Contribution of the MODIS instrument to observations of deep convective storms and stratospheric moisture detection in GOES and MSG imagery   总被引：1，自引：0，他引：1  

Martin Setvk  Robert M. Rabin  Pao K. Wang 《Atmospheric Research》2007,83(2-4):505-518

Past studies based on the NOAA/AVHRR and GOES I-M imager instruments have documented the link between certain storm top features referred to as the “cold-U/V” shape in the 10–12 μm IR band imagery and plumes of increased 3.7/3.9 μm band reflectivity. Later, similar features in the 3.7/3.9 μm band have been documented in the AVHRR/3 1.6 μm band imagery.The present work focuses on storm top observations utilizing the MODIS data. The MODIS instrument (available onboard NASA's EOS Terra and Aqua satellites) provides image data with significantly better geometrical resolution (in some of its bands) and broader range of spectral bands as compared to that from AVHRR/3 observations. One of the goals of this study is to evaluate the contribution of this new instrument to observations of convective storm tops. Besides the cloud top features linked to storm top microphysics and morphology, the paper also addresses the possibility of detection of lower stratospheric water vapor above cold convective storm tops. This issue is explored utilizing MODIS as well as GOES and MSG imagery.In addition, the paper discusses an alternative interpretation of the “cold-U/V” patterns at the top of intense storms by a mechanism of “plume masking” as suggested by some of the observations.  相似文献   

Pilot project for intensive surveillance of hail events in Terres de Ponent (Lleida)     

M. Aran  A. Sairouni  J. Bech  J. Toda  T. Rigo  J. Cunillera  J. Mor 《Atmospheric Research》2007,83(2-4):315-335

Hail is one of the most fearsome meteorological phenomena for agricultural areas. The harvest of the whole year can be destroyed in only a few minutes. A pilot project to characterise hail events and identify hail with the help of radar observations is described in this paper. This pilot project was carried out in Terres de Ponent, an area of about 200,000 ha in Lleida (Catalonia), in the NE of the Iberian Peninsula.The aim of the project was to characterise hail events, directly by radiosounding data and radar images, and indirectly by the evaluation of the radiosonde forecasted by the Numerical Weather Prediction (NWP) Mesoscale Atmospheric Simulation System (MASS) and several instability indices. In the first stage of the project several instability indices were calculated during the 5 months of the campaign and a comparison of these indices with those obtained with radiosounding data from Barcelona and Zaragoza was performed. An operative image of the probability of hail distribution in Catalonia (every 6 min, hourly and daily) was also made using the Waldvogel method for its detection. As a starting point, an empirical fit of POH (probability of hail) obtained recently in the Netherlands (POH = 0.319 + 0.133·ΔH, where ΔH is the difference between the 45 dBZ echo top height from radar image and the isozero forecast). Complementary to this, to detect the hail at the beginning of spring, the process was repeated with the 35 dBZ echo top.In a second stage of the project, the calculated POH was compared with the hail events measured by 171 hailpads of the observational network of the Agrupació de Defensa Vegetal (ADV) of Terres de Ponent and a new fit of the POH formula was obtained. It was also the aim of this second stage to validate the forecasted radiosoundings by the NWP MASS model in Lleida and Barcelona. Finally, a comparison between the radiosounding data from Barcelona, Lleida and Zaragoza was made to verify which radiosounding (Barcelona or Zaragoza) is more representative of the Lleida area.  相似文献   

新一代天气雷达中气旋产品特征值统计和个例分析   总被引：3，自引：1，他引：3  

方翀  郑媛媛 《气象》2007,33(11):16-20

利用合肥新一代天气雷达从2001年至2005年的中气旋产品,对中气旋产生的时间、空间和各种特征值进行相关统计分析,发现持续时间在3个体扫以上的中气旋与雷雨大风和龙卷有很好的对应关系,通过对典型强风过程分析,得出了底高、顶高和最强切变高度变化、最强切变与灾害性天气发生的对应关系,为预报员及时准确预报雷雨大风、龙卷提供参考依据。  相似文献   

防雹作业效果的多单体对比分析          下载免费PDF全文

罗保华聂德兴  温仁枚曾财兴 《气象科技》2007,35(B12):82-85,92

防雹效果检验问题仍然是人影工作的技术难题。针对2006年4月12日龙岩市长汀防雹作业过程，利用实施防雹作业的一个单体作业前后回波特征变化和同时出现的两个未作业单体自然发展情况进行对比分析，认为实施火箭防雹作业后效果明显，强回波中心逐渐减弱、回波面积加大并未出现冰雹，有效地保护了下游区域免遭冰雹袭击。  相似文献   

“碧利斯”的中尺度雨团和雷达回波分析     

周文志孙莹  唐熠廖慕科  蒋丽娟 《广西气象》2007,28(2):15-18,30

对“碧利斯”雷达回波分析表明：雷达回波受着三个阶段不同天气尺度的影响。第一阶段是台风低压强偏北气流的作用，强中尺度雨团出现在强风的左侧；第二阶段是台风辐合线与西南急流的共同作用，强中尺度雨团出现在西南急流左侧辐合线辐合最强的地方；第三阶段是台风低压过境时北侧强旋转风的作用，强中尺度雨团出现在东南急流与东北急流间气旋性曲率最大的地方。三个阶段的回波性质不尽相同，降水性质也差别很大。对这三个阶段主要的雷达资料进行分析研究，总结出一些规律性结论，有益于今后在雷达回波监测网中熟练掌握不同天气尺度的雷达回波中中尺度雨团的发生发展，使其在短时临近预报、联防预警信息及预警信号的发布中起到重要作用。  相似文献   

一次强飑线雷达回波和云图特征     

陈恒明 《广西气象》2007,28(2):23-26

通过分析050322强飑线过程的天气背景，卫星云图和雷达回波变化特征，进一步验证了珠江三角洲锋前暖区强对流带状回波的一种模式[1]。初步得出：飑线回波带初生阶段，母体回波中的40-55dBz强度廓线层水平尺度扩大明显，而且移向母体回波前边缘速度非常快。发展和成熟期强度廓线梯度大，弧形结构明显，40-55dBz强度廓线层顶部高，结构成柱状而且前进边缘比较整齐等特征。  相似文献   

天然气水合物稳定带顶界面确定研究进展     

黄国成  庄新国  吕万军  郭依群  王宏斌 《地质科技情报》2007,26(4):57-62

天然气水合物稳定带的顶、底界面在空间上限制了天然气水合物在自然界中的实际分布,同时也是进行天然气水合物资源评价的基础,对了解其成矿规律、指导勘探开发具有重要意义.确定天然气水合物稳定带顶界面的方法主要有3种:①利用理论模型模拟的方法;②利用地球化学异常的方法;③利用地球物理资料的方法,其中第一种方法比较粗略,后两种方法比较精确,但在数据处理上的难度较大.  相似文献   

合成孔径高度计的海面回波仿真   总被引：1，自引：0，他引：1  

杨双宝  刘和光  许可  王志森 《遥感学报》2007,11(4):446-451

本文首先采用经验海浪谱仿真了三维海面,进而在此基础上根据镜面反射理论计算了海面小面元散射系数。然后根据雷达方程和合成孔径高度计的合成孔径处理计算了海面回波信号的矩阵,以便给出最终的功率回波。在目前国内外缺少相应试验数据的条件下,验证了合成孔径高度计工作方式的有效性,经验证其回波模型基本正确。同时,为了与传统高度计比较,给出了传统高度计在相同参数下的回波仿真结果。文章还通过展示合成孔径高度计在同种波高、不同涌浪和风浪方向情况下的回波,说明波浪方向也会影响合成孔径高度计回波。  相似文献   

Radio‐echo layering in West Antarctica: a spreadsheet dataset     

Martin J. Siegert  Magdeline Pokar  Julian A. Dowdeswell  Toby Benham 《地球表面变化过程与地形》2005,30(12):1583-1591

Of the various information recovered from radio‐echo sounding (RES) of polar ice sheets, internal layering is currently under‐utilized by glaciologists, due in part to a lack of available data. Here, RES layering of the West Antarctic Ice Sheet, from the 1970s RES survey of approximately 70 per cent of this ice mass, is made available in a series of spreadsheets. Three types of internal layers are evident in the dataset. The first is continuous layers that have a stratigraphic appearance and can often be traced easily for hundreds of kilometres. The second is buckled layering, which also resembles stratigraphy and can sometimes be traced over tens of kilometres (although layer identification can often be difficult). The roughness of these layers is often greater than the bed at the same wavelength. The third is highly distorted or absent layering, which is not possible to trace laterally. Despite debate concerning the origin of RES layers, they are thought by most glaciologists to represent isochronous surfaces. The pattern of internal layering is potentially of importance to glaciologists for three reasons. (1) The position of undeformed layers below the ice surface is a function of accumulation rate, ice flow and basal melting conditions. Numerical modelling (including new ‘data assimilation’ techniques) could be used to discriminate between these processes, so revealing important information about the ice sheet and its environment. (2) Buckled layers are deformed by ice flow process, and so their occurrence can be related to the flow dynamics of the ice sheet. (3) Very buckled layers are often associated with ice stream flow, which allows their location to mark the positions of past and present fast‐flowing ice. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Zircon U-Pb Ages of Bottom and Top Parts of the Zhangjiakou Formation in Lingyuan Area （West Liaoning Province） and Luanping Area （North Hebei Province） and Their Significance     

ZhangHong LiuXiaoming ZhangYeqing YuanHonglin HuZhaochu DiwuChunrong 《中国地质大学学报(英文版)》2005,16(2):115-129

Thecharacteristicsofthetectonics,stratigraphy, paleontologyandvolcanicpetrologyoftheMesozoicin NorthHebeiandWestLiaoningaresimilarinmanyas pects,butthetworegionsalsohavesomeobvious differences.Thetworegionshavebeen“hotspots”inthegeologicalworldforafewy…  相似文献