Remote Sensing Observations of Ocean Surface Chlorophyll and Temperature with the Impact of Cyclones and Depressions over the Bay of Bengal Water

MODIS-Aqua derived eight-day composite chlorophyll concentration data analyzed to study the impact of cyclones and depressions on the Bay of Bengal productivity. A total of 15 cyclonic storms and depressions picked up from the India Meteorological Department datasets. MODIS-Aqua data analyzed during October 2002 to December 2009. There was observation of depressions (D), deep depressions (DD), cyclonic storms (CS), severe cyclonic storms (SCS), and very severe cyclonic storms (VSCS) with categories of intensities (“T” numbers 1.5–6) and wind speeds (25–108 knots). The chlorophyll concentration observed to be high (1.0–5.0 mg/m³) with the impact in the coastal and offshore waters. Quickscat scatterometer data showed high wind speed (about 10 meters/second). Sea surface temperature (SST) observed to be decreased (roughly 2°C) with effect of cyclones. The cyclone numbers, intensity, and chlorophyll concentration has been observed to be increasing from 2002 to 2009, with observation of VSCS “Sidr” during 2007. The study would be interesting to link carbon flux/sequestration, marine food chain, and harnessing fishery resources in a postcyclone period.     

HY-1C卫星海岸带成像仪叶绿素a浓度反演研究

叶绿素a作为最重要的水质参数之一,是评价水体富营养化和初级生产力状况的主要因素。我国海洋一号C（HY-1C）卫星海岸带成像仪（CZI）具有高时空分辨率的观测优势。本文基于东海和南海现场实测数据建立了HY-1C卫星CZI叶绿素a浓度反演模型并在实测水域进行反演,与MODIS叶绿素a浓度反演产品进行了对比验证,应用CZI叶绿素a浓度模型在珠江口、长江口、渤海湾水域进行了叶绿素a浓度反演示例试验。结果表明,叶绿素a浓度模型估算浓度与实测浓度相关系数为0.774 3,平均相对误差为24.58%,利用实测叶绿素a浓度对模型进行精度验证,相关系数达到0.993 9,平均相对误差为18.49%。模型在实测水域反演得到的叶绿素a浓度分布与MODIS叶绿素a浓度产品分布大体一致。在珠江口水域反演得到叶绿素a浓度空间分布为由西北向东南逐级递减,峰值出现在珠江口西沿岸。在长江口、渤海湾反演叶绿素a浓度空间分布均符合地理实情。研究表明HY-1C卫星CZI数据可应用于中国近海水色定量化研究。     

Inter-annual and seasonal variations in hydrological parameters and its implications on chlorophyll a distribution along the southwest coast of Bay of Bengal

Seasonal and inter-annual variability of hydrological parameters and its impact on chlorophyll distribution was studied from January 2009 to December 2011 at four coastal stations along the southwest Bay of Bengal. Statistical analysis(principal component analysis(PCA), two-way analysis of variance(ANOVA) and correlation analysis)showed the significant impact of hydrological parameters on chlorophyll distribution in the study area. The ranges of different parameters recorded were 23.8–33.8°C(SST), 4.00–36.00(salinity), 7.0–9.2(p H), 4.41–8.32 mg/L(dissolved oxygen), 0.04–2.45 μmol/L(nitrite), 0.33–16.10 μmol/L(nitrate), 0.02–2.51 μmol/L(ammonia),0.04–3.32 μmol/L(inorganic phosphate), 10.09–85.28 μmol/L(reactive silicate) and 0.04–13.8 μg/L(chlorophyll).PCA analysis carried out for different seasons found variations in the relationship between physico-chemical parameters and chlorophyll in which nitrate and chlorophyll were positively loaded at PC1(principal component1) during spring inter-monsoon and at PC2(principal component 2) during other seasons. Likewise correlation analysis also showed significant positive relationship between chlorophyll and nutrients especially with nitrate(r=0.734). Distribution of hydrobiological parameters between stations and distances was significantly varying as evidenced from the ANOVA results. The study found that the spatial and temporal distribution of chlorophyll was highly dependent on the availability of nutrients especially, nitrate in the southwest Bay of Bengal coastal waters.     

福建围填海及其对海洋环境影响的遥感初探

把遥感技术应用于海岸带现状的动态研究和遥感海洋环境反演是当前遥感应用的热点之一。文章主要利用美国资源卫星专题扫描仪(thematic mapper,TM)遥感影像研究福建围填海状况及大陆海岸线的变化,通过ENVI、ArcGIS软件对研究区遥感影像进行处理,实现海岸线的自动提取、土地分类,以监测福建围填海的动态变化。通过相同季节的中分辨率成像光谱仪(moderate-resolution imaging spectroradiometer,MODIS)遥感影像反演福建海域海水表层温度及叶绿素浓度等海洋参数来了解围填海对海洋环境的可能影响。     

Field measurements and numerical simulations of the 2004 tsunami impact on the south coast of Sri Lanka

This paper examines the factors that have contributed to the significant spatial variability of the impact of the December 2004 tsunami in the southern province of Sri Lanka. Documented observations of the evidence left behind by the 2004 tsunami together with numerical simulation of tsunami propagation have been utilized for this purpose. The field data examined in the present analysis comprise the maximum water levels, the horizontal inundation distances and the number of housing and other buildings damaged as a result of the 2004 tsunami whilst the numerical results considered include the distribution of the amplitude of the tsunami. The present model results confirm that source directivity controls the distribution of tsunami amplitudes farther offshore whilst large-scale bathymetric features significantly influence the tsunami propagating over the shelf. Our analyses of field data also show the dominant influence of coastal geomorphology and topography on the extent of tsunami inundation.     

Rethinking post-tsunami integrated coastal management for Asia-Pacific

The December 2004 Indian Ocean tsunami wrought environmental damage beyond the normal framework of integrated coastal management and has implications for coastal management in Asia-Pacific in the post-tsunami phase. Fieldwork conducted on the coasts of four tsunami-affected countries in 2005 and 2006 identified several “practitioner-type” issues that would have implications for ICM policy. These include the loss of land with accompanying land tenure problems; the safety zone in conflict with the buffer zone; the need for better integration of livelihoods restoration with the rehabilitation of coastal ecosystems; and the inclusion of tsunami mitigation in the larger framework of climate change mitigation. A discussion of these issues and future role of ICM would provide a fresh perspective to policy-practice of ICM. A proposal is made to study various development pathways of selected coastal villages as they recovered in the post-tsunami phase.     

Characterizing the influence of tide on the physico-chemical parameters and nutrient variability in the coastal surface water of the northern Bay of Bengal during the winter season

The spatial distribution of physico-chemical parameters(sea surface temperature(SST), p H, sea surface salinity(SSS), dissolved oxygen(DO) and Secchi depth) along with filterable nutrients(dissolved inorganic nitrate(DIN),dissolved inorganic phosphate(DIP) and reactive silicate(DSi)) are measured in the winter months of November,December, January and February for four consecutive years from 2009–2010 to 2012–2013 on the shallow continental shelf(20 m bathymetry) of the coastal waters(up to 18 km away from shoreline) of the northern Bay of Bengal(n Bo B) during the highest high tide(HHT) and lowest low tide(LLT) hours for the first time. The variability of the coastal biogeochemical environment is assessed during the HHT and LLT hours and for this purpose, seawater samples are collected from seven different locations of a transect in the coastal region. Physicochemical parameters(except SST) show significant difference in magnitude during the HHT and LLT hours respectively. p H, SSS and DO are found to increase in the HHT hours and vice-versa. The data reveal that during the LLT hours, a relative increase of freshwater input in the n Bo B can have elevated the nutrient concentration compared with that observed during the HHT hours. The ratio of nutrient concentration is found to deviate significantly from the Redfield ratio. The abundance of DIP is much higher compared with that of DIN and DSi.The anthropogenic sources of DIP from the upstream flow(especially the domestic effluent of several metropolises) can be mainly attributed behind such an observation. In order to characterize and establish the trend of such variation in such an important bio-climatic region, long-term and systematic ecosystem monitoring in the coastal water of the n Bo B northern Bay of Bengal should be carried out throughout the year.     

基于奇异谱分析的深圳近海净初级生产力时间序列研究

海洋净初级生产力(Net Primary Productivity, NPP)长时间序列分析可获取NPP多年变化趋势、季节变化等动态信息,对海洋环境的监测与预报具有重要意义。本文以2003～2013年月际尺度净初级生产力卫星遥感产品为数据源,通过奇异谱分析提取标准化净初级生产力时间序列的长期趋势和周期振荡特征。研究表明,①浮标监测数据的叶绿素a浓度、海表温度与MODIS的叶绿素a浓度、海表温度产品变化趋势基本一致,NPP时间序列产品可用于分析深圳近岸海域净初级生产力的变化趋势。②空间分布上,深圳西部海域的NPP和叶绿素a浓度远高于大鹏湾和大亚湾,大鹏湾和大亚湾的NPP和叶绿素a浓度均值及变化趋势非常接近。三个海区NPP、叶绿素a浓度、海表温度和光合有效辐射在季风转换期变化剧烈。③长期趋势上,深圳西部海域呈现2 a周期波动趋势,在均值附近以年为周期上下波动。大鹏湾和大亚湾2003～2006年NPP低于平均水平, 2008年后NPP开始以年为周期围绕平均值上下波动, 2012年后NPP整体与均值持平。④周期特征上,深圳西部海域、大鹏湾和大亚湾的NPP呈"W"或"M"型周年变化,存在夏季主高峰(6～7月)和冬季次高峰(12～1月)。     

Observation of Algal Bloom in the Northwest Arabian Sea Using Multisensor Remote Sensing Satellite Data

Algal bloom observed using Indian Remote Sensing Satellite IRS-P4 Ocean Color Monitor (OCM) derived chlorophyll images during December 23, 2003–January 8, 2004, off the Oman coast. High chlorophyll concentration (～20 mg m^?3) patches were observed. MODIS-Aqua data of January 1, 2004, were analyzed to generate normalized water leaving radiance (nLw) images for seven visible channels: 412, 443, 488, 531, 551, 667 and 678 nm. The channels 667 and 678 nm showed interesting algal bloom features. The bloom features were detected in OCM image of January 2, 2004, using Subramanian's Trichodesmium detection Protocol. MODIS-Aqua retrieved Sea Surface Temperature (SST) around the bloom patches was observed to be >240°C. The OCM chlorophyll mean observed to be very high (>10.0 mg m^?3) in two bloom pockets. Quickscat scatterometer derived wind speed was found to be optimum in the range of 3–5 m/sec.     

Impact of atmospheric and physical forcings on biogeochemical cycling of dissolved oxygen and nutrients in the coastal Bay of Bengal

Time-series observations were conducted off Visakhapatnam, central west coast of Bay of Bengal, from October 2007 to April 2009 to examine the influence of physical and atmospheric processes on water column nutrients biogeochemistry. The thermal structure displayed inversions of 0.5 to 1.0° C during winter and were weaker in summer. The water column was vertically stratified during the entire study period and was stronger during October–November 2007 and August–December 2008 compared to other study periods. High concentrations of chlorophyll-a and nutrients were associated with the extreme atmospheric events. The strong relationship of nutrients with salinity indicates that physical processes, such as circulation, mixing and river discharge, have a significant control on phytoplankton blooms in the coastal Bay of Bengal. Phosphate seems to be a controlling nutrient during winter whereas availability of light and suspended matter limits production in summer. Formation of low oxygen conditions were observed in the bottom waters due to enhanced primary production by extreme atmospheric events; however, re-oxygenation of bottom waters through sinking of oxygen-rich surface waters by a warm core (anticyclonic) eddy led to its near recovery. This study reveals that atmospheric and physical processes have significant impacts on the water column biogeochemistry in the coastal Bay of Bengal.     

Microbial status in seawater and coastal sediments during pre- and post-tsunami periods in the Bay of Bengal, India

Tsunami, the natural disaster, which occurred on December 26, 2004 in the Indian Ocean, caused severe damage to mankind in the coastal areas. Total loss of life and economic loss because of this disaster have been estimated by various agencies but its effect on microbial density has not been probed. With our previous results on microbial populations in four locations of the Chennai coast of the Bay of Bengal, India in the pre‐tsunami period, the change in microbial populations was studied after the tsunami at regular intervals in the same locations. Coastal sediment and seawater samples were collected from four different locations after 5–10 h and thereafter at intervals of every 7 days up to 28 days post‐tsunami. Bacteria, fungi and actinomycetes were isolated from the marine samples by serial dilution on respective media. Before the tsunami, the bacterial population was higher in seawater samples than the sediments, whereas fungi and actinomycetes were recorded only in the sediments. The microbial population remarkably increased 5–10 h post‐tsunami in all the marine samples irrespective of the location. However, it slowly declined in the subsequent days and became similar to that of the population recorded before the tsunami. The population of gram‐positive bacteria increased whereas the gram‐negative bacterial population decreased after the tsunami. Further, populations of pathogenic bacteria such as coliform and vibrios did not increase after the tsunami. It has been observed that the increase in populations of bacteria and actinomycetes even after 28 days of tsunami may be due to the introduction of foreign microorganisms that developed the ability to survive in the extreme environment by exhibiting special characteristics such as pigmentation and production of exopolysaccharides.     

南海中西部叶绿素时空变化特征分析

本文使用2003年1月—2019年12月MODIS遥感数据,结合海表温度、风速分析南海中西部叶绿素质量浓度分布特征和影响因素。结果显示南海中西部叶绿素质量浓度分布存在时空变化。EOF分解表明,EOF1可能反映台风等极端天气对叶绿素的影响;而EOF2 和EOF3均反映了夏季沿岸上升流对叶绿素分布的影响。相关分析表明南海中西部叶绿素质量浓度与海面风场呈正相关(r=0.87,p<0.01),与海表温度呈负相关(r=-0.59,p<0.05)。夏季在西南季风影响下越南东南沿海形成上升流,导致该区浮游植物旺发、叶绿素质量浓度升高;冬季受强东北季风影响,研究区海洋上层混合作用强烈,营养盐供应增加,促进了浮游植物生长,叶绿素质量浓度高于其他季节。     

莱州湾环境污染遥感信息提取试验

采用Landsat 图像跨度40 多年数据, 利用遥感手段对莱州湾7 大排污口环境污染状况进行了遥感信息提取试验, 结果显示与多年来分析调查的结果一致, 即通过入海排放口水色变化以及像素分析发现自20 世纪90 年代以来, 莱州湾海水污染逐年加重; 通过MODI 数据和ENVISATASAR数据分析提取了莱州湾2011 年的海温变化、叶绿素浓度分布和海面溢油信息, 结果显示该区域近岸海温和叶绿素浓度偏高, 海上溢油风险加大。研究结果表明, 利用遥感技术能有效地提取海区环境污染信息, 可以作为监控海水污染的有效手段之一。     

利用Landsat数据反演近岸海水表层温度的大气校正算法

介绍了一种将大气效应考虑在内、利用Landsat TM、ETM+热红外数据进行近海岸海表水温反演的单窗算法.在该算法中,将地表气温、相对湿度等常规气象资料作为初始参数,根据对流层中大气温度随高度呈线性降低、水汽随高度呈指数衰减的规律,建立了估算平均大气温度及水汽含量的通用模式.通过与实测数据及MODIS Terra海表水温产品比较发现,该算法能够提高运用TM/ETM+TIR单波段数据进行近岸海表水温(SST)反演的精度:一方面,反演所得结果更接近于海表实际水温;另一方面,它在一定程度上剔除大气中的水汽对SST反演的影响,进而提高海表水温的温度对比度.该提出的大气校正算法只需地表大气温度及相对湿度资料,该算法也无需进行大气模式的界定.     

Analysis of the Tsunami of December 26, 2004, on the Kerala Coast of India—Part I: Amplitudes

The Indian Ocean tsunami of December 26, 2004, not only affected the Bay of Bengal coast of India but also part of the Arabian Sea coast of India. In particular, the tsunami caused loss of life and heavy damage on some parts of the Kerala coast in southwest India. The tsunami traveled west, south of Sri Lanka, and some of the tsunami energy was diffracted around Sri Lanka and the southern tip of India and moved northward into the Arabian Sea. However, tsunami, being a long gravity wave with a wave length of a few hundred kilometers, has to take a wide turn. In that process, it missed the very southern part of the Kerala coast and did not achieve large amplitudes there. However, further north, the tsunami achieved amplitudes of upto 5 m and caused loss of life and significant damage. Here we identify the physical oceanographic processes that were responsible for selective amplification of the tsunami in certain locations.     

Observations of Tsunami Impact on the Coast of Kerala, India

The tsunami generated by the December 2004 Sumatra-Andaman earthquake had a devastating effect on some parts of Kerala coast, which is a coast located in southwest India. Results of post-tsunami field surveys carried out to understand the changes in coastal morphology and sediment characteristics in the worst affected Kayamkulam region of Kerala coast are documented in this study. Analysis of offshore bathymetric data indicates the shifting of depth contours towards shore, indicating erosion of sediments and deepening of innershelf due to the tsunami. Depth measurement along the backwater (T-S canal) in the hinterland region indicates siltation due to the inundation of the canal.     

Observations of Tsunami Impact on the Coast of Kerala,India

The tsunami generated by the December 2004 Sumatra-Andaman earthquake had a devastating effect on some parts of Kerala coast, which is a coast located in southwest India. Results of post-tsunami field surveys carried out to understand the changes in coastal morphology and sediment characteristics in the worst affected Kayamkulam region of Kerala coast are documented in this study. Analysis of offshore bathymetric data indicates the shifting of depth contours towards shore, indicating erosion of sediments and deepening of innershelf due to the tsunami. Depth measurement along the backwater (T-S canal) in the hinterland region indicates siltation due to the inundation of the canal.     

Analysis of the Tsunami of December 26, 2004, on the Kerala Coast of India—Part I: Amplitudes

The Indian Ocean tsunami of December 26, 2004, not only affected the Bay of Bengal coast of India but also part of the Arabian Sea coast of India. In particular, the tsunami caused loss of life and heavy damage on some parts of the Kerala coast in southwest India. The tsunami traveled west, south of Sri Lanka, and some of the tsunami energy was diffracted around Sri Lanka and the southern tip of India and moved northward into the Arabian Sea. However, tsunami, being a long gravity wave with a wave length of a few hundred kilometers, has to take a wide turn. In that process, it missed the very southern part of the Kerala coast and did not achieve large amplitudes there. However, further north, the tsunami achieved amplitudes of upto 5 m and caused loss of life and significant damage. Here we identify the physical oceanographic processes that were responsible for selective amplification of the tsunami in certain locations.     

深圳沿岸海域净初级生产力的遥感反演及其时空变化分析

以深圳沿岸海域为研究区,以MODIS/AQUA卫星遥感产品为数据源,结合实测浮标数据修正了VGPM中叶绿素a含量的估算进而分析深圳沿岸海域净初级生产力的时空分布规律.研究表明:(1)深圳沿岸海域2014年2、5、8、10月的净初级生产力在空间分布上从近海向外逐渐降低,初级生产力整体呈现出"西高东低"的局面,且未有明显的季节性波动.(2)4个海区的叶绿素a含量均表现为夏季最高秋冬季次之,但各海区主要影响因素不同,珠江口主要受季风造成的浮游植物种类与细胞密度的季节变化影响,大亚湾主要受营养盐限制,大鹏湾的主导因素为湾内余流的季节变化,深圳湾的叶绿素a含量主要与浮游植物细胞密度的季节变化有关.(3)珠江口的初级生产力春夏季高于秋冬季;大鹏湾的初级生产力夏季最高,且季节变化趋势与叶绿素a表现一致;深圳湾的初级生产力夏季最高,且季节变化趋势与海表温度表现一致;大亚湾的初级生产力波动明显,夏冬季海洋初级生产力数值总体高于春秋季.     

渤海海温与叶绿素季节空间变化特征分析

以2003年MODIS数据为数据源，在图像处理、空间插值的基础上作海温与叶绿素浓度的空间相关分析。结果表明，整个海域的叶绿素浓度和海温的分布具有明显的区域和季节变化特征。基本规律是叶绿素浓度从近岸向渤海中央递减；温度则随季节发生变化，随着温度升高，近海叶绿素浓度增高，而渤海中央区域叶绿素浓度降低。渤海叶绿素浓度的分布与河口径流、季节等因素有关。从空间关系看，海温与叶绿素浓度不存在很明显的空间分布相关性，但不同季节有不同的相关性。上述研究可用于估算海洋初级生产力。