Ocean Colour Monitor Research Articles

Seasonal nitrate algorithms for nitrate retrieval using OCEANSAT-2 and MODIS-AQUA satellite data.

In situ datasets of nitrate, sea surface temperature (SST), and chlorophyll a (chl a) collected during the monthly coastal samplings and organized cruises along the Tamilnadu and Andhra Pradesh coast between 2009 and 2013 were used to develop seasonal nitrate algorithms. The nitrate algorithms have been built up based on the three-dimensional regressions between SST, chl a, and nitrate in situ data using linear, Gaussian, Lorentzian, and paraboloid function fittings. Among these four functions, paraboloid was found to be better with the highest co-efficient of determination (postmonsoon: R2=0.711, n=357; summer: R2=0.635, n=302; premonsoon: R2=0.829, n=249; and monsoon: R2=0.692, n=272) for all seasons. Based on these fittings, seasonal nitrate images were generated using the concurrent satellite data of SST from Moderate Resolution Imaging Spectroradiometer (MODIS) and chlorophyll (chl) from Ocean Color Monitor (OCM-2) and MODIS. The best retrieval of modeled nitrate (R2=0.527, root mean square error (RMSE)=3.72, and mean normalized bias (MNB)=0.821) was observed for the postmonsoon season due to the better retrieval of both SST MODIS (28 February 2012, R2=0.651, RMSE=2.037, and MNB=0.068) and chl OCM-2 (R2=0.534, RMSE=0.317, and MNB=0.27). Present results confirm that the chl OCM-2 and SST MODIS retrieve nitrate well than the MODIS-derived chl and SST largely due to the better retrieval of chl by OCM-2 than MODIS.

Remote Sensing Observations on Impact of Phailin Cyclone on Phytoplankton Distribution in Northern Bay of Bengal

Remote sensing-based analysis has been carried out to study the impact of “Phailin” cyclone on ocean phytoplankton distribution off Odisha coast and on the northern Bay of Bengal water. Oceansat-2 Ocean Colour Monitor (OCM) and MODISTerra sensors-derived chlorophyll images have been generated over the study area during October 2013. There has been observation of drastic change in the chlorophyll concentration of the north-western Bay of Bengal water with effect of the cyclone “Phailin,” which hit Gopalpur, Odisha coast on 12 October night at around 21:00 h IST. The postcyclone images of Oceansat-2 OCM data and retrieved chlorophyll concentration were observed to be very high, 3.0-4.0 mg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> in coastal water, which was around 0.5-1.0 mg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> during precyclone. Similarly, the postcyclone chlorophyll was around 0.80-1.50 mg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> in the offshore water, unusually high compared to precyclone concentration (<;0.60 mg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ). The cyclone track of India Meteorological Department (IMD) has been superimposed on chlorophyll images and observed as proxy along the chlorophyll front with algal bloom features. There has been observation of cooling in the northern Bay of Bengal and off Odisha coast with impact of the induced upwelling, entrainment and mixing of the water column, as evident from the sea surface temperature (SST) data analysis. Interesting features such as cold core eddies and fronts have been visualized. This study is important to assess the impact of Phailin cyclone on ocean productivity on the local and basin scale and its deviation from seasonal trend as well.

SSC Analysis of South Maharashtra Coast: A Case Study from Vengurla Coastal Region

Suspended sediment transport plays a major role in many coastal, estuarine and offshore engineering applications. The transport of suspended sediment influences the constructions of harbours, constructions of coastal power stations and refineries, safety of offshore platforms and pipelines, erosion and accretion of beaches, quality of the water and many other applications. To understand the suspended sediment transport pattern along South Maharashtra coastal region, a case study was conducted at Vengurla coastal waters. In order to do that, the sea water samples at 6 transects (18 stations) were collected for analysis of suspended sediment concentration (SSC) during pre-monsoon and post-monsoon periods. The results showed that during post monsoon, the SSC pattern at surface, mid and bottom layers having 10-20mg/l, 10-19mg/l and 50-60mg/l respectively. But during the pre-monsoon, the respective layers show 5-20mg/l, 4-15mg/l and 70mg/l of SSC concentration. In addition, Ocean Colour Monitor (OCM) satellite images were analyzed in the same study area to know the SSC distribution pattern. In Vengurla, post-monsoon, the SSC values of surface coastal waters ranging from 5-15mg/l from OCM satellite images and also SSC is compared with OBS 5+ profiles. In this paper, the SSC distribution pattern of both seasons is narrated and the validations of SSC using OCM satellite data are also discussed.

Modeling and remote sensing of suspended sediments in the Gulf of Kachchh, India

This paper presents a comprehensive analysis of OCEANSAT-1 OCM (Ocean Color Monitor)-derived suspended sediment concentration (SSC), MIKE 21-simulated SSC, bathymetry, and tidal current speed and direction using tidal harmonic analysis to study the suspended sediments in the Gulf of Kachchh in the Arabian Sea for tidal and monsoonal changes. The spring tide and bathymetry predominantly control the sediment dynamics at Okha and Navlakhi ports as shown by the time series data. The sequential high temporal resolution of OCM-derived SSC images is near-ideal means for monitoring the Gulf. The abrupt OCM-derived SSC values were due to the combined influence of deficient monsoon in 2004, prevailing winds, and the re-suspension of bottom sediments.

Impact of Cyclone PHAILIN on Chlorophyll-a Concentration and Productivity in the Bay of Bengal

Ocean colour remote sensing is one of the conventional methods in satellite oceanography used to study the biological response of the upper ocean to the tropical cyclones. This paper aims to study the impact of the Very Severe Cyclonic storm PHAILIN, and its consequence on the surface chlorophyll-aconcentration distribution in the Bay of Bengal using Oceansat-2 Ocean Colour Monitor (OCM). The impact of this cyclone on ocean primary productivity has been studied using MODIS-A data. Sea surface temperature (SST) plays an important role in the generation of primary productivity along with the other oceanographic parameters; SST patterns in the Bay of Bengal during the cyclone period were studied. From the analysis, it is observed that the chlorophyll-aconcentration has increased from 1.08 (before) to 7.06 mg/m3 after the cyclone with an SST drop of ~3°C (29.19°C to 26°C). The primary productivity has increased from 410.0506 to 779.9814 mg/C/m2/day after the cyclone. In addition to the above analysis, an attempt has also been made to study the impact of cyclone intensity on the chlorophyll concentration. The study shows that the comparison between cyclone intensity (CI) and chlorophyll concentration shows a positive relationship.

Application of Numerical Model in Suspended Sediment Transport Studies along the Central Kerala, West-coast of India

The objective of the present study is to understand the sediment transport along the central Kerala coast. The data used in the study include winds, tides, bathymetry and the satellite derived suspended sediment concentrations (SSCs). A sediment transport model - MIKE 21 Mud Transport (MT) - for combinedcurrents, and SSCs is used to quantify and to find out the movement of fine sediments along the coast. MIKE MT is interrelated with the other modules of MIKE 21 Hydrodynamics (HD) module. The HD module simulate the water level variations and flows in response to a variety of forcing functions in coastal areas. Suspended sediment transport in the coastal waters of central Kerala is simulated utilizing the SSC data derived from Oceansat-2 Ocean Colour Monitor (OCM) satellite imagery, using the MIKE-21 MT model for the period 18thto 24thJanuary 2011. The SSCs of 18thJanuary 2011 are considered as the initial condition in MIKE 21 MT model and the model is simulated for the period from 18th to 24th January 2011. The simulated SSCs are compared with satellite derived SSCs. The results exhibit good coefficient of determination among these variables. Sediment dispersion patterns are explained in relation to simulated tidal currents, dominated by the southward flowing coastal currents, which are more consistent in its direction and magnitude along the coast. It is observed that tides, winds and currents arethe important physical factors that control the dispersal patterns. The results suggest that sediment transport is from north to south during the study period i.e., in January 2011.

Retrieval of Aerosol Optical Depth from Oceansat-2 OCM

Aerosols are the tiny suspended particles in the atmosphere playing a major role in influencing the net radiation budget of the earth. The aerosols also affect cloud microphysics and those with land origin, possibly reduce the monsoon rainfall. Dynamic and diverse nature of the aerosols varies according to different locations. The aerosols originating due to desert dust, rural atmospheric situations, urban pollutants and marine areas have wide variations and display specific characteristics. Routine monitoring of aerosol events and their subsequent dispersal pattern are important in order to understand their role in climatic process. Hence, it is very important to study the aerosols and their retrieval strategy from the ocean colour remote sensing sensors. The satellite sensors provide platform for making observations covering large area as also their short-term and frequent repetivity. Ocean-colour sensors e.g. CZCS, SeaWiFS, MODIS, POLDAR, Oceansat-1 & 2 OCM have been used to study aerosols, apart from being used to study ocean-colour. Most of the ocean-colour sensors are equipped with a few additional near infrared (NIR) bands (λ > 700 nm), which are helpful in providing vital information on atmospheric aerosols due to strong absorption by water in NIR wavelengths. The present work is an attempt to study the temporal and spatial variations of Aerosol Optical Depth (AOD) over the Bay of Bengal using Oceansat-2 Ocean Colour Monitor (OCM).

Simulating the Effects of Tidal Dynamics on the Biogeochemistry of the Hooghly Estuary

A three-dimensional coupled hydrodynamic biogeochemical sediment transport model is proposed to simulate the response of plankton dynamics in the Hooghly estuary to freshwater discharge under the presence and absence of tide, and in-depth understanding the significant processes involved in estuarine biogeochemistry based on Regional Ocean Modeling System (ROMS). Riverine-estuarine circulations are used to evaluate the tidal consequence on wavering of biogeochemical properties in the Hooghly estuary. Therefore, three numerical experiments are performed: 1) model run with tidal forcing, river discharge, and applied biogeochemical and sediment properties along with coastal current; 2) model run with tidal forcing along with coastal current plus applied biogeochemical and sediment properties; and 3) model run with river discharge along with coastal current plus applied biogeochemical and sediment properties to determine the chief role of this physical parameters on the transport of bloom in a well-mixed estuary using this coupled model for the first time in Hooghly estuary. The model divulges its capability in imitating observed temporal variability in tidal oscillation representing skill coefficients more than 0.80. The satellite remotely sensed Ocean Color Monitor Data is assimilated using an SOR algorithm to incorporate in the model as the initial field for chlorophyll-a concentration (chla) to retrieve the productivity of the estuary. Productivity is found maximum in the area of soaring suspended sediment implying maximum bottom stress contributed by tidal currents along with coastal currents evident from the realistic case. The RMSE calculated is less than 0.6, which implies that the model can perform reasonably well.

Time Series Analysis Of Primary Productivity Along The East Coast Of India Using Oceansat-2 Ocean Colour Monitor (O cm)

Abstract. Primary Productivity is the ultimate source of energy for all organisms in an ecosystem. It is associated with the food production and the global carbon cycle. Sensors on remote platforms (satellites) are capable of estimating the Chlorophyll-a concentration in surface waters by measurement of spectral changes of the upwelling light. From these data, which connected with other remotely sensed data, it is possible to use algorithms to estimate the primary production. In this paper, an initial attempt is made to estimate the Primary Productivity along the east coast of India. Vertically Generalized Productivity Model (VGPM) which is a depth (euphotic depth) integrated model is used for the estimation. The common input variables or geophysical parameters used for the model are chlorophyll-a concentration (chl-a), vertically diffuse attenuation coefficient (Kd-490), Photosynthetically Available Radiation (PAR), and Sea Surface Temperature (SST). The chlorophyll-a and Kd-490 parameters were estimated using Oceansat-2 OCM data whereas PAR and SST were taken from MODIS-aqua data. Oceansat-2 Ocean Colour Monitor (OCM) data for the year 2013 is used in the analysis to compute the primary productivity using the weekly (8-day) data products of all the parameters as mentioned above. These products were inter compared with the MODIS Weekly (8-day) Primary Productivity products which were estimated at a global scale using the modified Vertically Generalized Productivity Model (VGPM) with which uses the exponential function of Sea surface temperature (SST).

Seasonal variability of phytoplankton blooms in the coastal waters along the East coast of India

Abstract. Bay of Bengal (BOB) is a semi enclosed tropical basin located in the north eastern part of the Indian Ocean with high influence of fresh water discharge from major rivers and rainfall. Bay of Bengal (BOB) is highly influenced by monsoons and represents a natural laboratory to study the effect of fresh water fluxes on the marine ecosystem. Bay of Bengal (BOB) is very low in productivity often with the observations of Phytoplankton Blooms. Phytoplankton blooms are one of the prominent features of biological variability in the coastal ecosystems such as estuaries, lagoons, bays, and tidal rivers with rapid production and accumulation of phytoplankton biomass in the ocean. These blooms usually respond to changing physical forcings originating in the coastal ocean like tides, currents and river runoff and to the atmospheric forcing like wind. These physical forcings have different timescales of variability, so algal blooms can be short-term episodic events, recurrent seasonal phenomena, or rare events associated with exceptional climatic or hydrologic conditions. Bloom events and their variability on spatial &amp;amp; temporal scales monitoring through field measurements is difficult. Based on this key hypothesis an effort is made to understand the seasonal and spatial variability of Phytoplankton Blooms along the East Coast of India. In this paper we present the bloom dynamics in their context to the chlorophyll concentration along with species composition and abundance in estuarine and near shore coastal waters of Godavari basin using Oceansat-2 Ocean Colour Monitor (OCM). The initial results revealed that the quasi permanent phytoplankton blooms initiates in the month of mid- February and evolves for a period of two months and then slowly starts decaying by the mid of May month. The results also stand as a base for the study of influence of Phytoplankton Blooms on the carbon flux estimations and bio-geo-chemical processes in the Bay of Bengal.

Payload Configurations for Efficient Image Acquisition – Indian Perspective

Abstract. The world is increasingly depending on remotely sensed data. The data is regularly used for monitoring the earth resources and also for solving problems of the world like disasters, climate degradation, etc. Remotely sensed data has changed our perspective of understanding of other planets. With innovative approaches in data utilization, the demands of remote sensing data are ever increasing. More and more research and developments are taken up for data utilization. The satellite resources are scarce and each launch costs heavily. Each launch is also associated with large effort for developing the hardware prior to launch. It is also associated with large number of software elements and mathematical algorithms post-launch. The proliferation of low-earth and geostationary satellites has led to increased scarcity in the available orbital slots for the newer satellites. Indian Space Research Organization has always tried to maximize the utility of satellites. Multiple sensors are flown on each satellite. In each of the satellites, sensors are designed to cater to various spectral bands/frequencies, spatial and temporal resolutions. Bhaskara-1, the first experimental satellite started with 2 bands in electro-optical spectrum and 3 bands in microwave spectrum. The recent Resourcesat-2 incorporates very efficient image acquisition approach with multi-resolution (3 types of spatial resolution) multi-band (4 spectral bands) electro-optical sensors (LISS-4, LISS-3* and AWiFS). The system has been designed to provide data globally with various data reception stations and onboard data storage capabilities. Oceansat-2 satellite has unique sensor combination with 8 band electro-optical high sensitive ocean colour monitor (catering to ocean and land) along with Ku band scatterometer to acquire information on ocean winds. INSAT- 3D launched recently provides high resolution 6 band image data in visible, short-wave, mid-wave and long-wave infrared spectrum. It also has 19 band sounder for providing vertical profile of water vapour, temperature, etc. The same system has data relay transponders for acquiring data from weather stations. The payload configurations have gone through significant changes over the years to increase data rate per kilogram of payload. Future Indian remote sensing systems are planned with very high efficient ways of image acquisition. This paper analyses the strides taken by ISRO (Indian Space research Organisation) in achieving high efficiency in remote sensing image data acquisition. Parameters related to efficiency of image data acquisition are defined and a methodology is worked out to compute the same. Some of the Indian payloads are analysed with respect to some of the system/ subsystem parameters that decide the configuration of payload. Based on the analysis, possible configuration approaches that can provide high efficiency are identified. A case study is carried out with improved configuration and the results of efficiency improvements are reported. This methodology may be used for assessing other electro-optical payloads or missions and can be extended to other types of payloads and missions.

Monitoring Chlorophyll – a Concentration in the Coastal Waters of Kalpakkam (India): Application of a Regional Algorithm using Oceansat – 2 Ocean Colour Monitor

The study aims for the quantitative assessment of chlorophyll concentration and their distribution in the coastal waters of Kalpakkam (Tamil Nadu, India) using the normalised water leaving radiance from the OCEANSAT-2 Ocean Colour Monitor (OCM-2) with in situ chlorophyll concentration. The site specific regional algorithm is based on the sigmoid relationship of the band ratio (nLw490/nLw555) and generates a polynomial relation. The validation of chlorophyll concentration yields a high correlation (r2 = 0.92) with 21 independent in situ samples. The study demonstrated the application potential of OCM-2 in assessing the biological conditions of coastal waters. The chlorophyll distribution predominates towards north depending on the local climatic conditions.

Generation of Vegetation Fraction and Surface Albedo Products Over India from Ocean Colour Monitor (OCM) Data Onboard Oceansat-2

The use of Local Area Coverage (LAC) data from Ocean Color Monitor (OCM) sensor of Oceansat-2 with its high radiometric resolution (12 bits/pixel) and 2-day repeat cycle for rapid monitoring of vegetation growth and estimating surface albedo for the Indian region is demonstrated in this study. For the vegetation monitoring, normalized difference vegetation index (NDVI) and vegetation fraction (VF) products were estimated by maximum value composite approach fortnightly and were resampled to 1 km. The surface albedo products were realized by converting narrow-band eight-band spectral reflectance OCM data to a) visible (300–700 nm) and b) broad band (300–3,000 nm) data. For validation, the derived products were compared with respective MODIS global products and found to be in good agreement.

Atmospheric correction based on inherent optical properties of sea water at NIR wavelengths combined with an automated aerosol spectra determination (ASD) technique

Atmospheric correction is the process whereby atmospheric effects on sensor-recorded radiance are removed and the surface radiance is estimated. Atmospheric effects due to gaseous absorption, molecular scattering – and their seasonal as well as latitudinal variations – can be adequately accounted for by using pre-computed look-up tables. However, scattering by aerosol particles is difficult to correct. At-sensor radiance at near-infrared (NIR) wavelengths, after being corrected for gaseous absorption and molecular scattering, was assumed (in standard atmospheric correction) to have been entirely due to aerosol scattering and was used to calculate the aerosol parameters. This assumption, although valid for open ocean clear waters, is not valid for turbid waters due to scattering by suspended particles in the water, which results in an appreciable amount of water-leaving radiance in the NIR region. A new turbid water atmospheric correction scheme is described here for Oceansat-2 Ocean Colour Monitor (OCM-2) data based on inherent optical properties (IOPs) of sea water at NIR, and obtaining an accurate spectral profile of aerosol radiance.

Absorption characteristics of ocean water in the Arabian Sea during winter bloom from in situ measurements and Oceansat 2 OCM and MODIS data

In the northern Arabian Sea, blooms usually occur during the northeast monsoon (November–January) and inter-monsoon (February–April) periods. After death, these phytoplankton blooms produce massive subsurface zones of low dissolved oxygen levels that have a major impact on the ocean water ecosystem. Many studies have been done to identify the bloom in this region, but those on the optical properties of bloom water are scarce. The present study emphasizes the optical properties (inherent) of the bloom water in the study region using in situ and satellite data. The total absorption coefficient of ocean water was measured from in situ radiance data collected in the northern Arabian Sea from the Sagar Sampada cruise (SS-286) during March 2011. The same data were also derived from the top-of-atmosphere radiance and remote sensing reflectance of the Oceansat 2 Ocean Colour Monitor (OCM-2) and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, respectively. A comparison between measured (in situ) and retrieved total absorption coefficients from OCM-2 was made. The measured and retrieved absorption coefficients are in good agreement. Root mean square errors between measured and retrieved absorption coefficients are 0.018 m−1, 0.026 m−1, and 0.034 m−1 for 490 nm, 510 nm, and 555 nm, respectively. An inter-comparison of total absorption properties retrieved from OCM-2 and MODIS data in the region of one degree radius around the stations was also made. A fairly good match was observed on 10, 14, and 16 March 2011 (coefficient of determination, R2 = 0.75, 0.87, and 0.62, respectively) for the blue band (490 nm) and (R2 = 0.77, 0.79, and 0.71, respectively) the green band (555 nm). The study demonstrates the potential of using remote-sensing optical data for identifying bloom waters.

Improbability mapping: A metric for satellite-detection of submarine volcanic eruptions

Submarine volcanic eruptions can result in both real and apparent changes in marine algal communities, e.g., increases in phytoplankton biomass and/or growth rates that can cover thousands of square kilometers. Satellite ocean color monitoring detects these changes as increases in chlorophyll and particulate backscattering. Detailed, high resolution analysis is needed to separate the optical effects of volcanic products from the response of the marine algal community. It is possible to calculate an index, which maps the magnitude of improbable change (relative to long term average conditions) following known volcanic eruptions by using low resolution, initial estimates of chlorophyll and backscatter along with an archived history of satellite data. We apply multivariate probability analysis to changes in global satellite ocean chlorophyll and particulate backscatter data to create a new metric for observing apparent biological responses to submarine eruptions. Several examples are shown, illustrating the sensitivity of our improbability mapping index to known submarine volcanic events, yielding a potentially robust method for the detection of new events in remote locations.

A technique for estimation of suspended sediment concentration in very high turbid coastal waters: An investigation from Gulf of Cambay, India

Abstract This paper presents a technique to estimate the suspended sediment concentration (SSC) in Case-2 waters based on spectral similarity between satellite images and library spectra. Average Weighted Spectral Similarity (AWSS), a measure of spectral matching, is used to estimate SSC ranges in ocean color monitor (OCM) data of Gulf of Cambay (GC), India. For this, a spectral library comprising field and laboratory measured data representing diverse sediment mineralogy and grain sizes was generated. Results estimated by AWSS were compared with other published procedures and observed to be more accurate (R 2 = 0.95 at 99% significance). Further, in Case-2 waters reflectance in bands centered at 743 and 835 nm is more sensitive to SSC changes. Sediment concentration and grain size significantly affect reflectance of water.

An Algorithm for Estimating Suspended Sediment Concentrations in the Coastal Waters of India using Remotely Sensed Reflectance and its Application to Coastal Environments

This study presents an empirical relationship of suspended sediment concentrations (SSCs) inthe coastal waters, which is derived from the conventional methods, to radiometer remote sensing reflectance values (Rrs) and satellite data in coastal waters of Kerala. An algorithm is then developed to utilize both in situ SSCs measured from conventional methods and Rrs values. This algorithm is validated with the SSCs retrieved from Oceansat-2 Ocean Colour Monitor (OCM) data. A significant coefficient of determination (R2=0.62) is observed between the SSCs measured in situ and satellite derived SSCs. Reflectance values from more than two spectral wavelength bands are also employed to test the accuracy of results. Satellite derived SSCs range from 1- 40 mg/L in the coastal waters off Cochin, southwest India. The regional algorithm developed for the study area gives better results than Tassan’s algorithm, and this algorithm can be used in estimation of SSC for coastal waters of western India.

Evaluation of the VIIRS ocean color monitoring performance in coastal regions

Ocean color (OC) remote sensing has entered a new phase with the successful deployment of the Visible Infrared Imager Radiometer Suite (VIIRS) sensor aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite. The representativeness and accuracy of the VIIRS geophysical products need to be assessed before a wide use of these data by the scientific community. As an integral part of the VIIRS sensor calibration and validation efforts, our group has been continuously monitoring the validity of the VIIRS's OC and atmospheric data stream through time-series in-situ data acquired at the observatory sites which are part of the AERONET-OC network. This paper addresses the preliminary evaluations of the VIIRS sensor's performance for retrieving OC data of typical coastal water environments, by carrying out time-series, as well as qualitative and quantitative match-up comparisons analysis between in-situ and satellite retrieved OC data. Initial time-series match-up comparisons carried out for a year period (January to December, 2012) show that VIIRS data exhibits strong temporal and statistical agreements with AERONET-OC data demonstrating a potential in enhanced coastal water monitoring from space. VIIRS data of two NASA-OBPG processing schemes which apply different vicarious calibration gains and NOAA-IDPS system are analyzed based on in-situ data of LISCO and WaveCIS AERONET-OC sites which are located in Long Island Sound and Gulf of Mexico respectively as well as OC retrievals of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor aboard the Aqua satellite. The underlying cause of the discrepancies observed in VIIRS retrieved normalized water-leaving radiances is also investigated. Finally, as the NASA-OBPG and NOAA-IDPS processing schemes for ocean color data of the VIIRS sensor continue to evolve, the results underline the necessity for monitoring and assessing the validity and consistency of VIIRS' ocean color products, especially for coastal waters.

Suspended Sediment Concentration Profiles From Synoptic Satellite Observations

A method is developed to estimate vertical suspended sediment concentration (SSC) profiles in Gulf of Kachchh, from the sediment concentration values derived from synoptic observations of Ocean Colour Monitor (OCM). Under the influence of currents, vertical SSC profiles are defined by power law being based on the frictional velocities and sediment settling velocities. For each water pixel in OCM, the vertical variations in SSC are determined from the SSC profiles calculated from power law using corresponding simulated frictional velocities and sediment size parameters. OCM derived SSC is considered to be summation of sediment concentration values from surface to first attenuation depth (hereafter OCM-depth) with an exponential decay of values with depth. Vertical variation profiles from surface to OCM-depth are scaled with respect to the corresponding OCM SSC values and the projected concentrations at the bottom are derived. The bottom concentrations derived is observed to vary chiefly with the tidal conditions prevailing within the gulf, when during the slack hours increase in bottom SSC values get enhanced owing to the settling of sediments from suspension.