scholarly journals Determination and climatology of the diurnal cycle of the atmospheric mixing layer height over Beijing 2013–2018: lidar measurements and implications for air pollution

2020 ◽  
Vol 20 (14) ◽  
pp. 8839-8854 ◽  
Author(s):  
Haofei Wang ◽  
Zhengqiang Li ◽  
Yang Lv ◽  
Ying Zhang ◽  
Hua Xu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Diurnal Cycle ◽  
Mixing Layer ◽  
Daily Maximum ◽  
Layer Height ◽  
Stable Conditions ◽  
Lidar Measurements ◽  
Significant Phenomenon ◽  
Mixing Layer Height ◽  
Convective Layer

Abstract. The atmospheric mixing layer height (MLH) determines the space in which pollutants diffuse and is thus conducive to the estimation of the pollutant concentration near the surface. The study evaluates the capability of lidar to describe the evolution of the atmospheric mixing layer and then presents a long-term observed climatology of the MLH diurnal cycle. Detection of the mixing layer heights (MLHL and MLHL′) using the wavelet method based on lidar observations was conducted from January 2013 to December 2018 in the Beijing urban area. The two dataset results are compared with radiosonde as case studies and statistical forms. MLHL shows good performance in calculating the convective layer height in the daytime and the residual layer height at night. While MLHL′ has the potential to describe the stable layer height at night, the performance is limited due to the high range gate of lidar. A nearly 6-year climatology for the diurnal cycle of the MLH is calculated for convective and stable conditions using the dataset of MLHL from lidar. The daily maximum MLHL characteristics of seasonal change in Beijing indicate that it is low in winter (1.404±0.751 km) and autumn (1.445±0.837 km) and high in spring (1.647±0.754 km) and summer (1.526±0.581 km). A significant phenomenon is found from 2014 to 2018: the magnitude of the diurnal cycle of MLHL increases year by year, with peak values of 1.291±0.646 km, 1.435±0.755 km, 1.577±0.739 km, 1.597±0.701 km and 1.629±0.751 km, respectively. It may partly benefit from the improvement of air quality. As to converting the column optical depth to surface pollution, the calculated PM2.5 using MLHL data from lidar shows better accuracy than that from radiosonde compared with observational PM2.5. Additionally, the accuracy of calculated PM2.5 using MLHL shows a diurnal cycle in the daytime, with the peak at 14:00 LST. The study provides a significant dataset of MLHL based on measurements and could be an effective reference for atmospheric models of surface air pollution calculation and analysis.

scholarly journals Determination and climatology of diurnal cycle of atmospheric mixing layer height over Beijing 2013–2018: Lidar measurements and implication for airpollution

2020 ◽  
Author(s):  
Haofei Wang ◽  
Zhengqiang Li ◽  
Yang Lv ◽  
Ying Zhang ◽  
Hua Xu ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
Mixing Layer ◽  
Layer Height ◽  
Stable Conditions ◽  
Lidar Measurements ◽  
Significant Phenomenon ◽  
Mixing Layer Height ◽  
Convective Layer ◽  
Wavelet Methods

Abstract. The atmospheric mixing layer height (MLH) determines the volume available for the dispersion of pollutants and thus contributes to the assessment of the pollutant concentration near the surface. The study evaluates the capability of lidar to describe the evolution of atmospheric mixing layer and then presents a long term observed climatology of MLH diurnal cycle. A system for automatic detection of the mixing layer height based on two wavelet methods (MLH and MLH') applied to lidar observations was operated from January 2013 to December 2018 in the Beijing urban area. The two dataset results are compared with radiosonde as case studies and statistical form. MLH shows good performance to calculate the convective layer height at daytime and the residual layer height at night. While MLH' has the potential to describe the stable layer height as radiosonde at night, the performance is limited due to the high range gate of lidar. A nearly six year climatology for diurnal cycle of MLH is calculated for convective and stable conditions using the dataset of MLH from lidar. The MLH characteristics of seasonal change in Beijing indicate that it is low in winter and autumn, and high in spring and summer. A significant phenomenon is found that from 2013 to 2018, the diurnal cycle of MLH increase year by year. It may partly benefit from the improvement of air quality. As to converting the column optical depth to the surface pollution, MLH from lidar shows better accuracy than that from radiosonde. Additionally, the accuracy with lidar MLH shows a diurnal cycle, with the peak at time of 14:00 LST. The study provides a significant dataset of MLH based on measurement and could be an effective reference to atmospheric models for surface air pollution calculation and analysis.

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.

Mixing layer height and air pollution levels in urban area

2012 ◽  
Author(s):  
Klaus Schäfer ◽  
Patrick Wagner ◽  
Stefan Emeis ◽  
Carsten Jahn ◽  
Christoph Muenkel ◽  
...  
Keyword(s):  
Air Pollution ◽  
Urban Area ◽  
Mixing Layer ◽  
Layer Height ◽  
Pollution Levels ◽  
Mixing Layer Height

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 Determination of the mixing layer height from regular lidar measurements in the Barcelona area

2004 ◽  
Author(s):  
Michael Sicard ◽  
Carlos Perez ◽  
Adolfo Comeren ◽  
Jose M. Baldasano ◽  
Francesc Rocadenbosch
Keyword(s):  
Mixing Layer ◽  
Layer Height ◽  
Lidar Measurements ◽  
Mixing Layer Height

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 Mixing layer height retrievals by multichannel microwave radiometer observations

2013 ◽  
Vol 6 (3) ◽  
pp. 4971-4998 ◽  
Author(s):  
D. Cimini ◽  
F. De Angelis ◽  
J.-C. Dupont ◽  
S. Pal ◽  
M. Haeffelin
Keyword(s):  
Diurnal Cycle ◽  
Seasonal Variability ◽  
Microwave Radiometer ◽  
Mixing Layer ◽  
Atmospheric Temperature ◽  
Lidar System ◽  
Night Time ◽  
Mean Values ◽  
Layer Height ◽  
Mixing Layer Height

Abstract. The mixing layer height (MLH) is a key parameter for boundary layer studies, including meteorology, air quality, and climate. MLH estimates are inferred from in situ radiosonde measurements or remote sensing observations from instruments like lidar, wind profiling radar, or sodar. Methods used to estimate MLH from radiosonde profiles are also used with atmospheric temperature and humidity profiles retrieved by microwave radiometers (MWR). This paper proposes an alternative approach to estimate MLH from MWR data, based on direct observations (brightness temperatures, Tb) instead of retrieved profiles. To our knowledge, MLH estimates directly from Tb observations has never been attempted before. The method consists of a multivariate linear regression trained with an a priori set of collocated MWR Tb observations (multi-frequency and multi-angle) and MLH estimates from a state-of-the-art lidar system. Results show that the method is able to follow both the diurnal cycle and the day-to-day variability as suggested by the lidar measurements, and also it can detect low MLH values that are below the full overlap limit (~ 200 m) of the lidar system used. Statistics of the comparison between MWR- and reference lidar-based MLH retrievals show mean difference within 10 m, RMS within 340 m, and correlation coefficient higher than 0.77. Monthly mean analysis for day-time MLH from MWR, lidar, and radiosonde shows consistent seasonal variability, peaking at ~ 1200–1400 m in June and decreasing down to ~ 600 m in October. Conversely, night-time monthly mean MLH from all methods are within 300–500 m without any significant seasonal variability. The proposed method provides results that are more consistent with radiosonde estimates than MLH estimates from MWR retrieved profiles. MLH monthly mean values agree well within 1 std with bulk Richardson number method applied at radiosonde profiles at 11:00 and 23:00 UTC. The method described herewith operates continuously and it is expected to work with analogous performances for the entire diurnal cycle, except during considerable precipitation, demonstrating new potential for atmospheric observation by ground-based microwave radiometry.

scholarly journals Detailed Assessment of the Effects of Meteorological Conditions on PM10 Concentrations in the Northeastern Part of the Czech Republic

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 497 ◽  
Author(s):  
Vladimíra Volná ◽  
Daniel Hladký
Keyword(s):  
Air Pollution ◽  
Wind Direction ◽  
Mixing Layer ◽  
Meteorological Conditions ◽  
Pollution Sources ◽  
Pollution Level ◽  
Layer Height ◽  
Wind Speeds ◽  
Average Maximum ◽  
Mixing Layer Height

This article assessed the links between PM10 pollution and meteorological conditions over the Czech-Polish border area at the Třinec-Kosmos and Věřňovice sites often burdened with high air pollution covering the years 2016–2019. For this purpose, the results of the measurements of special systems (ceilometers) that monitor the atmospheric boundary layer were used in the analysis. Meteorological conditions, including the mixing layer height (MLH), undoubtedly influence the air pollution level. Combinations of meteorological conditions and their influence on PM10 concentrations also vary, depending on the pollution sources of a certain area and the geographical conditions of the monitoring site. Gen1erally, the worst dispersion conditions for the PM10 air pollution level occur at low air temperatures, low wind speed, and low height of the mixing layer along with a wind direction from areas with a higher accumulation of pollution sources. The average PM10 concentrations at temperatures below 1 °C reach the highest values on the occurrence of a mixing layer height of up to 400 m at both sites. The influence of a rising height of the mixing layer at temperatures below 1 °C on the average PM10 concentrations at Třinec-Kosmos site is not as significant as in the case of Věřňovice, where a difference of several tens of µg·m−3 in the average PM10 concentrations was observed between levels of up to 200 m and levels of 200–300 m. The average PM10 hourly concentrations at Třinec-Kosmos were the highest at wind speeds of up to 0.5 m·s−1, at MLH levels of up to almost 600 m; at Věřňovice, the influence of wind speeds of up to 2 m·s−1 was detected. Despite the fact that the most frequent PM10 contributions come to the Třinec-Kosmos site from the SE direction, the average maximum concentration contributions come from the W–N sectors at low wind speeds and MLHs of up to 400 m. In Věřňovice, regardless of the prevailing SW wind direction, sources in the NE–E sector from the site have a crucial influence on the air pollution level caused by PM10.

scholarly journals Influence of mixing layer height upon air pollution in urban and sub-urban areas

2006 ◽  
Vol 15 (6) ◽  
pp. 647-658 ◽  
Author(s):  
Klaus Schäfer ◽  
Stefan Emeis ◽  
Herbert Hoffmann ◽  
Carsten Jahn
Keyword(s):  
Air Pollution ◽  
Urban Areas ◽  
Mixing Layer ◽  
Layer Height ◽  
Mixing Layer Height
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