Advances on Technology and Application of Ocean Color Remote Sensing in China (2004 - 2006)

China has great progress in the technology and application of ocean color remote sensing during 2004-2006. In this report, firstly, four major technical advances are displaying, including (1) the vector radiative transfer numerical model of coupled ocean-atmosphere system; (2) the atmospheric correction algorithm specialized on Chinese high turbid water; (3) systematical research of hyper-spectrum ocean color remote sensing; (4) local algorithms of oceanic parameters, like ocean color components, ocean primary productivity, water transparency, water quality parameters, etc. On the foundation of technical advances, ocean color remote sensing takes effect on ocean environment monitoring, with four major kinds of application systems, namely, (1) the automatic multi-satellites data receiving, processing and application system; (2) the shipboard satellite data receiving and processing system for fishery ground information; (3) Coastal water quality monitoring system, integrating satellite and airborne remote sensing technology and ship measurement; (4) the preliminary system of airborne ocean color remote sensing application system. Finally, the prospective development of Chinese ocean color remote sensing is brought forward. With Chinese second ocean color satellite (HY-1B) orbiting, great strides will take place in Chinese ocean color information accumulation and application.     

基于X波段雷达海浪监测装置的设计与研究

针对舰船对浪高实时测量的需要,提出了基于x波段雷达海浪监测装置的设计方案,具体介绍了基于X波段雷达海浪监测装置的设计原则、功能设计、硬件设计以及基于VC 的软件实现,并给出基于x波段雷达海浪监测装置系统操作平台功能界面的参考实例,从一定程度上为舰船海浪测量装置的实现与应用提供可行性参考。     

低轨卫星的北斗反射信号海洋覆盖分析

北斗系统作为我国自行研制的导航系统，具有独特的混合星座特性，其反射事件在海洋上的空间分布和覆盖性能的研究成果较少。针对上述问题，模拟了北斗三号（Beidou System 3，BDS3）以及全球定位系统（Global Positioning System，GPS）空间星座，模拟不同性能参数的低轨接收卫星，在此仿真系统的基础上，计算反射事件在各仿真场景下的海洋覆盖率以及同时发生反射事件的卫星数量。结果表明：BDS3与GPS相比具有更大的反射事件海洋覆盖率，覆盖性能更优；仿真周期7天与1天相比,前者卫星产生的反射事件海洋覆盖率约为后者5倍；低轨道卫星（Low Earth Orbit,LEO）轨道高度越高，天线波束角度越大，反射事件海洋覆盖率越大；3颗LEO卫星下同时发生反射事件卫星数的平均值约为单颗LEO卫星的3倍。可通过设计多星组网来提高反射事件海洋覆盖率。研究结果对星载反射技术海洋遥感应用方面有一定的参考价值。     

Use of data from meteorological satellites in long-range weather forecasting

In the Soviet Union experiments on obtaining meteorological information by means of man-made Earth's satellites were initiated in 1966 (the “Meteor” meteorological system).Starting with 1975 the launches of the “Meteor-2” updated meteorological satellites of the second generation were carried out. The detailed information about the Soviet meteorological satellite system can be found in [9].Below, the problems concerning the use of satellite data in schemes of long-range weather forecasts are considered. Particular attention is paid to the role of external sources of energy. The role of cloud cover over the oceans is emphasized as a heat influx regulator in the process of absorption radiant solar heat by the ocean. The dynamic and statistical method of ocean heat memory parameterization is stated.     

Ocean Observation from Haiyang Satellites

In 2018, China successfully launched three new Haiyang (which means ocean in Chinese, referred to as HY) satellites which are an ocean color observation satellite HY-1C (operational), an ocean dynamics environment satellite HY-2B (operational) and the China-France ocean satellite CFOSAT (experimental). In 2019, all the three satellites had finished their commissioning phases and were declared operational. HY-2A satellite continues to operate in-orbit, and its operational status is basically normal. So in 2020, China has 4 Haiyang satellites in-orbit, China's ocean satellites enter into a new operational application phase. The operation of the ground application system of Chinese ocean satellites is stable. In 2019, Beijing, Hainan, Mudanjiang, and Hangzhou ocean satellite ground stations had received the data of HY-1C, HY-2A, HY-2B, and CFOSAT 5012 orbits and 26.46 TB data had been distributed to both domestic and international users. Chinese ocean satellite data has played an important role in marine disaster prevention and mitigation, development and management of marine resources, maintenance of marine rights and interests, marine environment protection, scientific researches, and blue economy development.      

构建中国海洋卫星体系提升海洋环境与灾害监测能力

海洋卫星是海洋环境与灾害监测数据的重要获取手段,在海洋防灾减灾和科学研究中发挥着巨大作用.分析了海洋环境观测要素和海洋卫星在海洋环境与灾害监测中的应用状况;结合国外海洋卫星发展趋势和中国实际发展需求,提出了构建中国海洋卫星体系的发展建议,为提升海洋环境与灾害监测能力,推动中国海洋事业发展,促进国民经济和海防安全建设服务.     

Investigation of the atmospheric aerosols by the visible and IR channels of the AVHRR radiometer on NOAA-6

The diffusely reflected radiation in the daytime and diffusely transmitted radiation at night from an inhomogeneous, plane parallel planetary atmosphere bounded by the ocean surface was calculated at the visible and IR region. In the daytime the effect of the solar radiation from top was taken into account. The present study has dealt with the problem of no cloud contamination in data. In the atmosphere, water vapor, molecular nitrogen, nitrous oxide, carbon dioxide and methane as absorbent constituents and aerosols as the scattering constituent were taken into account. The ocean surface as a lower boundary was simulated by many facets whose slopes are according to the isotropic Gaussian distribution [1]. It was found that it is suitable for deriving the total optical thickness in the direction of about 15 degrees away from the specular direction at 3.7μm in the daytime, with the aid of visible region of spectrum [2]. As for sea surface temperature, for a sample analysis, derived SST was within the accuracy of 1–2K at the center of the sun glint and within the accuracy of 0.5K in the rest of the region at 3.7μm in the daytime, Furthermore computational results suggest that the comparison of temperature in the daytime with that at night at 3.7μm make it possible to separate the effect of aerosols from the total optical thickness. Thus it was found from the computations that with the aid of daytime and night time data, it is possible to derive the atmospheric water vapor, aerosols and sea surface temperature simultaneously.     

Total column water vapor estimation over land using radiometer data from SAC-D/Aquarius

The aim of this study is retrieving atmospheric total column water vapor (CWV) over land surfaces using a microwave radiometer (MWR) onboard the Scientific Argentine Satellite (SAC-D/Aquarius). To research this goal, a statistical algorithm is used for the purpose of filtering the study region according to the climate type.A log-linear relationship between the brightness temperatures of the MWR and CWV obtained from Global Navigation Satellite System (GNSS) measurements was used. In this statistical algorithm, the retrieved CWV is derived from the Argentinian radiometer’s brightness temperature which works at 23.8?GHz and 36.5?GHz, and taking into account CWVs observed from GNSS stations belonging to a region sharing the same climate type. We support this idea, having found a systematic effect when applying the algorithm; it was generated for one region using the previously mentioned criteria, however, it should be applied to additional regions, especially those with other climate types.The region we analyzed is in the Southeastern United States of America, where the climate type is Cfa (Köppen - Geiger classification); this climate type includes moist subtropical mid-latitude climates, with hot, muggy summers and frequent thunderstorms. However, MWR only contains measurements taken from over ocean surfaces; therefore the determination of water vapor over land is an important contribution to extend the use of the SAC-D/Aquarius radiometer measurements beyond the ocean surface. The CWVs computed by our algorithm are compared against radiosonde CWV observations and show a bias of about ?0.6?mm, a root mean square (rms) of about 6?mm and a correlation of 0.89.     

Results About Ocean Satellite Observation

They have played more and more important roles in marine pollution monitoring, marine environment and marine disaster monitor and forecasting, marine resource investigation and marine scientific research. In this paper, the author will give a brief review of China's operational and scientific activities in satellites ocean observation during 2008 to 2010. These activities include the application of the HY-1B for red tide and green tide detecting and monitoring, sea ice monitoring, fishery resources assessment at coastal zone and ocean, marine water quality assessment, sea surface temperature monitoring and forecasting, ocean primary productivity and carbon cycle research, and the development in the ocean dynamic environment parameter application technology before launch of HY-2. The achievements we have made in the ocean observation and monitoring during the past 3 years indicate that, the development of the ocean satellite series and the application of the ocean satellite can greatly promote the development of China's three-dimensional marine observation system and earth-observation system from space, accordingly we can improve the ability of acquiring the marine environmental parameter to sustain the marine economy development and the sea defense construction.      

Seasonal-to-interannual variability of chlorophyll-a bloom timing associated with physical forcing in the Gulf of Cádiz

Seasonal-to-interannual variability of the winter-spring bloom in the Gulf of Cádiz, eastern North Atlantic, has been investigated using chlorophyll-a remote sensing (CHL). These data have been obtained from the GlobColour project; the temporal coverage extends from September 1997 to December 2010. In this study we develop a generic quantitative approach for describing the temporal variability in the shape of the winter-spring bloom within a region. Variability in both the timing and magnitude of the bloom in the basin has been evaluated as a function of physical properties in the water column such as Mixed Layer Depth (MLD, GODAS model), sea surface temperature (SST, from AVHRR radiometers), photosynthetically-active radiation (PAR, from ocean color data) and euphotic depth (Z_eu, from ocean color data). The analysis indicated that the timing, size and duration of the phytoplankton bloom in this area are largely controlled by both meteorological and oceanographic conditions at different scales; this means that it is likely to vary widely from one year to another.     

星载雷达测高计系统频率流程和指标分配

精密雷达测高计是海洋有源微波遥感中一种效益高、用途广的星载有效负荷,是全球海洋研究具有关键意义的全天候观测工具。在精密确定大地水准面的条件下,其结果对海洋学、测地学、深海测量、潮汐、冰、风、浪等的研究和发展都是十分有用的。文章仅限于研究该系统的频率流程和主要部件(和分系统)的指标分配。     

Ocean circulation studies in the vicinity of Southern Africa: Preliminary results using FGGE drifters and remote sensing

The three highly variable ocean circulation systems which meet south of South Africa have been studied by combining the use of satellite thermal infra-red imagery, hydrographic measurements and drifting buoys. We present a few preliminary examples where this method has been successful. These include the sources of the Agulhas Current, the influence of the Agulhas Current on the Cape upwelling region as well as the interaction of the Agulhas Current with the Subtropical Convergence. An example is also given of how a biological hypothesis concerning the recruitment of a rock lobster species at Vema Seamount has been supported by the analysis of the drifts of FGGE buoys in the South Atlantic Ocean.     

Anomalous increase of chlorophyll concentrations associated with earthquakes

Recent studies have shown land, ocean, atmosphere and ionospheric anomalies prior to earthquakes. The optical and microwave sensors onboard satellites are now capable of monitoring land, ocean, atmosphere and ionosphere which provide changes associated with natural hazards. In this paper, we have analyzed remote sensing data of the ocean coasts lying near the epicenters of recent four major earthquakes (Gujarat of January 26, 2001, Andaman of September 13, 2002, Algeria of May 21, 2002 and Bam, Iran earthquake of December 26, 2003), our detailed analysis shows increase of Chlorophyll-a (Chl-a) concentration associated with these recent earthquakes. The increase of Chl-a concentration is due to the change in sea surface temperature (SST) associated with the changes in stress regime in the epicentral region which is responsible for modifying the in situ thermal structure of the water and enhancing the upwelling of nutrient-rich water. The increase of Chl-a concentration also shows one to one relation with the increase of surface latent heat flux (SLHF) which is found to increase significantly prior to the earthquake events. Due to cloud cover, it has not been possible to quantify the effect of the chlorophyll concentrations associated with the earthquake events for each successive day during an event. However, the limited data from the adjacent oceanic regions provide strong evidence of the increase in Chl-a concentration. The monitoring of chlorophyll concentrations with higher spatial and temporal resolutions may provide early information about impending coastal earthquakes.     

Dielectric properties and microwave remote sensing

The importance of the dielectric properties of earth, ocean and snow surfaces in microwave remote sensing is reviewed. Data on dielectric properties of materials in the microwave frequency range are very scarce and their behaviour is not fully understood. In this paper the need for dielectric properties of ocean and snow surfaces, the earth's surface and subsurface materials is discussed for the quantitative and qualitative interpretation of microwave remote sensing data of developing countries.     

A modern robust approach to remotely estimate chlorophyll in coastal and inland zones

The chlorophyll concentration of a water body is an important proxy for representing the phytoplankton biomass. Its estimation from multi or hyper-spectral remote sensing data in natural waters is generally achieved by using (i) the waveband ratioing in two or more bands in the blue-green or (ii) by using a combination of the radiance peak position and magnitude in the red-near-infrared (NIR) spectrum. The blue-green ratio algorithms have been extensively used with satellite ocean color data to investigate chlorophyll distributions in open ocean and clear waters and the application of red-NIR algorithms is often restricted to turbid productive water bodies. These issues present the greatest obstacles to our ability to formulate a modern robust method suitable for quantitative assessments of the chlorophyll concentration in a diverse range of water types. The present study is focused to investigate the normalized water-leaving radiance spectra in the visible and NIR region and propose a robust algorithm (Generalized ABI, GABI algorithm) for chlorophyll concentration retrieval based on Algal Bloom index (ABI) which separates phytoplankton signals from other constituents in the water column. The GABI algorithm is validated using independent in-situ data from various regional to global waters and its performance is further evaluated by comparison with the blue-green waveband ratios and red-NIR algorithms. The results revealed that GABI yields significantly more accurate chlorophyll concentrations (with uncertainties less than 13.5%) and remains more stable in different waters types when compared with the blue-green waveband ratios and red-NIR algorithms. The performance of GABI is further demonstrated using HICO images from nearshore turbid productive waters and MERIS and MODIS-Aqua images from coastal and offshore waters of the Arabian Sea, Bay of Bengal and East China Sea.     

Ocean Observation from Haiyang Satellites: 2012–2014

During 2012 and 2014, China has two Haiyang(which means ocean in Chinese, referred to as HY) satellites operating normally in space which are HY-1B and HY-2A. HY-1B is an ocean color environment satellite which was launched in April 2007 to observe global ocean color and sea surface temperature, and HY-2A is an ocean dynamic environment satellite which was launched in August 2011 to obtain global marine dynamic environment parameters including sea surface height,significant wave height, ocean wind vectors, etc. Ocean observation data provided by HY-1B and HY-2A have been widely used by both domestic and international users in extensive areas such as ocean environment protection, ocean disaster prevention and reduction, marine environment forecast,ocean resource development and management, ocean investigations and scientific researches, etc.     

面向海洋机动目标跟踪监视的卫星重构组网优化与仿真

摘要： 针对海洋机动目标跟踪监视问题，提出通过卫星相位重构调整进行机动目标搜索跟踪的监视策略，构建地理坐标系下机动目标航位预测模型及基于霍曼转移的卫星调相组网方式，并采用NSGA II算法进行优化求解，对比分析卫星重构组网前后的机动目标发现概率.仿真结果表明：在卫星能量消耗允许范围内进行重构组网，能够有效提升对机动目标的发现概率，为海洋机动目标的搜索跟踪问题提供了一定的方法支持.     

Semi-automatic determination of the Azores Current axis using satellite altimetry: Application to the study of the current variability during 1995–2006

Satellite altimetry has been widely used to study the variability of the ocean currents such as the Azores Current (AzC) in the North Atlantic. Most analyses are performed over the region that encloses the current, thus being somehow affected by other oceanographic signals, e.g., eddies. In this study, a new approach for extracting the axis of a zonal current solely based on satellite altimetry is presented. This is a semi-automatic procedure that searches for the maximum values of the gradient of absolute dynamic topography (ADT), using the geostrophic velocity as auxiliary information. The advantage of this approach is to allow the analyses to be performed over a buffer centered on the current axis instead of using a wider region. It is here applied to the AzC for the period June 1995–October 2006.     

基于GPS遥感的延迟映射接收机关键技术

全球卫星定位系统GPS(Global Positioning System)广泛应用于定位和导航,还可利用海面对GPS信号产生的散射效应进行微波遥感,是一种新型微波遥感手段.首先介绍了GPS海洋遥感测风技术产生背景及特点,给出了GPS散射信号测量技术理论基础,重点分析了延迟映射接收机设计中提高采样信号信噪比、双射频前端电路设计、计算反射点延迟、接收机工作模式、内嵌软件处理等5项关键技术.设计的延迟映射接收机样机在天津近海完成了首次搭载飞行试验,试验结果表明,延迟映射接收机可同时接收直射和海面散射卫星信号并输出导航定位解,正确计算镜面散射点码延迟,准确接收海面散射的GPS卫星信号,且散射信号信噪比达到了14.9 dB以上,接收机输出为反演海面风场提供了准确的基础数据,这种方式可推广到遥感探测陆地土壤湿度、海冰厚度、海浪高度等领域.      

Gravity model development for precise orbit computations for satellite altimetry

Satellite altimeters have been developed which have the capability of measuring the surface topography of the ocean over entire basins for time periods of several years with a precision of a few cm. The combination of these data with accurate satellite position information, subsurface measurements and models of the density field can be used to determine the general circulation of the ocean and its variability. The Topex altimeter oceanographic experiment proposed for the early 1990's requires a radial orbit accuracy approaching 10 cm. Considerable progress has been made at the Goddard Space Flight Center in developing precision orbit determination to support satellite altimetry analysis. This progress is attributed to the development of more accurate models of the earth gravity field, earth and ocean tidal effects, a reference coordinate system as well as improved drag and solar radiation pressure computations. This computational system has been used for the Seasat data acquired during the 1978 time period and has produced an rms radial accuracy of about 50 cm. A first step towards the development of a new Interim gravity model is presented. Global orbit determination accuracies have been improved using these new PGS-T1 and T2 fields.