- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Study of the effects of phytoplankton morphology and vertical profile on lidar attenuated backscatter and depolarization ratio
摘要： Propagation of a lidar beam in a coupled atmosphere-ocean model consisting of multiple atmospheric and upper oceanic layers and a rough ocean surface is studied by using a vectorized Monte Carlo radiative transfer solver optimized specifically for lidar-based remote sensing applications. The effects of assumed phytoplankton morphology variations and its vertical distribution on the lidar attenuated backscatter and depolarization ratio are studied. In this study, a phytoplankton particle is assumed to be a sphere, a sphere with a core, or a randomly distorted hexahedron with or without a core. The single-scattering properties of the nonspherical/inhomogeneous particles are computed using appropriate state-of-the-art light-scattering computational capabilities. Vertical variation of the phytoplankton distribution is derived explicitly using a PAR (photosynthetically active radiation) limited carbon biomass balance equation that is subsequently coupled with the Monte Carlo solver.
关键词： Radiative transfer,Lidar,Ocean optics,Monte Carlo,Phytoplankton,Net primary production,Remote sensing
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Oil Slick Detection in the Offshore Domain: Evaluation of Polarization-Dependent Sar Parameters
摘要： Remote sensing technology is an essential link in the global monitoring of the ocean surface and radars are efficient sensors for detecting marine pollution. When used operationally, a tradeoff must usually be made between the covered area and the quantity of information collected by the radar. To identify the most appropriate imaging mode, a methodology based on Receiver Operating Characteristic (ROC) curve analysis has been applied to an original dataset collected by an airborne system, SETHI, characterized by a very low instrument noise floor. The dataset was acquired during an oil spill clean-up exercise carried out in 2015 in the North Sea. Various polarization-dependent quantities are investigated and a relative ordering of the main polarimetric parameters is reported. VV offers the best tradeoff between the benefit of detection performance and the instrument and data requirements. When the sensor has a sufficiently low noise floor, HV is also recommended because it provides strong slick-sea contrast. Among all the investigated quad-polarimetric settings, no significant added value compared to single-polarized data was found.
关键词： NESZ,noise floor,sea,spill,detection,SAR,noise,slick,radar,marine pollution,probability of detection,oil,ROC curves,probability of false alarm,ocean,polarization
更新于2025-09-23 15:23:52
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Ship-borne aerosol profiling with lidar over the Atlantic Ocean: From pure marine conditions to complex dust-smoke mixtures
摘要： The multiwavelength Raman lidar PollyXT has been regularly operated aboard the research vessel Polarstern on expeditions across the Atlantic Ocean from North to South and vice versa. The lidar measurements of the Polarstern cruises PS95 from Bremerhaven to Cape Town (November 2015) and PS98 from Punta Arenas to Bremerhaven (April/May 2016) are presented and analysed in detail. The latest setup of PollyXT allows improved coverage of the marine boundary layer (MBL) due to an additional near-range receiver. Three case studies provide an overview of the detected aerosol over the Atlantic Ocean. In the first case, marine conditions were observed near South Africa on the autumn cruise PS95. Values of optical properties (depolarisation ratios close to zero, lidar ratios of 23 sr at 355 nm and 532 nm) within the MBL indicate pure marine aerosol. A layer of dried marine aerosol, indicated by an increase of the particle depolarisation ratio to about 10% at both wavelengths and thus confirming the non-sphericity of these particles, could be detected on the top of the MBL. On the same cruise, an almost pure Saharan dust plume was observed near the Canary Islands, presented in the second case. The third case deals with several layers of Saharan dust partly mixed with biomass-burning smoke measured on PS98 near the Cape Verde Islands. While the MBL was partly mixed with dust in the pure Saharan dust case, an almost marine MBL was observed in the third case. A statistical analysis showed latitudinal differences in the optical properties within the MBL, caused by the down-mixing of dust in the tropics and anthropogenic influences in the northern latitudes whereas the optical properties of the MBL in the southern hemisphere correlate with typical marine values. The particle depolarisation ratio of dried marine layers ranged between 4–9%. Night measurements from PS95 and PS98 were used to illustrate the potential of aerosol classification using lidar ratio, particle depolarisation ratio and ?ngstr?m exponent. Lidar ratio and particle depolarisation ratio have been found to be the main indicator for the particle type, whereas the ?ngstr?m exponent is rather variable.
关键词： PollyXT,Atlantic Ocean,depolarisation,marine boundary layer,Polarstern,lidar,aerosol
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Wind Direction Ambiguity Removal Using Along-Track Insar: A Case Study
摘要： The main problem in wind retrieval using SAR imagery is the lack of the wind direction information. A few methods have been proposed to extract the wind direction from SAR images. The main limitation of these methods is the 180o ambiguity in the direction. Usually, an external source of wind direction is used to remove this ambiguity. This study exploits the Along-track Interferometric SAR (ATI-SAR) phase to demonstrate its usefulness to tackle this problem. A method is proposed to remove the wind direction ambiguity using the ATI-SAR phase information. This is based on the fact that the interferometric phase is related to the sea surface motion direction. Depending on the sign convention, the phase is positive/negative for advancing/receding target respectively. This effect is used to assist the wind extraction algorithm to select the most plausible direction. The results show a very good agreement with atmospheric model and visual investigation.
关键词： InSAR,TerraSAR-X,wind direction,ocean surface wind
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Numerical Study for Ocean Wave Measurement by High Resolution Along-Track Interferometric Sar
摘要： National institute of Information and Communications Technology (NICT) developed the along-track interferometry SAR (AT-InSAR) with 50cm resolution for the airborne SAR system (Pi-SAR X2) in 2011, and new antennas for the AT-InSAR with 30cm resolution in 2016. The preliminary wave height observation was performed, and it was confirmed that the ocean wave height distribution could be estimated from the sea surface currents measured by the high-resolution AT-InSAR. However, it was difficult to retrieve ocean wave information such as the wave height, period and direction from the sea surface currents with high accuracy because ocean waves imaging mechanism on the SAR image was governed by the nonlinear mapping (the velocity bunching nonlinearity). In this study, to clarify the relationship the sea surface velocity derived by the ocean waves and it measured by the AT-InSAR, the numerical simulation of the sea surface velocity measured by the AT-InSAR was carried out. In addition, the modulation of the AT-InSAR images by the velocity bunching was evaluated.
关键词： Ocean wave,Pi-SAR X2,Along-track interferometry
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Shallow Water Ocean Color Observations Inversion Using Particle Swarm Optimization and Genetic Algorithm
摘要： In this work, Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) optimization techniques are used to retrieve water column inherent optical properties (IOPs), bottom reflectance and geometric depth from a simulated hyperspectral dataset. The synthetic dataset (N=6000) is created using two different bottom types (Sand and seagrass), three levels of depth, 20 concentrations of Chlorophyll – a (Chl-a) with a wide range of modelled IOP variations resembling natural clear and optically complex waters. Results indicate that PSO and GA showed similar retrieval results in IOPs. Bottom reflectance values from PSO are near to input bottom substrate values compared to GA. In case of Geometric depth also, average depth value retrieved by PSO are better than GA retrieved. In terms of processing time, PSO exhibited higher computational efficiency than GA by five times. Further studies can use PSO to process Hyperspectral remote sensing Imagery in shallow waters.
关键词： PSO,Shallow waters,Ocean color inversion,Optimization,GA
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - The Wind Speed Inversion and In-Orbit Assessment of Imaging Altimeter on Tiangong-2 Space Station
摘要： Imaging ALTimeter (IALT) is a new type of radar altimeter system, which observes the earth from 2° to 7° incident angles. In comparison to the conventional altimeters such as HY-2A altimeter, Jason-1/2, TOPEX/Poseidon, which observe the ocean at nadir, the swath of IALT is much wider and its spatial resolution is much higher. The IALT on board Tiangong-2 space station is launched on 15th September, 2016 at Jiuquan Satellite Launch Center. The in-orbit assessment of IALT is done until 30th April, 2017. In this paper, the ocean surface wind speed inversion method based on IALT is established. The neural network algorithm is used for ocean surface wind speed retrieval, and the spatial resolution of retrieved wind speed is 25km. The wind speed inversion accuracy is evaluated by comparing with the ECMWF reanalysis wind speed, buoy wind speed, and boat measurement wind speed. The results show that the Root-Mean-Square (RMS) of retrieved wind speed is 1.85m/s, and the Bias of retrieved wind speed is about -0.21m/s. The wind speed inversion accuracy satisfies performance requirement.
关键词： in-orbit assessment,Imaging ALTimeter,ocean surface wind speed,inversion accuracy
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A Study on the Information Content of Along-Track Interferometric Coherence Using Dual Co-Polarized Tandem-X Data
摘要： This paper discusses the use of the along-track interferometric coherence as a radar observable with geophysical information rather than as a mere quality indicator. The use of dual co-polarized data to estimate the temporal decorrelation factor is explained, and preliminary results using TanDEM-X data are shown.
关键词： ocean currents,bistatic,ATI
更新于2025-09-23 15:21:21
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Ocean Dynamics Observed by VIIRS Day/Night Band Satellite Observations
摘要： Three cases of Day/Night Band (DNB) observations of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) are explored for applications to assess the ocean environment and monitor ocean dynamics. An approach to use the ratio between the target radiance and the reference radiance was developed in order to better assess the ocean diurnal and short-term environmental changes with VIIRS DNB observations. In the La Plata River Estuary, the sediment fronts showed 20–25 km diurnal inshore-offshore movements on 13 March 2017. In the waters off the coast of Argentina in the South Atlantic, VIIRS DNB measurements provided both daytime and nighttime observations and monitoring of the algal bloom development and migration between 24 and 26 March 2016. This algal bloom generally kept the same spatial patterns, but moved nearly 20 km eastward in the three-day period. In the Yangtze River Estuary and Hangzhou Bay region along China’s east coast, VIIRS DNB observations also revealed complicated coastal dynamic changes between 12 and 14 April 2017. Even though there are still some challenges and limitations for monitoring the ocean environment with VIIRS DNB observations, this study shows that satellite DNB observations can provide additional data sources for ocean observations, especially observations during the nighttime.
关键词： satellite remote sensing,VIIRS,DNB observation,ocean color,nocturnal study,ocean dynamics
更新于2025-09-23 15:21:01
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Continuous in situ measurement of dissolved methane in Lake Kivu using a membrane inlet laser spectrometer
摘要： We report the ?rst high-resolution continuous pro-?le of dissolved methane in the shallow water of Lake Kivu, Rwanda. The measurements were performed using an in situ dissolved gas sensor, called Sub-Ocean, based on a patented membrane-based extraction technique coupled with a highly sensitive optical spectrometer. The sensor was originally designed for ocean settings, but both the spectrometer and the extraction system were modi?ed to extend the dynamical range up to 6 orders of magnitude with respect to the original prototype (from nmol L?1 to mmol L?1 detection) to ?t the range of concentrations at Lake Kivu. The accuracy of the instrument was estimated to ±22 % (2σ ) from the standard deviation of eight pro?les at 80 m depth, corresponding to ±0.112 mbar of CH4 in water or ±160 nmol L?1 at 25 ?C and 1 atm. The instrument was able to continuously pro?le the top 150 m of the water column within only 25 min. The maximum observed mixing ratio of CH4 in the gas phase concentration was 77 %, which at 150 m depth and under thermal conditions of the lake corresponds to 3.5 mmol L?1. Deeper down, dissolved CH4 concentrations were too large for the methane absorption spectrum to be correctly retrieved. Results are in good agreement with discrete in situ measurements conducted with the commercial HydroC? sensor. This fast-pro?ling feature is highly useful for studying the transport, production and consumption of CH4 and other dissolved gases in aquatic systems. While the sensor is well adapted for investigating most environments with a concentration of CH4 up to a few millimoles per liter, in the future the spectrometer could be replaced with a less sensitive analytical technique possibly including simultaneous detection of dissolved CO2 and total dissolved gas pressure, for exploring settings with very high concentrations of CH4 such as the bottom waters of Lake Kivu.
关键词： Lake Kivu,dissolved methane,membrane inlet laser spectrometer,Sub-Ocean sensor,HydroC? sensor
更新于2025-09-23 15:21:01