This research was an effort to select best imputation method for missing upper air temperature data over 24 standard pressure levels. We have implemented four imputation techniques like inverse distance weighting, Bil...This research was an effort to select best imputation method for missing upper air temperature data over 24 standard pressure levels. We have implemented four imputation techniques like inverse distance weighting, Bilinear, Natural and Nearest interpolation for missing data imputations. Performance indicators for these techniques were the root mean square error (RMSE), absolute mean error (AME), correlation coefficient and coefficient of determination ( R<sup>2</sup> ) adopted in this research. We randomly make 30% of total samples (total samples was 324) predictable from 70% remaining data. Although four interpolation methods seem good (producing <1 RMSE, AME) for imputations of air temperature data, but bilinear method was the most accurate with least errors for missing data imputations. RMSE for bilinear method remains <0.01 on all pressure levels except 1000 hPa where this value was 0.6. The low value of AME (<0.1) came at all pressure levels through bilinear imputations. Very strong correlation (>0.99) found between actual and predicted air temperature data through this method. The high value of the coefficient of determination (0.99) through bilinear interpolation method, tells us best fit to the surface. We have also found similar results for imputation with natural interpolation method in this research, but after investigating scatter plots over each month, imputations with this method seem to little obtuse in certain months than bilinear method.展开更多
Typhoon Meranti originated over the western North Pacific off the south tip of the Taiwan Island in 2010.It moved westward entering the South China Sea,then abruptly turned north into the Taiwan Strait,got intensified...Typhoon Meranti originated over the western North Pacific off the south tip of the Taiwan Island in 2010.It moved westward entering the South China Sea,then abruptly turned north into the Taiwan Strait,got intensified on its way northward,and eventually made landfall on Fujian province.In its evolution,there was a northwest-moving cold vortex in upper troposphere to the south of the Subtropical High over the western North Pacific(hereafter referred to as the Subtropical High).In this paper,the possible impacts of this cold vortex on Meranti in terms of its track and intensity variation is investigated using typhoon best track data from China Meteorological Administration,analyses data of 0.5×0.5 degree provided by the global forecasting system of National Centers for Environmental Prediction,GMS satellite imagery and Taiwan radar data.Results show as follows:(1)The upper-level cold vortex was revolving around the typhoon anticlockwise from its east to its north.In the early stage,due to the blocking of the cold vortex,the role of the Subtropical High to steer Meranti was weakened,which results in the looping of the west-moving typhoon.However,when Meranti was coupled with the cold vortex in meridional direction,the northerly wind changed to the southerly at the upper level of the typhoon;at the same time the Subtropical High protruded westward and its southbound steering flow gained strength,and eventually created an environment in which the southerly winds in both upper and lower troposphere suddenly steered Meranti to the north;(2)The change of airflow direction above the typhoon led to a weak vertical wind shear,which in return facilitated the development of Meranti.Meanwhile,to the east of typhoon Meranti,the overlapped southwesterly jets in upper and lower atmosphere accelerated its tangential wind and contributed to its cyclonic development;(3)The cold vortex not only supplied positive vorticity to the typhoon,but also transported cold advection to its outer bands.In conjunction with the warm and moist air masses at the lower levels,the cold vortex increased the vertical instability in the atmosphere,which was favorable for convection development within the typhoon circulation,and its warmer center was enhanced through latent heat release;(4)Vertical vorticity budget averaged over the typhoon area further shows that the intensification of a typhoon vorticity column mainly depends on horizontal advection of its high-level vorticity,low-level convergence,uneven wind field distribution and its convective activities.展开更多
The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments u...The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model.The mid-level RH was lowered in different regions relative to TC Durian(2001)’s genesis location.Results suggest that the location of dry air was important to Durian(2001)’s genesis and intensification.The rapid development of the TC was accompanied by sustained near-saturated mid-and upper-level air,whereas low humidity decelerated its development.Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms,and consumed by the condensation process.The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process.With a dryer mid-and upper-level environment,convective and stratiform precipitation were both inhibited.The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed.Generally,convection played the dominant role,since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker.The vorticity budget showed that the negative vorticity convergence term,which was closely related to the inhibited convection,caused the vorticity to decrease above the lower troposphere in a dryer environment.The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs.展开更多
This study examined the dynamic characteristics of upper airway collapse at soft palate level in patients with obstructive sleep apnea/hypopnea syndrome(OSAHS) by using dynamic 3-Dimensional(3-D) CT imaging.A tota...This study examined the dynamic characteristics of upper airway collapse at soft palate level in patients with obstructive sleep apnea/hypopnea syndrome(OSAHS) by using dynamic 3-Dimensional(3-D) CT imaging.A total of 41 male patients who presented with 2 of the following symptoms,i.e.,daytime sleepiness and fatigue,frequent snoring,and apnea with witness,were diagnosed as having OSAHS.They underwent full-night polysomnography and then dynamic 3-D CT imaging of the upper airway during quiet breathing and in Muller's maneuver.The soft palate length(SPL),the minimal cross-sectional area of the retropalatal region(mXSA-RP),and the vertical distance from the hard palate to the upper posterior part of the hyoid(hhL) were compared between the two breathing states.These parameters,together with hard palate length(HPL),were also compared between mild/moderate and severe OSAHS groups.Association of these parameters with the severity of OSAHS [as reflected by apnea hypopnea index(AHI) and the lowest saturation of blood oxygen(LSaO2)] was examined.The results showed that 31 patients had severe OSAHS,and 10 mild/moderate OSAHS.All the patients had airway obstruction at soft palate level.mXSA-RP was significantly decreased and SPL remarkably increased during Muller's maneuver as compared with the quiet breathing state.There were no significant differences in these airway parameters(except the position of the hyoid bone) between severe and mild/moderate OSAHS groups.And no significant correlation between these airway parameters and the severity of OSAHS was found.The position of hyoid was lower in the severe OSAHS group than in the mild/moderate OSAHS group.The patients in group with body mass index(BMI)≥26 had higher collapse ratio of mXSA-RP,greater neck circumference and smaller mXSA-RP in the Muller's maneuver than those in group with BMI26(P0.05 for all).It was concluded that dynamic 3-D CT imaging could dynamically show the upper airway changes at soft palate level in OSAHS patients.All the OSAHS patients had airway obstruction of various degrees at soft palate level.But no correlation was observed between the airway change at soft palate level and the severity of OSAHS.The patients in group with BMI≥26 were more likely to develop airway obstruction at soft palate level than those with BMI26.展开更多
BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic charac...BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic characteristics of the upper lumbar spine,conventional transforaminal PELD may fail to remove the highly migrated upper lumbar disc nucleus pulposus.Therefore,the purpose of this study was to describe a novel surgical technique,two-level PELD,for the treatment of highly migrated upper lumbar disc herniations and to report its related clinical outcomes.CASE SUMMARY A 60-year-old male presented with a complaint of pain at his lower back and right lower limb.The patient received 3 mo of conservative treatments but the symptoms were not alleviated.Physical examination revealed a positive femoral nerve stretch test and a negative straight leg raise test for the right leg,and preoperative visual analog scale(VAS)score for the lower back was 6 points and for the right leg was 8 points.Magnetic resonance imaging(MRI)demonstrated L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.According to physical examination and imaging findings,surgery was the primary consideration.Therefore,the patient underwent surgical treatment with two-level PELD.The pain symptom was relieved and the VAS score for back and thigh pain was one point postoperatively.The patient was asymptomatic and follow-up MRI scan 1 year after operation revealed no residual nucleus pulposus.CONCLUSION Two-level PELD as a transforaminal approach can be a safe and effective procedure for highly migrated upper lumbar disc herniation.展开更多
Twelve paleocommunities dominated by benthic brachiopod are recognized in the Givetian-Frasnian stages of the Devonian in the Longmenshan area, southwestern China, in which two kinds of brachiopod community replacemen...Twelve paleocommunities dominated by benthic brachiopod are recognized in the Givetian-Frasnian stages of the Devonian in the Longmenshan area, southwestern China, in which two kinds of brachiopod community replacement are classified. One is the abrupt replacement, represented by abrupt alternation between the Leiorhynchus community and Zhonghuacoelia-Striatopugnax community in the Frasnian Tuqiaozi Formation. The other is the gradual one, developed in the Givetian Guanwushan Formation, which had been completed by the shift of the Independatrypa lemma-Uncinulus heterocostellis-Emanuella takwanensis community via the Sinospongophyllum irregulare-Pseudomicroplasma fongi community to the Clathrocoilona spissa-Hexagonaria composite reef community. According to analyses of the paleocommunities, either the abrupt or gradual paleocommunity replacement of the Middle-Upper Devonian in the Longmenshan area is suggested as a response to the 5th-order sea level fluctuation due to the replacements of the paleocommunities in a tracts-system of depositional sequence. It is supposed that changes of paleocommunity diversity, one of the results of paleocommunity replacement, are depended on the range and magnitude of sea level fluctuation, but there is not a linear relationship between them. Furthermore, a suggestion is proposed that the concept of paleocommunity succession seem to be abandoned in the paleocommunity analysis because it almost never be practiced to recover the information of community succession in the geological record at present.展开更多
受登陆北上台风“利奇马”等影响,2019年8月9~12日山东省出现连续暴雨,其中10日夜间出现降雨峰值。利用中国气象局上海台风研究所(Shanghai Typhoon Institute of China Meteorological Administration,简称CMA-STI)热带气旋最佳路径数...受登陆北上台风“利奇马”等影响,2019年8月9~12日山东省出现连续暴雨,其中10日夜间出现降雨峰值。利用中国气象局上海台风研究所(Shanghai Typhoon Institute of China Meteorological Administration,简称CMA-STI)热带气旋最佳路径数据、山东省自动气象站逐时降雨量、常规观测资料、中国风云二号地球静止气象卫星(FY-2G)0.1°×0.1°逐小时云顶相当黑体亮温和美国环境预报中心(National Center of Environmental Prediction,简称NCEP)1°×1°逐6 h再分析等资料,主要运用纬向风局地变化方程与大气动能方程,诊断分析降雨明显增幅与高、低层风场变化的关系。结果表明:(1)暴雨主要影响系统有高低空急流、500 hPa西风槽、850 hPa台风倒槽及“利奇马”本体环流等。10日200 hPa中纬度大尺度西南风急流东南移影响鲁西北,当天08:00(北京时,下同)850 hPa因双台风活动而形成的大尺度东南风急流突然北伸越过山东省。台风倒槽对流云与本体环流对流云先、后北移经鲁中,累积效应造成该地区10日夜间雨量最大。(2)10日20:00850 hPa章丘站东北侧出现了过程最快东风增幅,纬向运动方程诊断结果表明,东风平流是东风增加最主要原因,地转偏向力项则不利于东风增加。(3)10日20:00章丘站200 hPa西南风风力明显加大形成急流,10日08:00至11日08:00青岛站850 hPa维持东南风低空急流。同时位于高空急流右后侧与低空急流左前方是鲁中附近10日夜间降雨增幅的重要原因。章丘200 hPa与青岛850 hPa都是在最大风力之前12 h动能增加最快。动能方程诊断表明,最有利于鲁西北高空急流形成的是位能平流项,最有利于鲁东南低空急流形成的是动能垂直通量散度项。(4)10日20:00至13日08:00“利奇马”本体环流一直在影响山东,暴雨期间山东中部地形的动力作用也一直存在,而降雨的峰值是出现在10日夜间,说明10日20:00前后高、低空急流的耦合可能是山东暴雨增幅的主要影响因子。其主要作用至少有加强山东中部的垂直运动、整层水汽输送与静力不稳定度等方面。展开更多
利用山东省84个气象台站的逐日降水资料、美国国家环境预测中心和国家大气研究中心(National Centers for Environmental Prediction and National Center for Atmospheric Research, NCEP/NCAR)逐日再分析资料以及中国气象局(CMA)热带...利用山东省84个气象台站的逐日降水资料、美国国家环境预测中心和国家大气研究中心(National Centers for Environmental Prediction and National Center for Atmospheric Research, NCEP/NCAR)逐日再分析资料以及中国气象局(CMA)热带气旋资料中心的CMA最佳路径数据集,对1969—2020年夏季(6—8月)发生在山东的857例极端暴雨事件(Extreme rainstorm events, EREs)的时空分布特征及影响环流分型进行了分析。结果表明:山东夏季EREs主要集中在7和8月,8月极端暴雨降水量占当月总降水量的比值最大,可达53.5%。山东夏季极端暴雨降水量以及极端暴雨发生日数呈现不显著的增加趋势,8月的增加趋势最明显。使用经验正交函数分解对影响山东夏季EREs的大气环流系统进行分型,发现影响山东夏季出现EREs的环流系统主要有4类,其中,影响ERE最多的环流系统是北方气旋型,约占事件总频次的33.1%;其次是高空急流型,占比约11.3%;南方气旋型和热带气旋型的环流型影响相当,出现的概率分别为9.7%和9.4%。展开更多
In this paper,by carrying out sensitivity tests of initial conditions and diagnostic analysis of physical fields,the impact factors and the physical mechanism of the unusual track of Morakot in the Taiwan Strait are d...In this paper,by carrying out sensitivity tests of initial conditions and diagnostic analysis of physical fields,the impact factors and the physical mechanism of the unusual track of Morakot in the Taiwan Strait are discussed and examined based on the potential vorticity(PV)inversion.The diagnostic results of NCEP data showed that Morakot's track was mainly steered by the subtropical high.The breaking of a high-pressure zone was the main cause for the northward turn of Morakot.A sensitivity test of initial conditions showed that the existence of upper-level trough was the leading factor for the breaking of the high-pressure zone.When the intensity was strengthened of the upper-level trough at initial time,the high-pressure zone would break ahead of time,leading to the early northward turn of Morakot.Conversely,when the intensity was weakened,the breaking of the high-pressure zone would be delayed.Especially,when the intensity was weakened to a certain extent,the high-pressure zone would not break.The typhoon,steered by the easterly flow to the south of the high-pressure zone,would keep moving westward,with no turn in the test.The diagnostic analysis of the physical fields based on the sensitivity test revealed that positive vorticity advection and cold advection associated with the upper-level trough weakened the intensity of the high-pressure zone.The upper-level trough affected typhoon's track indirectly by influencing the high-pressure zone.展开更多
文摘This research was an effort to select best imputation method for missing upper air temperature data over 24 standard pressure levels. We have implemented four imputation techniques like inverse distance weighting, Bilinear, Natural and Nearest interpolation for missing data imputations. Performance indicators for these techniques were the root mean square error (RMSE), absolute mean error (AME), correlation coefficient and coefficient of determination ( R<sup>2</sup> ) adopted in this research. We randomly make 30% of total samples (total samples was 324) predictable from 70% remaining data. Although four interpolation methods seem good (producing <1 RMSE, AME) for imputations of air temperature data, but bilinear method was the most accurate with least errors for missing data imputations. RMSE for bilinear method remains <0.01 on all pressure levels except 1000 hPa where this value was 0.6. The low value of AME (<0.1) came at all pressure levels through bilinear imputations. Very strong correlation (>0.99) found between actual and predicted air temperature data through this method. The high value of the coefficient of determination (0.99) through bilinear interpolation method, tells us best fit to the surface. We have also found similar results for imputation with natural interpolation method in this research, but after investigating scatter plots over each month, imputations with this method seem to little obtuse in certain months than bilinear method.
基金Natural Fundamental Research and Development Project"973"Program(2009CB421504)Natural Science Foundation of China(40975032+2 种基金4073094841075037)Special Project of Chinese Academy of Meteorological Sciences(2007Y006)
文摘Typhoon Meranti originated over the western North Pacific off the south tip of the Taiwan Island in 2010.It moved westward entering the South China Sea,then abruptly turned north into the Taiwan Strait,got intensified on its way northward,and eventually made landfall on Fujian province.In its evolution,there was a northwest-moving cold vortex in upper troposphere to the south of the Subtropical High over the western North Pacific(hereafter referred to as the Subtropical High).In this paper,the possible impacts of this cold vortex on Meranti in terms of its track and intensity variation is investigated using typhoon best track data from China Meteorological Administration,analyses data of 0.5×0.5 degree provided by the global forecasting system of National Centers for Environmental Prediction,GMS satellite imagery and Taiwan radar data.Results show as follows:(1)The upper-level cold vortex was revolving around the typhoon anticlockwise from its east to its north.In the early stage,due to the blocking of the cold vortex,the role of the Subtropical High to steer Meranti was weakened,which results in the looping of the west-moving typhoon.However,when Meranti was coupled with the cold vortex in meridional direction,the northerly wind changed to the southerly at the upper level of the typhoon;at the same time the Subtropical High protruded westward and its southbound steering flow gained strength,and eventually created an environment in which the southerly winds in both upper and lower troposphere suddenly steered Meranti to the north;(2)The change of airflow direction above the typhoon led to a weak vertical wind shear,which in return facilitated the development of Meranti.Meanwhile,to the east of typhoon Meranti,the overlapped southwesterly jets in upper and lower atmosphere accelerated its tangential wind and contributed to its cyclonic development;(3)The cold vortex not only supplied positive vorticity to the typhoon,but also transported cold advection to its outer bands.In conjunction with the warm and moist air masses at the lower levels,the cold vortex increased the vertical instability in the atmosphere,which was favorable for convection development within the typhoon circulation,and its warmer center was enhanced through latent heat release;(4)Vertical vorticity budget averaged over the typhoon area further shows that the intensification of a typhoon vorticity column mainly depends on horizontal advection of its high-level vorticity,low-level convergence,uneven wind field distribution and its convective activities.
基金supported by the National Basic Research (973) Program of China (Grant No.2015CB452804)
文摘The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model.The mid-level RH was lowered in different regions relative to TC Durian(2001)’s genesis location.Results suggest that the location of dry air was important to Durian(2001)’s genesis and intensification.The rapid development of the TC was accompanied by sustained near-saturated mid-and upper-level air,whereas low humidity decelerated its development.Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms,and consumed by the condensation process.The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process.With a dryer mid-and upper-level environment,convective and stratiform precipitation were both inhibited.The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed.Generally,convection played the dominant role,since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker.The vorticity budget showed that the negative vorticity convergence term,which was closely related to the inhibited convection,caused the vorticity to decrease above the lower troposphere in a dryer environment.The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs.
文摘This study examined the dynamic characteristics of upper airway collapse at soft palate level in patients with obstructive sleep apnea/hypopnea syndrome(OSAHS) by using dynamic 3-Dimensional(3-D) CT imaging.A total of 41 male patients who presented with 2 of the following symptoms,i.e.,daytime sleepiness and fatigue,frequent snoring,and apnea with witness,were diagnosed as having OSAHS.They underwent full-night polysomnography and then dynamic 3-D CT imaging of the upper airway during quiet breathing and in Muller's maneuver.The soft palate length(SPL),the minimal cross-sectional area of the retropalatal region(mXSA-RP),and the vertical distance from the hard palate to the upper posterior part of the hyoid(hhL) were compared between the two breathing states.These parameters,together with hard palate length(HPL),were also compared between mild/moderate and severe OSAHS groups.Association of these parameters with the severity of OSAHS [as reflected by apnea hypopnea index(AHI) and the lowest saturation of blood oxygen(LSaO2)] was examined.The results showed that 31 patients had severe OSAHS,and 10 mild/moderate OSAHS.All the patients had airway obstruction at soft palate level.mXSA-RP was significantly decreased and SPL remarkably increased during Muller's maneuver as compared with the quiet breathing state.There were no significant differences in these airway parameters(except the position of the hyoid bone) between severe and mild/moderate OSAHS groups.And no significant correlation between these airway parameters and the severity of OSAHS was found.The position of hyoid was lower in the severe OSAHS group than in the mild/moderate OSAHS group.The patients in group with body mass index(BMI)≥26 had higher collapse ratio of mXSA-RP,greater neck circumference and smaller mXSA-RP in the Muller's maneuver than those in group with BMI26(P0.05 for all).It was concluded that dynamic 3-D CT imaging could dynamically show the upper airway changes at soft palate level in OSAHS patients.All the OSAHS patients had airway obstruction of various degrees at soft palate level.But no correlation was observed between the airway change at soft palate level and the severity of OSAHS.The patients in group with BMI≥26 were more likely to develop airway obstruction at soft palate level than those with BMI26.
文摘BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic characteristics of the upper lumbar spine,conventional transforaminal PELD may fail to remove the highly migrated upper lumbar disc nucleus pulposus.Therefore,the purpose of this study was to describe a novel surgical technique,two-level PELD,for the treatment of highly migrated upper lumbar disc herniations and to report its related clinical outcomes.CASE SUMMARY A 60-year-old male presented with a complaint of pain at his lower back and right lower limb.The patient received 3 mo of conservative treatments but the symptoms were not alleviated.Physical examination revealed a positive femoral nerve stretch test and a negative straight leg raise test for the right leg,and preoperative visual analog scale(VAS)score for the lower back was 6 points and for the right leg was 8 points.Magnetic resonance imaging(MRI)demonstrated L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.According to physical examination and imaging findings,surgery was the primary consideration.Therefore,the patient underwent surgical treatment with two-level PELD.The pain symptom was relieved and the VAS score for back and thigh pain was one point postoperatively.The patient was asymptomatic and follow-up MRI scan 1 year after operation revealed no residual nucleus pulposus.CONCLUSION Two-level PELD as a transforaminal approach can be a safe and effective procedure for highly migrated upper lumbar disc herniation.
基金The National Natural Science Foundation of China(Grant 40273014)has funded the project.
文摘Twelve paleocommunities dominated by benthic brachiopod are recognized in the Givetian-Frasnian stages of the Devonian in the Longmenshan area, southwestern China, in which two kinds of brachiopod community replacement are classified. One is the abrupt replacement, represented by abrupt alternation between the Leiorhynchus community and Zhonghuacoelia-Striatopugnax community in the Frasnian Tuqiaozi Formation. The other is the gradual one, developed in the Givetian Guanwushan Formation, which had been completed by the shift of the Independatrypa lemma-Uncinulus heterocostellis-Emanuella takwanensis community via the Sinospongophyllum irregulare-Pseudomicroplasma fongi community to the Clathrocoilona spissa-Hexagonaria composite reef community. According to analyses of the paleocommunities, either the abrupt or gradual paleocommunity replacement of the Middle-Upper Devonian in the Longmenshan area is suggested as a response to the 5th-order sea level fluctuation due to the replacements of the paleocommunities in a tracts-system of depositional sequence. It is supposed that changes of paleocommunity diversity, one of the results of paleocommunity replacement, are depended on the range and magnitude of sea level fluctuation, but there is not a linear relationship between them. Furthermore, a suggestion is proposed that the concept of paleocommunity succession seem to be abandoned in the paleocommunity analysis because it almost never be practiced to recover the information of community succession in the geological record at present.
文摘受登陆北上台风“利奇马”等影响,2019年8月9~12日山东省出现连续暴雨,其中10日夜间出现降雨峰值。利用中国气象局上海台风研究所(Shanghai Typhoon Institute of China Meteorological Administration,简称CMA-STI)热带气旋最佳路径数据、山东省自动气象站逐时降雨量、常规观测资料、中国风云二号地球静止气象卫星(FY-2G)0.1°×0.1°逐小时云顶相当黑体亮温和美国环境预报中心(National Center of Environmental Prediction,简称NCEP)1°×1°逐6 h再分析等资料,主要运用纬向风局地变化方程与大气动能方程,诊断分析降雨明显增幅与高、低层风场变化的关系。结果表明:(1)暴雨主要影响系统有高低空急流、500 hPa西风槽、850 hPa台风倒槽及“利奇马”本体环流等。10日200 hPa中纬度大尺度西南风急流东南移影响鲁西北,当天08:00(北京时,下同)850 hPa因双台风活动而形成的大尺度东南风急流突然北伸越过山东省。台风倒槽对流云与本体环流对流云先、后北移经鲁中,累积效应造成该地区10日夜间雨量最大。(2)10日20:00850 hPa章丘站东北侧出现了过程最快东风增幅,纬向运动方程诊断结果表明,东风平流是东风增加最主要原因,地转偏向力项则不利于东风增加。(3)10日20:00章丘站200 hPa西南风风力明显加大形成急流,10日08:00至11日08:00青岛站850 hPa维持东南风低空急流。同时位于高空急流右后侧与低空急流左前方是鲁中附近10日夜间降雨增幅的重要原因。章丘200 hPa与青岛850 hPa都是在最大风力之前12 h动能增加最快。动能方程诊断表明,最有利于鲁西北高空急流形成的是位能平流项,最有利于鲁东南低空急流形成的是动能垂直通量散度项。(4)10日20:00至13日08:00“利奇马”本体环流一直在影响山东,暴雨期间山东中部地形的动力作用也一直存在,而降雨的峰值是出现在10日夜间,说明10日20:00前后高、低空急流的耦合可能是山东暴雨增幅的主要影响因子。其主要作用至少有加强山东中部的垂直运动、整层水汽输送与静力不稳定度等方面。
文摘利用山东省84个气象台站的逐日降水资料、美国国家环境预测中心和国家大气研究中心(National Centers for Environmental Prediction and National Center for Atmospheric Research, NCEP/NCAR)逐日再分析资料以及中国气象局(CMA)热带气旋资料中心的CMA最佳路径数据集,对1969—2020年夏季(6—8月)发生在山东的857例极端暴雨事件(Extreme rainstorm events, EREs)的时空分布特征及影响环流分型进行了分析。结果表明:山东夏季EREs主要集中在7和8月,8月极端暴雨降水量占当月总降水量的比值最大,可达53.5%。山东夏季极端暴雨降水量以及极端暴雨发生日数呈现不显著的增加趋势,8月的增加趋势最明显。使用经验正交函数分解对影响山东夏季EREs的大气环流系统进行分型,发现影响山东夏季出现EREs的环流系统主要有4类,其中,影响ERE最多的环流系统是北方气旋型,约占事件总频次的33.1%;其次是高空急流型,占比约11.3%;南方气旋型和热带气旋型的环流型影响相当,出现的概率分别为9.7%和9.4%。
基金National Public Benefit(Meteorology)Research Foundation of China(GYHY201106004)National Basic Research Program"973"of China(2009CB421502)National Nature Science Foundation of China (40730948,41005029)
文摘In this paper,by carrying out sensitivity tests of initial conditions and diagnostic analysis of physical fields,the impact factors and the physical mechanism of the unusual track of Morakot in the Taiwan Strait are discussed and examined based on the potential vorticity(PV)inversion.The diagnostic results of NCEP data showed that Morakot's track was mainly steered by the subtropical high.The breaking of a high-pressure zone was the main cause for the northward turn of Morakot.A sensitivity test of initial conditions showed that the existence of upper-level trough was the leading factor for the breaking of the high-pressure zone.When the intensity was strengthened of the upper-level trough at initial time,the high-pressure zone would break ahead of time,leading to the early northward turn of Morakot.Conversely,when the intensity was weakened,the breaking of the high-pressure zone would be delayed.Especially,when the intensity was weakened to a certain extent,the high-pressure zone would not break.The typhoon,steered by the easterly flow to the south of the high-pressure zone,would keep moving westward,with no turn in the test.The diagnostic analysis of the physical fields based on the sensitivity test revealed that positive vorticity advection and cold advection associated with the upper-level trough weakened the intensity of the high-pressure zone.The upper-level trough affected typhoon's track indirectly by influencing the high-pressure zone.