Validation and inter- comparison of multi-satellite merged sea surface temperature products in the South China Sea and its adjacent waters

利用2008年—2009年ArgO、ArgOS现场观测海表面温度SST,对OSTIA、MISST、MWSST以及ngSST4种融合SST产品在南海及其周边海域的适用性进行评估。验证结果表明,4种融合SST产品在外海的均方根误差rMS介于0.3—1.0℃,bIAS介于-0.1—0.6℃;除了ngSST在近岸出现明显暖偏外,其他3种融合SST与现场SST基本一致,OSTIA与现场SST的偏差为最小。对4种融合SST产品彼此间的互较也表明,它们在水深大于80 M的海区没有显著性差异,但彼此间的偏差会随水深变浅而增大。此外,各产品间偏差在冬季最大,夏季最小。本文为具有高时空覆盖度的融合SST产品在南海及其周边海域的应用提供了一个可靠的依据。Sea Surface Temperature( SST) is a basic parameter in characterizing the ocean-atmosphere system and serves an important function in climate change.Many types of cloud-free,high-spatial,and temporal coverage merged SST products have been generated by the Group for High Resolution Sea Surface Temperature.These products provide important data sources that can be used in a wide variety of operational and scientific applications.However,differences are existed among these products,due to their specific research requirements,different blending algorithms,different satellite SST sources for blending,and quality control methods.Therefore,monitoring the quality of these products is necessary,particularly at shelf and coastal seas around China,which are characterized by complex atmospheric conditions and hydrodynamics.This study compares four types of merged SST products in the South China Sea and adjacent waters in the years 2008 and 2009.Four multi-satellite merged SST products—the Operational SST and Sea Ice Analysis( OSTIA),microwave / infrared optimally interpolated SST,microwave optimally interpolated SST,and new generation SST( NGSST) —are validated with the Argo SST in the shelf sea and Argos SST in the shallow coast.The match-up data are collected on the same day and location.The Root Mean Square( RMS),bias,and correlation coefficients are calculated and used to quantify the errors.These products are projected into the same grid of NGSST using the nearest-neighbor sampling method for comparison.OSTIA is selected as the basis,and the relative differences between OSTIA and the other three products are computed and visualized using maps,box-plot,and time series plots.The statistical results show that the RMS between the merged SSTs and Argo temperature ranged between 0.3 ℃ and 1.0 ℃,whereas the bias ranged between- 0.1 ℃ and 0.6 ℃ in the shelf sea( water depth > 80 m).The other three merged SSTs were consistent with the in situ data in the coastal area,except for NGSST,which had a significantly warm bias(- 1 ℃) and the largest RMS(- 1.5 ℃).The bias and RMS of OSTIA were the smallest.An inter-comparison indicates no significant differences among the four merged SST products in the shelf sea.Their biases were within ± 0.3 ℃.However,the deviation increases in shallow water.The largest bias was found in winter because of the poor weather conditions,whereas the smallest bias was found in summer.In summary,the four merged SST products were consistent with in situ data in the study region,except for the NGSST in the shallow coastal sea and the OSTIA product exhibited the best performance.This study has provided a reliable basis for the effective application of these merged SSTs with high spatial and temporal coverage in the South China Sea and its adjacent waters.国家自然科学基金(编号:U1305231;40706041); 福建省自然科学基金(编号:2011J01278); 海洋赤潮灾害立体监测技术与应用国家海洋局重点实验室开放基金资助项目(编号:MATHAB20100313

台湾海峡真光层有机碳动力学研究──DOC大幅度的日变化

1994年8月和1995年2月在台湾海峡对dOC作定点连续观测，发现dOC日变化很大（2~4Mg/dM3），且变化的幅度有季节差异和空间差异；dOC昼夜变化的总的规律是白天比晚上高，夜晚始终处于低值；依据dOC的昼夜变化可将dOC分为dOCnEW和dOCOld两部分；d0CnEW在真光层中快速地产生、消耗、再循环；dOCOld则相对稳定，可从真光层底部输出；dOC的快速变化表明dOC的产生和被细菌消耗利用的速度都非常快.文中还尝试快速富丽叶变换（ffT）来分离引起dOC日变化的物理因子和生物因子，并依据实验结果讨论了初级生产力，微生物对dOC的利嵱茫模希檬涑錾Φ任侍狻国家教委和福建省重点课题基

Advances inthe studies onlight absorption properties of phyto-plankton

国家自然科学基金资助项目(40376031);; 国家863计划资助项目(2002AA639540);; 国家自然科学重点基金资助项目(40331004

Satellite-derived surface water pCO(2) and air-sea CO2 fluxes in the northern South China Sea in summer

An empirical approach is presented for the estimation of the partial pressure of carbon dioxide (pCO(2)) and air-sea CO2 fluxes in the northern South China Sea in summer using satellite-derived sea surface temperatures (SSTs), chlorophyll-a (Chl a) concentrations, and wind fields. Two algorithms were tested. The first used an SST-dependent equation, and the other involved the introduction of Chl a. Regression equations were developed for summer based on in situ data obtained in July, 2004. Using the monthly average SST and Chl a fields derived from the advanced very high resolution radiometer (AVHRR) and the SeaWiFS (sea-viewing wide field of view sensor), respectively, the monthly pCO(2) fields were computed. The derived pCO(2) was compared with the shipboard pCO(2) observations conducted in July, 2000. This resulted in a root-mean-square error of 4.6 mu atm, suggesting that the satellite-derived pCO(2) was in general agreement with the in situ observations. The air-sea CO2 flux was further computed with the aid of the monthly mean QuikSCAT wind speed. We contend that more shipboard data are necessary for refining the empirical algorithms and reducing the uncertainty in the results. (C) 2009 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved.National Basic Research Program of China [2009CB421200, 2009CB421201]; National Natural Science Foundation of China [40521003, 90711005]; High-Tech R&D Program of China [2006AA09A302, 2007AA09Z127

An evaluation of two semi-analytical ocean color algorithms for waters of the South China Sea

基于42组不同年份不同季节获得的遥感反射率、水体各组分吸收系数的实测数据,对QAA(QuASI-AnAlyTICAl AlgOrITHM)和gSM(gArVEr-SIEgEl-MArITOrEnA)算法在寡营养的南海和富营养的福建沿岸两种不同类型水体的吸收系数反演进行了检验。以水样测量值为参考,两种算法在本研究水体中的反演成效与他人在其它水域的研究结果相当。QAA算法在南海的反演成效高于福建沿岸水体。对于443nM的总吸收系数A(443),南海的对数均方根误差rMSE为0.044,平均相对误差ε为7.9%,对数平均偏差δ为0;福建沿岸水体rMSE=0.190,ε=30.6%,δ=-0.167。gSM算法在两类水体的反演成效类似,A(443)之rMSE和ε,南海分别为0.156和27.7%,福建沿岸分别为0.146和32.1%;但从A(443)的δ值看,其在南海反演值低于实测值(δ=-0.142),在福建沿岸则略呈高于实测值(δ=0.016)。两种算法中的部分经验参数与实测值之间的差异是产生反演误差的主要原因,为了提高反演精度,对算法中经验参数的更进一步区域化调整可能是必要的。With 42 in situ measurements of remote sensing reflectance and component absorption coefficients taken in the South China Sea and coastal waters off Fujian, China during different seasons, the authors evaluate the performance of the Quasi-Analytical Algorithm (QAA) and the Garver-Siegel-Maritorena (GSM) algorithm for water absorption coefficients.It is found that the retrieval performances of the two algorithms are similar to those of the algorithms by other researchers conducted in other regions.In this study , QAA performs better in the South China Sea than in the waters off coastal Fujian.For the total absorption coefficient at 443 nm a(443), the rootmean-square error (RMSE) is 0.046 in the South China Sea, with an averaged percentage error (ε) of 7.9% , and averaged error in log scale (δ) close to 0.For the waters off coastal Fujian, RMSE, ε and δ are 0.194, 30.6%, and -0.167, respectively.The performance of the GSM is similar for the two waters.For a(443), RMSE and ε are 0.161 and 27.7% in the South China Sea and 0.149 and 32.1% in the waters off coastal Fujian , respectively; their δ values, however, are negative (-0.142; indicating underestimation) in the South China Sea and positive (0.016; indicating slight overestimation)in the waters off coastal Fujian.Further analysis indicates that the differences between the empirical parameters employed in the algorithms and actual values of the studied waters are the main reasons causing the errors in remote sensing retrievals, therefore, it is necessary to regionally refine those parameters in order to improve the algorithm performance.863计划项目(2006AA09A302;2008AA09Z108);国家自然科学基金项目(40521003

Monitoring of Inshore Aquaculture Cages Using Unmanned Aerial Vehicle

无人机(unmanned aerial vehicle,UAV)遥感具有高时效、机动灵活、高分辨率的特点,探索应用UAV遥感平台对沿海养殖区进行监测,实时掌握养殖发展动态,开展灾后应急监测,显然具有重要意义.利用UAV获取的CCD相机光谱信息,建立渔排监测指数,提出了渔排监测指数阈值快速提取算法;并针对渔排本身混合了水体和木筏2种目标物的特性,对提取结果进行图像闭合算子运算.在福建沿海古雷和可门港的实验结果表明,基于UAV获取的数据影像,利用渔排监测指数快速提取算法估算的渔排面积精度在两个区域分别达到98.9%和97.4%,与传统遥感分类方法——最大似然法相比,在同一计算平台上,计算速度提高5倍,无论精度或速度都可满足海洋与渔业管理部门在业务上的快速响应需求.此外应用UAV,以苏迪罗台风过后的三都澳海区为例,尝试开展了台风灾害造成的渔排损毁分析,初步推算出台风造成的渔排损毁面积比例.该研究表明利用UAV遥感可以为渔业管理提供有效的技术支持.Unmanned aerial vehicle( UAV) may provide a quick means to gather information of inshore aquaculture cages for the government to have an emergency response to events such as typhoons.Based on CCD imageries with 0. 1 meter resolution acquired with UAV platform and its spectral features,here we proposed a threshold method to quickly detect the distribution of aquaculture cages in two bays of southern Fujian.An identification accuracy of 98. 9% and 97. 4%,for Gulei and Kemen bays,respectively,was obtained.Meanwhile,the image processing time is reduced by 5 times,compared to the time needed using the widely accepted conventional approach-maximum likelihood method.In addition,a rough evaluation on the ruin extent of aquaculture cages by typhoon was also attempted,using UAV acquired imageries and satellite images.This study suggests that optical remote sensing with UAV holds promise for better management of inshore aquaculture activities.国家科技支撑计划(2013BAB04B01);; 厦门大学海洋科学基地科研训练及科研能力提高项目(J1210050);厦门大学大学生创新创业训练计划(201510384091

Upwelling induced variability of chlorophyll in the Taiwan Strait as observed by SeaWiFS and AVHRR

SeaWIFS SeaWiFS Chl and AVHRR SST time-series in August, 1998 were used to evaluate short-term variability of Chl associated with upwelling events in the western Taiwan Strait. Extents of eutrophic waters(SeaWiFS Chlorophyll > 1 mg/m(3)) and extents of colder than non-upwelling waters were calculated for the western strait and for the north and south portions, respectively. High extents of eutrophic waters were always accompanied by high extents of colder than nonupwelling waters, indicative of tight coupling of Chi with SST evolution and thus with upwelling activities. Only one-day lag of phytoplankton growth to upwelling was detected. The temporal patterns of upwelling events were found different in the northwestern and southwestern Taiwan Strait. In the north portion, a short relaxation of upwelling probably occur-red between early and mid-August. One unique strong upwelling event was likely going from early through mid-August, peaking before Aug.13(th) in the south portion. It resulted in chlorophyll enhancement developing and reaching peaks not concurrently in these two upwelling zones, The duration of one upwelling event in the western Taiwan Strait in August was estimated to be ca.12days. Two distinctive upwelling systems located in the northwestern and southwestern Taiwan Strait were further inferred

基于可见光与近红外遥感反射率关系的藻华水体识别模式

极轨气象卫星AVHRR红光波段(波段1,波长580~680nm)和近红外波段(波段2,波长720~1100nm)的水体遥感反射率关系函数Rrs(2)-1=α0Rrs(1)-1+g-1(1?α0)中,参数α0=(bb(1)/bb(2))(a(2)/a(1))对叶绿素浓度敏感且相对独立于浊度,以1.6<α0<5.6和0.01<Rrs(2)/g<0.2为判据,可以实现叶绿素浓度为64~256μg/L的近海藻华水体识别.在2003年6月闽江口藻华水体的AVHRR遥感信息识别基础上,进行了该识别模式与传统的单波段模式,以及与比值法、NDVI法、差值法等双波段模式的比较,建议将该识别模式发展为近海藻华水体遥感的普适模式

Remote sensing of algal blooms using a turbidity-free function for near-infrared and red signals

This article presents a method for real-time mapping of algal blooms in turbid coastal waters using the remote sensing reflectance of red band (Channel 1, 580-680 nm) and near-infrared band (Channel 2, 720-1100 nm) of the AVHRR sensor on the NOAA series satellites. A turbidity-free function for near-infrared and red signals, alpha(0) = (b(b)((1))/b(b)((2)))(a((2))/ a((1))) based on the first order b(b)(a+b(b)) model deducing equation R-rs((2)-1) = alpha(0) R-rs((1)-1)+ g(-1) (1 - alpha(0)), were selected as a chlorophyll-a related index for detecting algal blooms, and the algal blooms with chlorophyll-a concentration of 64-256 mg/L could be defined by window of 1.6 < alpha(0) < 5.2 and 0.01 < R-rs((2))/g < 0.2. Such turbidity-free two-band method is supported by both sea-truth data and remote sensing experiment for an algal blooms event on the near-shore water off the Minjiang estuary of southeastern China during early June of 2003. Comparisons of this algorithm with other published algorithms, one-band method (i.e. method of bright water) or two-band methods (i.e. method of ratio, method of NDVI, and method of subtracting) have suggested that the turbidity-free function method could be regarded as a standard algorithm in capabilities of AVHRR imagery or other high resolution but wide near-infrared and red band imagery for detecting algal blooms events in coastal waters

A preliminary study of the variation of phytoplankton absorption coefficients in the northern South China Sea

The temporal and spatial variabilities of phytoplankton absorption coefficients (a(ph)(lambda)) and their relationships with physical processes in the northern South China Sea were examined., based on in situ data collected from two cruise surveys during May 14 to 25 2001. and November 2 to 21, 2002. Significant changes in the surface water in a,h values and B/R ratios (a(ph)(440)/a(ph)(675)) were observed in May, which were caused by a phytoplankton bloom on the inner shelf stimulated by a large river plume due to heavy precipitation. This is consistent with the observed one order of magnitude elevation of chlorophyll a and a shift from a pico/nano dominated phytoplankton community to one dominated by micro-algae. Enhanced vertical mixing due to strengthened northeast monsoon in November has been observed to result in higher surface a(ph)(675) (0.002-0.006 m(-1) higher) and less pronounced subsurface maximum on the outer shelf/slope in November as compared with that in May. Measurements of a(ph) and B/R ratios from three transects in November revealed a highest surface a(ph)(675) immediately outside the mouth of the Zhujiang (Pearl) River Estuary, whereas lower a(ph)(675) and higher B/R ratios were featured in the outer shelf/slope waters, demonstrating the respective influence of the Zhujiang River plume and the oligotrophic water of the South China Sea. The difference in spectral shapes of phytoplankton absorption (measured by B/R ratios and bathochromic shifts) on these three transects infers that picoprocaryotes are the major component of the phytoplankton community on the outer shelf/slope rather than on the inner shelf. A regional tuning of the phytoplankton absorption spectral model (Carder et al., 1999) was attempted, demonstrating a greater spatial variation than temporal variation in the lead parameter a(0)(lambda). It was thus implicated that region-based parameterization of ocean color remote sensing algorithms in the northern South China Sea was mandatory.National Basic Research Program of China [2009CB421200, 2009CB421201]; National Natural Science Foundation of China [40821063]; High-Tech R&D Program of China [2006AA09A302, 2008AA09Z108