Earth Observation (EO) from satellites has opened a new dimension toward understanding our planet, enabling significant insights into its dynamics, environment, and changes over time. The satellites have a unique capability of providing data at the synoptic scale in physically inaccessible areas at longer time scales. The satellites equipped with advanced sensors capture data across various spectrums, from visible light to microwaves, offering a comprehensive view of the Earth’s surface, including the atmosphere and ocean. This capability supports numerous applications in environmental monitoring, disaster management, land use, urban planning, etc. Although there are few limitations in the satellite-based EO, in terms of accuracy and estimation of errors, the emerging technologies and novel algorithms have made this one of the best techniques to foster sustainable development and safeguard the Earth’s ecosystems for future generations.
The ocean covers approximately 71% of the earth’s surface and has excellent potential to provide food and resources for livelihood and, thus, socio-economic development. Significantly, the coastal communities primarily depend on the ocean for economic activities such as fishing and tourism, highlighting its vital role in socio-economic development. In addition, the ocean also plays a significant role in modulating the Earth’s climate by absorbing heat and dispersing it by means of currents through circulation. This temperature regulation is essential for maintaining stable climatic conditions that significantly influence regional weather patterns to extreme events such as cyclones and storms. The oceans serve as a carbon sink, taking in significant human activity-generated CO2 emissions from the land. This process helps alleviate the effects of climate change by lowering the concentration of greenhouse gases, which are responsible for the rise in the earth’s temperature. Therefore, observing and monitoring the ocean for sustainable exploration of food and resources and assessing climate change for mitigation measures is essential.
MINING INFORMATION ON OCEAN
Indian National Centre for Ocean Information Services (INCOIS) provides ocean information and advisory services to various stakeholders through sustained ocean observations and systematic and focused research. INCOIS provides various ecosystem and disaster-related services using EO satellite data on an operational basis, which includes Potential Fishing Zone Advisory Service, Algal Bloom Information Service, Coral Bleaching Alerts, Marine Heatwave Advisory Service, and Coastal Geospatial Information. Similarly, the Indian Meteorological Department (IMD) provides cyclone warning services using EO satellite data.
India ranks as the third-largest fish producer globally, directly supporting 16 million fishers and fish farmers, with nearly double that number involved along the value chain. Since Independence, the country’s fish production has steadily increased from 0.75 million tonnes to 14.16 million tonnes in 2019-20, with about 74 % of this coming from inland sources and the remainder from marine capture fisheries. India’s total fisheries potential is estimated at 22.31 million metric tons, with marine fisheries potential accounting for 5.31 million metric tons. With a synoptic view, the EO satellite data can detect mesoscale features and, when combined with conventional knowledge, has provided a powerful tool for identifying the Potential Fishing Zone (PFZ).
The identification of PFZ using EO satellite data primarily uses Sea Surface Temperature (SST) from the infrared or microwave sensor and phytoplankton pigment from the visible sensor. The SST indicates the physical process, whereas the chlorophyll provides information on food availability. In addition, the wind field from the Scatterometer data is used to provide a shift in the features. The lower SST indicates the presence of high nutrient and oxygen-rich waters, which may result from horizontal or vertical movement of the water mass, which can be detected using a satellite-based altimeter. These productive fronts provide necessary and sufficient conditions for phytoplankton growth, indicated by high chlorophyll. The fronts with lower SST and higher chlorophyll concentration are identified as potential grounds for fisheries using EO satellite data. The PFZ Advisory Service, provided by INCOIS on an operational basis, is one of the most mature applications of the EO satellite data. The fishermen can directly navigate to these areas without continuing to search for the shoals, resulting in a reduction in search time and also the emission of CO2 into the atmosphere. Several researchers and institutes have conducted independent studies on the economic benefits of PFZ advisory services towards socio-economic and environmental benefits, indicating a significant increase in fish catch and a reduction in CO2 emission.
India’s productive coastal waters sustain extensive fisheries. However, an increasing threat is posed by the growing frequency of Harmful Algal Bloom (HABs). These blooms are considered harmful due to their negative impacts on marine flora, fauna, and the environment, and they can also adversely affect fisheries. Factors such as ballast water exchange, aquaculture practices, climate change, and pollution due to human activities contribute to the increasing frequency and spatial extent of these blooms. Toxic HABs directly impact human health, while non-toxic blooms indirectly affect the ecosystems by causing hypoxia/anoxia, reducing food web efficiency, increasing pathogenic bacteria, etc. INCOIS’ Algal Bloom Information service (ABIS) provides near real-time information on the bloom occurrences in the North Indian Ocean region. The EO satellite-based standard and value-added products are used to provide ABIS at four hotspots: the Northern Arabian Sea, Kerala, the Gulf of Mannar, and Gopalpur.
Like phytoplankton, coral reefs are abundant in Indian waters and play a crucial role in providing habitats for a diverse range of marine species. These massive biological structures have evolved over millennia in coastal oceans. However, in India, coral reefs are being damaged and destroyed at an alarming rate due to anthropogenic pressures and interventions. INCOIS’ Coral Bleaching Alert System (CBAS) utilizes SST data from the EO satellite to assess the thermal stress on the coral reef environments. This thermal stress is calculated using bi-weekly composite SST data observed from the EO satellite and simulated using ocean models.
Image Courtesy: Dr T Srinivasa Kumar & Dr Aneesh A Lotliker
EO DATA FOR DISASTER WARNING
The EO satellite data is crucial in understanding disaster-related processes, particularly cyclones, storms, Marine Heat Wave (MHW), etc. The Indian Meteorological Department (IMD) issues cyclone warnings to safeguard coastal communities and mariners using a combination of EO satellite data, weather models, and ground observations. The EO satellites with various sensors, such as infrared and microwave radiometers, scatterometers and altimeters, provide essential data to analyse cyclone formation, intensity, and movement. These warnings are disseminated through various channels, including media, government agencies, and disaster management authorities, to ensure timely preparedness and response measures. These warnings are categorised based on their severity, providing detailed information on the cyclone track as well as on weather parameters and expected impact zones. This proactive approach enables authorities to implement evacuation plans, deploy relief efforts, and coordinate emergency response operations effectively, minimizing the loss of life and property during cyclonic events.
The MHWs, caused by a combination of atmospheric and oceanographic processes, significantly impact fisheries and coral reefs. Recently, frequent MHW events have led to marine habitat degradation, intense cyclones, and socioeconomic losses. The evolution and mechanisms behind these events depend on local air-sea coupling, atmospheric conditions, oceanic preconditions, and remote climatic teleconnections. INCOIS has researched the frequency and intensity of MHW variability in intra and interannual cycles and their forcing mechanisms using EO satellite and model-derived SST. To address their impact, INCOIS provides daily MHW advisories in the Indian Ocean and South China Sea. These advisories help understand the effects on marine habitats and the frequency and intensity of disaster events for Indian Ocean-rim countries and research communities.
Image Courtesy: Dr T Srinivasa Kumar & Dr Aneesh A Lotliker
SWIFT APPLICATION OF EO DATA
By integrating satellite observations with ground-based data and advanced ocean models, the agencies can accurately provide advisories and timely warnings and mitigate potential impacts on vulnerable populations and infrastructure. Communication satellites play a pivotal role in efficiently transferring real-time in situ data from various sensors and instruments, such as weather stations, ocean buoys, and environmental monitoring devices. By relaying this data to ground stations or other satellites in the network, communication satellites enable timely analysis and dissemination of critical information. This capability is crucial for applications ranging from ecosystem monitoring, weather forecasting, disaster management, scientific research and resource monitoring. Communication satellites ensure that the valuable in situ data can be accessed and utilized promptly, enhancing decision-making processes.
The observation and advisories on potential resources and disasters using EO satellites are of high importance due to their ability to provide comprehensive and continuous monitoring of the earth’s oceans on a global scale. Satellites equipped with advanced sensors such as UV-VIS-IR-Microwave radiometers, Scatterometer, and altimeters have unique capabilities to measure SST, ocean colour, sea level rise, ocean currents, etc. These observations are critical for understanding and predicting the impacts of climate change on marine ecosystems, including ocean acidification, coral bleaching, and shifts in ocean circulation patterns. The EO satellite data also plays a vital role in coastal zone management by providing comprehensive information at a synoptic scale that can be used for the sustainable management of coastal zones, offering valuable insights that support decision-making and help address the complex challenges faced by coastal environments. This integrated approach underscores the importance of satellite technology in enhancing our understanding and response to catastrophic events. Such insights are crucial for policymakers, researchers, and stakeholders involved in marine resource management, conservation efforts, and disaster preparedness.
*Dr T Srinivasa Kumar is Director, Indian National Centre for Ocean Information Services (INCOIS), Hyderabad, where Dr Aneesh A Lotliker is Scientist-F and Divisional Head, Ocean Observation Network.
