Preface: Interdisciplinary multi-sensor studies of the Pacific and Indian Oceans

This article refers to:

Analysis of surfactant-associated bacteria in the sea surface microlayer using deoxyribonucleic acid sequencing and synthetic aperture radar

1. Introduction

This is a special issue featuring a selection of research papers presented at the 14th Biennial Pan Ocean Remote Sensing Conference (PORSEC) in November 2018, and follows six previous special IJRS issues of PORSEC meetings held in Busan, Korea; Guangzhou, China; Keelung, Taiwan; Kochi, India; Bali, Indonesia; and Fortaleza, Brazil (Levy and Gower 2008, 2010, 2012; Gower and Levy 2014; Levy, Vigundelli, and Gower 2016, 2018). PORSEC was initially established during the International Space Year 1990, as the Pacific Ocean Remote Sensing Conference – an organization dedicated to helping developing nations around the Pacific Rim stimulate their science programmes focused on the applications of remote sensing technology to Ocean Sciences. Primarily through volunteer efforts, and with some support from the host countries and national and international agencies that share its principles, the PORSEC Association has held biennial scientific meetings since 1992, which have rapidly expanded and gained global status as prestigious remote sensing conferences, with a scope covering all the world’s oceans. The goal of the meetings and the associated training courses, held regularly since 2000, is to further the understanding of the Earth’s environmental processes, and to assist in training, education, and capacity-building. As the landscape of earth observing systems has been changing in the past three decades, with many nations moving forward with missions, many with a regional focus, PORSEC has continued in its efforts to advance science capabilities and to build a bridge to the future, while expanding to new regions and countries, such as India and the Indian Ocean, and Brazil and the Atlantic. Conferences take advantage of the unique perspectives provided by satellite remote sensing technology and those of the host country/region, while striving to protect the ocean and atmosphere and promote sustainable use and development of oceanic and coastal resources. PORSEC 2018 and the preceding capacity-building course were held in Jeju Island, the Republic of Korea, and hosted by the Korea Ocean Satellite Centre (KOSC) of the Korea Institute of Ocean Science and Technology (KIOST) that is in charge of the operation of the Geostationary Ocean Colour Imager (GOCI), and provides real-time satellite operation, scientific algorithm, and application technique development, operational computing system development, and sensor/hardware development for GOCI/GOCI-II. In kind and financial support from domestic organizations (Korea Aerospace Research Institute (KARI), Jeju Convention & Visitors Bureau (JejuCVB), Korea Tourism Organization) and international space science and research agencies (CNES (the French Centre National des Etudes Spatiales), INCOIS (Indian National Centre for Ocean Information Services, Ministry of Earth Sciences), NESDIS (the US National Environmental Satellite, Data, and Information Service), ONRG (the US Office of Naval Research Global)).

2. PORSEC2018 location, themes, and scope

Jeju Island is the largest volcanic island in Korea and it has a mild oceanic climate throughout the year with the smallest annual temperature range in South Korea. Officially called Jeju Special Self-Governing Province, this destination boasts mild maritime weather, as well as scenic beaches, waterfalls, cliffs, and caves. The island is 73 km wide and 31 km long with a total area of 1,848 ㎢.

The conference general theme was: ‘Interdisciplinary multi-sensor studies of the Pacific and Indian Oceans’. A total of 151 abstracts were submitted to the meeting by 170 attendees, representing 15 countries. The conference was organized in 10 thematic sessions:

1. Sea surface roughness from high-resolution SAR – a session focused on satellite observations and investigations of sea surface features including upwelling, oceanic fronts, coastal processes on reefs, lee waves, swell, wind shadows, wind rolls, internal structures of hurricanes, oil seepage and natural slicks, internal waves, and turbulent effects due to wakes. Studies on turbulent features at the air–sea interface at a resolution below 10 m using a combination of remote sensing, in situ and modelling techniques were also presented.

2. Satellite radar altimetry: progress in observing open oceans to coastal zone – Radar altimetry is a remote sensing technique capable of providing a unique long-term observational dataset to characterize how sea level and sea state variability evolve from the open ocean to the coastal zone. This session highlighted how altimeter data are improved, for example, with new technologies and algorithms, and used, often in combination with in situ or modelling tools, to contribute to the study, research, and operational monitoring of oceans. Applications included ocean circulation, storm surges and hurricanes, ocean wave field, water properties, air-sea transfer, biological–physical interactions, ecosystem dynamics, shelf processes, coral reefs, algal blooms, tsunamis, climate change, etc.

3. Remote-sensing of coastal ecosystems and intertidal flats – a session devoted to the capability of satellites to provide longitudinal remote sensing data for environmental impact assessment. Topics included combining new satellites with old ones, satellite constellation designs, and high-resolution images that allow monitoring and assessment of how the coastal area ecosystems, and in particular, intertidal flats are changing. This session also discussed themes such as mangroves, algal blooms, sediment transport, and sea-level rise impacts.

4. Air-sea fluxes estimated from remotely sensed data – This session focused on remotely sensed observations, theory, and model studies dealing with air–sea interaction process. The objective was to demonstrate the importance and benefit of satellite observations as related to air–sea interactions, climate monitoring, operational oceanography, coastal oceanography, marine ecosystems, sea-ice monitoring, and applications in seasonal forecasting. A particular emphasis was given to the accuracy of flux estimates currently attainable at global and regional scales, analysis of the fluxes at various temporal and spatial scales including trend investigations, and demonstration of the usefulness of these data in forcing and/or assimilation applied to numerical models.

5. GOCI-II development and application – Papers in this session addressed research and operational topics about developments and applications of Geostationary Ocean Colour Imager-II (GOCI-II) and its ground system (G2GS) based on state-of-the-art remote sensing and information technologies.

6. Ocean colour application – Satellite ocean colour observations have been used as a cost-effective tool to understand biological ocean responses to global climate changes and vice versa. This session addressed the scientific efforts of ocean colour remote sensing observations and analysis using various ocean colour remote sensing applications including physical-biogeochemical property changes, long-term trends, seasonal and interannual changes of ocean colour measurements, ocean colour mesoscale manifestation of internal waves, river plumes, eddies, upwelling, and fronts. The session also addressed biogeochemical variations resulting from regional and climate changes.

7. Sustainable development of Fisheries and Aquaculture using the multi-remote sensing technology and GIS – This session focused on satellite remote sensing and marine-GIS operational tools that address the global concern for sustainable use of fisheries and aquaculture resources. The design and implementation of a suite of ecological indicators capable of detecting a change in the marine ecosystem in response to perturbations caused by climate change or overfishing were also discussed.

8. Operational Oceanography – Visible, infrared, and microwave remote sensing have been used for operational applications in multidisciplinary areas. Considering the availability of multi-sensor, multi-temporal, multi-resolution and multi-frequency data from Earth Observation Satellites, the focus in this session was on the operational aspects of different techniques and applications for ocean and fisheries (e.g., oil spills, and ocean state).

9. Satellite remote sensing application to meteorology, air quality, and climate – Application of ocean remote sensing has been extended to monitoring atmosphere, land, and air quality, and the long-term accumulated satellite datasets have been used for diagnosing climate variability and change. Similarly, meteorological and other satellites have been utilized for oceanic application. This session discussed: ocean satellite application to weather and air quality; meteorological and environmental satellite applications to ocean monitoring; climate change and variability study using satellite remote sensing; synergistic use of ocean satellite with meteorological and environmental satellites; and other relevant studies encompassing atmosphere-ocean-land surface.

10. Machine learning applications to ocean satellite remote sensing – Machine learning has recently gained great popularity in various application fields, including remote sensing, pattern recognition, image analysis, and time series analysis (i.e., monitoring and forecasting). Not only rule-based machine learning approaches, but also more advanced deep learning methods have been evaluated for remote sensing-based classification and regression tasks. Amongst the topics covered were a range of ocean applications utilizing machine learning: water quality, coastal management, red tide, sea ice, oil spill, primary productivity, bathymetry, sea surface temperature, sea surface salinity, and carbon fluxes.

The 21 research papers in this issue cover the broad range of problems in satellite observations of the ocean, atmosphere, ice, coastal and inland waters covered in the 10 themes outlined above, some covering overlapping topics (see Table 1). They also cover many oceanic areas and remote sensors (Table 1). They are authored by scientists from 10 countries, and are tabulated in Table 1 by theme or session, remote-sensors/satellite mission, and geographic area, ocean, or sea. Prior to the main conference, a tutorial for capacity building (Katsaros et al. 2017), where students and early career scientists presented individual and team projects was held at KIOST campus on Jeju Island. Tutorial students’ projects at the capacity building course were presented in the main conference, and some tutorial students’ work is incorporated in two of the papers in this issue and in Table 1 (Oh et al. 2019; Parks et al. 2020).

Table 1. Paper classification by theme, sensor/mission and region/ocean.

Paper	Theme(s)/Session	Remote Sensor(s)/Mission(s)	Region(s)/Ocean(s)/Sea(s)
Choung and Myung-Hee 2019	Machine learning applications to ocean satellite remote sensing	High-resolution satellite imagery	South Sea of South Korea
Gower and King 2019	Ocean colour application	OLCI on the Sentinel 3a satellite & MERIS	Equatorial Atlantic, Caribbean, and Gulf of Mexico
Idris 2019	Satellite radar altimetry: progress in observing open oceans to coastal zone	Altimeter	Southeast Asia Seas & Maritime Continent
Jang, Park, and Isoguchi 2020	Sea surface roughness from high resolution SAR/Satellite remote sensing application to meteorology, and climate	SAR [Advanced Land Observing Satellite-2 Phased Array L-band Synthetic Aperture Radar-2 (ALOS-2 PALSAR-2)] & in-situ (buoys) & model data.	Southern Coast of Korean Peninsula
Karang, Chonnaniyah, and Osawa 2019	Operational Oceanography	Himawari-8 Geostationary Satellite/Advanced Himawari Imager (AHI); MODIS; Sentinel-1A SAR	Java Sea, Sumba Strait, & Savu Sea
Kerrigan and Adem Ali 2020	Ocean colour application/of coastal ecosystems and intertidal flats	Landsat Operational Land Imager (OLI) & in-situ measurements	North Atlantic & Caribbean Coast/US Virgin Islands
Koizumi et al. 2019	Air-sea fluxes estimated from remotely sensed data	Multiple satellites: Japanese Ocean Flux Data with Use of Remote-Sensing Observations (J-OFURO3) & in situ measurement data from moored buoys	Global Ocean
Nimit et al. 2020	Sustainable development of Fisheries & Aquaculture/Operational Oceanography/Remote-Sensing of Coastal ecosystems & intertidal flats	Multiple satellite telemetry/PSATs (Pop-up Satellite Archival Tags)	Northern Indian Ocean – Bay of Bengal & Arabian Sea
Lebedev et al. 2019	Remote-Sensing of Coastal ecosystems & intertidal flats	Medium Resolution Imaging Spectrometer (MERIS) on Envisat	Coastal zone of NE Black Sea
Lee et al. 2019a	Sustainable development of Fisheries & Aquaculture	Multi-Satellite Remote Sensing data & Taiwanese long-line fisheries data	North Pacific Ocean
Lee et al. 2019b	Machine learning applications/Remote-sensing of coastal ecosystems/Sustainable development of Fisheries & Aquaculture	Landsat-8 OLI & in-situ measurements	Southern Coast of Korean Peninsula
Mitnik, Khazanova, and Dubina 2019	Sea surface roughness from high resolution SAR/Satellite remote sensing application to meteorology, air quality, and climate/Air-sea fluxes estimated from remotely sensed data	SAR, Sentinel-1, ALOS, PALSAR, Envisat ASAR satellite visible and infrared images (NOAA AVHRR, Terra and Aqua MODIS, Landsat-8 OLI and TIRS, SNPP VIIRS)	Northwest Pacific Ocean
Oh et al. 2019	Operational Oceanography/Fisheries and Aquaculture/GOCI-II development and application	Day/Night Band (DNB) images of Geostationary Meteorological Satellite, GOCI	East Japan Sea
Park et al. 2020a	Operational Oceanography/Machine learning applications	High-resolution optical geostationary satellite images	Korean coastal region
Park et al. 2020b	Operational Oceanography/Machine learning applications	airborne and ground experimental data	Korean coastal region
Park, Woo, and Lee 2019	Operational Oceanography; Satellite remote sensing application to meteorology, air quality, and climate	Meteorological Imager of the first Korean geostationary satellite	Northwest Pacific Ocean
Parks et al. 2020	Sea surface roughness from high resolution SAR/Remote-sensing of coastal ecosystems and intertidal flats	Syntheric Apature Radar (SAR): RADARSAT-2 (Wide Scan mode), TerraSAR-X (Stripmap mode), and Sentinel-1	Gulf of Mexico
Pramanik et al. 2020	Ocean Colour Application; Air-sea fluxes estimated from remotely sensed data	MODIS-Aqua; Models	Northern Indian Ocean – Bay of Bengal
Shunmugapandi, Inamdar, and Gedam 2020	Ocean Colour Application; Air-sea fluxes estimated from remotely sensed data	MODIS-Aqua	Northern Indian Ocean – Arabian Sea
Tang and Liu (2020)	Ocean Colour Application	CZCS, SeaWiFS and MODIS	South China Sea
Yagi and Kutsuwada (2020)	Air-sea fluxes estimated from remotely sensed data; Operational Oceanography; Satellite remote sensing application to meteorology, air quality, and climate	Microwave Scatterometers and Radiometers (multiples); Models	Global Ocean

3. Conclusions

The 14^th PORSEC conference, held at Jeju Island, Republic of Korea, reviewed and discussed the state of ocean remote sensing observations, showcasing research work carried out using remote sensing techniques from various satellite missions and the applications of ocean remote sensing for societal benefits, with an emphasis on the Pacific and the Indian Ocean. Aiming at helping scientists and students involved in ocean-atmosphere studies using remote sensing techniques to benefit from interactions with experts from all over the globe, a capacity-building tutorial was held in conjunction with the conference. The conference attracted over two hundred registrants from 15 countries. KOIST’s research facility on the northwest coast of Jeju Island provided an excellent location for the tutorial, attended by 17 students and early career scientists from 6 countries, who then were given the opportunity to present their projects at the main conference. The conference and this issue, featuring 21 research papers, demonstrate the wide variety of ways that satellite sensors contribute to the study of every part of the earth, especially deep and coastal oceans, where much denser monitoring is still required. The research presented at the conference and in this issue provides a much-needed integration of satellite remote sensing observations into the ocean and climate science and will continue. It coincided with the beginning of, and provides an introduction to, two major international projects: Years of the Maritime Continent (YMC), and the United Nations Decade of Ocean Science for Sustainable Development. YMC is an international project that started in 2017 and will last till 2020. Its goal is to expedite the progress of improving understanding and prediction of local multi-scale variability of the MC weather-climate-ocean systems and its global impact through observations and modelling. The Decade of Ocean Science for Sustainable Development, to be held from 2021 to 2030, will provide a common framework to ensure that ocean science can fully support countries’ actions to sustainably manage the Oceans and achieve the 2030 Agenda for Sustainable Development. The 15^th PORSEC conference is planned to be held in the MC, presenting continuing research at the conclusion of the YMC and the beginning of the decade.

Disclosure statement

No potential conflict of interest was reported by the authors.