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
The tropopause height and the atmospheric boundarylayer （PBL） height as well as the variation of inversion layer above the floating ice surface are presented using GPS （global position system ） radiosonde sounding...The tropopause height and the atmospheric boundarylayer （PBL） height as well as the variation of inversion layer above the floating ice surface are presented using GPS （global position system ） radiosonde sounding data and relevant data obtained by Chinas fourth arctic scientific expedition team over the central Arctic Ocean （86°-88°N, 144°-170°W） during the summer of 2010. The tropopause height is from 9.8 to 10.5 km, with a temperature range between -52.2 and -54.10C in the central Arctic Ocean. Two zones of maximum wind （over 12 m/s） are found in the wind profile, namely, low- and upper-level jets, located in the middle troposphere and the tropopause, respectively. The wind direction has a marked variation point in the two jets from the southeast to the southwest. The average PBL height determined by two methods is 341 and 453 m respectively. These two methods can both be used when the inversion layer is very low, but the results vary significantly when the inversion layer is very high. A significant logarithmic relationship exists between the PBL height and the inversion intensity, with a correlation coefficient of 0.66, indicating that the more intense the temperature inversion is, the lower the boundary layer will be. The observation results obviously differ from those of the third arctic expedition zone （800-85° N）. The PBL height and the inversion layer thickness are much lower than those at 870-88° N, but the inversion temperature is more intense, meaning a strong ice- atmosphere interaction in the sea near the North Pole. The PBL structure is related to the weather system and the sea ice concentration, which affects the observation station.展开更多
2020年2月13-14日北京地区出现一次极端雨雪天气过程,利用EC再分析数据、风廓线雷达、气候资料等,采用诊断分析、风廓线产品反演、气候异常分析等方法,对这次伴有复杂相态转换、对流、累计降水量破历史同期极值的极端雨雪天气过程进行...2020年2月13-14日北京地区出现一次极端雨雪天气过程,利用EC再分析数据、风廓线雷达、气候资料等,采用诊断分析、风廓线产品反演、气候异常分析等方法,对这次伴有复杂相态转换、对流、累计降水量破历史同期极值的极端雨雪天气过程进行分析和异常诊断,结果表明:(1)大尺度低涡、高/低空急流、锋面等天气系统为降水提供良好的背景条件。(2)河北中部的中尺度涡旋,是这次极端雨雪天气的重要成因之一。(3)对流活动的参与提高了降水效率,致使过程累计降水量进一步增大。(4)850 h Pa切变线北侧强盛的偏东气流,在动力抬升、水汽输送及辐合中发挥重要作用。(5)-8~-20℃层云冰含量低,且0℃层高度>700 m是造成北京平原地区相态转换时间延迟的直接原因。(6)边界层回流冷空气由平原东部进入北京,是雨雪相态转换由东向西发生的根本原因。(7)极端的水汽通量辐合异常,是此次天气过程累计雨量突破同期历史极值的重要原因之一。展开更多
Previous studies have shown that wind-forced baroclinic Rossby waves can capture a large portion of lowfrequency steric sea surface height(SSH)variations in the North Atlantic.In this paper,the classical wind-driven R...Previous studies have shown that wind-forced baroclinic Rossby waves can capture a large portion of lowfrequency steric sea surface height(SSH)variations in the North Atlantic.In this paper,the classical wind-driven Rossby wave model derived in a 1.5-layer ocean is extended to include surface buoyancy forcing,and the new model is then used to assess the contribution from buoyancy-forced Rossby waves to low-frequency North Atlantic steric SSH variations.Buoyancy forcing is determined from surface heating as freshwater fluxes are negligible.It is found that buoyancy-forced Rossby waves are important in only a few regions belonging to the subtropicaltomidlatitude and eastern subpolar North Atlantic.In these regions,the new Rossby wave model accounts for 25%-70% of low-frequency steric SSH variations.Furthermore,as part of the analysis it is also shown that a simple static model driven by local surface heat fluxes captures 60%-75% of low-frequency steric SSH variations in the Labrador Sea,which is a region where Rossby waves are found to have no influence on the steric SSH.展开更多
Shallow layer method(SLM)based on the definition of the geoid can determine the gravity field inside the shallow layer.In this study,the orthometric height of Mount Everest(HME)is calculated based on SLM,in which the ...Shallow layer method(SLM)based on the definition of the geoid can determine the gravity field inside the shallow layer.In this study,the orthometric height of Mount Everest(HME)is calculated based on SLM,in which the key is to construct the shallow layer model.The top and bottom boundaries of the shallow layer model are the natural surface of the Earth and the surface at a certain depth below the reference geoid,respectively.The model-combined strategies to determine the geoid undulation(N)based on SLM are applied to calculate the HME by two approaches:(1)direct calculation by combining N and geodetic height(h);(2)calculation by the segment summation approach(SSA)using the gravity field inside the shallow layer.On December 8,2020,the Chinese and Nepalese governments announced an authoritative value of 8848.86 m,which is referred to a geoid determined by the International Height Reference System(IHRS)(i.e.,the geopotential is 62636853.4 m^(2) s^(-2)).Here,our results(combined strategies(1)EGM2008 and CRUST1.0,(2)EGM2008 and CRUST2.0,(3)EIGEN-6 C4 and CRUST1.0,and(4)EIGEN-6 C4 and CRUST2.0)are referred to the geoid defined by WGS84(i.e.,the geopotential is 62636851.7 m^(2) s^(-2)).The differences between our results and the authoritative value(8848.86 m)are 0.448 m,-0.009 m,-0.295 m,and -0.741 m by the first approach,and 0.539 m,0.083 m,-0.214 m,and -0.647 m by the second approach.When the reference surface WGS84 geoid is converted to the IHRS geoid,the differences are 0.620 m,0.163 m,-0.123 m,and -0.569 m by the first approach,and0.711 m,0.225 m,-0.042 m,and -0.475 m by the second approach.展开更多
In order to understand the effect of mining height and floor lithology at the upper protective layer face on the pressure relief of protected coal seams, this paper uses a numerical simulation method to model the pres...In order to understand the effect of mining height and floor lithology at the upper protective layer face on the pressure relief of protected coal seams, this paper uses a numerical simulation method to model the pressure changes at protected coal seam during mining upper protective layer. The results show that the taller the mining height at the upper protective layer face, the greater the protection on protected coal seam due to the higher level of pressure release; the upper protective layer face with hard rock floor impedes the pressure release at the protected coal seam, which affects the overall effect of the pressure release at protected coal seam using the protective layer mining method.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The Program of China Polar Environment Investigation and Assessment under contract No.CHINARE2011-2015
文摘The tropopause height and the atmospheric boundarylayer （PBL） height as well as the variation of inversion layer above the floating ice surface are presented using GPS （global position system ） radiosonde sounding data and relevant data obtained by Chinas fourth arctic scientific expedition team over the central Arctic Ocean （86°-88°N, 144°-170°W） during the summer of 2010. The tropopause height is from 9.8 to 10.5 km, with a temperature range between -52.2 and -54.10C in the central Arctic Ocean. Two zones of maximum wind （over 12 m/s） are found in the wind profile, namely, low- and upper-level jets, located in the middle troposphere and the tropopause, respectively. The wind direction has a marked variation point in the two jets from the southeast to the southwest. The average PBL height determined by two methods is 341 and 453 m respectively. These two methods can both be used when the inversion layer is very low, but the results vary significantly when the inversion layer is very high. A significant logarithmic relationship exists between the PBL height and the inversion intensity, with a correlation coefficient of 0.66, indicating that the more intense the temperature inversion is, the lower the boundary layer will be. The observation results obviously differ from those of the third arctic expedition zone （800-85° N）. The PBL height and the inversion layer thickness are much lower than those at 870-88° N, but the inversion temperature is more intense, meaning a strong ice- atmosphere interaction in the sea near the North Pole. The PBL structure is related to the weather system and the sea ice concentration, which affects the observation station.
文摘2020年2月13-14日北京地区出现一次极端雨雪天气过程,利用EC再分析数据、风廓线雷达、气候资料等,采用诊断分析、风廓线产品反演、气候异常分析等方法,对这次伴有复杂相态转换、对流、累计降水量破历史同期极值的极端雨雪天气过程进行分析和异常诊断,结果表明:(1)大尺度低涡、高/低空急流、锋面等天气系统为降水提供良好的背景条件。(2)河北中部的中尺度涡旋,是这次极端雨雪天气的重要成因之一。(3)对流活动的参与提高了降水效率,致使过程累计降水量进一步增大。(4)850 h Pa切变线北侧强盛的偏东气流,在动力抬升、水汽输送及辐合中发挥重要作用。(5)-8~-20℃层云冰含量低,且0℃层高度>700 m是造成北京平原地区相态转换时间延迟的直接原因。(6)边界层回流冷空气由平原东部进入北京,是雨雪相态转换由东向西发生的根本原因。(7)极端的水汽通量辐合异常,是此次天气过程累计雨量突破同期历史极值的重要原因之一。
文摘Previous studies have shown that wind-forced baroclinic Rossby waves can capture a large portion of lowfrequency steric sea surface height(SSH)variations in the North Atlantic.In this paper,the classical wind-driven Rossby wave model derived in a 1.5-layer ocean is extended to include surface buoyancy forcing,and the new model is then used to assess the contribution from buoyancy-forced Rossby waves to low-frequency North Atlantic steric SSH variations.Buoyancy forcing is determined from surface heating as freshwater fluxes are negligible.It is found that buoyancy-forced Rossby waves are important in only a few regions belonging to the subtropicaltomidlatitude and eastern subpolar North Atlantic.In these regions,the new Rossby wave model accounts for 25%-70% of low-frequency steric SSH variations.Furthermore,as part of the analysis it is also shown that a simple static model driven by local surface heat fluxes captures 60%-75% of low-frequency steric SSH variations in the Labrador Sea,which is a region where Rossby waves are found to have no influence on the steric SSH.
文摘本文选用2007年1月—2010年2月的Cloud Sat卫星94 GHz探测资料（2B-GEOPROF）对淮河流域混合云出现频率、云高以及含水量分布规律进行了研究。研究结果表明：（1）混合云出现频率和云高具有显著的季节性变化特征,均表现为夏季值高、冬季低;（2）Cloud Sat 2B-CWC-RO反演产品在假设混合云冰水混合比与云内温度（-20-0℃）成线性关系条件下反演的液态水含量（LWP）与地面观测值相差较大,本文利用冰水混合比与云内温度成指数函数关系反演的LWP更接近地面观测值;（3）反演的LWP具有明显的季节分布特征,其季节平均值夏秋季高、春冬季低。混合云随着LWP值的增加,其对应的雷达反照率因子范围和出现的高度层越来越集中,混合云在对流层中下层的出现频率随LWP的增加而增多,出现频率高值区及其分布的高度层也具有明显的季节性特征,并与混合云零度层高度有密切关系。
基金supported in part by the National Natural Science Foundations of China under Grants Nos.41631072,42030105,41721003,41804012,and 41874023。
文摘Shallow layer method(SLM)based on the definition of the geoid can determine the gravity field inside the shallow layer.In this study,the orthometric height of Mount Everest(HME)is calculated based on SLM,in which the key is to construct the shallow layer model.The top and bottom boundaries of the shallow layer model are the natural surface of the Earth and the surface at a certain depth below the reference geoid,respectively.The model-combined strategies to determine the geoid undulation(N)based on SLM are applied to calculate the HME by two approaches:(1)direct calculation by combining N and geodetic height(h);(2)calculation by the segment summation approach(SSA)using the gravity field inside the shallow layer.On December 8,2020,the Chinese and Nepalese governments announced an authoritative value of 8848.86 m,which is referred to a geoid determined by the International Height Reference System(IHRS)(i.e.,the geopotential is 62636853.4 m^(2) s^(-2)).Here,our results(combined strategies(1)EGM2008 and CRUST1.0,(2)EGM2008 and CRUST2.0,(3)EIGEN-6 C4 and CRUST1.0,and(4)EIGEN-6 C4 and CRUST2.0)are referred to the geoid defined by WGS84(i.e.,the geopotential is 62636851.7 m^(2) s^(-2)).The differences between our results and the authoritative value(8848.86 m)are 0.448 m,-0.009 m,-0.295 m,and -0.741 m by the first approach,and 0.539 m,0.083 m,-0.214 m,and -0.647 m by the second approach.When the reference surface WGS84 geoid is converted to the IHRS geoid,the differences are 0.620 m,0.163 m,-0.123 m,and -0.569 m by the first approach,and0.711 m,0.225 m,-0.042 m,and -0.475 m by the second approach.
文摘In order to understand the effect of mining height and floor lithology at the upper protective layer face on the pressure relief of protected coal seams, this paper uses a numerical simulation method to model the pressure changes at protected coal seam during mining upper protective layer. The results show that the taller the mining height at the upper protective layer face, the greater the protection on protected coal seam due to the higher level of pressure release; the upper protective layer face with hard rock floor impedes the pressure release at the protected coal seam, which affects the overall effect of the pressure release at protected coal seam using the protective layer mining method.
