Retrieval of sea surface velocities using sequential Ocean Colour Monitor (OCM) data

The Indian remote sensing satellite, IRS-P4 (Oceansat-I) launched on May 26th, 1999 carried two sensors on board, i.e., the Ocean Colour Monitor (OCM) and the Multi-frequency Scanning Microwave Radiometer (MSMR) dedicated for oceanographic research. Sequential data of IRS-P4 OCM has been analysed over parts of both east and west coast of India and a methodology to retrieve sea surface current velocities has been applied. The method is based on matching suspended sediment dispersion patterns, in sequential two time lapsed images. The pattern matching is performed on a pair of atmospherically corrected and geo-referenced sequential images by Maximum Cross-Correlation (MCC) technique. The MCC technique involves computing matrices of cross-correlation coefficients and identifying correlation peaks. The movement of the pattern can be calculated knowing the displacement of windows required to match patterns in successive images. The technique provides actual flow during a specified period by integrating both tidal and wind influences. The current velocities retrieved were compared with synchronous data collected along the east coast during the GSI cruise ST-133 of R.V. Samudra Kaustubh in January 2000. The current data were measured using the ocean current meter supplied by the Environmental Measurement and CONtrol (EMCON), Kochi available with the Geological Survey of India, Marine Wing. This current meter can measure direction and magnitude with an accuracy of ±5‡ and 2% respectively. The measurement accuracies with coefficient of determination (R2 ) of 0.99, for both magnitude (cm.s-1) and direction (deg.) were achieved

Retrieval of sea surface velocities using sequential Ocean Colour Monitor (OCM) data

he Indian remote sensing satellite, IRS-P4 (Oceansat-I) launched on May 26th, 1999 carried two sensors on board, i.e., the Ocean Colour Monitor (OCM) and the Multi-frequency Scanning Microwave Radiometer (MSMR) dedicated for oceanographic research. Sequential data of IRS-P4 OCM has been analysed over parts of both east and west coast of India and a methodology to retrieve sea surface current velocities has been applied. The method is based on matching suspended sediment dispersion patterns, in sequential two time lapsed images. The pattern matching is performed on a pair of atmospherically corrected and geo-referenced sequential images by Maximum Cross-Correlation (MCC) technique. The MCC technique involves computing matrices of cross-correlation coefficients and identifying correlation peaks. The movement of the pattern can be calculated knowing the displacement of windows required to match patterns in successive images. The technique provides actual flow during a specified period by integrating both tidal and wind influences. The current velocities retrieved were compared with synchronous data collected along the east coast during the GSI cruise ST-133 of R.V. Samudra Kaustubh in January 2000. The current data were measured using the ocean current meter supplied by the Environmental Measurement and CONtrol (EMCON), Kochi available with the Geological Survey of India, Marine Wing. This current meter can measure direction and magnitude with an accuracy of ±5‡ and 2% respectively. The measurement accuracies with coefficient of determination (R2) of 0.99, for both magnitude (cm.s-1) and direction (deg.) were achieved

Studies on mineral dust using airborne lidar, ground-based remote sensing, and in situ instrumentation

© 2018 The Author(s). Published by EDP Sciences. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (http://creativecommons.org/licenses/by/4.0/).In August 2015, the AER-D campaign made use of the FAAM research aircraft based in Cape Verde, and targeted mineral dust. First results will be shown here. The campaign had multiple objectives: (1) lidar dust mapping for the validation of satellite and model products; (2) validation of sunphotometer remote sensing with airborne measurements; (3) coordinated measurements with the CATS lidar on the ISS; (4) radiative closure studies; and (5) the validation of a new model of dustsonde.Peer reviewe

Monsoon oscillations regulate fertility of the Red Sea

Tropical ocean ecosystems are predicted to become warmer, more saline, and less fertile in a future Earth. The Red Sea, one of the warmest and most saline environments in the world, may afford insights into the function of the tropical ocean ecosystem in a changing planet. We show that the concentration of chlorophyll and the duration of the phytoplankton growing season in the Red Sea are controlled by the strength of the winter Arabian monsoon (through horizontal advection of fertile waters from the Indian Ocean). Furthermore, and contrary to expectation, in the last decade (1998–2010) the winter Red Sea phytoplankton biomass has increased by 75% during prolonged positive phases of the Multivariate El Niño–Southern Oscillation Index. A new mechanism is reported, revealing the synergy of monsoon and climate in regulating Red Sea greenness

Application of IRS-P4 OCM data to study the impact of tidal propagation on sediment dynamics in the Gulf of Kachchh

129-137This paper reports observations with respect to suspended sediment dispersal pattern at various stages of the tide cycles using the Indian Remote Sensing Satellite (IRS-P4) Ocean Colour Monitor (OCM) data, exploiting the high temporal resolution of two days and specific narrow spectral channels suitable to retrieve suspended sediment concentration. The shelf region of the Gulf, west of its mouth, plays a key role in sediment dispersal pattern within the Gulf of Kachchh as is evidenced by different linear shaped, clockwise and anticlockwise circulation patterns. The suspended sediments are transported as a V-shaped front into the Gulf during flooding conditions and as linear plumes fanning out of the Gulf during ebb conditions. Sediments are being transported into the Gulf along the northern shore from the Indus delta during flooding phase, whereas the southern shore gets sediments from the southern parts of the mouth. The study of sediment dispersal pattern led to dividing the Gulf of Kachchh into six zones, having characteristic sediment dispersal patterns. The information is useful for maintaining the approach channels of ports in addition to understanding dispersal of pollutants such as oil slicks under tidal influence

Application of IRS-P4 OCM data to study the impact of tidal propagation on sediment dynamics in the Gulf of Kachchh

This paper reports observations with respect to suspended sediment dispersal pattern at various stages of the tide cycles using the Indian Remote Sensing Satellite (IRS-P4) Ocean Colour Monitor (OCM) data, exploiting the high temporal resolution of two days and specific narrow spectral channels suitable to retrieve suspended sediment concentration. The shelf region of the Gulf, west of its mouth, plays a key role in sediment dispersal pattern within the Gulf of Kachchh as is evidenced by different linear shaped, clockwise and anticlockwise circulation patterns. The suspended sediments are transported as a V-shaped front into the Gulf during flooding conditions and as linear plumes fanning out of the Gulf during ebb conditions. Sediments are being transported into the Gulf along the northern shore from the Indus delta during flooding phase, whereas the southern shore gets sediments from the southern parts of the mouth. The study of sediment dispersal pattern led to dividing the Gulf of Kachchh into six zones, having characteristic sediment dispersal patterns. The information is useful for maintaining the approach channels of ports in addition to understanding dispersal of pollutants such as oil slicks under tidal influence

Coastal processes along the Indian coast - Case studies based on synergistic use of IRS-P4 OCM and IRS-1C/1D data

459-472The sequential Suspended Sediment Concentration (SSC) maps were generated using IRS-P4 OCM (Ocean Color Monitor) data for selected tide dominated, wave dominated and deltaic coasts around the Indian subcontinent. Patterns of SSC were studied to understand the sediment dynamics, circulation patterns, fronts and consequent impact on coastal processes. Hitherto, unknown sediment plumes extending for large distance into deep offshore areas could be identified from the major deltaic regions. The high temporal capability of OCM data was extremely useful to understand sediment dynamics in tide-dominated regions of the Gulf of Khambhat, the Gulf of Kachchh and the Hoogli estuary. SSC maps in conjunction with corresponding tide and bathymetry data could be sequenced as per flooding and ebb cycles. Development, formation, shifting nature of shoals and sediment curls during a tide cycle could be studied. It is observed that during the North-East (NE) monsoon suspended sediment influx of the Ganga-Brahmaputra system influences the coastal processes along the continental margins of the Orissa and the Northern Andhra Pradesh along east coast of India. The occurrence of cyclone aids in entrapment of fluvial discharge into the coastal waters, leading to a reduced offshore influx into deeper regions of the Bay of Bengal and high sedimentation near to the coast. Seasonal changes along wave-dominated west coast showed net sediment transport from north to south in the pre-monsoon season and south to north in post-monsoon season. Significant onshore- offshore transport along west coast was also observed. The impact of the regional sediment dynamics on the site-specific local coastal environment was studied by integrating observations derived from OCM and IRS-1C/1D data. The paper concludes the utility of Ocean Color Monitor and IRS-1C/1D data in studying various coastal processes and regional sediment dynamics

Radiant heating rates and surface biology during the Arabian Sea Monsoon Experiment

Radiometric observations are carried out to estimate the net shortwave solar radiation in the upper ocean during the Arabian Sea Monsoon Experiment Phase II (ARMEX-II). Radiant heating rates in the Arabian Sea Warm Pool (ASWP) region from in situ radiometric measurements are presented for the first time. The estimated shortwave fluxes (300-700nm) from the observed data are 101, 62, 40 and 29 W m(-2) at 10, 20, 30and 40 m depths respectively. About 5% of the surface light reaches below 50 m. Heating of the water column by penetrating solar radiationis substantial and estimated to be 0.18, 0.11, 0.08 and 0.07 degrees Cday(-1) in the upper 10, 20, 30 and 40 m respectively. Simultaneous observations from space-based sensors (SeaWiFS and IRS-P4 Ocean ColourMonitor) show an increase in solar absorption in regions with enhanced concentration of biologically active constituents

Improved regional algorithm to retrieve total suspended particulate matter using IRS-P4 ocean colour monitor data

Data from seven validation campaigns in the coastal waters of the Bay of Bengal (BOB) were used to develop a regional SPM (suspended particulate matter) algorithm. The in situ data sets for this algorithm are obtained from 86 stations with optical and 68 stations with total SPM measurements encompassing SPM concentrations between 10 and 189 mg l−1, where most of the observations are in shallow (case 2, average depth ~45 m) waters and a limited number of samples in open case 1 waters. From simple statistical analyses we found a close relationship between SPM concentration and diffuse attenuation coefficient at 555 nm (K555) in the BOB coastal waters. The linear regression to the fit has a coefficient of determination (r2) 0.96 with a standard error of estimates (σ)12.5 mg l−1 for the above SPM range. The algorithm relating K555 to [Lwn443/Lwn670] has been evaluated through a regression analysis of radiometric profiles in the BOB. However, the new SPM algorithm overestimates in case 1 waters (SPM range 0.05–25.0 mg l−1), where a spectral reflectance ratio algorithm (Tassan 1994 Appl. Opt. 33 2369–78) appears to produce better results. An integration of both the approaches performs better in generating the routine IRS-P4 OCM (ocean colour monitor) SPM mapped product

Coastal processes along the Indian coast - case studies based on synergistic use of IRS-P4 OCM and IRS-1C/1D data

The sequential Suspended Sediment Concentration (SSC) maps were generated using IRS-P4 OCM (Ocean Color Monitor) data for selected tide dominated, wave dominated and deltaic coasts around the Indian subcontinent. Patterns of SSC were studied to understand the sediment dynamics, circulation patterns, fronts and consequent impact on coastal processes. Hitherto, unknown sediment plumes extending for large distance into deep offshore areas could be identified from the major deltaic regions. The high temporal capability of OCM data was extremely useful to understand sediment dynamics in tide-dominated regions of the Gulf of Khambhat, the Gulf of Kachchh and the Hoogli estuary. SSC maps in conjunction with corresponding tide and bathymetry data could be sequenced as per flooding and ebb cycles. Development, formation, shifting nature of shoals and sediment curls during a tide cycle could be studied. It is observed that during the North-East (NE) monsoon suspended sediment influx of the Ganga-Brahmaputra system influences the coastal processes along the continental margins of the Orissa and the Northern Andhra Pradesh along east coast of India. The occurrence of cyclone aids in entrapment of fluvial discharge into the coastal waters, leading to a reduced offshore influx into deeper regions of the Bay of Bengal and high sedimentation near to the coast. Seasonal changes along wave-dominated west coast showed net sediment transport from north to south in the pre-monsoon season and south to north in post-monsoon season. Significant onshore- offshore transport along west coast was also observed. The impact of the regional sediment dynamics on the site-specific local coastal environment was studied by integrating observations derived from OCM and IRS-1C/1D data. The paper concludes the utility of Ocean Color Monitor and IRS-1C/1D data in studying various coastal processes and regional sediment dynamics