共查询到20条相似文献，搜索用时 140 毫秒
1.
Zhaoyang Chai Minghua Zhang Qingcun Zeng He Zhang Jiangbo Jin Jinbo Xie Ting You 《大气和海洋科学快报》2021,14(2):35-41
提高大气环流模式的模式顶层高度对中高层大气(如平流层准两年振荡)的准确模拟至关重要.本研究将IAP大气环流模型(IAP-AGCM)延伸至中层大气顶(～0.01 hPa,～80 km)并提高垂直方向分辨率(91层),发展了一个中高层大气环流模型(IAP-AGCML91).结果表明,与低层模式相比,该中高层大气模式在整体上显著减小了平流层尤其是上平流层的冷偏差.研究发现这种改善与两种机制有关:与低层模式相比,高层模式模拟的短波加热更大,极区平流层附近的经向涡动热通量更大.上述结果表明,垂直分辨率和模式顶层高度对IAP-AGCML91的气候模拟有重要影响. 相似文献
2.
《大气和海洋科学快报》2021,(2)
提高大气环流模式的模式顶层高度对中高层大气(如平流层准两年振荡)的准确模拟至关重要.本研究将IAP大气环流模型(IAP-AGCM)延伸至中层大气顶(～0.01 hPa,～80 km)并提高垂直方向分辨率(91层),发展了一个中高层大气环流模型(IAP-AGCML91).结果表明,与低层模式相比,该中高层大气模式在整体上显著减小了平流层尤其是上平流层的冷偏差.研究发现这种改善与两种机制有关:与低层模式相比,高层模式模拟的短波加热更大,极区平流层附近的经向涡动热通量更大.上述结果表明,垂直分辨率和模式顶层高度对IAP-AGCML91的气候模拟有重要影响. 相似文献
3.
华北地区一次中尺度对流系统上方的Sprite放电现象及其对应的雷达回波和闪电特征 总被引：3，自引：3，他引：0
利用低光度相机首次观测到了2013年7月31日华北地区一次中尺度对流系统(MCS)上空产生的中高层Sprite放电现象。结合闪电定位、天气雷达等同步观测, 对一次MCS诱发的Sprite的形态学特征及其对应的母体闪电和雷暴系统的雷达回波特征等进行了详细分析。研究除发现了2例圆柱型、3例胡萝卜型和1例舞蹈型 Sprite外, 还发现了2例发光主体发育不完全的Y字型Sprite。估算的Sprite的底部平均高度低于61.8±3.5 km, 顶部平均高度为84.3±6.8 km。Sprite持续时间算术平均值为25.7±9.8 ms, 几何平均值为24.4 ms。Sprite的母体闪电均为正地闪, 峰值电流在+62.5～+106.2 kA之间, 算术平均值为+77.1±22.2 kA, 是本次MCS所有正地闪平均峰值电流的1.4倍。Sprite母体闪电的脉冲电荷矩变化(iCMC)在+475～+922 C km之间, 几何平均值为+571.0 C km。Sprite母体闪电发生在MCS雷达回波25～35 dBZ的层状云降水区, 弱回波(<30 dBZ)面积的突然增加对Sprite的产生有重要指示作用。Sprite易发生在MCS成熟—消散阶段正地闪比例(POP)显著增加的时段。在本次MCS消散阶段中, 有两个时间段可能有利于产生Sprite。在Sprite集中发生时间段, 北京闪电综合探测网(BLNET)探测到的正地闪比例为54.2%, 正地闪连续电流比例70.24%, 连续电流持续时间为58.17±50.31 ms, 有利于Sprite的产生。 相似文献
4.
雷暴云顶和低电离层之间的大气放电是20世纪90年代(1989年)新发现的一类大空间尺度(垂直尺度几十千米,水平尺度甚至达到几百千米)放电现象,由于它们的持续时间比较短(ms量级),因此又被称为瞬态发光事件(Transient Luminous Events,TLEs)。由于瞬态发光事件连接对流层、平流层、中间层、低热层等多个大气层,因此是对流层与上层大气之间物质能量交换的重要瞬态物理过程,对这类放电现象的研究,有助于揭示整层大气间的耦合机制问题。瞬态发光事件对中高层大气的物理性质、化学性质、空间电磁环境及临近空间内飞行器的安全运行有直接影响。截至目前,已经发现的瞬态发光现象包括红色精灵(又称为"红闪",sprites)、淘气精灵(elves)、蓝色喷流(blue jets)、蓝色启辉器(blue starters)、巨大喷流(gigantic jets)和光晕(halos)等多种形式。以上述几种放电现象为主线,对相关研究成果进行了介绍,同时对未来的研究工作进行了展望。 相似文献
5.
8719号台风途经日本期间,用MU(中、高层大气)雷达对对流层和平流层低层进行了60小时的连续观测.以150m的高度分辨率每隔2.5分钟测量风速矢量的高度廓线.1987年10月17日,8719号台风袭击了日本,并在距MU雷达100km的范围内通过.18km以下都能观测到清晰的台风旋转结构,往上直到24km,风有短时的振动,表明受台风的强烈影响.整个观测期间,都发现有垂直波长为2-4km,周期为10小时的主波.高空风分析图显示,这些波从一个逆温层附近向上和向下传播,这意味着波动是在逆温层上生成的. 相似文献
6.
中层大气重力波的研究 总被引：2，自引：0，他引：2
中层大气(Middle Atmosphere)是近十多年来被广泛使用的一个新名词,它是指从对流层顶的10——16km到湍流层顶约100km之间的大气层,即中层大气由平流层、中间层加上热成层下部的一小部分组成。黄荣辉对中层大气的一般动力学、行星波动力学和赤道平流层波动及其与基本气流相互作用的近期研究作了评述。本文侧重综述中层大气内的重力波及其与基本气流的相互作用。 相似文献
7.
2016年初冬陕西一次高架雷暴天气过程分析 总被引：3，自引：2，他引：1
利用常规地面高空观测资料、西安和安康多普勒天气雷达观测资料、欧洲中心细网格模式预报等资料对2016年11月22日发生在陕西地区的一次雷暴过程进行诊断分析,结果表明：陕西中南部雷暴区位于地面冷锋后350~500 km的区域内,雷暴区3 km以下是深厚的冷垫,同时中低层存在明显的逆温层,低层是绝对稳定的大气层结,这说明此次雷暴天气为高架雷暴。通过诊断饱和假相当位温、假相当位温、湿位涡和绝对涡度表明不同地区不稳定机制是不同的。西安地区不稳定机制为条件性对称不稳定,安康地区不稳定机制为条件性不稳定。在条件性对称不稳定区域,降雪回波呈现出数个平行带状回波,与0~6 km风切变矢量(西西南风)平行;在条件性不稳定区域,降水回波为小尺度的块状回波。强垂直风切变表明大气斜压性强,中高层暖湿气流增强了大气的湿斜压性,从而使中高层形成条件性对称不稳定,产生倾斜对流;中低层偏南气流输送暖平流和水汽,使得大气较为暖湿,中高层温度平流较弱,大气较干,形成位势不稳定,锋面抬升中低层暖湿大气使其饱和,位势不稳定转化为条件性不稳定,产生垂直对流。不稳定与上升运动及回波高度有着较好的对应关系。 相似文献
8.
伴随超强VHF辐射的闪电双极性窄脉冲初步观测 总被引：5，自引：1，他引：5
闪电过程中一类双极性脉冲辐射伴随的超过常规闪电一个数量级的VHF辐射是卫星观测的穿越电离层的脉冲对(TIPPs)的来源。文中给出了在中国上海地区观测到的该类放电事件产生的78例双极性窄脉冲。典型的双极性窄脉冲上升时间约1.2μs,初始峰宽度约2—3μs、半宽约1μs,整个脉冲持续时间约15μs,脉冲幅度与地闪首次回击幅度相当,过冲幅度约为初始峰幅度的1/3。这类脉冲波形特征与普通闪电双极性脉冲波形特征差异明显。根据空间双极性脉冲被电离层以及地面-电离层反射的时间延迟并假定电离层高度为85 km,估算了这些双极性窄脉冲发生高度。11例负极性脉冲(对应上面负电荷区对下部正电荷区之间的放电)中有10例脉冲发生高度在海拔14.0—15.0 km,一例出现在负地闪初始击穿阶段的脉冲发生高度为海拔6.4 km。67例正极性窄脉冲发生高度位于海拔7—12 km,平均海拔9.4 km。利用传输线电流模式以及偶极子辐射近似估计了电流在通道内传播时间以及放电电流参数,78例平均结果显示电流从通道底部传播到顶部经历的时间约1μs,电流矩约为5 kA.km量级。我们推断放电通道长度约100—300 m,放电电流幅度具有20 kA量级,电流传播速度与光速可比拟、具有108m/s量级。 相似文献
9.
利用美国大气辐射测量项目(ARM)制作的“气候模拟最佳估计”(CMBE)观测数据集,检验美国环境预报中心(NCEP)全球预报系统(GFS)2001～2008年在ARM Southern Great Plains(SGP)站点预报的大气温度、相对湿度和云量的垂直分布,主要结论如下:(1)NCEP GFS较好地预报出了温度和相对湿度的季节变化.就各个季节平均而言,NCEP GFS高估了1.5～12km的大气温度,同时低估了春冬季13～16km和秋冬季1.5km以下的大气温度,各高度上温度偏差绝对值小于1℃;NCEP GFS预报结果再现了观测到的相对湿度垂直分布的双峰结构,但是高估了4～12 km的相对湿度.模式分辨率提高(T170L42更新为T254L64)显著改进了14～18 km相对湿度的预报.(2)预报的云量在10 km以下小于观测值,在10～13 km则高于观测值,而且,NCEPGFS没有预报出非降水性低云的云量,其预报的降水云的云量在8km以下也低于观测值,反映出NCEP GFS模式中浅对流和深对流活动不够活跃.(3)NCEP GFS模式用预报的相对湿度和云水/云冰混合比(qc)诊断云量,采用同样的诊断公式由观测的相对湿度和NCEP GFS预报输出的qc计算云量,得到的云量在11 km以下所有高度上都更加显著地小于观测值,即比NCEP GFS对云量的低估更加严重,说明NCEP GFS可能低估了此高度区间的qc.(4)2001～2008年间NCEP GFS预报的温度、湿度和云量改进不显著,其预报云量和qc的误差很可能与模式中深对流和浅对流方案、层云微物理方案的不确定性有关. 相似文献
10.
基于麦克斯韦方程组,通过综合考虑电子热效应和电离、吸附效应的非线性变化,利用二维时域有限差分算法(2D FDTD),建立了对流层-中高层大气电动力耦合模式,分析了中高层大气电参数的非线性效应对地闪回击电磁场传播的影响。结果表明,对微秒量级的地闪回击辐射场而言,在60 km以下,由于弛豫时间为毫秒量级,不需要考虑电参数的非线性效应。而在60 km以上的空间,由于弛豫时间快速减小至小于微秒量级,必须考虑电参数非线性效应带来的影响。如果考虑中高层大气电参数非线性效应,距地面90 km高度处地闪回击辐射场峰值明显减小,其中,垂直电场受影响最明显,场峰值最大可减小75%左右,而水平电场受影响相对较小。因为垂直电场脉冲持续时间为几百微秒,而水平电场脉冲持续时间仅为几十微秒,电磁场脉冲持续时间越长,受微秒量级中高层大气电介质弛豫时间的影响越大。 相似文献
11.
利用中国气象局雷电野外科学试验基地(CMA_FEBLS)三维闪电观测数据,结合广州双偏振雷达观测数据,分析了2017年5月7日广东一次暖云强降水对流单体的闪电活动及其与云降水结构的关系。该单体在4 h内产生1250个闪电,地闪比例约24%。绝大多数闪电出现在4~12 km高度,对应温度层为0℃至-40℃;闪电放电活动的峰值高度出现在8.5 km,对应环境温度约-19℃。分析的强降水单体宏观上呈现上正、中负、下正的三极性电荷结构,中部负电荷核心区约为-8℃至-15℃。在闪电活动区域中,由干雪粒子主导区域占比约82%,霰粒子主导区域占比约11%,且大部分与闪电活动关联的霰粒子主要位于4~8 km高度。总闪频数与30 dBZ雷达回波顶高、-20℃温度层上大于20 dBZ的回波体积具有较好的相关性。闪电活动的平均位置高度与20 dBZ雷达回波顶高和-20℃温度层上大于30 dBZ的回波体积具有较好的相关关系。闪电活动与最大降水强度之间具有较好的时序对应关系,单个闪电表征降水量的值为107 kg/fl量级。 相似文献
12.
利用天气雷达观测资料预报小流域流量 总被引：3，自引：0，他引：3
将天气雷达降水临近预报与半分布式水文模型TOPMODEL(TOPography based hydrological MODEL)相结合,研究了降水临近预报延伸小流域流量预报预见期的可行性。研究流域为淠河(安徽省内)上游的佛子岭流域(1813km~2)内划分出的6个上游源头小流域(约60—100km~2)。用雷达估测的降水得到的流量输出作为参考,与1h降水临近预报得到的流量输出进行比较。结果表明:定量降水临近预报准确率是延伸小流域流量预报预见期的关键;基于所研究的个例,定量降水临近可以延长小流域流量预报预见期平均约0.7h左右,但其延长程度还受到具体降水过程、流域属性等的影响。 相似文献
13.
C. E. Coulman 《Boundary-Layer Meteorology》1973,4(1-4):169-177
Measurements of air temperature fluctuations at frequencies from 1–100 Hz have been made with instruments carried by free-flying balloons. Structure functions and spectra of the temperature field have been calculated for various heights within the range 0.1–8 km above ground. The frequent occurrence of shallow regions, possibly layers, which exhibit locally enhanced values of the structure coefficient has been confirmed. 相似文献
14.
The diurnal and semidiurnal tidal wind field variations in the altitudes between 80 and 100 km of the earth’s atmosphere over a mid-latitude station are studied by means of the phases of the zonal and meridional wind measurements made at Atlanta (34oN, 84oW). The rotation of diurnal tidal wind vector is seen to be clockwise at lower heights (80-86 km), swinging between clockwise and unti-clockwise at intermediate heights (88-96 km) and anti-clockwise at higher-heights (96- 100 km). The senses of rotation of diurnal and semidiurnal tidal wind vectors are compared between the stations located in the same and opposite hemispheres. The results are consistent with the tidal theory in the case of Atlanta and Adelaide (35oS, 139oE) whereas in the case of other stations considered in the present study, they showed marked variations. 相似文献
15.
M. A. Novitskii L. K. Kulizhnikova M. K. Matskevich N. F. Mazurin 《Russian Meteorology and Hydrology》2012,37(4):235-239
Presented are the results of measurements of air temperature, wind direction, and relative humidity of the air at the high-altitude meteorological mast in the town of Obninsk. The measurements were carried out in the period of hot weather in July?CAugust 2010 near the Earth??s surface, as well as at the heights of 121 and 301 m. The wind roses and maximum daily temperatures are compared with the similar climatic characteristics obtained for the period of 1970?C2009. It is shown that the period from July 15 to August 18, 2010 was abnormal both in the air temperature characteristics and in the distribution of wind direction at all mentioned heights. 相似文献
16.
Comparison of cloud-top height retrievals from ground-based 35 GHz MMCR and GMS-5 satellite observations at ARM TWP Manus site 总被引：2，自引：0，他引：2
Retrievals of cloud-top heights from the ARM 35 GHz Millimeter Wave Cloud Radar (MMCR) located on Manus Island are compared to those from the GMS-5 satellite as a means to evaluate the accuracy of both MMCR and GMS-5 retrievals, as well as to ascertain their limitations. Comparisons are carried out for retrievals of both single-layer and multilayer clouds as seen by radar, but only for satellite-detected clouds with 100% amount within a 0.3×0.3° domain centered at the ARM site of one cloud type (i.e., low, middle, or high). Mean differences, with 95% confidence limits, between radar- and satellite-retrieved cloud-top heights (i.e., radar-retrieved cloud-top heights−satellite-retrieved cloud-top heights) are 0.3±0.3 km for single-layer clouds and −0.7±0.3 km for multilayer clouds. The study reveals that for thick clouds (i.e., cloud base ≤1 km and cloud thickness ≥10 km), which are representative of convective towers with no/light precipitation as well as thick anvil clouds, retrievals from the MMCR agree well with those from satellite with mean differences of 0.0±0.4 and −0.2±0.3 km for single-layer and multilayer clouds, respectively. For clouds of lesser thickness, mean cloud-top heights derived from satellite are lower than those derived from radar by as much as 2.0 km. It is also shown that for convective clouds with heavy precipitation, MMCR retrievals underestimate the cloud-top heights significantly. 相似文献
17.
激光雷达反演边界层高度方法评估及在北京的应用 总被引：3，自引：0，他引：3
边界层高度是影响大气边界层发展和空气污染程度的重要因子,是环境和气候研究的重要参数。本文利用激光雷达对北京地区2011年5月至2012年4月的边界层高度进行探测分析,采用小波协方差方法反演边界层高度,评估了该方法的适用性。得到基于小波协方差方法自动判断边界层高度的最优参数组合,激光雷达与飞机探测结果对比一致性较好;与探空结果相关系数0.88,激光雷达反演的边界层高度略偏高。当激光雷达的垂直分辨率为30 m时,更加适合北京地区的步长和阈值分别为210 m和0.05;当激光雷达的垂直分辨率为15 m时,步长和阈值分别为135 m和0.05。分析期间,不同季节边界层高度日变化有明显的不同,夏季14:00（北京时）左右达到最高,较高的边界层高度可维持3~4 h,平均可达1.30 km;冬季较高边界层高度只能维持2 h左右,平均为1.08 km。有云与无云天气边界层日变化特征以及边界层高度存在显著的差异,云的存在减少了到达地面的直接辐射,抑制了湍流的发展,进一步抑制了边界层的发展;本文也将激光雷达反演边界层高度结果应用于观测时期边界层高度与地面污染的关系研究中,统计得到边界层高度与PM2.5浓度的相关系数为－0.340。 相似文献
18.
Using a 3D lightning radiation source locating system (LLS), three pairs of associated lightning discharges (two or more adjacent lightning discharges following an arbitrary rule that their space-gap was less than 10 km and their time-gap was less than 800 ms) were observed, and the interaction between associated lightning discharges was analyzed. All these three pairs of associated lightning discharges were found to involve three or more charge regions (the ground was considered as a special charge region). Moreover, at least one charge region involved two lightning discharges per pair of associated lightning discharges. Identified from electric field changes, the subsequent lightning discharges were suppressed by the prior lightning discharges. However, it is possible that the prior lightning discharge provided a remaining discharge channel to facilitate the subsequent lightning discharge. The third case provided evidence of this possibility. Together, the results suggested that, if the charges in the main negative charge region can be consumed using artificial lightning above the main negative charge regions, lightning accidents on the ground could be greatly reduced, on the condition that the height of the main negative charge region and the charge intensity of the lower positive charge region are suitable. 相似文献
19.
The convective charging mechanism of thunderclouds is based on the vertical transport of space charge generated by corona from ground irregularities under the influence of the surface electric field. The present work estimates the amount of charge which is expected to reach cloud base by conduction and convection processes during the lifetime of a thunderstorm. This estimate is made using the numerical model PICASSO, previously designed to characterize the evolution of this corona space charge between ground level and cloud base. Experimentally determined values of surface electric field are introduced into the model in order to initiate the computation. These values are based on six events documented during four different field experiments carried out in Florida and in France. As an upper limit, the convective transport is uniformly applied as a linearly increasing vertical air speed profile and competes with the conductive transport. The fraction of the positive charge generated at the surface by corona which finally reaches the upper limit of the layer varies between 26 and 86%, essentially depending on the electric field evolution at altitude. Assuming that the vertical transport conditions remain the same over an area of 10 km×10 km, the overall charge amount can be roughly estimated. It ranges between about 63 and over 300 C. Because the present assumptions probably lead to an overestimate of these amounts, such a range suggests that the convective charging mechanism is unlikely to be able to account for the major electrification process of the thundercloud. However, it could be considered as a relevant mechanism contributing to the lower positive charge center of the thundercloud, often observed close to cloud base. 相似文献
20.
This study conducted meteorological simulations in northern Colombia by analyzing different planetary boundary layer (PBL) schemes available in the numerical Weather Research and Forecasting (WRF) model. The study area included three nested domains with horizontal resolutions of 18 km, 6 km, and 2 km, with 38 vertical levels. The evolution and structure of the PBL were analyzed during the driest months (March, April, and May 2016) and in regions with the highest particulate matter concentrations. Sensitivity analysis of the WRF model was performed with two local and two non-local PBL schemes. The results were validated using observations of the surface air temperature, relative humidity, and surface wind speed collected from three meteorological stations in the area. The PBL heights were experimentally determined using radiosonde data provided by a station located in the center of the study area. Variations in PBL heights were estimated using linear regression methods and minimization of statistical errors for the bulk Richardson number, as well as analysis of vertical temperature and wind profiles. The WRF model reliably reproduced the daily values and diurnal cycles of temperature, relative humidity, and wind speed within the PBL and accounted for the influence of topography and sea breezes. Horizontal heat advection dominates the upwelling of air masses when sea breezes are active. The onshore wind direction starts to change from east to northwest, implying a decay in the land breeze regime. All schemes overestimate the mixing height and tend to underestimate surface air temperature values at night. All show wetter conditions and underestimate wind speed. Although the non-local Yonsei University (YSU) scheme shows the best performance, it also shows the largest sources of errors when determining the behavior of the surface layer during stable conditions. Relative humidity and wind speed estimates provided by the local Mellor‐Yamada‐Nakanishi‐Niino (MYNN) scheme were closer to those recorded at the meteorological stations. 相似文献