Research ReportDiurnal global ocean surface CO and air-sea CO flux reconstructed from spaceborne LiDAR data.

The ocean absorbs a significant amount of carbon dioxide (CO) from the atmosphere, helping regulate Earth's climate. However, our knowledge of ocean CO sink levels remains limited. This research focused on assessing daily changes in ocean CO sink levels and air-sea CO exchange, using a new technique.

Neural network spectral relationship to improve an inherent optical properties data processing system for residual error correction.

The residual error was a critical indicator to measure the data quality of ocean color products, which allows a user to decide the valuable envisioned application of these data. To effectively remove the residual errors from satellite remote sensing reflectance (R) using the inherent optical data processing system (IDAS), we expressed the residual error spectrum as an exponential plus linear function, and then we developed neural network models to derive the corresponding spectral slope coefficients from satellite R data. Coupled with the neural network models-based spectral relationship, the IDAS algorithm (IDAS) was more effective than an invariant spectral relationship-based IDAS algorithm (IDAS) in reducing the effects of residual errors in R on IOPs retrieval for our synthetic, field, and Chinese Ocean Color and Temperature Scanner (COCTS) data.

The carbon sink of the Coral Sea, the world's second largest marginal sea, weakened during 2006-2018.

The latest reports show that the ocean absorbs approximately 26 % of anthropogenic CO and that the carbon sink of the global ocean (air-sea CO flux) is continually increasing, while variations in different marginal seas are complicated. The Coral Sea, the second largest marginal sea in the world, is characterized by a generally oligotrophic basin and borders the biodiversity hotspot of Great Barrier Reef. In this study, we proposed a semianalytical method and reconstructed the first high-resolution satellite-based pCO and air-sea CO flux dataset from 2006 to 2018 for the Coral Sea.

Remote sensing of seawater optical properties and the subsurface phytoplankton layer in coastal waters using an airborne multiwavelength polarimetric ocean lidar.

The vertical profiles of the seawater optical properties and subsurface phytoplankton layer observed during an airborne lidar flight experiment carried out on 29 January 2021 in the coastal waters near Qionghai city were studied. We employed a hybrid inversion model combining the Klett and perturbation retrieval methods to estimate the seawater optical properties, while the vertical subsurface phytoplankton layer profiles were obtained by an adaptive evaluation. The airborne lidar data preprocessing scheme and inversion of the seawater optical properties were described in detail, and the effects of water environment parameters on the airborne lidar detection performance in coastal waters were discussed.

Forward volume scattering function (0.03°-60°) measured using an oblique-incidence particle sizer.

The forward volume scattering function (VSF) is an inherent optical property important in ocean lidar and underwater imaging and communication. The scattered power within 60° contains >90% of total scattered power, making it essential for determining the asymmetry parameter g. Thus, the new oblique-incidence-design Bettersize BT-3000 particle sizer was utilized to measure forward VSF (0.

Iterative retrieval method for ocean attenuation profiles measured by airborne lidar.

Lidar remote sensing for ocean optical properties has been increasingly applied because of its ability to provide vertical structure information, which cannot be directly obtained by ocean color remote sensing. However, the application of this technology demands an inversion method to infer two quantities, i.e.

Impact of ENSO events on phytoplankton over the Sulu Ridge.

Phytoplankton response to interannual climate variability has an important regulatory effect on the regional marine ecological environment and carbon cycle. In this study, we focused on the phytoplankton response in the upwelling region of the Sulu Ridge to the El Niño-Southern Oscillation (ENSO) based on monthly remote sensing chlorophyll-a concentration (Chl-a) and physical parameters from various sources from September 1997 to December 2017. We selected two El Niño events in 1997/1998 and 2015/2016 and two La Niña events in 1998/1999 and 2010/2011 to examine the response of Chl-a to ENSO events in this region.

Detecting subsurface phytoplankton layer in Qiandao Lake using shipborne lidar.

Qiandao Lake is located in the northern edge of subtropics, and its water body is thermally stratified in summer. It is of great scientific significance to study the vertical physical and chemical indexes and phytoplankton characteristics of the Qiandao Lake to reveal the aquatic ecosystem structure of the thermally stratified lake. Conventional observation uses in-situ profile instruments, which is time consuming and labor intensive.

Changes in riverine organic carbon input to the ocean from mainland China over the past 60 years.

Compared to rivers in Europe and North America, Chinese rivers that discharge into oceans have different organic carbon (OC) transport characteristics. Out of the top 25 largest rivers worldwide, three (Changjiang, Huanghe, and Zhujiang rivers) are located in China, along with numerous small rivers. Thus, synthesized estimates of total riverine OC flux from Chinese rivers into marginal seas are critical but remain deficient.

Subsurface plankton layers observed from airborne lidar in Sanya Bay, South China Sea.

In recent years, airborne lidar has been used in a wide range of oceanic applications, including detection of bathymetry, bubbles, internal waves, and schools of fish. However, it has not yet been extensively applied in Chinese seas. For example, there have been no studies to detect subsurface plankton layers in the South China Sea (SCS) by airborne lidar.

Coastal and inland water monitoring using a portable hyperspectral laser fluorometer.

The potential for a ship-mounted laser fluorometer to provide rapid, non-intrusively measurements in both coastal and lake conditions are investigated. The instrument consists of a high pulse repetition frequency (10-kHz) microchip laser for fluorescence excitation, a broadband hyperspectral micro spectrometer for spectral detection, and a confocal reflective fluorescent probe for signal collection; it weighs only about 1.7kg.

High-Frequency Observation of Water Spectrum and Its Application in Monitoring of Dynamic Variation of Suspended Materials in the Hangzhou Bay.

In situ measurement of water spectrum is the basis of the validation of the ocean color remote sensing. The traditional method to obtain the water spectrum is based on the shipboard measurement at limited stations, which is difficult to meet the requirement of validation of ocean color remote sensing in the highly dynamic coastal waters. To overcome this shortage, continuously observing systems of water spectrum have been developed in the world.

Variation of dissolved organic carbon transported by two Chinese rivers: The Changjiang River and Yellow River.

Real-time monitoring of riverine dissolved organic carbon (DOC) and the associated controlling factors is essential to coastal ocean management. This study was the first to simulate the monthly DOC concentrations at the Datong Hydrometric Station for the Changjiang River and at the Lijin Hydrometric Station for the Yellow River from 2000 to 2013 using a multilayer back-propagation neural network (MBPNN), along with basin remote-sensing products and river in situ data. The average absolute error between the modeled values and in situ values was 9.

Detection of water quality parameters in Hangzhou Bay using a portable laser fluorometer.

A field, light-weight laser fluorometer based on the method of laser induced fluorescence was developed for water quality monitoring. The basic instrument configuration uses a high pulse repetition frequency microchip laser, a confocal reflective fluorescent probe and a broadband hyperspectral micro spectrometer; it weights only about 1.7 kg.

A new simple concept for ocean colour remote sensing using parallel polarisation radiance.

Ocean colour remote sensing has supported research on subjects ranging from marine ecosystems to climate change for almost 35 years. However, as the framework for ocean colour remote sensing is based on the radiation intensity at the top-of-atmosphere (TOA), the polarisation of the radiation, which contains additional information on atmospheric and water optical properties, has largely been neglected. In this study, we propose a new simple concept to ocean colour remote sensing that uses parallel polarisation radiance (PPR) instead of the traditional radiation intensity.

Atmospheric correction of satellite ocean color imagery using the ultraviolet wavelength for highly turbid waters.

Instead of the conventionally atmospheric correction algorithms using the near-infrared and shortwave infrared wavelengths, an alternative practical atmospheric correction algorithm using the ultraviolet wavelength for turbid waters (named UV-AC) is proposed for satellite ocean color imagery in the paper. The principle of the algorithm is based on the fact that the water-leaving radiance at ultraviolet wavelengths can be neglected as compared with that at the visible light wavelengths or even near-infrared wavelengths in most cases of highly turbid waters due to the strong absorption by detritus and colored dissolved organic matter. The UV-AC algorithm uses the ultraviolet band to estimate the aerosol scattering radiance empirically, and it does not need any assumption of the water's optical properties.

Evaluation of the aerosol models for SeaWiFS and MODIS by AERONET data over open oceans.

The operational atmospheric correction algorithm for Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer (MODIS) uses the predefined aerosol models to retrieve aerosol optical properties, and their accuracy depends on how well the aerosol models can represent the real aerosol optical properties. In this paper, we developed a method to evaluate the aerosol models (combined with the model selection methodology) by simulating the aerosol retrieval using the Aerosol Robotic Network (AERONET) data. Our method can evaluate the ability of aerosol models themselves, independent of the sensor performance.

Ecological anomalies in the East China Sea: impacts of the Three Gorges Dam?

In this study, we examined possible impacts of the Yangtze River Three Gorges Dam (TGD), the world largest hydroelectric construction, on the adjacent marine ecosystem of the East China Sea (ECS) during its initial water storage period. The TGD filled the first one-third of its storage capacity of 39 billion m3 in 10 days in June 2003, causing an abrupt reduction in the river flow into the ECS. Noticeable changes in the microbial community structure including pico-sized autotrophs, heterotrophic bacteria and microbial diversity in the estuary and the ECS were observed 2 months later.