Atmospheric boundary layer height(ABLH)is an important parameter used to depict characteristics of the planetary boundary layer(PBL)in the lower troposphere.The ABLH is strongly associated with the vertical distributi...Atmospheric boundary layer height(ABLH)is an important parameter used to depict characteristics of the planetary boundary layer(PBL)in the lower troposphere.The ABLH is strongly associated with the vertical distributions of heat,mass,and energy in the PBL,and it is a key quantity in numerical simulation of the PBL and plays an essential role in atmospheric environmental assessment.In this paper,various definitions and methods for deriving and estimating the ABLH are summarized,from the perspectives of turbulent motion,PBL dynamics and thermodynamics,and distributions of various substances in the PBL.Different methods for determining the ABLH by means of direct observation and remote sensing retrieval are reviewed,and comparisons of the advantages and disadvantages of these methods are presented.The paper also summarizes the ABLH parameterization schemes,discusses current problems in the estimation of ABLH,and finally points out the directions for possible future breakthroughs in the ABLHrelated research and application.展开更多
A study was conducted on aerosol-radiation interactions over six cities in this region within the 2015–2019 period.WRF-Chem simulations on 2017 showed that based on the six-city average,the aerosol load(PM_(2.5)conce...A study was conducted on aerosol-radiation interactions over six cities in this region within the 2015–2019 period.WRF-Chem simulations on 2017 showed that based on the six-city average,the aerosol load(PM_(2.5)concentrations)of 121.9,49.6,43.3,and 66.3μg/m^(3)in January,April,July,and October,mainly lowered the level of downward shortwave radiation by 38.9,24.0,59.1,and 24.4 W/m~2and reduced the boundary layer height by 79.9,40.8,87.4,and 31.0 m,via scattering and absorbing solar radiation.The sensitivity of meteorological changes to identical aerosol loads varied in the order July>January>October and April.Then,the cooling and stabilizing effects of aerosols further led to increases in PM_(2.5),by23.0,3.4,4.6,and 7.3μg/m^(3)respectively in the four months.The sensitivity of the effect of aerosols on PM_(2.5)was greatest in January rather than in July,contrary to the effect on meteorology.Moreover,a negative linear relation was observed between daily BLH reductions and aerosol loads in fall and winter,and between PM_(2.5)increases and aerosol loads in all seasons.With the PM_(2.5)pollution improvements in this region,the aerosol radiative forcing was effectively reduced.This should result in daily BLH increases of 10–24 m in fall and winter,and the estimates in Beijing agreed well with the corresponding results based on AMDAR data.Additionally,the reduction in aerosol radiation effects brought about daily PM_(2.5)decreases of 1.6-2.8μg/m^(3),accounting for 7.0%–17.7%in PM_(2.5)improvements.展开更多
With the intensification of pollution and urbanization, the aerosol radiation effect continues to play an important role in the urban boundary layer. In this paper, a winter pollution process in Beijing has been taken...With the intensification of pollution and urbanization, the aerosol radiation effect continues to play an important role in the urban boundary layer. In this paper, a winter pollution process in Beijing has been taken as an example, and a new aerosol vertical profile in the radiative parameterization scheme within the Weather Forecast Research and Forecasting(WRF) model has been updated to study the effect of aerosols on radiation and the boundary layer. Furthermore, the interactions among aerosols,urbanization, and planetary boundary layer(PBL) meteorology were discussed through a series of numerical experiments. The results show the following:(1) The optimization improves the performance of the model in simulating the distribution features of air temperature, humidity, and wind in Beijing.(2) The aerosols reduce the surface temperature by reducing solar radiation and increasing the temperature in the upper layer by absorbing or backscattering solar radiation. The changes in the PBL temperature lead to more stable atmospheric stratification, reducing the energy transfer from the surface and the height of the boundary layer.(3) With the increase in the aerosol optical depth, the atmospheric stratification most likely becomes stable over rural areas, most likely becomes stable over suburb areas, and has great difficultly becoming stable over urban areas. Aerosol radiative forcing,underlying urban surfaces, and the interaction between them are the main factors that affect the changes in the meteorological elements in the PBL.展开更多
The North China Plain(NCP)is troubled by severe haze pollution and the evolution of haze pollution is closely related to the atmospheric boundary layer(ABL).However,experimental and theoretical studies on the physical...The North China Plain(NCP)is troubled by severe haze pollution and the evolution of haze pollution is closely related to the atmospheric boundary layer(ABL).However,experimental and theoretical studies on the physical-chemical processes of the ABL in the NCP are lacking,with many scientific problems to be addressed.To solve these problems,the Comprehensive Observation on the Atmospheric boundary layer Three-dimensional Structure(COATS)during haze pollution was carried out in the NCP from 2016 to 2020.The COATS experiment adopted a"point-line-surface"spatial layout,obtaining both spatial-temporal profiles of the meteorological and environmental elements in the ABL and the turbulent transport data of fine particulate matter(PM_(2.5))in winter and summer.The research achievements are as follows.The spatial-temporal distribution characteristics of the ABL structure and PM_(2.5)concentrations in NCP were determined.The typical thermal structure of persistent heavy haze events and the pollutant removal mechanism by low-level jets were revealed.It was determined that the spatial structure of the ABL adjusted by the Taihang Mountains is responsible for the heterogeneous distribution of haze pollution in the NCP,and that mountain-induced vertical circulations can promote the formation of elevated pollution layers.The restraints of the atmospheric internal boundaries on horizontal diffusion of pollutants were emphasized.The contribution of the ABL to haze pollution in winter and summer was qualitatively compared and quantitatively estimated.The turbulent transport nature behind the relationship between the atmospheric boundary layer height(ABLH)and surface PM_(2.5)concentrations was analyzed.The concept of"aerosol accumulation layer"was defined,and the applicability of the material method in determining ABLH was clarified.A measurement system for obtaining the turbulent flux of PM_(2.5)concentrations was developed,and the turbulence characteristics of PM_(2.5)concentrations were demonstrated.The COATS experiment is of grea展开更多
Measurements of atmospheric aerosols and trace gases using the laser radar (lidar) techniques, have been in progress since 1985 at the Indian Institute of Tropical Meteorology, Pune (18°32'N, 73°51'E...Measurements of atmospheric aerosols and trace gases using the laser radar (lidar) techniques, have been in progress since 1985 at the Indian Institute of Tropical Meteorology, Pune (18°32'N, 73°51'E, 559 m AMSL), India. These observations carried out during nighttime in the lower atmosphere (up to 5.5 km AGL), employing an Argon ion / Helium-Neon lidar provided information on the nature, size, concentration and other characteristics of the constituents present in the tropical atmosphere. The time-height variations in aerosol concentration and associated layer structure exhibit marked differences between the post-sunset and pre-sunrise periods besides their seasonal variation with maximum concentration during pre-monsoon / winter and minimum concentration during monsoon months. These observations also revealed the influence of the terrain of the experimental site and some selected meteorological parameters on the aerosol vertical distributions. The special observations of aerosol vertical profiles obtained in the nighttime atmospheric boundary layer during October 1986 through September 1989 showed that the most probable occurrence of mixing depth lies between 450 and 550 m, and the multiple stably stratified aerosol layers present above the mixing depth with maximum frequency of occurrence at around 750 m. This information on nighttime mixing depth / stable layer derived from lidar aerosol observations showed good agreement with the height of the ground-based shear layer / elevated layer observed by the simultaneously operated sodar at the lidar site.展开更多
As a passive remote sensing technique,MAX-DOAS method was widely used to investigate the vertical profiles of aerosol and trace gases in the lower troposphere.However,the measurements for midlatitude marine boundary l...As a passive remote sensing technique,MAX-DOAS method was widely used to investigate the vertical profiles of aerosol and trace gases in the lower troposphere.However,the measurements for midlatitude marine boundary layer are rarely reported,especially during the storm weather system.In this study,the MAX-DOAS was used to retrieve the aerosol,HCHO and NO_(2) vertical distribution at Huaniao Island of East China Sea in summer 2018,during which a strong tropical cyclone developed and passed through the measurement site.The observed aerosol optical depth(AOD),HCHO-and NO_(2)-VCDs(Vertical Column Density)were in the range of 0.19-0.97,(2.57-12.27)×10^(15) molec/cm^(2),(1.24-4.71)×10^(15) molec/cm^(2),which is much higher than remote ocean area due to the short distance to continent.The vertically resolved aerosol extinction coefficient(AEC),HCHO and NO_(2) presented the decline trend with the increase of height.After the typhoon passing through,the distribution of high levels of aerosol and HCHO stretched to about 1 kmand the abundances of the bottom layer were found as double higher than before,reaching 0.51 km^(−1) and 2.44 ppbv,while NO_(2) was still constrained within about 300 m with 2.59 ppbv in the bottom layer.The impacts of typhoon process forced air mass were also observed at the suburban site in Shanghai in view of both the aerosol extinction and chemical components.The different changes on air quality associated with typhoon and its mechanism in two different environments:coastal island and coastal city are worthy of further investigation as it frequent occurred in East Asia during summer and fall.展开更多
Visibility observed at different altitudes is favorable to understand the causes of air pol-lution.We conducted 4-years of observations of visibility at 2.8 and 60 m and particulate matter(PM)concentrations from 2015 ...Visibility observed at different altitudes is favorable to understand the causes of air pol-lution.We conducted 4-years of observations of visibility at 2.8 and 60 m and particulate matter(PM)concentrations from 2015 to 2018 in Shenyang,a provincial city in Northeast China.The results indicated that visibility increased with the increasing height in winter(especially at night),and decreased with height in summer(especially at the daytime).PM concentration exhibited opposite vertical variation to visibility,reflecting that visibility de-grades with the increase of aerosol concentration in the air.The radiosonde meteorological data showed that weak turbulence in the planetary boundary layer(PBL)in winter favored aerosols'accumulation near the surface.Whereas in summer,unstable atmospheric con-ditions,upper-level moister environment,and regional transport of air pollutants resulted in the deterioration of upper-level visibility.Inter-annual variation in the two-level visibility indicated that the upper-level visibility improved more significantly than low-level visibil-ity,much likely due to the reduction in emission of elevated point sources in Shenyang.Our study suggested that strengthening the control of surface non-point emissions is a promis-ing control strategy to improve Shenyang air quality.展开更多
基金Supported by the National Key Research and Development Program of China(2016YFC0203300 and 2017YFC0209600)National Research Program for Key Issues in Air Pollution Control(DQGG0104 and DQGG0106)National Natural Science Foundation of China(91544216).
文摘Atmospheric boundary layer height(ABLH)is an important parameter used to depict characteristics of the planetary boundary layer(PBL)in the lower troposphere.The ABLH is strongly associated with the vertical distributions of heat,mass,and energy in the PBL,and it is a key quantity in numerical simulation of the PBL and plays an essential role in atmospheric environmental assessment.In this paper,various definitions and methods for deriving and estimating the ABLH are summarized,from the perspectives of turbulent motion,PBL dynamics and thermodynamics,and distributions of various substances in the PBL.Different methods for determining the ABLH by means of direct observation and remote sensing retrieval are reviewed,and comparisons of the advantages and disadvantages of these methods are presented.The paper also summarizes the ABLH parameterization schemes,discusses current problems in the estimation of ABLH,and finally points out the directions for possible future breakthroughs in the ABLHrelated research and application.
基金funded by the National Natural Science Foundation of China (Nos.51978010 and 52022005)。
文摘A study was conducted on aerosol-radiation interactions over six cities in this region within the 2015–2019 period.WRF-Chem simulations on 2017 showed that based on the six-city average,the aerosol load(PM_(2.5)concentrations)of 121.9,49.6,43.3,and 66.3μg/m^(3)in January,April,July,and October,mainly lowered the level of downward shortwave radiation by 38.9,24.0,59.1,and 24.4 W/m~2and reduced the boundary layer height by 79.9,40.8,87.4,and 31.0 m,via scattering and absorbing solar radiation.The sensitivity of meteorological changes to identical aerosol loads varied in the order July>January>October and April.Then,the cooling and stabilizing effects of aerosols further led to increases in PM_(2.5),by23.0,3.4,4.6,and 7.3μg/m^(3)respectively in the four months.The sensitivity of the effect of aerosols on PM_(2.5)was greatest in January rather than in July,contrary to the effect on meteorology.Moreover,a negative linear relation was observed between daily BLH reductions and aerosol loads in fall and winter,and between PM_(2.5)increases and aerosol loads in all seasons.With the PM_(2.5)pollution improvements in this region,the aerosol radiative forcing was effectively reduced.This should result in daily BLH increases of 10–24 m in fall and winter,and the estimates in Beijing agreed well with the corresponding results based on AMDAR data.Additionally,the reduction in aerosol radiation effects brought about daily PM_(2.5)decreases of 1.6-2.8μg/m^(3),accounting for 7.0%–17.7%in PM_(2.5)improvements.
基金supported by the Ministry of Science and Technology of China (Grant No. 2015DFA20870)the Beijing Municipal Science and Technology Commission (Grant Nos. D171100000717003, Z161100001116065 & Z151100002115045)
文摘With the intensification of pollution and urbanization, the aerosol radiation effect continues to play an important role in the urban boundary layer. In this paper, a winter pollution process in Beijing has been taken as an example, and a new aerosol vertical profile in the radiative parameterization scheme within the Weather Forecast Research and Forecasting(WRF) model has been updated to study the effect of aerosols on radiation and the boundary layer. Furthermore, the interactions among aerosols,urbanization, and planetary boundary layer(PBL) meteorology were discussed through a series of numerical experiments. The results show the following:(1) The optimization improves the performance of the model in simulating the distribution features of air temperature, humidity, and wind in Beijing.(2) The aerosols reduce the surface temperature by reducing solar radiation and increasing the temperature in the upper layer by absorbing or backscattering solar radiation. The changes in the PBL temperature lead to more stable atmospheric stratification, reducing the energy transfer from the surface and the height of the boundary layer.(3) With the increase in the aerosol optical depth, the atmospheric stratification most likely becomes stable over rural areas, most likely becomes stable over suburb areas, and has great difficultly becoming stable over urban areas. Aerosol radiative forcing,underlying urban surfaces, and the interaction between them are the main factors that affect the changes in the meteorological elements in the PBL.
基金supported by the National Natural Science Foundation of China(Grant Nos.42090031,42175092,92044301&91544216)the National Key R&D Program of China(Grant Nos.2016YFC0203306&2017YFC0209600)the National Research Program for Key Issues in Air Pollution Control(Grant Nos.DQGG0104&DQGG0106)。
文摘The North China Plain(NCP)is troubled by severe haze pollution and the evolution of haze pollution is closely related to the atmospheric boundary layer(ABL).However,experimental and theoretical studies on the physical-chemical processes of the ABL in the NCP are lacking,with many scientific problems to be addressed.To solve these problems,the Comprehensive Observation on the Atmospheric boundary layer Three-dimensional Structure(COATS)during haze pollution was carried out in the NCP from 2016 to 2020.The COATS experiment adopted a"point-line-surface"spatial layout,obtaining both spatial-temporal profiles of the meteorological and environmental elements in the ABL and the turbulent transport data of fine particulate matter(PM_(2.5))in winter and summer.The research achievements are as follows.The spatial-temporal distribution characteristics of the ABL structure and PM_(2.5)concentrations in NCP were determined.The typical thermal structure of persistent heavy haze events and the pollutant removal mechanism by low-level jets were revealed.It was determined that the spatial structure of the ABL adjusted by the Taihang Mountains is responsible for the heterogeneous distribution of haze pollution in the NCP,and that mountain-induced vertical circulations can promote the formation of elevated pollution layers.The restraints of the atmospheric internal boundaries on horizontal diffusion of pollutants were emphasized.The contribution of the ABL to haze pollution in winter and summer was qualitatively compared and quantitatively estimated.The turbulent transport nature behind the relationship between the atmospheric boundary layer height(ABLH)and surface PM_(2.5)concentrations was analyzed.The concept of"aerosol accumulation layer"was defined,and the applicability of the material method in determining ABLH was clarified.A measurement system for obtaining the turbulent flux of PM_(2.5)concentrations was developed,and the turbulence characteristics of PM_(2.5)concentrations were demonstrated.The COATS experiment is of grea
文摘Measurements of atmospheric aerosols and trace gases using the laser radar (lidar) techniques, have been in progress since 1985 at the Indian Institute of Tropical Meteorology, Pune (18°32'N, 73°51'E, 559 m AMSL), India. These observations carried out during nighttime in the lower atmosphere (up to 5.5 km AGL), employing an Argon ion / Helium-Neon lidar provided information on the nature, size, concentration and other characteristics of the constituents present in the tropical atmosphere. The time-height variations in aerosol concentration and associated layer structure exhibit marked differences between the post-sunset and pre-sunrise periods besides their seasonal variation with maximum concentration during pre-monsoon / winter and minimum concentration during monsoon months. These observations also revealed the influence of the terrain of the experimental site and some selected meteorological parameters on the aerosol vertical distributions. The special observations of aerosol vertical profiles obtained in the nighttime atmospheric boundary layer during October 1986 through September 1989 showed that the most probable occurrence of mixing depth lies between 450 and 550 m, and the multiple stably stratified aerosol layers present above the mixing depth with maximum frequency of occurrence at around 750 m. This information on nighttime mixing depth / stable layer derived from lidar aerosol observations showed good agreement with the height of the ground-based shear layer / elevated layer observed by the simultaneously operated sodar at the lidar site.
基金supported by National Natural Science Foundation of China (No. 41775113)。
文摘As a passive remote sensing technique,MAX-DOAS method was widely used to investigate the vertical profiles of aerosol and trace gases in the lower troposphere.However,the measurements for midlatitude marine boundary layer are rarely reported,especially during the storm weather system.In this study,the MAX-DOAS was used to retrieve the aerosol,HCHO and NO_(2) vertical distribution at Huaniao Island of East China Sea in summer 2018,during which a strong tropical cyclone developed and passed through the measurement site.The observed aerosol optical depth(AOD),HCHO-and NO_(2)-VCDs(Vertical Column Density)were in the range of 0.19-0.97,(2.57-12.27)×10^(15) molec/cm^(2),(1.24-4.71)×10^(15) molec/cm^(2),which is much higher than remote ocean area due to the short distance to continent.The vertically resolved aerosol extinction coefficient(AEC),HCHO and NO_(2) presented the decline trend with the increase of height.After the typhoon passing through,the distribution of high levels of aerosol and HCHO stretched to about 1 kmand the abundances of the bottom layer were found as double higher than before,reaching 0.51 km^(−1) and 2.44 ppbv,while NO_(2) was still constrained within about 300 m with 2.59 ppbv in the bottom layer.The impacts of typhoon process forced air mass were also observed at the suburban site in Shanghai in view of both the aerosol extinction and chemical components.The different changes on air quality associated with typhoon and its mechanism in two different environments:coastal island and coastal city are worthy of further investigation as it frequent occurred in East Asia during summer and fall.
基金This work was supported by the National Natural Science Foundation of China(No.41730647)the Natural Science Foundation of Liaoning Province(No.2020-MS-350)+3 种基金the Science&Technology Project of Liaoning Province(No.2019JH8/10300095)the Key Program of Science Foundation of Liaoning Meteorological Office(Nos.201904,D202101)the Basic Research Funds of Central Public Welfare Research Institutes(Nos.2018SYIAEZD4,2020SYIAEZD1)the Open Project of Shangdianzi National Atmosphere Background Station(No.SDZ2020620)
文摘Visibility observed at different altitudes is favorable to understand the causes of air pol-lution.We conducted 4-years of observations of visibility at 2.8 and 60 m and particulate matter(PM)concentrations from 2015 to 2018 in Shenyang,a provincial city in Northeast China.The results indicated that visibility increased with the increasing height in winter(especially at night),and decreased with height in summer(especially at the daytime).PM concentration exhibited opposite vertical variation to visibility,reflecting that visibility de-grades with the increase of aerosol concentration in the air.The radiosonde meteorological data showed that weak turbulence in the planetary boundary layer(PBL)in winter favored aerosols'accumulation near the surface.Whereas in summer,unstable atmospheric con-ditions,upper-level moister environment,and regional transport of air pollutants resulted in the deterioration of upper-level visibility.Inter-annual variation in the two-level visibility indicated that the upper-level visibility improved more significantly than low-level visibil-ity,much likely due to the reduction in emission of elevated point sources in Shenyang.Our study suggested that strengthening the control of surface non-point emissions is a promis-ing control strategy to improve Shenyang air quality.
