Wavelet analysis was applied to lidar observations to retrieve the planetary boundary layer height(PBLH)over Guangzhou from September 2013 to November 2014 over Guangzhou.Impact of the boundary effect and the wavelet ...Wavelet analysis was applied to lidar observations to retrieve the planetary boundary layer height(PBLH)over Guangzhou from September 2013 to November 2014 over Guangzhou.Impact of the boundary effect and the wavelet scale factor on the accuracy of the retrieved PBLH has been explored thoroughly.In addition,the PBLH diurnal variations and the relationship between PM_(2.5) concentration and PBLH during polluted and clean episodes were studied.Results indicate that the most steady retrieved PBLH can be obtained when scale factor is chosen between 300-390 m.The retrieved maximum and minimum PBLH in the annual mean diurnal cycle were~1100 m and~650 m,respectively.The PBLH was significantly lower in the dry season than in the wet season,with the average highest PBLH in the dry season and the wet season being~1050 m and~1200 m respectively.Compared to the wet season,the development of PBLH in the dry season was delayed by at least one hour due to the seasonal cycle of solar radiation.Episode analysis indicated that the PBLH was~50%higher during clean episodes than during haze episodes.The average highest PBLH in the haze episodes and clean episodes were~800 m and~1300 m,respectively.A significant negative correlation between PBLH and PM_(2.5) concentration(r=-0.55**)is discovered.According to China"Ambient Air Quality Standard",the PBLH values in good and slightly polluted conditions were 1/6-1/3 lower than that in excellent conditions,while the corresponding PM_(2.5) concentration were~2-2.5 times higher.展开更多
The investigations on the dynamies of the PBL have been developed in recent years. Some authors emphasized macro-dynamics and others emphasized micro-structure of the PBL. In this paper, we study and review some main ...The investigations on the dynamies of the PBL have been developed in recent years. Some authors emphasized macro-dynamics and others emphasized micro-structure of the PBL. In this paper, we study and review some main characteristics of the wind field in the PBL from the view point connecting the macro-dynamics and micro-stucture of the PBL, thus providing the physical basis for the further research of the dynamics and the parameterization of the PBL.展开更多
A latent heating peak in the PBL was detected in a simulation by a global GCM that failed to reproduce Madden Julian Oscillation （MJO）. The latent heating peak in the PBL was generated by very shallow convection, wh...A latent heating peak in the PBL was detected in a simulation by a global GCM that failed to reproduce Madden Julian Oscillation （MJO）. The latent heating peak in the PBL was generated by very shallow convection, which prevented moisture from being transported to the free troposphere. Large amount of moisture was therefore confined to the PBL, leading to a dry bias in the free atmosphere. Suffering from this dry bias, deep convection became lethargic, and MJO signals failed to occur. When the latent heating peak in the PBL was removed in another simulation, reasonable MJO signals, including the eastward propagation and the structure of its large-scale circulation, appeared. We therefore propose that the excessive latent heating peak in the PBL due to hyperactive shallow convection may be a reason for a lack of MJO signals in some simulations by other GCMs as well.展开更多
A field experiment was conducted in Tianjin, China from September 9-30, 2010, focused on the evolution of Planetary Boundary Layer （PBL） and its impact on surface air pollutants. The experiment used three remote sen...A field experiment was conducted in Tianjin, China from September 9-30, 2010, focused on the evolution of Planetary Boundary Layer （PBL） and its impact on surface air pollutants. The experiment used three remote sensing instruments, wind profile radar （WPR）, microwave radiometer （MWR） and micro-pulse lidar （MPL）, to detect the vertical profiles of winds, temperature, and aerosol backscattering coefficient and to measure the vertical profiles of surface pollutants （aerosol, CO, SO2, NOx）, and also collected sonic anemometers data from a 255-m meteorological tower. Based on these measurements, the evolution of the PBL was estimated. The averaged PBL height was about 1000-1300 m during noon/afternoon-time, and 200-300 m during night-time. The PBL height and the aerosol concentrations were anti-correlated during clear and haze conditions. The averaged maximum PBL heights were 1.08 and 1.70 km while the averaged aerosol concentrations were 52 and 17 μg/m＆3 under haze and clear sky conditions, respectively, The influence of aerosols and clouds on solar radiation was observed based on sonic anemometers data collected from the 255-m meteorological tower. The heat flux was found significantly decreased by haze （heavy pollution） or cloud, which tended to depress the development of PBL, while the repressed structure of PBL further weakened the diffusion of pollutants, leading to heavy pollution. This possible positive feedback cycle （more aerosols→lower PBL height → more aerosols） would induce an acceleration process for heavy ground pollution in megacities.展开更多
A comprehensive measurement of planetary boundary layer(PBL)meteorology was conducted at 140 and 280 m on a meteorological tower in Beijing,China,to quantify the effect of aerosols on radiation and its role in PBL dev...A comprehensive measurement of planetary boundary layer(PBL)meteorology was conducted at 140 and 280 m on a meteorological tower in Beijing,China,to quantify the effect of aerosols on radiation and its role in PBL development.The measured variables included four-component radiation,temperature,sensible heat flux(SH),and turbulent kinetic energy(TKE)at 140 and 280 m,as well as PBL height(PBLH).In this work,a method was developed to quantitatively estimate the effect of aerosols on radiation based on the PBLH and radiation at the two heights(140 and 280 m).The results confirmed that the weakened downward shortwave radiation(DSR)on hazy days could be attributed predominantly to increased aerosols,while for longwave radiation,aerosols only accounted for around onethird of the enhanced downward longwave radiation.The DSR decreased by 55.2 W m^(-2) on hazy days during noontime(1100–1400 local time).The weakened solar radiation decreased SH and TKE by enhancing atmospheric stability,and hence suppressed PBL development.Compared with clean days,the decreasing rates of DSR,SH,TKE,and PBLH were 11.4%,33.6%,73.8%,and 53.4%,respectively.These observations collectively suggest that aerosol radiative forcing on the PBL is exaggerated by a complex chain of interactions among thermodynamic,dynamic,and radiative processes.These findings shed new light on our understanding of the complex relationship between aerosol and the PBL.展开更多
In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u_*/A(A is the win...In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u_*/A(A is the wind speed at the top of PBL)and ■(the angle between winds near the surface and at the top of PBL)of PBL are investigated in which the wind direction at the top of PBL is a periodic function of time but the wind speed at the top of PBL does not change.The u_*/A increases and ■ decreases when the wind direction at the top of PBL rotates anticlockwise and vice versa.Hence the parameterization of PBL in the large-scale models derived under the stationary condition should be corrected by accounting for the nonstationary process.The similar results are obtained in the numerical solution of the motion equation of PBL.The influences of this nonstationary process on the profiles of the wind in PBL are also analyzed.展开更多
以北京市观象台2010年8月、2011年8月每日3次(08:00,14:00,20:00,北京时,下同)L波段探空秒间隔数据为实况,对BJ-RUC系统(rapid updated cycle system for the Beijing area)分析和预报边界层性能进行了初步评估。结果表明:BJ-RUC系统对...以北京市观象台2010年8月、2011年8月每日3次(08:00,14:00,20:00,北京时,下同)L波段探空秒间隔数据为实况,对BJ-RUC系统(rapid updated cycle system for the Beijing area)分析和预报边界层性能进行了初步评估。结果表明:BJ-RUC系统对北京地区夏季白天边界层的细致特征具有较好的预报能力,但也存在明显的系统性误差。08:00边界层偏冷;14:00和20:00 1 km以下的边界层则显著偏暖,边界层内明显偏湿。整体上模式对边界层内温度、湿度的预报误差均高于自由大气。该系统对北京地区边界层内早晨(08:00)从夜间山风向白天谷风环流过渡、午后(14:00)到日落后(20:00)1500 m以下盛行西南偏南气流的日变化特征具有较强的预报能力。系统预报的14:00边界层顶高度与评估时段内实际对流边界层高度的变化趋势一致。但预报的对流边界层顶偏高,这与BJ-RUC系统采用YSU边界层参数化方案的垂直混合更强有关。展开更多
基金National Key R&D Program of China(2019YFC0214605,2018YFC0213901)National Natural Science Foundation of China(41775037)+1 种基金Guangdong Provincial Key R&D Program(2020B1111360003)Scientific and Technological Innovation Team Project of Guangdong Meteorological Service(GRMCTD202003)。
文摘Wavelet analysis was applied to lidar observations to retrieve the planetary boundary layer height(PBLH)over Guangzhou from September 2013 to November 2014 over Guangzhou.Impact of the boundary effect and the wavelet scale factor on the accuracy of the retrieved PBLH has been explored thoroughly.In addition,the PBLH diurnal variations and the relationship between PM_(2.5) concentration and PBLH during polluted and clean episodes were studied.Results indicate that the most steady retrieved PBLH can be obtained when scale factor is chosen between 300-390 m.The retrieved maximum and minimum PBLH in the annual mean diurnal cycle were~1100 m and~650 m,respectively.The PBLH was significantly lower in the dry season than in the wet season,with the average highest PBLH in the dry season and the wet season being~1050 m and~1200 m respectively.Compared to the wet season,the development of PBLH in the dry season was delayed by at least one hour due to the seasonal cycle of solar radiation.Episode analysis indicated that the PBLH was~50%higher during clean episodes than during haze episodes.The average highest PBLH in the haze episodes and clean episodes were~800 m and~1300 m,respectively.A significant negative correlation between PBLH and PM_(2.5) concentration(r=-0.55**)is discovered.According to China"Ambient Air Quality Standard",the PBLH values in good and slightly polluted conditions were 1/6-1/3 lower than that in excellent conditions,while the corresponding PM_(2.5) concentration were~2-2.5 times higher.
文摘The investigations on the dynamies of the PBL have been developed in recent years. Some authors emphasized macro-dynamics and others emphasized micro-structure of the PBL. In this paper, we study and review some main characteristics of the wind field in the PBL from the view point connecting the macro-dynamics and micro-stucture of the PBL, thus providing the physical basis for the further research of the dynamics and the parameterization of the PBL.
基金supported by National Science Foundation of U.S.A.(Grant No. ATM0739402)the National Natural Science Foundation of China (Grant Nos. U0833602 and 40905035)
文摘A latent heating peak in the PBL was detected in a simulation by a global GCM that failed to reproduce Madden Julian Oscillation （MJO）. The latent heating peak in the PBL was generated by very shallow convection, which prevented moisture from being transported to the free troposphere. Large amount of moisture was therefore confined to the PBL, leading to a dry bias in the free atmosphere. Suffering from this dry bias, deep convection became lethargic, and MJO signals failed to occur. When the latent heating peak in the PBL was removed in another simulation, reasonable MJO signals, including the eastward propagation and the structure of its large-scale circulation, appeared. We therefore propose that the excessive latent heating peak in the PBL due to hyperactive shallow convection may be a reason for a lack of MJO signals in some simulations by other GCMs as well.
基金supported by National Natural Science Foundation of China(NSFC) under Grant Nos.41175007 and 40905060the Project of Scientific and Technological New Star of Beijing under Grant No.2010B029+1 种基金the National Basic Research Program of China(2011CB403401)China Meteorological Administration (CMA) under Grant No.GYHY200806001-4
文摘A field experiment was conducted in Tianjin, China from September 9-30, 2010, focused on the evolution of Planetary Boundary Layer （PBL） and its impact on surface air pollutants. The experiment used three remote sensing instruments, wind profile radar （WPR）, microwave radiometer （MWR） and micro-pulse lidar （MPL）, to detect the vertical profiles of winds, temperature, and aerosol backscattering coefficient and to measure the vertical profiles of surface pollutants （aerosol, CO, SO2, NOx）, and also collected sonic anemometers data from a 255-m meteorological tower. Based on these measurements, the evolution of the PBL was estimated. The averaged PBL height was about 1000-1300 m during noon/afternoon-time, and 200-300 m during night-time. The PBL height and the aerosol concentrations were anti-correlated during clear and haze conditions. The averaged maximum PBL heights were 1.08 and 1.70 km while the averaged aerosol concentrations were 52 and 17 μg/m＆3 under haze and clear sky conditions, respectively, The influence of aerosols and clouds on solar radiation was observed based on sonic anemometers data collected from the 255-m meteorological tower. The heat flux was found significantly decreased by haze （heavy pollution） or cloud, which tended to depress the development of PBL, while the repressed structure of PBL further weakened the diffusion of pollutants, leading to heavy pollution. This possible positive feedback cycle （more aerosols→lower PBL height → more aerosols） would induce an acceleration process for heavy ground pollution in megacities.
基金the National Key Research and Development Program of China(2017YFC0209604 and 2018YFF0300101)Beijing Natural Science Foundation(8204062)。
文摘A comprehensive measurement of planetary boundary layer(PBL)meteorology was conducted at 140 and 280 m on a meteorological tower in Beijing,China,to quantify the effect of aerosols on radiation and its role in PBL development.The measured variables included four-component radiation,temperature,sensible heat flux(SH),and turbulent kinetic energy(TKE)at 140 and 280 m,as well as PBL height(PBLH).In this work,a method was developed to quantitatively estimate the effect of aerosols on radiation based on the PBLH and radiation at the two heights(140 and 280 m).The results confirmed that the weakened downward shortwave radiation(DSR)on hazy days could be attributed predominantly to increased aerosols,while for longwave radiation,aerosols only accounted for around onethird of the enhanced downward longwave radiation.The DSR decreased by 55.2 W m^(-2) on hazy days during noontime(1100–1400 local time).The weakened solar radiation decreased SH and TKE by enhancing atmospheric stability,and hence suppressed PBL development.Compared with clean days,the decreasing rates of DSR,SH,TKE,and PBLH were 11.4%,33.6%,73.8%,and 53.4%,respectively.These observations collectively suggest that aerosol radiative forcing on the PBL is exaggerated by a complex chain of interactions among thermodynamic,dynamic,and radiative processes.These findings shed new light on our understanding of the complex relationship between aerosol and the PBL.
文摘In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u_*/A(A is the wind speed at the top of PBL)and ■(the angle between winds near the surface and at the top of PBL)of PBL are investigated in which the wind direction at the top of PBL is a periodic function of time but the wind speed at the top of PBL does not change.The u_*/A increases and ■ decreases when the wind direction at the top of PBL rotates anticlockwise and vice versa.Hence the parameterization of PBL in the large-scale models derived under the stationary condition should be corrected by accounting for the nonstationary process.The similar results are obtained in the numerical solution of the motion equation of PBL.The influences of this nonstationary process on the profiles of the wind in PBL are also analyzed.
文摘以北京市观象台2010年8月、2011年8月每日3次(08:00,14:00,20:00,北京时,下同)L波段探空秒间隔数据为实况,对BJ-RUC系统(rapid updated cycle system for the Beijing area)分析和预报边界层性能进行了初步评估。结果表明:BJ-RUC系统对北京地区夏季白天边界层的细致特征具有较好的预报能力,但也存在明显的系统性误差。08:00边界层偏冷;14:00和20:00 1 km以下的边界层则显著偏暖,边界层内明显偏湿。整体上模式对边界层内温度、湿度的预报误差均高于自由大气。该系统对北京地区边界层内早晨(08:00)从夜间山风向白天谷风环流过渡、午后(14:00)到日落后(20:00)1500 m以下盛行西南偏南气流的日变化特征具有较强的预报能力。系统预报的14:00边界层顶高度与评估时段内实际对流边界层高度的变化趋势一致。但预报的对流边界层顶偏高,这与BJ-RUC系统采用YSU边界层参数化方案的垂直混合更强有关。
