scholarly journals Rapid formation of intense haze episodes via aerosol–boundary layer feedback in Beijing

2020 ◽  
Vol 20 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Yonghong Wang ◽  
Miao Yu ◽  
Yuesi Wang ◽  
Guiqian Tang ◽  
Tao Song ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollutants ◽  
Mixing Layer ◽  
Feedback Mechanism ◽  
Field Observations ◽  
Layer Height ◽  
Rapid Formation ◽  
Mixing Layer Height ◽  
Haze Episode ◽  
Reduced Surface

Abstract. Although much effort has been put into studying air pollution, our knowledge of the mechanisms of frequently occurring intense haze episodes in China is still limited. In this study, using 3 years of measurements of air pollutants at three different height levels on a 325 m Beijing meteorology tower, we found that a positive aerosol–boundary layer feedback mechanism existed at three vertical observation heights during intense haze polluted periods within the mixing layer. This feedback was characterized by a higher loading of PM2.5 with a shallower mixing layer. Modelling results indicated that the presence of PM2.5 within the boundary layer led to reduced surface temperature, relative humidity and mixing layer height during an intensive haze episode. Measurements showed that the aerosol–boundary layer feedback was related to the decrease in solar radiation, turbulent kinetic energy and thereby suppression of the mixing layer. The feedback mechanism can explain the rapid formation of intense haze episodes to some extent, and we suggest that the detailed feedback mechanism warrants further investigation from both model simulations and field observations.

scholarly journals Rapid formation of intense haze episode in Beijing

2018 ◽  
Author(s):  
Yonghong Wang ◽  
Yuesi Wang ◽  
Guiqian Tang ◽  
Tao Song ◽  
Putian Zhou ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Particulate Matter ◽  
Kinetic Energy ◽  
Air Pollutants ◽  
Mixing Layer ◽  
Feedback Mechanism ◽  
Quality Models ◽  
Rapid Formation ◽  
Haze Episode

Abstract. Although much efforts have been put on studying air pollution, our knowledge on the mechanisms of frequently occurred intense haze episodes in China is still limited. In this study, using three years of measurements of air pollutants at three different height levels on a 325-meter Beijing meteorology tower, we found that a positive particulate matter-boundary layer feedback mechanism existed at three vertical observation heights during intense haze polluted periods within the mixing layer. This feedback was characterized by a higher loading of PM2.5 with a shallower mixing layer. Measurements showed that the feedback was related to the decrease of solar radiation, turbulent kinetic energy and thereby suppression of the mixing layer. The feedback mechanism can explain the rapid formation of intense haze episodes to some extent, and we suggest that the feedback mechanism should be considered in air quality models for better predictions.

scholarly journals Lidar-based remote sensing of atmospheric boundary layer height over land and ocean

2014 ◽  
Vol 7 (1) ◽  
pp. 173-182 ◽  
Author(s):  
T. Luo ◽  
R. Yuan ◽  
Z. Wang
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Marine Boundary Layer ◽  
Mixing Layer ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Lidar Measurements ◽  
Mixing Layer Height ◽  
Atmospheric Radiation Measurement ◽  
Atmospheric Boundary Layer Height

Abstract. Atmospheric boundary layer (ABL) processes are important in climate, weather and air quality. A better understanding of the structure and the behavior of the ABL is required for understanding and modeling of the chemistry and dynamics of the atmosphere on all scales. Based on the systematic variations of the ABL structures over different surfaces, different lidar-based methods were developed and evaluated to determine the boundary layer height and mixing layer height over land and ocean. With Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) micropulse lidar (MPL) and radiosonde measurements, diurnal and season cycles of atmospheric boundary layer depth and the ABL vertical structure over ocean and land are analyzed. The new methods are then applied to satellite lidar measurements. The aerosol-derived global marine boundary layer heights are evaluated with marine ABL stratiform cloud top heights and results show a good agreement between them.

scholarly journals Boundary Layer Characteristics over the Central Area of the Kathmandu Valley as Revealed by Sodar Observation

2015 ◽  
Vol 20 (1) ◽  
pp. 28-35
Author(s):  
Sajan Shrestha ◽  
Saraswati Shrestha ◽  
Sangeeta Maharjan ◽  
Ram P. Regmi
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Diurnal Variation ◽  
Mixing Layer ◽  
Central Area ◽  
Kathmandu Valley ◽  
Pollution Dispersion ◽  
Easterly Wind ◽  
Layer Height ◽  
Mixing Layer Height

The characteristic behavior of prevailing boundary layer over the central area of the Kathmandu valley was continuously monitored by deploying a monostatic flat array sodar during the period of 03 to 16 March 2013. Diurnal variation of wind and mixing layer height were chosen to describe the boundary layer activities over the area by considering the day of 12 March 2013 as the representative day for the period of observation. The study shows that central area of the valley remains calm or windless under stable stratification throughout the night and early morning frequently capped by northeasterly or easterly wind aloft. Strong surface level thermal inversion prevails during the period up to the height of 80m above the surface. This inversion tends to lift up as the morning progresses and reaches to the height of 875 m or so close to the noontime. Intrusion of regional winds as westerly/northwesterly and the southerly/southwesterly from the western and southwestern low-mountain passes and the river gorge in the afternoon tends to reduce the noontime mixing layer height to about 700 m. The diurnal variation of wind and mixing layer height suggest that Kathmandu valley possesses a poor air pollution dispersion power and hence the valley is predisposed to high air pollution potential.Journal of Institute of Science and Technology, 2015, 20(1): 28-35

scholarly journals Lidar-based remote sensing of atmospheric boundary layer height over land and ocean

2013 ◽  
Vol 6 (5) ◽  
pp. 8311-8338
Author(s):  
T. Luo ◽  
R. Yuan ◽  
Z. Wang
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Marine Boundary Layer ◽  
Layer Structure ◽  
Mixing Layer ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Lidar Measurements ◽  
Mixing Layer Height ◽  
Atmospheric Radiation Measurement

Abstract. Atmospheric boundary layer (ABL) processes are important in climate, weather and air quality. A better understanding of the structure and the behavior of the ABL is required for understanding and modeling of the chemistry and dynamics of the atmosphere on all scales. Based on the systematic variations of ABL structures over different surfaces, different lidar-based methods were developed and evaluated to determine the boundary layer height and mixing layer height over land and ocean. With Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) micropulse lidar (MPL) and radiosonde measurements, diurnal and season cycles of atmospheric boundary layer depth and ABL vertical structure over ocean (TWP_C2 cite) and land (SGP_C1) are analyzed. The new methods are also applied to satellite lidar measurements. The derived global marine boundary layer structure database shows good agreement with marine ABL stratiform cloud top height.

scholarly journals The role of subsidence in a weakly unstable marine boundary layer: a case study

2014 ◽  
Vol 21 (2) ◽  
pp. 489-501
Author(s):  
I. M. Mazzitelli ◽  
M. Cassol ◽  
M. M. Miglietta ◽  
U. Rizza ◽  
A. M. Sempreviva ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Mixed Layer ◽  
Marine Boundary Layer ◽  
Mesoscale Model ◽  
Mixing Layer ◽  
Layer Height ◽  
Mixing Layer Height

Abstract. The diurnal evolution of a cloud free, marine boundary layer is studied by means of experimental measurements and numerical simulations. Experimental data belong to an investigation of the mixing height over inner Danish waters. The mixed-layer height measured over the sea is generally nearly constant, and does not exhibit the diurnal cycle characteristic of boundary layers over land. A case study, during summer, showing an anomalous development of the mixed layer under unstable and nearly neutral atmospheric conditions, is selected in the campaign. Subsidence is identified as the main physical mechanism causing the sudden decrease in the mixing layer height. This is quantified by comparing radiosounding profiles with data from numerical simulations of a mesoscale model, and a large-eddy simulation model. Subsidence not only affects the mixing layer height, but also the turbulent fluctuations within it. By analyzing wind and scalar spectra, the role of subsidence is further investigated and a more complete interpretation of the experimental results emerges.

scholarly journals Inter-comparison of lidar and ceilometer retrievals for aerosol and Planetary Boundary Layer profiling over Athens, Greece

2011 ◽  
Vol 4 (6) ◽  
pp. 1261-1273 ◽  
Author(s):  
G. Tsaknakis ◽  
A. Papayannis ◽  
P. Kokkalis ◽  
V. Amiridis ◽  
H. D. Kambezidis ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Mixing Layer ◽  
Radiosonde Data ◽  
Lidar System ◽  
Height Range ◽  
Layer Height ◽  
Tropospheric Aerosol ◽  
Filter Radiometer ◽  
Mixing Layer Height

Abstract. This study presents an inter-comparison of two active remote sensors (lidar and ceilometer) to determine the mixing layer height and structure of the Planetary Boundary Layer (PBL) and to retrieve tropospheric aerosol vertical profiles over Athens, Greece. This inter-comparison was performed under various strongly different aerosol loads/types (urban air pollution, biomass burning and Saharan dust event), implementing two different lidar systems (one portable Raymetrics S.A. lidar system running at 355 nm and one multi-wavelength Raman lidar system running at 355 nm, 532 nm and 1064 nm) and one CL31 Vaisala S.A. ceilometer (running at 910 nm). Spectral conversions of the ceilometer's data were performed using the Ångström exponent estimated by ultraviolet multi-filter radiometer (UV-MFR) measurements. The inter-comparison was based on two parameters: the mixing layer height determined by the presence of the suspended aerosols and the attenuated backscatter coefficient. Additionally, radiosonde data were used to derive the PBL height. In general, a good agreement was found between the ceilometer and the lidar techniques in both inter-compared parameters in the height range from 500 m to 5000 m, while the limitations of each instrument are also examined.

scholarly journals Boundary Layer Characteristics over Aindanda Low-Mountain Pass of Kathmandu Valley, Nepal

2015 ◽  
Vol 20 (2) ◽  
pp. 22-30 ◽  
Author(s):  
Saraswati Shrestha ◽  
Sajan Shrestha ◽  
Sangeeta Maharjan ◽  
Ram P. Regmi
Keyword(s):  
Boundary Layer ◽  
Mixing Layer ◽  
Central Area ◽  
Mountain Pass ◽  
Kathmandu Valley ◽  
Night Time ◽  
Air Mass ◽  
Layer Height ◽  
Late Afternoon ◽  
Mixing Layer Height

The early monsoon time boundary layer characteristics prevailing over Aindanda low-mountain pass of Kathmandu valley has been continuously monitored for the period of 11 to 24 June 2013. The study reveals that the Aindanda pass channels regional air masses from the western neighboring valley up into the Kathmandu valley as westerly/ northwesterly winds during the daytime whereas it drains air mass out of the valley during night-time. The speed of the westerly/northwesterly wind over the pass often exceeds 6.5 ms-1 during the late afternoon. Nighttime mixing layer height (MLH) was highly fluctuating with an average around 300m whereas daytime MLH was suppressed limiting it in between 290-450m above the ground in early part of the day but reduced to 210-270m during the late afternoon. Comparison of diurnal variation of mixing layer height at Aindanda with that of the central area of the valley floor strongly suggests that air mass intruding into the Kathmandu valley through this pass is a cool density flow over the weakly stratified mixed layer of valley. The structure of the wind channeled through this pass indicates the possibility of making hydraulic jump in the western part of the Kathmandu valley, particularly, during the late afternoon time.Journal of Institute of Science and Technology, 2015, 20(2): 22-30

scholarly journals Erratum to: Observed and Modelled Convective Mixing-Layer Height at Dome C, Antarctica

2014 ◽  
Vol 153 (1) ◽  
pp. 163-164 ◽  
Author(s):  
Giampietro Casasanta ◽  
Ilaria Pietroni ◽  
Igor Petenko ◽  
Stefania Argentini
Keyword(s):  
Mixing Layer ◽  
Layer Height ◽  
Convective Mixing ◽  
Mixing Layer Height
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