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 investigated the effects of upper-level descending inflow(ULDI)associated with inner-eyewall convection on the formation of the moat in tropical cyclones(TCs)with secondary eyewall formation(SEF).In our num...This study investigated the effects of upper-level descending inflow(ULDI)associated with inner-eyewall convection on the formation of the moat in tropical cyclones(TCs)with secondary eyewall formation(SEF).In our numerical experiments,a clear moat with SEF occurred in TCs with a significant ULDI,while no SEF occurred in TCs without a significant ULDI.The eyewall convection developed more vigorously in the control run.A ULDI occurred outside the inner-eyewall convection,where it was symmetrically unstable.The ULDI was initially triggered by the diabatic warming released by the inner eyewall and later enhanced by the cooling below the anvil cloud.The ULDI penetrated the outer edge of the inner eyewall with relatively dry air and prevented excessive solid-phase hydrometeors from being advected further outward.It produced extensive sublimation cooling of falling hydrometeors between the eyewall and the outer convection.The sublimation cooling resulted in negative buoyancy and further induced strong subsidence between the eyewall and the outer convection.As a result,a clear moat was generated.Development of the moat in the ongoing SEF prevented the outer rainband from moving farther inward,helping the outer rainband to symmetrize into an outer eyewall.In the sensitivity experiment,no significant ULDI formed since the eyewall convection was weaker,and the eyewall anvil developed relatively lower,meaning the formation of a moat and thus an outer eyewall was less likely.This study suggests that a better-represented simulation of inner-eyewall convective structures and distribution of the solid-phase hydrometeors is important to the prediction of SEF.展开更多
Various approaches have been proposed to minimize the upper-level systematic biases in global numerical weather prediction(NWP)models by using satellite upper-air sounding channels as anchors.However,since the China M...Various approaches have been proposed to minimize the upper-level systematic biases in global numerical weather prediction(NWP)models by using satellite upper-air sounding channels as anchors.However,since the China Meteorological Administration Global Forecast System(CMA-GFS)has a model top near 0.1 hPa(60 km),the upper-level temperature bias may exceed 4 K near 1 hPa and further extend to 5 hPa.In this study,channels 12–14 of the Advanced Microwave Sounding Unit A(AMSU-A)onboard five satellites of NOAA and METOP,whose weighting function peaks range from 10 to 2 hPa are all used as anchor observations in CMA-GFS.It is shown that the new“Anchor”approach can effectively reduce the biases near the model top and their downward propagation in three-month assimilation cycles.The bias growth rate of simulated upper-level channel observations is reduced to±0.001 K d^(–1),compared to–0.03 K d^(–1)derived from the current dynamic correction scheme.The relatively stable bias significantly improves the upper-level analysis field and leads to better global medium-range forecasts up to 10 days with significant reductions in the temperature and geopotential forecast error above 10 hPa.展开更多
晴空颠簸是影响飞机安全运行和旅客旅行舒适度的重要恶劣天气之一。为了研究2017年6月6日02:10(协调世界时)发生在山西省长治市上空的一次强烈的晴空颠簸事件的产生机制,本文使用常规观测资料、NOAA-15和NOAA-18卫星辐射资料并通过天气...晴空颠簸是影响飞机安全运行和旅客旅行舒适度的重要恶劣天气之一。为了研究2017年6月6日02:10(协调世界时)发生在山西省长治市上空的一次强烈的晴空颠簸事件的产生机制,本文使用常规观测资料、NOAA-15和NOAA-18卫星辐射资料并通过天气学分析和中尺度WRF数值模式以及GSI(Grid point Statistical Interpolation)同化系统同化等方法,对此次事件开展了数值模拟和机理研究。结果表明:该次飞机颠簸事件是一个典型的高空急流—锋区耦合系统导致的晴空湍流所致,高空急流是导致晴空湍流的主要因素之一。导致该次晴空湍流事件发生的是大气一系列要素对冷空气入侵的响应。高空冷云(冷空气)发展南下是促进此次强颠簸事件发生的重要诱因。由于高空冷云的南下,使得长治上空温度经向梯度增加,而长治上空温度经向梯度增加,使得中纬度风切变增大,增大的水平风垂直切变,导致理查森数(Ri)数值变小,而较小的Ri值是产生KH(Kelvin-Helmholtz)不稳定的必要条件,由于K-H不稳定导致了长治上空出现晴空湍流。此外,中尺度WRF模式以及GSI同化系统能够较好地模拟颠簸区附近的大气温度场特征,表明文中的数值预报流程对于大气温度、风场以及晴空湍流的发展具有一定的预报能力。展开更多
This paper investigates the effects of surface drag on upper-level front with a three-dimensional nonhy- drostatic mesoscale numerical model （MM5）. To this end, a new and simple potential vorticity intrusion （PVI）...This paper investigates the effects of surface drag on upper-level front with a three-dimensional nonhy- drostatic mesoscale numerical model （MM5）. To this end, a new and simple potential vorticity intrusion （PVI） index is proposed to quantitatively describe the extent and path that surface drag affects upper-level front. From a PV perspective, the formation of the upper-level front is illustrated as the tropopause folding happens from the stratosphere. The PVI index shows a good correlation with the minimum surface pres- sure, and tends to increase with the deepening of the surface cyclone and upper-level front. The surface drag acts to damp and delay the development of upper-level front, which could reduce the growth rate of the PVI index. However, the damping presents different effects in different development stages. It is the most significant during the rapid development stage of the surface cyclone. Compared with no surface drag cases, the tropopause is less inclined to intrude into the troposphere due to the surface drag. Positive feedback between the surface cyclone and upper-level front could accelerate the development of the frontal system.展开更多
目的:探索适宜的上消化道癌机会性筛查质量综合评价方法,为提高筛查质量提供依据。方法:采用TOPSIS法(Technique for Order Preference by Similarity to an Ideal Solution)、RSR法(Rank-Sum Ratio,RSR)及二者联合评价法,对2022年四川...目的:探索适宜的上消化道癌机会性筛查质量综合评价方法,为提高筛查质量提供依据。方法:采用TOPSIS法(Technique for Order Preference by Similarity to an Ideal Solution)、RSR法(Rank-Sum Ratio,RSR)及二者联合评价法,对2022年四川省61家县级公立医院上消化道癌机会性筛查质量进行综合评价,评价指标包括无痛率、活检率、染色率、检出率和早诊率。结果:TOPSIS法、RSR法和TOPSIS法与RSR法模糊联合法三种评价方法评价结果虽然不完全一致,但总体趋势趋于一致。在TOPSIS法与RSR法模糊联合的评价中,排名前5名的是H9、H33、H30、H45、H8;排名后5名的是H50、H43、H15、H21、H49。筛查质量排名靠前的县级公立医院主要分布在南充市、绵阳市、德阳市,筛查质量排名靠后的主要分布阿坝州、凉山州、雅安市。结论:TOPSIS法、RSR法以及三种比例的TOPSIS法与RSR法模糊联合综合评价排序虽然有一定差异,但总体结果基本一致。运用TOPSIS法与RSR法模糊联合的方法能够更加科学合理、客观准确地评价四川省县级公立医院上消化道癌机会性筛查质量。四川省县级公立医院上消化道癌机会性筛查质量参差不齐,机构之间和地区之间差异较大。展开更多
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.
基金supported by the National Natural Science Foundation of China(Grant Nos.42192552,42192551,42150710531,42175016,and 42075072)the Shanghai Typhoon Research Fund(Grant No.TFJJ202207)the Basic Research Fund of CAMS(Grant No.2023Y010)。
文摘This study investigated the effects of upper-level descending inflow(ULDI)associated with inner-eyewall convection on the formation of the moat in tropical cyclones(TCs)with secondary eyewall formation(SEF).In our numerical experiments,a clear moat with SEF occurred in TCs with a significant ULDI,while no SEF occurred in TCs without a significant ULDI.The eyewall convection developed more vigorously in the control run.A ULDI occurred outside the inner-eyewall convection,where it was symmetrically unstable.The ULDI was initially triggered by the diabatic warming released by the inner eyewall and later enhanced by the cooling below the anvil cloud.The ULDI penetrated the outer edge of the inner eyewall with relatively dry air and prevented excessive solid-phase hydrometeors from being advected further outward.It produced extensive sublimation cooling of falling hydrometeors between the eyewall and the outer convection.The sublimation cooling resulted in negative buoyancy and further induced strong subsidence between the eyewall and the outer convection.As a result,a clear moat was generated.Development of the moat in the ongoing SEF prevented the outer rainband from moving farther inward,helping the outer rainband to symmetrize into an outer eyewall.In the sensitivity experiment,no significant ULDI formed since the eyewall convection was weaker,and the eyewall anvil developed relatively lower,meaning the formation of a moat and thus an outer eyewall was less likely.This study suggests that a better-represented simulation of inner-eyewall convective structures and distribution of the solid-phase hydrometeors is important to the prediction of SEF.
基金supported by the Hunan Provincial Natural Science Foundation of China(Grant No.2021JC0009)the Natural Science Foundation of China(Grant Nos.U2142212 and 42105136)。
文摘Various approaches have been proposed to minimize the upper-level systematic biases in global numerical weather prediction(NWP)models by using satellite upper-air sounding channels as anchors.However,since the China Meteorological Administration Global Forecast System(CMA-GFS)has a model top near 0.1 hPa(60 km),the upper-level temperature bias may exceed 4 K near 1 hPa and further extend to 5 hPa.In this study,channels 12–14 of the Advanced Microwave Sounding Unit A(AMSU-A)onboard five satellites of NOAA and METOP,whose weighting function peaks range from 10 to 2 hPa are all used as anchor observations in CMA-GFS.It is shown that the new“Anchor”approach can effectively reduce the biases near the model top and their downward propagation in three-month assimilation cycles.The bias growth rate of simulated upper-level channel observations is reduced to±0.001 K d^(–1),compared to–0.03 K d^(–1)derived from the current dynamic correction scheme.The relatively stable bias significantly improves the upper-level analysis field and leads to better global medium-range forecasts up to 10 days with significant reductions in the temperature and geopotential forecast error above 10 hPa.
文摘晴空颠簸是影响飞机安全运行和旅客旅行舒适度的重要恶劣天气之一。为了研究2017年6月6日02:10(协调世界时)发生在山西省长治市上空的一次强烈的晴空颠簸事件的产生机制,本文使用常规观测资料、NOAA-15和NOAA-18卫星辐射资料并通过天气学分析和中尺度WRF数值模式以及GSI(Grid point Statistical Interpolation)同化系统同化等方法,对此次事件开展了数值模拟和机理研究。结果表明:该次飞机颠簸事件是一个典型的高空急流—锋区耦合系统导致的晴空湍流所致,高空急流是导致晴空湍流的主要因素之一。导致该次晴空湍流事件发生的是大气一系列要素对冷空气入侵的响应。高空冷云(冷空气)发展南下是促进此次强颠簸事件发生的重要诱因。由于高空冷云的南下,使得长治上空温度经向梯度增加,而长治上空温度经向梯度增加,使得中纬度风切变增大,增大的水平风垂直切变,导致理查森数(Ri)数值变小,而较小的Ri值是产生KH(Kelvin-Helmholtz)不稳定的必要条件,由于K-H不稳定导致了长治上空出现晴空湍流。此外,中尺度WRF模式以及GSI同化系统能够较好地模拟颠簸区附近的大气温度场特征,表明文中的数值预报流程对于大气温度、风场以及晴空湍流的发展具有一定的预报能力。
基金Supported by the National Key Basic Research Program of China(2012CB417201)National Natural Science Foundation of China(41275059,41275055,and 41461164008)
文摘This paper investigates the effects of surface drag on upper-level front with a three-dimensional nonhy- drostatic mesoscale numerical model （MM5）. To this end, a new and simple potential vorticity intrusion （PVI） index is proposed to quantitatively describe the extent and path that surface drag affects upper-level front. From a PV perspective, the formation of the upper-level front is illustrated as the tropopause folding happens from the stratosphere. The PVI index shows a good correlation with the minimum surface pres- sure, and tends to increase with the deepening of the surface cyclone and upper-level front. The surface drag acts to damp and delay the development of upper-level front, which could reduce the growth rate of the PVI index. However, the damping presents different effects in different development stages. It is the most significant during the rapid development stage of the surface cyclone. Compared with no surface drag cases, the tropopause is less inclined to intrude into the troposphere due to the surface drag. Positive feedback between the surface cyclone and upper-level front could accelerate the development of the frontal system.
文摘目的:探索适宜的上消化道癌机会性筛查质量综合评价方法,为提高筛查质量提供依据。方法:采用TOPSIS法(Technique for Order Preference by Similarity to an Ideal Solution)、RSR法(Rank-Sum Ratio,RSR)及二者联合评价法,对2022年四川省61家县级公立医院上消化道癌机会性筛查质量进行综合评价,评价指标包括无痛率、活检率、染色率、检出率和早诊率。结果:TOPSIS法、RSR法和TOPSIS法与RSR法模糊联合法三种评价方法评价结果虽然不完全一致,但总体趋势趋于一致。在TOPSIS法与RSR法模糊联合的评价中,排名前5名的是H9、H33、H30、H45、H8;排名后5名的是H50、H43、H15、H21、H49。筛查质量排名靠前的县级公立医院主要分布在南充市、绵阳市、德阳市,筛查质量排名靠后的主要分布阿坝州、凉山州、雅安市。结论:TOPSIS法、RSR法以及三种比例的TOPSIS法与RSR法模糊联合综合评价排序虽然有一定差异,但总体结果基本一致。运用TOPSIS法与RSR法模糊联合的方法能够更加科学合理、客观准确地评价四川省县级公立医院上消化道癌机会性筛查质量。四川省县级公立医院上消化道癌机会性筛查质量参差不齐,机构之间和地区之间差异较大。
