A New Retracking Technique for Brown Peaky Altimetric Waveforms     

Fukai Peng 《Marine Geodesy》2018,41(2):99-125

A new Brown-Peaky (BP) retracker has been developed for peaky waveforms that usually appear within ～10 km to the coastline. The main feature of the BP is that it fits peaky waveforms using the Brown model without introducing a peak function. The retracking strategy first detects the peak location and width of a waveform using an adaptive peak detection method, and then estimates retracking parameters using a weighted least squares (WLS) estimator. The WLS assigns a downsized weight to corrupted waveform gates, but an equal weight to other normal waveform gates. The BP retracker has been applied to 4-year Jason-1 waveform (2002–2006) in two Australian coastal zones. The results retracked by BP, MLE4 and ALES retrackers have been validated against tide-gauge observations located at Burnie, Lorne and Broome. The comparison results show that three retrackers have similar performance over open oceans with the correlation coefficient (～0.7) and RMSE (～13 cm) between altimetric and tide-gauge sea levels for distance >7 km offshore. The main improvement of BP retracker occurs for distance ≤7 km to the coastline, where validation results indicate that data retracked by BP are more accurate (15–21 cm) than those by ALES (16–24 cm) and MLE4 (19–37 cm).  相似文献   

Stokes漂流对全球海表面温度模拟的影响     

肖林  史剑  蒋国荣  刘子龙  张成成 《海洋通报》2018,(1):55-87

Stokes漂流对海洋上混合层中的流场和温度场结构具有不可忽视的作用。本文基于WAVEWATCHⅢ海浪模式模拟的海浪要素计算得到Stokes漂流,将其引入SBPOM模式的动量方程中,从体积输运的角度研究Stokes漂流对全球海表面温度的影响。分析发现Stokes漂流与Stokes输运在全球呈现高纬度强于中低纬度的带状分布特征,且这种流动与输运对全球海表面温度具有降温作用,该降温作用的分布与全球Stokes输运强度相对应,高纬降温作用大于中低纬度,特别是南极绕极流海域平均降温明显大于其余海域,最大降温可达1.5℃,且全球月平均降温超过0.1℃。  相似文献   

低轨道人造卫星(CHAMP、GRACE、GOCE)与高精度地球重力场——卫星重力大地测量的最新发展及其对地球科学的重大影响   总被引：33，自引：26，他引：7  

孙文科 《大地测量与地球动力学》2002,22(1):92-100

评述了卫星重力大地测量的最新发展及其对地球科学的重大影响。为了更好地理解地球内部物理构造与海洋动力学，以及大陆，冰川和海洋的相互作用，改善现有地球重力场模型（包括精度和空间解析度）是非常重要的。IUGG等国际组织对此已经强调了很多年。最近，由德国的GFZ（GeoForschungsZentrum)，美国的NASA（National Aeronautics and Space Adminitration)以及欧洲宇航局ESA（European Space Agency)开发研制了最先进的地球监测技术－SST（Satellite-to-Sateilite Tracking)。其主要特点是利用现有的GPS连续追踪新发射低轨道卫星，并由低轨道卫星对地球重力场作精密观测。已经发射和即将发射的卫星有3颗：GHAMP（Challenging Mini-Satellite Payload for Geophysical Research an Application)已经于2000年发射；GRACE（Gravity Recovery and Climate Experimert)定于2002年发射；GOCE（Gravity Field and Steady-state Ocean Cirulation Explorer)计划2004年发射，它们可以统称为重力卫星。载有SST技术的人造卫星的主要目的是获得具有前所未有的高精度和高空间解析度的全球重力场和大地水准面模型，加强人们对地球内部构造的理解并为海洋和气象研究提供更好地参考。上述3个重力卫星工作在有明显区别的不同波谱内，它们有不同的科学应用，仅有一小部分重合。所以，就应用而言它们是完全互补的。它们在地球科学中的应用将是广泛的，特别对于固体地球物理学，海洋学以及大地测量学等领域，它们将会带来革命性的变化，其意义不亚于GPS。  相似文献   

对地方电视台转播CCTV时延的测定     

任燕  梁双有 《时间频率学报》1997,(1)

讲述了同步广播卫星电视时间信号的测量方法和测量结果，获得了CCTV1、CCTV2通过同一颗卫星（亚太－1A）转播的时延差值为16333μs，测量精度在10ns以内；CCTV2、CCTV4分别经两颗卫星（亚太－1A、亚洲－Ⅱ）转播，在陕西天文台卫星地面接收站时延差值为1644．20μs，精度为50μs，并分析了影响时延差值和精度的原因。同时测量了地方电视台转播亚太－1A的CCTV信号与直接接收亚太－1A的CCTV信号的时延差值，其测量精度为0．1μs。这些结果为利用同步广播卫星的电视信号进行高精度的时间服务提供了参考依据。  相似文献   

Flexure of Europa's lithosphere due to ridge-loading     

T.A. Hurford  R.A. Beyer  B. Schmidt  B. Preblich  A.R. Sarid  R. Greenberg 《Icarus》2005,177(2):380-396

Using photoclinometry, topographic profiles across europan ridges have been produced. These profiles allow the identification of bulges in the terrain adjacent to the ridges. The bulges are assumed to have been produced by flexure of the elastic lithosphere due to the load of the ridges, which lie along cracks in the crust. The distance from the crack to these “fore-bulges” depends on the thickness of the elastic plate being flexed. Based on a survey of ridges in Galileo images with resolution <300 m/pixel, the thickness of the elastic lithosphere has been determined by this method at a wide variety of sites along the leading and trailing hemispheres of Europa. The average thickness is about 200 m. The elastic lithosphere underneath smooth dilational bands tends to be thicker than plains morphology, an effect that is pronounced at Thynia Linea and Astypalaea Linea. Among the ridges investigated here, more recent loading correlates with a thicker elastic lithosphere, which may either reflect an intrinsically thicker layer, or less viscous relaxation over the shorter time period.  相似文献   

卫星激光测距的新进展   总被引：6，自引：0，他引：6  

张忠萍  杨福民 《天文学进展》2001,19(2):283-288

扼要综述了近几年国际上卫星激光测距的进展，介绍了国内激光测距网的现状，展望了未来卫星激光测距的发展。  相似文献   

Analysis of mapping coverage obtained from spacecraft     

Anastassios E. Petropoulos  James M. Longuski 《Celestial Mechanics and Dynamical Astronomy》1994,60(4):431-454

An exact analysis of the coverage obtained by spacecraft using cross-track scanning and nadir-centered conical imaging, under imposed viewing obliqueness and resolution requirements, is presented. In addition to exact expressions for the area acquired and the area acquisition rate, envelope theory is introduced to obtain the boundary of the imaged area. These expressions are relatively compact, allowing rapid machine computation. The effects of the sun phase angle, and of imaging system limitations are also examined. The Galileo mission encounter with Callisto is used as a numerical example, from which certain general conclusions are drawn regarding optimal imaging trajectories.  相似文献   

The spectral variability of Triton from 1997-2000     

Michael D Hicks  Bonnie J Buratti 《Icarus》2004,171(1):210-218

We present the results of a three-year observational program of long-slit spectroscopy and UBVRI photometry of Triton. We find evidence for short-lived albedo variations at wavelengths less than 0.5 μm with the most notable reddening event measured in October 1997 and “normal” colors returning by May 1998. We report a possible variation in the relative 0.73/0.89 μm methane absorption band strengths, suggesting that the transport or denudation of this species may play a major role in the reddening events.  相似文献   

卫星电视授时系统及精度估计   总被引：1，自引：0，他引：1  

宋金安 《时间频率学报》1994,(Z1)

我国已建成短波、长波授时台，进行毫秒级、微秒级的时间服务．随着现代科技和经济的发展，上述方法已不能满足国家及国际交流的需要．本文提出卫星电视授时系统，同步卫星定位精度小于１１０ｍ，卫星授时精度为亚微秒。两原子钟利用卫星进行时刻同步，其精度与两原子钟的距离有关，相距３千多公里的两钟同步精度小于３５ｎｓ，相距数百公里的两原子钟同步精度小于２０ｎｓ  相似文献   

Sea‐surface temperature and salinity changes in the northwest Pacific since the Last Glacial Maximum     

Tadamichi Oba  Masafumi Murayama 《第四纪科学杂志》2004,19(4):335-346

The oxygen isotope records of both benthic and planktonic Foraminifera in five piston cores, collected from the region between the Oyashio and Kuroshio Currents near Japan, clearly show the marked latitudinal shifts of these two currents during the past 25 kyr. Under the present hydrographic condition, a clear relationship between the sea‐surface temperature (SST) and oxygen isotope differences from benthic to planktonic Foraminifera is observed in this region. Using this relationship, we find decreased SSTs of 12–13°C (maximum 15°C) in the southernmost core site at the Last Glacial Maximum (LGM), indicating the Oyashio Current shifted southward. The SSTs at the southern two core sites abruptly increased more than 10°C at 10–11 ka, suggesting the Kuroshio Current shifted northward over these sites at 10–11 ka. In contrast, the northern two core sites have remained under the influence of the cold Oyashio Current for the past 25 kyr. With the reasonable estimate of bottom‐water temperature decrease of 2.5°C at the LGM, the SSTs estimated by this new method give exactly the same SST values calculated from Mg/Ca ratio of planktonic Foraminifera, allowing palaeosea‐surface salinities to be reconstructed. The result suggests that the ice volume effect was 1.0 ± 0.1‰ at the LGM. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献