. A down-valley jet (DVJ) was observed on about 50% of the nights during VTMX, with the maximum winds usually occurring within 150 m of the surface. The DVJ was associated with abrupt warming at low levels as a result of downward mixing and vertical transport of warm air from the inversion layer above. Several processes were observed to contribute to vertical transport and mixing at the NCAR site. Pulses in the strength of the DVJ contributed to vertical transport by creating localized areas of low-level convergence. Gravity waves and Kelvin–Helmholtz waves, which facilitated vertical mixing near the surface and atop the DVJ, were observed with a sodar and an aerosol backscatter lidar that were deployed as part of the enhanced ISS. The nonlocal nature of the processes responsible for generating turbulence in strongly stratified surface layers in complex terrain confounds surface flux parameterizations typically used in mesoscale models that rely on Monin–Obukhov similarity theory. This finding has major implications for modeling NBL structure and drainage flows in regions of complex terrain.

scholarly journals Land-Use Improvements in the Weather Research and Forecasting Model over Complex Mountainous Terrain and Comparison of Different Grid Sizes

2021 ◽  
Author(s):  
Alessio Golzio ◽  
Silvia Ferrarese ◽  
Claudio Cassardo ◽  
Gugliemina Adele Diolaiuti ◽  
Manuela Pelfini
Keyword(s):  
Boundary Layer ◽  
Land Use ◽  
Land Cover ◽  
Mixing Layer ◽  
Local Area ◽  
Heat Fluxes ◽  
Weather Research And Forecasting ◽  
Forecasting Model ◽  
Mountainous Terrain ◽  
Weather Research

AbstractWeather forecasts over mountainous terrain are challenging due to the complex topography that is necessarily smoothed by actual local-area models. As complex mountainous territories represent 20% of the Earth’s surface, accurate forecasts and the numerical resolution of the interaction between the surface and the atmospheric boundary layer are crucial. We present an assessment of the Weather Research and Forecasting model with two different grid spacings (1 km and 0.5 km), using two topography datasets (NASA Shuttle Radar Topography Mission and Global Multi-resolution Terrain Elevation Data 2010, digital elevation models) and four land-cover-description datasets (Corine Land Cover, U.S. Geological Survey land-use, MODIS30 and MODIS15, Moderate Resolution Imaging Spectroradiometer land-use). We investigate the Ortles Cevadale region in the Rhaetian Alps (central Italian Alps), focusing on the upper Forni Glacier proglacial area, where a micrometeorological station operated from 28 August to 11 September 2017. The simulation outputs are compared with observations at this micrometeorological station and four other weather stations distributed around the Forni Glacier with respect to the latent heat, sensible heat and ground heat fluxes, mixing-layer height, soil moisture, 2-m air temperature, and 10-m wind speed. The different model runs make it possible to isolate the contributions of land use, topography, grid spacing, and boundary-layer parametrizations. Among the considered factors, land use proves to have the most significant impact on results.

scholarly journals Nocturnal Boundary Layer Erosion Analysis in the Amazon Using Large-Eddy Simulation during GoAmazon Project 2014/5

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 240
Author(s):  
Rayonil Carneiro ◽  
Gilberto Fisch ◽  
Theomar Neves ◽  
Rosa Santos ◽  
Carlos Santos ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Rainy Season ◽  
Nocturnal Boundary Layer ◽  
Enso Event ◽  
Dry Season ◽  
Dry Period ◽  
Additional Energy ◽  
Eddy Simulation ◽  
Large Eddy

This study investigated the erosion of the nocturnal boundary layer (NBL) over the central Amazon using a high-resolution model of large-eddy simulation (LES) named PArallel Les Model (PALM) and observational data from Green Ocean Amazon (GoAmazon) project 2014/5. This data set was collected during four intense observation periods (IOPs) in the dry and rainy seasons in the years 2014 (considered a typical year) and 2015, during which an El Niño–Southern Oscillation (ENSO) event predominated and provoked an intense dry season. The outputs from the PALM simulations represented reasonably well the NBL erosion, and the results showed that it has different characteristics between the seasons. During the rainy season, the IOPs exhibited slow surface heating and less intense convection, which resulted in a longer erosion period, typically about 3 h after sunrise (that occurs at 06:00 local time). In contrast, dry IOPs showed more intensive surface warming with stronger convection, resulting in faster NBL erosion, about 2 h after sunrise. A conceptual model was derived to investigate the complete erosion during sunrise hours when there is a very shallow mixed layer formed close to the surface and a stable layer above. The kinematic heat flux for heating this layer during the erosion period showed that for the rainy season, the energy emitted from the surface and the entrainment was not enough to fully heat the NBL layer and erode it. Approximately 30% of additional energy was used in the system, which could come from the release of energy from biomass. The dry period of 2014 showed stronger heating, but it was also not enough, requiring approximately 6% of additional energy. However, for the 2015 dry period, which was under the influence of the ENSO event, it was shown that the released surface fluxes were sufficient to fully heat the layer. The erosion time of the NBL probably influenced the development of the convective boundary layer (CBL), wherein greater vertical development was observed in the dry season IOPs (~1500 m), while the rainy season IOPs had a shallower layer (~1200 m).

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