Future U.S. ocean color missions—OCI,MODIS and HIRIS

The Coastal Zone Color Scanner (CZCS) launched by the National Aeronautics and Space Administration (NASA) on the Nimbus-7 Satellite in 1978 has provided exceptionally valuable data for studies of the productivity of the ocean, fisheries, the detection of oceanic fronts and currents, and the optical properties of the ocean. NASA has been working with the scientific community, the National Oceanographic and Atmospheric Administration (NOAA), France's Centre National d'Etudes Spatiales (CNES), and industry to develop an Ocean Color Imager (OCI), a follow-on instrument which would provide the near real-time and global data necessary to fill these needs in the 1990's. The Earth Observing Satellite Company (EOSAT) is considering flying an ocean and land wide-field color instrument which would meet these needs on Landsat 6 or 7 planned for launch in 1989 and 1991, respectively. It would provide eight ocean color channels for improved atmospheric correction and in-water algorithms, global coverage and near real-time data for operational uses. In the mid 1990's NASA is planning to fly a Moderate Resolution Imaging Spectrometer (MODIS) and a High Resolution Imaging Spectrometer (HIRIS) as part of the Earth Observing System (Eos) on the Polar Platform of the Space Station. These instruments are array spectrometers which would provide full spectral resolution in the visible and infrared. This opens the possibility of separating different groups of phytoplankton, suspended sediments and other substances in the water. Also, HIRIS would have across track pointing ability which will allow high resolution rapid sampling of dynamic coastal areas and estuaries.     

Application of CZCS data to productivity and water quality studies in the Northern Adriatic Sea

The Northern Adriatic Sea is a shallow ocean basin with considerable fresh water input and presents some unique water-optical features realted to:- suspended matter input caused by rivers and resuspension of bottom sediments;- phytoplankton production because of nutrient input from rivers and bottom;- dissolved organic matter (yellow substance) production by decomposition processes of the organic material.All these features influence the spectral reflectance of the water and make the algorithms for CZCS data interpretation quite different from those used in open ocean (type I) water. Therefore, special test-site specific algorithms must be derived from in-situ measurements of water-optical parameters and the water constituents. The results from such measurements are presented together with the algorithms and the evaluated CZCS data obtained from them. It is then discussed how the experimental and evaluated satellite data can be used to evaluate standing crop and productivity.     

Enhanced Landsat and HCMM imagery for mineral exploration in contrasting areas of subtropical humid and semi-arid terrain

The role of multispectral and thermal imagery in mineral exploration is evaluated for two areas with favourable geological conditions within contrasting physical environments — one in the semi-arid low tree and shrub savannas of western Queensland and northern South Australia, the other in the humid subtropical forest zone of western Yunnan, China.For both areas Landsat imagery was used to identify structures and lithologies favourable for mineralization and locate ironstones/gossans indicative of mineralized bedrock. HCMM imagery was used alongside Landsat imagery to identify former and ephemeral drainage patterns important for the interpretation of geochemical data over covered ground in Australia. Interpretations were made of enhanced colour composites, outputs of MSS band ratios and colour rotated images generated from both NASA film products and CCTs. These were checked by field studies during which plant, soil and rock chip samples for subsequent metals analyses were collected from areas of anomalous vegetation and from barren ironstones. Some rock chip samples from Australia contained concentrations of copper or lead or small amounts of other metals. In China geobotanical anomalies over ironstones from which soil and rock samples yielded copper, lead, zinc, tin and silver suggest the presence of a major belt of potential multi-metal mineralization.     

Satellite observed dynamics of chlorophyll and suspended sediments in a shallow,high latitude embayment

A study of the distribution of chlorophyll and suspended sediments in Norton Sound, Alaska, in May and July 1979 and 1980, was made using imagery from both raw and processed data collected by the Nimbus-7 CZCS. False color images generated from the raw data in bands 1,2, and 4 showed the large seasonal changes which take place in the north and easterly movement of suspended sediments from the Yukon River. The atmospherically corrected pigment images suggest that, except in open waters, the outflow from the Yukon and other local rivers strongly influences the nature of the planktonic environment in Norton Sound. Comparison of the patterns shown by the two different kinds of imagery sometimes reveals features which would otherwise have been masked in waters with such a significant sediment load. In general, the distribution and concentration of chlorophyll and suspended sediments in the imagery provided a useful means for determining the relative importance of winds, currents, ice, and river runoff in the biological and physical oceanography of the surface waters of Norton Sound.     

Remote sensing of coccolithophore blooms

CZCS and AVHRR images have been used to study the spatial, temporal and spectral development of coccolithophore blooms in the NE Atlantic. It is suggested that variations in colour and reflectance in the images are due to differences in the relative concentrations of coccolithophore cells and detached plates. Also the formation and disappearance of an intense bloom in the English Channel is related to changes in water-column stability during the spring-neap tidal cycle.     

CZCS-derived pigment concentration fields in Japanese coastal area

About ten CZCS scenes were atmospherically corrected to investigate chlorophyll-like pigment concentration levels around Japan.¹ Three of the images were compared to ship-sampled data which were obtained within 5 days from satellite overpasses, showing fairly good agreement with the pigment range of 0.1 to 5μg/l. Highly reflective patterns were observed in a late spring scene, suspected to be due to abundance of coccolithophorids which are algae with calcium carbonate shell. Some problems in processing CZCS data in Japanese area are also discussed.     

Ocean Observation from Haiyang Satellites: 2012–2014

During 2012 and 2014, China has two Haiyang(which means ocean in Chinese, referred to as HY) satellites operating normally in space which are HY-1B and HY-2A. HY-1B is an ocean color environment satellite which was launched in April 2007 to observe global ocean color and sea surface temperature, and HY-2A is an ocean dynamic environment satellite which was launched in August 2011 to obtain global marine dynamic environment parameters including sea surface height,significant wave height, ocean wind vectors, etc. Ocean observation data provided by HY-1B and HY-2A have been widely used by both domestic and international users in extensive areas such as ocean environment protection, ocean disaster prevention and reduction, marine environment forecast,ocean resource development and management, ocean investigations and scientific researches, etc.     

Interaction of Rossby waves with the Gulf Stream and Kuroshio using altimetry in a framework of a vortex layer model

In this paper, we show the potential of satellite altimetry to study the interaction of Rossby waves with the shear flow. The Miles-Ribner approach, which was developed in gas dynamics in the 1960 s, is used to describe Rossby waves interacting with the Gulf Stream and Kuroshio areas. The region of interaction is approximated by a nonzonal vortex layer. We apply the main formulations of the problem of a nonzonal vortex layer on the β-plane in the formulation of Miles-Ribner to observations in the real ocean. Earlier, we showed that the interaction of waves with a nonzonal flow gives rise to a new class of solutions, which is absent in the case of a zonal flow. This new class of solutions can be interpreted as the pure emission of Rossby waves by the nonzonal flow. We apply this theoretical approach to the areas of the Gulf Stream and Kuroshio as well. We use for analysis altimetry data available at Copernicus Marine Environment Monitoring Service. The analysis of Hovmöller diagrams in the areas under consideration confirms the previously obtained theoretical conclusions of the problem of the interaction of planetary waves with a nonzonal flow on the β-plane in the formulation of Miles-Ribner. The incident waves, as well as refracted and reflected waves are distinguished. The speed of refracted and reflected waves exceeds the speed of incident waves, which confirms the conclusions about the existence of mechanisms for the amplification of planetary waves when they interact with a nonzonal flow.     

Ocean circulation studies in the vicinity of Southern Africa: Preliminary results using FGGE drifters and remote sensing

The three highly variable ocean circulation systems which meet south of South Africa have been studied by combining the use of satellite thermal infra-red imagery, hydrographic measurements and drifting buoys. We present a few preliminary examples where this method has been successful. These include the sources of the Agulhas Current, the influence of the Agulhas Current on the Cape upwelling region as well as the interaction of the Agulhas Current with the Subtropical Convergence. An example is also given of how a biological hypothesis concerning the recruitment of a rock lobster species at Vema Seamount has been supported by the analysis of the drifts of FGGE buoys in the South Atlantic Ocean.     

Spatial variability of the ocean color field in CZCS imagery

The mesoscale ocean color field has been investigated by means of a statistical approach to the analysis of Coastal Zone Color Scanner imagery. A quantitative assessment of ocean color was provided by deriving large scale, high resolution images of the diffuse attenuation coefficient at 490 nm, K(490), for several open ocean areas in the North Atlantic and North Pacific (around 30°, 40° and 60° N). Linear trends, power spectra and structure functions were determined for one-dimensional transects extracted from the images. These results can be interpreted as a composite statistical signature of the oceanic regions examined. In light of the relationship between ocean optical properties and concentration of dissolved and suspended materials in the water, the statistical parameters obtained provide an insight into the relative intensity and scales of patchiness of water constituents, and of the planktonic environment.     

Satellite ocean colour algorithm for Prochlorococcus, Synechococcus, and picoeukaryotes concentration retrieval in the South China Sea

An algorithm for retrieval of surface waters cell concentrations (in cell/ml) for three picophytoplankton components, Prochlorococcus (Pro), Synechococcus (Syn), and picoeukaryotes (Peuk) in the South China Sea (SCS), from ocean colour satellite data was developed and tested. Level 3 merged multisensor Ocean Colour Climate Change Initiative satellite data is used. Training is performed using in situ data on abundances of the three phytoplankton components. Several predictors derived from satellite reflectance data were tested. The regression form that assures the highest accuracy of the algorithm was chosen based on cross-validation (CV). According to the CV on test data subset, the algorithm performance is characterized by the r value 0.89, 0.72, and 0.73 and MAPD 38, 71 and 51% for Peuk, Pro, and Syn respectively. This is one of the few studies aimed at the Peuk, Pro, and Syn distribution research in the northern SCS using ocean colour satellite data. This is the only research providing algorithm with accuracy estimates of the Peuk, Pro, and Syn concentrations retrieval from the ocean colour data. Analysis of the developed algorithm allows us to conclude that both mechanisms (specific spectral features caused by pigments composition and spectrum features sensitive to general primary productivity, e.g. band ratios in 443–510?nm range and spectrum absolute values) are important for getting accurate information on the picophytoplankton composition.     

Use of meteosat ISCCP B2 data for the study of interannual variations of climatic elements in Africa

Composite monthly images corresponding to West African rainy seasons of 1983, 1984, and 1985, have been constructed from ISCCP B2 Meteosat data. Average and standard deviation images from thermal infrared and water vapor channels are studied. In the thermal infrared, differences between the three years appear principally in the mean structure of the ITCZ, North-South extend, northward boundary, longitudinal variations of the convection. In the water vapor channel, well defined “dry” areas appear, showing the location and extent of subsidence regions on a large scale. These locations and extents also vary from year to year.     

Spectral characterization of arid rangelands in the high atlas mountains,Morocco

Considering an arid area in the High Atlas mountains of Morocco, the assessment of vegetation cover is carried out from ground spectral measurements and analysis of satellite imagery. Ground measurements have been made with SPOT simulation radiometer; results are related to reflectance-vegetation coverage relationships and to spectral responses obtained at a local level (120m transects). Analysis of Thematic Mapper and SPOT data includes visual interpretation of color composite imagery for geomorphological units delineation, principal component analysis and examination of bispectral scatter plots.     

Mineral mapping in the Kap Simpson complex,central East Greenland,using HyMap and ASTER remote sensing data

This research focuses on the application of HyMap airborne hyperspectral data and ASTER satellite multispectral data to mineral exploration and lithologic mapping in the Arctic regions of central East Greenland. The study area is the Kap Simpson complex in central East Greenland. The Kap Simpson complex is one of the largest exposed Palaeogene felsic complexes of East Greenland. It has been the target of several mineral exploration projects. The analysis of the HyMap data produced a detailed picture of the spatial distribution of the alteration minerals in the Kap Simpson complex, unavailable from field-based studies in the area. The analysis of the ASTER data produced mineral maps which due to the moderate spatial and spectral resolution of the ASTER imagery can be useful for reconnaissance level mineral exploration. Colour composites of the mean normalized ASTER thermal bands display lithological information and detected a large felsic igneous intrusion that has not been shown on the recently compiled geological maps of the area. The results of this research have considerable potential to evaluate the use of hyperspectral and multispectral remote sensing for geological purposes in the Arctic regions of central East Greenland.     

Applicationof remote sensing techniques in geological studies of various mineralized belts in India. (National paper on IGCP — 143)

Geological interpretation, analysis and evaluation of LANDSAT and airborne MSS data, panchromatic and colour infrred photographs and spectral reflectance data for a number of test sites in different mineralized belts in India have led to certain significant results. Lithological discrimination on digitally processed enhanced MSS data products has helped in further subdivisions of major rock groups. Lineament pattern analyses reveals three prominent sets of fractures in Indian Precambrian Shield with predominant ENE-WSW megalineament probably representing earliest deep crustal fractures and subsequent NNW-SSE and NE-SW fractures, associated with polyphase tectonic movements. Correlation of structures and mineralization indicate structural control for most of the mineralized belts with intersecting locii type concentration of ore deposits in some cases. In a few cases control of mineralization is lithology and stratigraphy. Spectral groundtruth and laboratory studies indicate that major rock types have characteristic spectral patterns (signatures) which would be useful for lithological mapping by automatic classification techniques. The work also has led to the improvement of enhanced MSS data products for geological studies.     

Determination of the mean dynamic ocean topography model through combining multi-source gravity data and DTU15 MSS around China's coast

Mean dynamic ocean topography (or MDT) is closely related to ocean circulation and global climate change. It has important scientific significance and application value for the development and utilization of marine resources in China's coastal areas. Based on the terrain gravity, marine gravity, and SRTM 3?s data, an algorithm to reduce the problem of gravity data gaps between land and sea is proposed. A consistent land-sea gravity model is established based on point-mass fusion method. Then geoid model, which accuracy was estimated to be 8.5?cm through the verification of 348 GNSS/level data from the coastal provinces, of China's coastal areas was calculated through remove-restore technique. Connecting the above geoid model with DTU15 MSS model to establish a MDT model in China's coastal areas using the direct method in space domain. The effect of gravity field model, dominant factors of sea surface topography, and low pass filter are analyzed. Taking Bohai Sea and Yellow Sea as an example, and comparing MDT with the two international models CNES_2013_MDT and DTU15_MDT. The results show that the MDT has the potential to construct a vertical datum of the ocean and carry out related scientific research and application.     

Venus atmospheric circulation: Observations and implications of the thermal structure

Continued analysis of Pioneer Venus imaging and polarimetry data indicates that the average cloud-top level circulation is mainly zonal (east to west) with a small meridional component. Presence of planetary scale waves and a possible sun-related component are evident in the data. If the tracked features refer to the same vertical level, then some variability of the circulation would have to be present to account for the Pioneer and Mariner 10 cloud-tracking results. However, the implied balanced flow from the observed thermal structure analysis strongly suggests that at least some of the variations in these observations is due to apparent cloud-top variations and that the circulation itself is relatively stable.Direct cyclostrophic calculations based on the observed thermal structure of the atmosphere yield a balanced zonal circulation with distinct mid-latitude jets (peak velocities about 110–120 ms^?1) located between 50 and 40 mb in each hemisphere of the planet near 45° latitude. The calculations which extend to about 40 km altitude from 80 km above the surface agree well with the observed entry probe zonal components and indicate breakdown of the balance condition near the upper and lower boundaries at low latitudes.The balanced flow results are consistent with the Mariner 10 and Pioneer cloud tracked estimates of the zonal circulation provided the effective altitude of the tracked features is slightly different at different observation periods. The features in the Pioneer Venus data would then lie on a sloping surface that extends from about 68 km (40 mb) at low latitudes to about 75 km (10 mb) in mid-latitudes. The polarization features would occur on a roughly parallel surface that is 1–2 km above the effective cloud-height surface, and Mariner 10 features would have effective altitudes somewhat lower than the Pioneer ultraviolet features. A slight asymmetry is evident in the balanced zonal circulation arising out of an asymmetry in the thermal field.Finally, the solenoids formed by intersecting isobaric and isosteric (constant specific volume) surfaces deduced from the Pioneer Venus radio occultation data show distinct evidence of a direct meridional circulation that may be important in sustaining the Venus atmospheric circulation.     

Ocean Observation from Haiyang Satellites

In 2018, China successfully launched three new Haiyang (which means ocean in Chinese, referred to as HY) satellites which are an ocean color observation satellite HY-1C (operational), an ocean dynamics environment satellite HY-2B (operational) and the China-France ocean satellite CFOSAT (experimental). In 2019, all the three satellites had finished their commissioning phases and were declared operational. HY-2A satellite continues to operate in-orbit, and its operational status is basically normal. So in 2020, China has 4 Haiyang satellites in-orbit, China's ocean satellites enter into a new operational application phase. The operation of the ground application system of Chinese ocean satellites is stable. In 2019, Beijing, Hainan, Mudanjiang, and Hangzhou ocean satellite ground stations had received the data of HY-1C, HY-2A, HY-2B, and CFOSAT 5012 orbits and 26.46 TB data had been distributed to both domestic and international users. Chinese ocean satellite data has played an important role in marine disaster prevention and mitigation, development and management of marine resources, maintenance of marine rights and interests, marine environment protection, scientific researches, and blue economy development.      

Boundary layer aerosol retrieval from thermal infrared nadir sounding – Preliminary results

A non-empirical algorithm is presented to retrieve the optical depth in the 750–1250 cm⁻¹ spectral range, of aerosol located in the boundary layer over the ocean, from nadir high-resolution radiance spectra in the thermal infrared. The algorithm is based on a line-by-line radiative transfer forward model and used the Optimal Estimation Method for the retrieval. Its performance strongly depends on the quality of the a priori temperature and H₂O atmospheric profiles. To demonstrate the relevance of the algorithm, distributions of maritime aerosol parameters have been retrieved from IMG/ADEOS data for December 1996, using the algorithm with the LBLRTM radiative transfer code, and ERA40 (ECMWF) a priori atmospheric profiles and surface conditions.