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地面加热对飞机颠簸影响的动力学初步分析 总被引:2,自引:0,他引:2
邹波 《南京气象学院学报》2004,27(4):527-531
用积分变换法求解考虑了地面加热作用的中尺度二维不可压缩流体的Boussinesq方程,得到一组描述地面加热作用激发的垂直风场、水平扰动风场、扰动气温场的解析解,进而用动力学分析的观点定性讨论了飞机颠簸与地面加热场、风场、温度场空间分布及时间变化的关系,对动力和热力性气象因子对于飞机颠簸的影响进行了初步分析。 相似文献
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第二类条件不稳定(CISK)是热带气旋发展的重要机制,Rasmussen(1979)在研究所谓极地低压时首先指出了温带CISK扰动的存在和性质。但对于温带扰动的发展,除了积云对流凝结的反馈外,下垫面的感热和对流层低层风的垂直切变有相当重要的作用。因此,感热加热和垂直风切变对温带CISK扰动的影响是一个有意义的研究课题。 将下垫面感热加热和对流层低层风的垂直切变分别引入温带CISK模式,其结果表明:下地面感热加热可以明显地加速温带CISK扰动的发展,这可能是一些温带小气旋急速发展(例如美国的炸弹气旋等)的原因之一;对流层低层的垂直风切变既可以加强也可以削弱温带CISK扰动,其影响依赖于垂直风切变的类型;下垫面感热加热和垂直风切变的共同作用则反映了复杂而有意义的性质。一般情况下,对流层低层垂直风切变对CISK扰动的发展有抑制作用。 相似文献
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Energy-Casimir方法在中尺度扰动稳定性研究中的应用 总被引:3,自引:0,他引:3
考虑湿空气中的水汽效应,引进Casimir函数(它是虚位温的单值函数),在x方向动量方程和总能量方程的基础上,采用Energy-Casimir方法建立了三维非地转平衡和非静力平衡的拟能量波作用方程,由于该方程建立在非地转平衡和非静力平衡的动力框架下,因此可用于讨论层结稳定大气内中尺度扰动系统的发展演变.理论分析表明,拟能量波作用方程具有非守恒形式,其中的拟能量波作用密度主要由扰动动能、有效化能和浮力能三部分组成;拟能量波作用密度局地变化除了受拟能量波作用通量散度影响之外,纬向基本气流切变、科氏力作功以及山非绝热加热和水汽相变所构成的波作用源汇项对其也都有贡献.诊断分析结果表明,对流层中低层的拟能量波作用密度与观测的6 h累积地面降水在水平空间分布和时间演变趋势上比较接近,说明拟能量波作用密度能够较好地抓住强降水区上空对流层中低层动力场和热力场的扰动特征,并在一定程度上可以有效地表征降水系统的发展演变,因而与地面降水量存在紧密联系.波作用方程各项的计算分析表明,波作用通量散度与拟能量波作用密度局地变化的倾向以及强降水区的变化比较一致,并且在强度上强于纬向基本气流切变项和科氏力作功项,因此波作用通量散度对拟能量波作用密度的局地变化具有重要贡献. 相似文献
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本文利用欧洲中心再分析资料、FY-2G卫星云导风资料,多普勒雷达组网资料、风廓线、加密自动站资料,分析了2017年8月2日由北上台风残涡引起的天津局地暴雨过程中的中尺度对流过程,研究其触发条件,并探讨了形成原因。结果表明:在局地对流发生前,天津中北部地面附近并没有较好的动力以及湿度条件,且存在扰动逆温,扰动温度负值区(冷垫)厚度达到50 hPa以上,较大的水平风垂直切变在东南斜升气流下,水平涡管发生扭曲,产生垂直涡度,在边界层以上正负涡度之间形成辐合线,触发条件不稳定能量释放,在天津中北部产生局地对流,对流在触发后不断发展并向西北方向移动,与其西北侧线状多单体合并,导致天津北部的短时强降水天气。 相似文献
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东南风气流对夏季北京局地暴雨的影响 总被引:3,自引:0,他引:3
利用北京地区风廓线雷达和地面自动气象站观测资料,分析局地暴雨过程中的东南风,普查2006年8次局地暴雨过程中风廓线雷达探测的东南风,并详细分析2次典型局地暴雨过程的风廓线资料。结果表明:降水前和降水过程中东南风的大小、厚度与雨量存在相关关系;降水前东南风指数IE的大小和波动加强对局地暴雨的临近预报有一定的指示意义。初步从理论上解释了东南风对北京局地暴雨强度的影响:东南风加强并上传,导致了上升速度和水汽输送的层次快速增加,对暴雨的触发和加强都有一定作用。由于北京特殊的地形,东南风的存在使得局地暴雨容易在山前地区产生。 相似文献
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利用Doppler雷达、地面自动站、Profile垂直风廓线及GPS水汽分布等多种新型探测资料, 对2006年7月9日夜间发生在北京西郊香山附近的局地大暴雨天气的影响系统和γ-中尺度强降雨落区形成的动力机理进行了精细分析。对雷达等本地多种探测资料的精细研究表明:地形辐合回波带是造成这次过程的主要影响系统。地形辐合回波带上中气旋回波块的滚动更迭是大暴雨落区形成的直接原因; 近地面辐合对大暴雨落区强降雨的发生具有重要作用。大暴雨落区形成阶段近地面3种辐合同时存在:平原东南风与山区偏北风风向切变辐合、平原东南风在山脉阻挡作用下的抬升辐合、大暴雨落区中心的γ-中尺度气旋性辐合。研究还表明:山前近地面地形辐合扰动, 向上传播, 引发边界层扰动的动力过程是香山大暴雨落区形成的主要动力源, 而来自东南方向近地面层的暖湿平流为大暴雨提供了有效的水汽和能量。 相似文献
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利用位涡方程和热力适应原理,讨论了因非绝热加热的空间不均匀性导致的大气 动力特征的变化,进一步阐明了副热带地区的深对流凝结潜热加热的垂直非均匀性使副热带高压在中低空出现在热源区以东,在高空出现在热源区以西。在此基础上,深入研究了水平非均匀加热对大气环流的影响。结果表明加热区以北,虽然非绝热加热消失,但存在加热的水平梯度在西风环流的背景下在高低层造成深厚的负涡度强迫。因而高层热源北部边界附近的西风向南偏转进入加热区,造成加热区北部边界及其以北发生次级辐散;低层热源区的南风发生反气旋偏转,汇入加热区外的西风气流中,造成低层加热区北部边界及其以北发生次级辐合。结果该区域产生了垂直上升运动及负的涡度强迫源,对应着异常强烈的反气旋环流。该负涡度强迫源还通过能量频散,在西风带中以Rossby波的形式向中高纬传播,影响中高纬地区的异常环流型。 相似文献
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热力适应、过流、频散和副高Ⅱ.水平非均匀加热与能量频散 总被引:3,自引:2,他引:3
利用位涡方程和热力适应原理,讨论了因非绝热加热的空间不均匀性导致的大气动力特征的变化,进一步阐明了副热带地区的深对流凝结潜热加热的垂直非均匀性使副热带高压中低空出现在低源区以东,在高空出现在热源区以西。在此基础上,深入研究了水平非均匀加热对大气环流的影响。结果表明加热区以北,虽然非绝热加热消失,但存在加热的水平梯度在西风环流的背景下在高低层造成深厚的负涡度强迫。因而高层热源北部边界附近的西风向南偏转进入加热区,造成加热区北部边界及其以北发生次级辐散;低层热源区的南风发生反气旋偏转,汇入加热区外的西风气流中,造成低层加热区北部边界及其以北发生次级辐合。结果该区域产生了垂直上升运动及负的涡度强迫源,对应着异常强烈的反气旋环流。该负涡强度迫源还通过能量散射,在西风带中以Rossby波的形式向中高纬传播,影响中高纬地区的异常环流型。 相似文献
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赤道反气旋的合成结构和涡度收支 总被引:1,自引:0,他引:1
本文通过普查1979—1983年7—9月在10°S—15°N、90°E—140°E范围内的赤道反气旋活动情况,从中选出15个强度和范围较接近的赤道反气旋进行综合分析,得到它们的平均三维结构特征。结果表明,赤道反气旋是一个暖性的中低层系统。反气旋环流与涡度、散度及垂直运动有较好的配合。在赤道反气旋的低层,环流中心为负涡度区和辐散区,并与下沉运动区相对应,四周为正涡度和辐合区,以及上升运动区。高层正好相反。加热场与垂直运动场有较好的对应关系,中心区是干绝热下沉增温区。对涡度收支的计算表明,中低层有负涡度积累,上层有正涡度积累,局地涡度变化主要决定于散度项、平流项和垂直输送项。 相似文献
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《气象科学》2014,(2)
Based on diagnostic analysis of reanalysis data for 58-year,the distribution characteristics of decadal variability in diabatic heating,transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature(SST)anomalies over the North Pacific,as well as their relationship with anomalous atmospheric circulation have been investigated in this paper.A linear baroclinic model(LBM)was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies,and then to compare relative roles of different kinds of forcing in terms of geopotential height responses.The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic.The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow,as well as to the vertical profile of heating.The response to the idealized deep heating over the eastern North Pacific,mimicking the observed heating anomaly,is baroclinic.The atmospheric response to the mid-latitude vorticity forcing is always barotropic,resulting in a geopotential low that is in phase with the forcing.The atmospheric responses to the realistic heat and vorticity forcing show the similar results,suggesting that diabatic heating,transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies. 相似文献
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Mid-latitude atmospheric responses to heat and vorticity forcing using a linear baroclinic model 总被引:1,自引:0,他引:1
Based on diagnostic analysis of reanalysis data for 58-year, the distribution characteristics of decadal variability in diabatic heating, transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature (SST) anomalies over the North Pacific, as well as their relationship with anomalous atmospheric circulation have been investigated in this paper. A linear baroclinic model(LBM) was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies, and then to compare relative roles of different kinds of forcing in terms of geopotential height responses. The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic. The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow, as well as to the vertical profile of heating. The response to the idealized deep heating over the eastern North Pacific, mimicking the observed heating anomaly, is baroclinic. The atmospheric response to the mid-latitude vorticity forcing is always barotropic, resulting in a geopotential low that is in phase with the forcing. The atmospheric responses to the realistic heat and vorticity forcing show the similar results, suggesting that diabatic heating, transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies. 相似文献
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An experiment was performed in which the horizontal divergence and vertical vorticity were estimated within thermal structures that are found in the surface layer. Ultrasonic anemometer/thermometers were mounted on top of 13 m masts on the vertices of an equilateral triangle with sides of 100 m. A planimetric method in combination with conditional averaging was used to assess the kinematics. Statistical validation of the technique is based on precise measurement, optinization by excluding the smaller length scales (<50 m), and by theoretical agreement. Already in the raw signals of horizontal divergence and vertical velocity, it can be seen that warmer rising air coincides with surface convergence spots whereas the surrounding downward movements result in divergence flow fields. The dependencies of the kinematic parameters on atmospheric stability are discussed. Two regions of opposite vorticity within thermal structures are measured. 相似文献
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THE RELATIONSHIP BETWEEN HORIZONTAL VORTICITY INDUCED BY
VERTICAL SHEAR AND VERTICAL MOTION DURING A SQUALL LINE
PROCESS 总被引:2,自引:0,他引:2
The horizontal vorticity equation used in this study
was obtained using the equations of motion in the pressure
coordinate system without considering friction, to reveal its
relationship with vertical shear. By diagnostically analyzing
each term in the horizontal vorticity equation during a squall
line process that occurred on 19 June 2010, we found that the
non-thermal wind term had a negative contribution to the local
change of upward movement in the low-level atmosphere, and that
its impact changed gradually from negative to positive with
altitude, which could influence upward movement in the mid- and
upper-level atmosphere greatly. The contribution of upward
vertical transport to vertical movement was the largest in the
low-level atmosphere, but had negative contribution to the
upper-level atmosphere. These features were most evident in the
development stage of the squall line. Based on analysis of
convection cells along a squall line, we found that in the
process of cell development diabatic heating caused the
subsidence of constant potential temperature surface and non-
geostrophic motion, which then triggered strong convergence of
horizontal acceleration in the mid-level atmosphere and
divergence of horizontal acceleration in the upper-level
atmosphere. These changes of horizontal wind field could cause a
counterclockwise increment of the horizontal vorticity around
the warm cell, which then generated an increase of upward
movement. This was the main reason why the non-thermal wind term
had the largest contribution to the strengthening of upward
movement in the mid- and upper-level atmosphere. The vertical
transport of large value of horizontal vorticity was the key to
trigger convection in this squall line process. 相似文献
18.
覃皓 《沙漠与绿洲气象(新疆气象)》2024,18(2):68-75
利用常规观测、卫星数据及ERA5再分析数据,从动力和热力角度对引发2020年5月24-25日广西北部暴雨过程的低涡发展维持机制进行了诊断分析。结果表明:低涡在滇黔桂交界一带生成,随后逐渐发展东移,对流云团及降水落区主要分布在低涡东侧及南侧。涡度方程诊断表明,低涡的发展维持主要受涡度平流项和水平散度项影响。水平风场对涡度的输送使得局地涡度减小,而水平风场的辐合效应使得局地涡度增大。将原始风场分解为地转风和非地转风分量后发现,非地转风分量主导了局地涡度的变化,非地转风水平散度项正贡献最大,扭转项次之,两者是造成低涡发展维持的主要原因。在热力作用方面,低涡发展移动过程中对流层中层附近的潜热加热正反馈也有利于低层低涡的发展维持。 相似文献
19.
本文利用Ekman动量近似研究了斜压性对Ekman层动力学的影响,得到了一些新的结果。大气斜压性对Ekman层的水平风速分布及近地面的风速矢的水平分量夹角有重要的改变作用。斜压边界层顶部的非线性Ekman抽吸(垂直运动)由三个不同的物理因子决定,第一、正压性的地面地转涡度,第二、斜压性作用产生的热成风涡度,第三、正压性的地面地转涡度与斜压性的热成风涡度的非线性相互作用。这些理论结果为边界层的参数化及数值模拟结果的解释提供物理基础。 相似文献
20.
M. L. Kaplan A. W. Huffman K. M. Lux J. D. Cetola J. J. Charney A. J. Riordan Y.-L. Lin K. T. Waight III 《Meteorology and Atmospheric Physics》2005,88(3-4):153-173
Summary Simulation experiments reveal key processes that organize a hydrostatic environment conducive to severe turbulence. The paradigm requires the juxtaposition of the entrance region of a curved jet streak, which is highly subgeostrophic, with the entrance region of a straight jet streak, which is highly supergeostrophic. The wind and mass fields become misphased as the entrance regions converge, resulting in significant spatial variation of inertial forcing, centripetal forcing, as well as along and cross-stream pressure gradient forcing over a meso- scale region. Maxima of these forces are misphased where the two dissimilar jet streaks converge and geostrophic balance is disrupted. Velocity divergence within the subgeostrophic region of largest upstream-directed pressure gradient force and velocity convergence near the region of largest downstream-directed centripetal/inertial-advective forcing act to produce a mesoscale front due to spatially varying confluent flow flanked by zones of increasing velocity divergence. This results in frontogenesis as well as the along-stream divergence of cyclonic and convergence of cyclonic ageostrophic vertical vorticity. The nonuniform centripetally forced mesoscale front becomes the locus of large gradients of ageostrophic vertical vorticity along an overturning isentrope. This region becomes favorable for streamwise vorticity gradient formation enhancing the environment for the organization of horizontal vortex tubes in the presence of buoyant forcing. This is because the mesoscale convergence of vertical vorticity on an overturning isentropic surface creates vertical rotation for the development of horizontal vorticity in regions where isentropic surfaces overturn. Vorticity, shear, and buoyancy are focused in one location by this front thus favoring an environment favorable for microvortex formation leading to turbulence. 相似文献