Wetland hydroperiod classification in the western prairies using multitemporal synthetic aperture radar

Wetlands represent one of the world's most biodiverse and threatened ecosystem types and were diminished globally by about two‐thirds in the 20th century. There is continuing decline in wetland quantity and function due to infilling and other human activities. In addition, with climate change, warmer temperatures and changes in precipitation and evapotranspiration are reducing wetland surface and groundwater supplies, further altering wetland hydrology and vegetation. There is a need to automate inventory and monitoring of wetlands, and as a study system, we investigated the Shepard Slough wetlands complex, which includes numerous wetlands in urban, suburban, and agricultural zones in the prairie pothole region of southern Alberta, Canada. Here, wetlands are generally confined to depressions in the undulating terrain, challenging wetlands inventory and monitoring. This study applied threshold and frequency analysis routines for high‐resolution, single‐polarization (HH) RADARSAT‐2, synthetic aperture radar mapping. This enabled a growing season surface water extent hyroperiod‐based wetland classification, which can support water and wetland resource monitoring. This 3‐year study demonstrated synthetic aperture radar‐derived multitemporal open‐water masks provided an effective index of wetland permanence class, with overall accuracies of 89% to 95% compared with optical validation data, and RMSE between 0.2 and 0.7 m between model and field validation data. This allowed for characterizing the distribution and dynamics of 4 marsh wetlands hydroperiod classes, temporary, seasonal, semipermanent, and permanent, and mapping of the sequential vegetation bands that included emergent, obligate wetland, facultative wetland, and upland plant communities. Hydroperiod variation and surface water extent were found to be influenced by short‐term rainfall events in both wet and dry years. Seasonal hydroperiods in wetlands were particularly variable if there was a decrease in the temporary or semipermanent hydroperiod classes. In years with extreme rain events, the temporary wetlands especially increased relative to longer lasting wetlands (84% in 2015 with significant rainfall events, compared with 42% otherwise).     

天气雷达数据处理系统人控应用软件

天气雷达用于抗灾和减灾很重要,本文提出一种人工降雨和驱冰雹软件,给出了程序流图,对编程的关键进行了分析,最后结果表明它能提高人控作业效率。     

Enhancing understanding of breakdown and collapse in the Yorkshire Dales using ground penetrating radar on cave sediments

Historical evidence shows block breakdown and collapse are actively occurring in large fault aligned caverns in the Yorkshire Dales karst. Deployment of ground penetrating radar at two such sites has provided detailed images of the sedimentary sequences below the present day cavern floor but no large blocks are imaged within the sediments. Solutional processes must be removing limestone from the sediment to allow continued cavern growth. Possible mechanisms to account for the lack of large blocks within the sediment fill are discussed.     

GPS卫星反射信号增强技术研究

本文根据GPS卫星反射信号在海洋参数测量、无源雷达目标探测以及大地测绘中的应用,从天线接收、信号处理运算和多路径信号抵消角度,详细地研究了GPS卫星反射信号增强技术,给出了相应天线和电路结构及信号处理方法,并进行了计算机仿真,结果表明所提出的技术能增强GPS卫星反射信号。     

基于雷达海冰图像互相关的冰漂流场测量

我国的渤海和黄海北部在每年冬季都出现不同程度的冰情,它直接影响结冰海区的石油平台、船舶以及港口等设施的正常作业,对海冰的观测与预报随着上述海区的开发利用越发显得重要,利用航海雷达连续准确地跟踪海冰漂移运动轨迹,是当今观测、调查、研究冰漂流移动规律的有效方法之一,我国的科研人员利用雷达成像技术对渤海的冰情进行了长期的雷达海冰观测、研究,在由雷达海冰图像对海冰的物理特征的识别、分类以及冰漂流场测量方面取得了一些进展[1-4]。     

东海区近海强风预报模式

本文探讨东海区近海强风预报模式，首先介绍建立预报模式的思路和步骤，及使用说明，为了验证强风预报模式和判别条件，用１９８６、１９８７上日本传真天气图进行试报，准确和基本准确度为９１．１％，并给出了１９８９、１９９５年随船试验预报结果，准确和基本准确率为９０％以上。     

机载雷达高度计对海况及海面风速的测量研究

运用我国自行研制的ＺＨＧ－１型Ｘ波段机载雷达高度计于１９９５年４月１３日－４月１８日在青岛附近海域进行的海上飞行实验数据，及导出的均方根波高、有效波高、均方根波陡算法模型，得到了上述海况参数值。     

0421号热带风暴"海马"登陆前后环境场对其移向和强度影响的分析

0421号热带风暴“海马(Haima)”于2004年9月13日12:00在浙江省温州市沿海登陆,登陆后迅速减弱为热带低压,20:00在浙江境内消失.本研究采用物理量诊断分析法,探讨该热带风暴登陆前后涡度场、湿焓场变化对其移向和强度的影响.结果表明,该热带风暴登陆后,涡度(ξ)明显减弱.涡度局地变化(ξ/t)值分布显示,风暴移动方向的后方,涡度减弱的趋势比前方涡度增大的趋势更剧烈;风暴有向其外围(ξ/t)正值中心(即涡度增幅最大)移动的趋势.该热带风暴登陆前、后,湿焓都增大,但登陆后湿焓增大趋势已大大减弱;风暴有向湿焓局地变化(E/t)正值中心移动的趋势,即向能量增强最大的方向移动.     

A climatology of mesoscale model simulated low-level wind jets over Cook Inlet and Shelikof Strait, Alaska

Weather in the North Gulf of Alaska is characterized by a high frequency of deep synoptic-scale low-pressure systems, especially during the cold season. The strong pressure gradients of these storms interact with the extremely rugged terrain of the coastal mountains to produce a variety of channeled flows. These surface wind regimes are not well documented in the scientific community, due to the paucity of observations. Modeling of these phenomena in regions of complex terrain is of great interest to those working with hydrodynamic, wave, and pollutant transport models in coastal and shelf areas. Such models, when coupled with ocean and coastal-ecology counterparts, give a broad view of the role surface winds play in shaping local coastal marine ecosystem in this region. This paper presents a climatology of simulated low-level wind jets over the domain of Cook Inlet and Shelikof Strait along Alaska's south-central coast. Daily simulations using the RAMS model were conducted in a 36-h forecast mode for the cold-season period 10/1/03 to 3/31/04. Systematic analysis of the resulting simulated low-level wind field makes it possible to characterize these jets and gap flows in spatial and temporal detail. The comparison between the RAMS winds and the Synthetic Aperture Radar (SAR)-derived winds when available verifies the existence of these wind jets and the capability of the model to simulate these cases. Clearly, the results of a study in this region depend on the fidelity of the model at these scales (O[5 km]). The SAR comparisons attempt to help establish this. From the 6 months of simulations over Cook Inlet and Shelikof Strait, the low-level wind jets are classified into 10 different regimes by location and orientation. These regimes are categorized into four more general groups: cross-channel westerly, easterly, and up and down Inlet flows. The nature of a particular regime is largely a function of pressure gradient orientation and local topography. Jets in the same group have a similar occurrence distribution with time. Some form of jet occurred in the study region almost daily each month of the period, with December 2003 having the highest frequency of wind jets.