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981.
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
982.
983.
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
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
984.
A three-dimensional variational method is proposed to simultaneously retrieve the 3-D atmospheric temperature and moisture profiles from satellite radiance measurements. To include both vertical structure and the horizontal patterns of the atmospheric temperature and moisture, an EOF technique is used to decompose the temperature and moisture field in a 3-D space. A number of numerical simulations are conducted and they demonstrate that the 3-D method is less sensitive to the observation errors compared to the 1-D method. When the observation error is more than 2.0 K, to get the best results, the truncation number for the EOF's expansion have to be restricted to 2 in the 1-D method, while it can be set as large as 40 in a 3-D method. This results in the truncation error being reduced and the retrieval accuracy being improved in the 3-D method. Compared to the 1-D method, the rms errors of the 3-D method are reduced by 48% and 36% for the temperature and moisture retrievals, respectively. Using the real satellite measured brightness temperatures at 0557 UTC 31 July 2002, the temperature and moisture profiles are retrieved over a region (20°-45°N, 100°- 125°E) and compared with 37 collocated radiosonde observations. The results show that the retrieval accuracy with a 3-D method is significantly higher than those with the 1-D method. 相似文献
985.
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
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
986.
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
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
987.
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
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
988.
989.
用FY-2C/D卫星等综合观测资料反演云物理特性产品及检验 总被引:10,自引:0,他引:10
云的宏微观物理特性参数无论对天气、气候还是人工影响天气的研究和业务都有十分重要的应用价值.基于FY-2C/D静止卫星遥感观测,融合高空和地面等其它观测资料,研发了近10种云宏微观物理特性参数的反演技术方法,并实现业务化运行.简单介绍反演得到的云顶高度、云顶温度、云过冷层厚度、云暖层厚度、云底高度、云体厚度、云光学厚度、云粒子有效半径和云液水路径等近10种云宏微观物理参数产品的物理意义、反演技术方法和业务流程等;对主要云参数产品,利用最新获得的Cioudsat云卫星实测结果进行了对比检验和可用性分析;将反演产品同MODIS反演的同类产品进行对比分析,发现两者具有较好的一致性. 相似文献
990.