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
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
Based on turbulence theory,a 1.5-order closure turbulence model is established.The model incorporating with the ground surface energy budget equation is constructed by means of a vertical one-dimensional(1-D)40-level ...Based on turbulence theory,a 1.5-order closure turbulence model is established.The model incorporating with the ground surface energy budget equation is constructed by means of a vertical one-dimensional(1-D)40-level grid-mesh.The numerical results reveal the 24-h evolution of the clear planetary boundary layer comparing with the Wangara boundary layer data of days 33—34.The model also takes into account some physical processes of radiative transfer and baroclinicity,revealing some important characteristics observed in the boundary layer,especially for the evolution of the mixed layer and low-level jet.The calculated results are in good agreement with the observational data. On the other hand,we also run the high-resolution model of the planetary boundary layer in the Mesoscale Model Ver- sion 4(MM4)with the same physical processes and initial conditions.The results show that the high-resolution model can not reveal those important characteristics as the 1.5-order closure model did.In general,it is shown that the 1.5-or- der closure turbulence model based on turbulence theory is better in rationality and reality.展开更多
In this paper, the eddy coefficient and the treatment for dividing layers of Estoque's numerical model in modern PBL dynamics have been applied to derive order-zero and order-one analytic solutions over large-scal...In this paper, the eddy coefficient and the treatment for dividing layers of Estoque's numerical model in modern PBL dynamics have been applied to derive order-zero and order-one analytic solutions over large-scale topography, the solutions are used to obtain the divergence and vertical velocity, improving the previous results.展开更多
Vertical profiles of virtual potential temperature,specific humidity,temperature at saturation points,moist static energies along with parcel condensing levels using minisonde data are analysed for two stations throug...Vertical profiles of virtual potential temperature,specific humidity,temperature at saturation points,moist static energies along with parcel condensing levels using minisonde data are analysed for two stations through which a mon- soon depression passed.The height of the cloud base came down as low as 910 hPa level from 835 hPa.Equivalent po- tential temperature increased in the vertical profile as well as in the conserved variable diagram as the depression ap- proached the station.Parcel condensing levels showed clearly inversion top and cloud top but not in all cases.Moist stat- ic energy showed an increase upto 10 kJ/kg as the depression approached.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
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。
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.
文摘Based on turbulence theory,a 1.5-order closure turbulence model is established.The model incorporating with the ground surface energy budget equation is constructed by means of a vertical one-dimensional(1-D)40-level grid-mesh.The numerical results reveal the 24-h evolution of the clear planetary boundary layer comparing with the Wangara boundary layer data of days 33—34.The model also takes into account some physical processes of radiative transfer and baroclinicity,revealing some important characteristics observed in the boundary layer,especially for the evolution of the mixed layer and low-level jet.The calculated results are in good agreement with the observational data. On the other hand,we also run the high-resolution model of the planetary boundary layer in the Mesoscale Model Ver- sion 4(MM4)with the same physical processes and initial conditions.The results show that the high-resolution model can not reveal those important characteristics as the 1.5-order closure model did.In general,it is shown that the 1.5-or- der closure turbulence model based on turbulence theory is better in rationality and reality.
基金This work was supported by National Natural Science Foundation of China
文摘In this paper, the eddy coefficient and the treatment for dividing layers of Estoque's numerical model in modern PBL dynamics have been applied to derive order-zero and order-one analytic solutions over large-scale topography, the solutions are used to obtain the divergence and vertical velocity, improving the previous results.
文摘Vertical profiles of virtual potential temperature,specific humidity,temperature at saturation points,moist static energies along with parcel condensing levels using minisonde data are analysed for two stations through which a mon- soon depression passed.The height of the cloud base came down as low as 910 hPa level from 835 hPa.Equivalent po- tential temperature increased in the vertical profile as well as in the conserved variable diagram as the depression ap- proached the station.Parcel condensing levels showed clearly inversion top and cloud top but not in all cases.Moist stat- ic energy showed an increase upto 10 kJ/kg as the depression approached.
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.
