用红外和水汽两个通道的卫星测值指定云迹风的高度   总被引：24，自引：8，他引：24  

许健民  张其松  方翔 《气象学报》1997,55(4):408-417

提出了一种改进的用红外和水汽两个通道的测值指定云迹风高度的算法。利用红外水汽散点图和云迹风本身自动地将有低云的目标区、有半透明卷云的目标区、有密蔽高云的目标区分开。在有低云的目标区和有密蔽高云的目标区用红外一个通道指定云高。在有半透明卷云的目标区用红外和水汽两个通道指定云高。在用两个通道的测值指定云高时，假定卷云高度以上不存在水汽，以红外和水汽两个通道亮温相同这个方程与两个通道辐射测值线性相关的方程联立解出云的高度  相似文献   

Ionospheric corrections of MARSIS subsurface sounding signals with filters including collision frequency     

Zhenfei Zhang  Erling Nielsen  Roberto Orosei 《Planetary and Space Science》2009,57(3):393-403

Ionospheric corrections of Mars advanced radar for subsurface and ionosphere sounding (MARSIS) subsurface sounding signals are necessary before they can be further analyzed. Usually the ionosphere correction only considers the phase dispersion owing to the electron densities. In this paper we show that if the electron-neutral collision frequency is included in the correction filter, the signal-to-noise ratio of the processed signal can be further maximized and the spatial resolution of the signal be improved. Three different models of the ionosphere profile have been studied, and it is shown that a uniform slab model, of both densities and collisions, is feasible and probably the best choice when implementing the correction filter including collisions. The physical significance of the parameters obtained with the uniform model (equivalent parameters) is discussed, and it is shown that they are useful for the estimation of the real physical parameters of the ionosphere. We developed a recursive, random search algorithm to facilitate the realization of the correction process with the filter including collision frequency.  相似文献   

基于PS-VF-TBD的地波雷达船只目标航迹起始方法     

高昆鹏  纪永刚  王祎鸣  孟俊敏 《海洋科学》2022,46(4):13-24

针对地波雷达低信噪比目标信号"闪烁"导致的航迹起始困难问题,本文提出了一种基于PS-VF-TBD的航迹起始方法.该方法综合利用了地波雷达回波谱中目标信号的展宽特征和运动特性,利用PS-VF-TBD方法对运动目标能量有效积累的特点,提高对疑似目标多帧信号间的关联概率,进而提高对真实目标的搜索概率和航迹起始成功率.通过地波...  相似文献   

A comparison of the midlevel kinematic characteristics of a pair of supercell thunderstorms observed by airborne Doppler radar   总被引：1，自引：0，他引：1  

Paul M. Markowski   《Atmospheric Research》2008,88(3-4):314-322

The midlevel kinematic characteristics of two supercell thunderstorms observed during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX), one tornadic and the other nontornadic, are compared using airborne pseudo-dual-Doppler wind retrievals. The most significant difference between the two cases was that a midlevel rear-inflow jet was observed in the nontornadic supercell (12 May 1995), whereas such rear-to-front, storm-relative flow was absent at midlevels in the tornadic supercell (16 May 1995). The midlevel jet in the nontornadic supercell was located on the north flank of a prominent region of anticyclonic vertical vorticity. Some speculations are provided pertaining to the possible importance of the midlevel kinematic differences between the two storms.  相似文献   

An economical optical cloud/fog detector     

Jacqueline H. Carrillo  Scott E. Emert  D. Eli Sherman  Pierre Herckes  Jeffrey L. Collett Jr.   《Atmospheric Research》2008,87(3-4):259

A new, relatively low cost instrument has been developed to detect the presence of fog or cloud for fog/cloud sampling applications. The instrument uses attenuation of an 880 nm light emitting diode signal to detect cloud/fog drops in the optical path between a sending and receiving arm. Laboratory and field testing under a variety of conditions and fog types were carried out to determine the ability of the optical fog detector (OFD) to accurately detect cloud/fog presence as well as to provide some measure of liquid water content. Results indicated that the OFD provided a reliable estimate of fog presence as well as a reasonable estimate of liquid water content (LWC) under several different conditions. The OFD does appear to have an interference from rain, resulting in an overestimation of LWC during rainfall. This may occasionally give a false positive indication of fog presence.  相似文献   

X波段双线偏振雷达不同衰减订正方法对比及其对降水估测影响研究   总被引：6，自引：1，他引：5  

胡志群  刘黎平  楚荣忠  金荣花 《气象学报》2008,66(2):251-261

文中分析了X波段双线偏振雷达衰减订正各种方法的特点,考虑到差传播相移率(KDP)作为衰减订正的一种有效途径,以及由于KDP值较小,数据质量不稳定,往往导致订正误差较大,因此提出了同时利用水平反射率因子ZH与KDP进行衰减订正的ZH-KDP综合法.基于同样的考虑,在随后利用ZH、KDP进行降水估测时,提出了ZH-KDP-R综合估测方法.利用中国科学院寒区旱区环境与工程研究所和成都锦江电子系统工程有限公司,在研制3.2 cm波长同时收发式多普勒偏振天气雷达过程中,2005年8月在平凉外场试验取得的一批观测资料,对提出的衰减订正综合法及降水估测综合法的效果进行了分析检验,结果表明,ZH-KDP综合法对ZH、ZDR有稳定的订正效果,并且订正速度快,能够达到实时运行的要求.2005年8月11日15:08:03-22:05:46,间隔5-12 min不等,雷达开机取得了连续的观测资料,通过对这次降水过程的对比分析表明,ZH-KDP-R综合估测法比单因子KDP-R法、Z-R关系法,适用估测的降水强度变化范围广,与自动雨量记的观测结果较为吻合.Z-R关系法中,利用订正后的ZH值,比利用订正前的ZH值,降水估测值与雨量记实测值的误差明显减小,说明衰减订正后的雷达数据质量有明显的改善.  相似文献   

Application of Radar Reflectivity Factor in Initializing Cloud-Resolving Mesoscale Model. Part Ⅰ: Retrieval of Microphysical Elements and Vertical Velocity          下载免费PDF全文

LIU Hongya  XU Haiming  HU Zhijin  XUE Jishan  SHEN Tongli 《Acta Meteorologica Sinica》2008,22(2)

Assuming that cloud reaches static state in the warm microphysical processes, water vapor mixing ratio(qv), cloud water mixing ratio (qc), and vertical velocity (w) can be calculated from rain water mixing ratio (qr)- Through relation of Z-qr, qr can be retrieved by radar reflectivity factor (Z). Retrieval results indicate that the distributions of mixing ratios of vapor, cloud, rain, and vertical velocity are consistent with radar images, and the three-dimensional spatial structure of the convective cloud is presented. Treating q,v saturated at the echo area, the retrieved qr is about 0.1 g kg-1, qc is always less than 0.3 g kg-1, w is usually below 0.5 m s-1, and rain droplet terminal velocity (vr) is around 5.0 m s-1 in the place where radar reflectivity factor is about 25 dBz; in the place where echo is 45 dBz, the retrieved qr and qc are always about 3.0 g kg-1, w is greater than 5.0 m s-1, and vr is around 7.0 m s-1. In the vertical, the maximum updraft velocity is greater than 3.0 m s-1 at the height of around 5.0 kin, the maximum cloud water content is about 3.0 g kg-1 above 5 km and the maximum rain water content is about 3.0 g kg-1 below 6 kin. Due to the assumption that the cloud is in static state, there will be some errors in the retrieved variables within the clouds which axe rapidly growing or dying-out, and in such cases, more sophisticated radar data control technique will help to improve the retrieval results.  相似文献   

Cloud radiative forcing of subtropical low level clouds in global models     

Johannes Karlsson  Gunilla Svensson  Henning Rodhe 《Climate Dynamics》2008,30(7-8):779-788

Simulations of subtropical marine low clouds and their radiative properties by nine coupled ocean-atmosphere climate models participating in the fourth assesment report (AR4) of the intergovernmental panel on climate change (IPCC) are analyzed. Satellite observations of cloudiness and radiative fluxes at the top of the atmosphere (TOA) are utilized for comparison. The analysis is confined to the marine subtropics in an attempt to isolate low cloudiness from tropical convective systems. All analyzed models have a negative bias in the low cloud fraction (model mean bias of −15%). On the other hand, the models show an excess of cloud radiative cooling in the region (model mean excess of 13 W m⁻²). The latter bias is shown to mainly originate from too much shortwave reflection by the models clouds rather than biases in the clear-sky fluxes. These results confirm earlier studies, thus no major progress in simulating the marine subtropical clouds is noted. As a consequence of the combination of these two biases, this study suggests that all investigated models are likely to overestimate the radiative response to changes in low level subtropical cloudiness.  相似文献   

甘肃河西走廊两次强对流天气对比分析   总被引：1，自引：0，他引：1  

王伏村  李耀辉  牛金龙  张得玉 《气象》2008,34(1):48-53

使用地面高空观测资料、NCEP 1°×1°6小时再分析数据和张掖CINRAD/CC雷达观测数据,对2006年7月7日、8月10日发生在甘肃河西走廊中部的两次强对流天气的环流形势、大气稳定度、相对风暴螺旋度(SRH)、天气雷达回波特征进行了对比分析.分析结果表明:产生这两次强对流天气环流形势不同.7月7日飑线对流系统产生于北部沙漠戈壁由北向南移动,右移飑线前部结构为气旋式旋转;8月10日对流系统产生于青藏高原由南向北移动,来自高原上的暖湿气流水汽充足,不稳定层比7月7日深厚,产生冰雹的左移超级单体结构为反气旋式旋转.7月7日右移飑线相对风暴螺旋度降雹前为正值,降雹开始后转为负值;8月10日左移反气旋超级单体相对风暴螺旋度在发展期为负值,降雹开始后跃增到60m2·s-2以上.  相似文献   

多普勒雷达速度场特征在人工增雨作业中的判据指标应用   总被引：7，自引：0，他引：7  

李红斌  何玉科  姚展予  赵繁盛  张家伟 《气象》2008,34(6):102-106

对大连市2003年6月至2005年10月43次降水天气过程的多普勒雷达速度场资料进行了统计和分析,给出了几种常见的雷达回波零速度线特征分别呈"S"型、"弓"型和速度不对称型等分布特征时对人工增雨作业潜力分析和作业条件判别的几个判据指标,作为增雨作业决策的辅助判别指标.  相似文献