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An ultraviolet to visible scheme to estimate chromophoric dissolved organic matter absorption in a Case-2 water from remote sensing reflectance

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Frontiers of Earth Science 2020年第2期14卷 384-400页

作者： Xia LEI jiayi pan Adam DEVLIN Institute of Space and Earth Information Science The Chinese University of Hong KongHong KongChina School of Geography and Environment Jiangxi Normal UniversityNanchang 330022China

In a typical Case-2 coastal water environment(here,the Pearl River Estuary(PRE),China),chromophoric dissolved organic matter(CDOM)and suspended particulates dominate the water optical properties,and CDOM fluorescence contributes considerably to surface water *** this paper,an ultraviolet(UV)to visible scheme to retrieve CDOM absorption(ag)is developed based on a set of in situ ***,the CDOM UV absorption and spectral slope(Sg)are derived directly from the visible remote sensing reflectance;then the Sg is extrapolated to obtain the spectrum from UV to visible spectral *** algorithm performs well,with an overall mean absolute percent difference(MAPD)of^30%,~5%and^6%for the estimation of ag in 250–450 nm,Sg over 250–400 nm,and 250–700 nm,*** effectiveness and stability of the algorithm is further demonstrated in capturing the distribution pattern of CDOM absorption in the PRE from satellite ocean color imagery with multiple spatial and spectral resolution,namely:the Visible Infrared Imaging Radiometer Suite(VIIRS)(750 m/Multispectral),the Ocean and Land Color Instrument(OLCI)(300 m/Multispectral),the Hyperspectral Imager for the Coastal Ocean(HICO)(100 m/Hyperspectral),and the Landsat 8 Operational Land Imager(OLI)(30 m/Multispectral).The UV to visible scheme can benefit the CDOM absorption estimation in two aspects:1)it is free from the disturbance of suspended matter;2)it avoids uncertainties caused by the low signalto-noise ratio(SNR)of ag measurements in the visible *** algorithm is effective in revealing multiple scales of variation of CDOM absorption from ocean color observations.

关键词： Chromophoric dissolved organic matter ocean color remote sensing Pearl River Estuary ultraviolet

Multi-regional observations and validation of the M_(3)ocean tide

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Science China Earth Sciences 2023年第10期66卷 2265-2277页

作者： Adam Thomas DEVLIN jiayi pan Déborah IDIER School of Geography and Environment Jiangxi Normal UniversityNanchang330022China Cooperative Institute for Marine and Atmospheric Research School of Ocean and Earth Science and TechnologyUniversity of Hawai’i at MānoaHonoluluHI96822USA Department of Oceanography University of Hawai’i at MānoaHonoluluHI96822USA The Chinese University of Hong Kong Hong Kong999077China Key Laboratory of Poyang Lake Wetland and Watershed Research of Ministry of Education Nanchang330022China BRGM Orléans45060France

Improved determinations of the oft-ignored third-degree ocean tides can yield better accuracy for tidal predictions,numerical model solutions,and *** only a small part of tidal range,these components can be larger at certain coastal locations due to shelf resonances and other ***,we discuss observations of the M3lunar terdiurnal tide using 9-year windowed tidal harmonic analyses at 157 tide gauges compares to a global assimilation model(TPXO9v5a),with a focus on the Western Pacific and the European ***9v5a does well in estimating the observed M_(3)amplitudes and phase lags in most regions,though determinations in coastal zones and in morphologically complex areas are coarse and often *** also employ a shallow-water model(MARS)on the European Shelf,which can yield localized improvement over *** five subregions of the European Shelf,regional root-mean-squared-errors(RMSEs)are lower(and thus a better fit)at three locations for TPXO for amplitudes,and three for phase lags,with MARS simulations being a better fit in the other *** also show that some locations have experienced significant long-term increases and/or decreases in the M_(3)amplitude over time,likely related to resonance changes under sea level rise(SLR)which can modulate the oceanic response to astronomical *** hypothesis is explored for Europe using the MARS model by applying various sea level rise scenarios,showing that the directionality(positive or negative)of the long-term changes in M_(3)amplitudes over time match the model results for more than half of our validation stations.

关键词： Third-degree tides M_(3)tide Altimetry Numerical simulation Sea level rise

Modified optical remote sensing algorithms for the Pearl River Estuary

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Frontiers of Earth Science 2015年第4期9卷 732-741页

作者： Man-Chung CHIM jiayi pan Wenfeng LAI Institute of Space and Earth Information Science The Chinese University of Hong Kong Hong Kong SAR China

This study aims to develop new algorithms to retrieve sea surface parameters including concentrations of Chlorophyll a （Chl a） and Suspended Particulate Matter （SPM）, and absorbance of Colored Dissolved Organic Matter （aCDOM） by incorporating the contribution of red bands to make them more adaptable to case 2 waters. Optical remote sensing algorithms have demonstrated efficient retrieval of Chl a, SPM, and aCDOM, yet they are not very accurate especially for coastal areas. It has also been found that the default algorithm has overestimated Chl a in the Pearl River Estuary, and shown poor correlation for CDOM absorbance. By incorporating the red band ratios into the algorithm, a correction effect has been shown, which improves the accuracy of quantifying the actual concentration. Modeling and data fitting of the algorithm have been done based on 61 data samples collected in the Pearl River estuary during a cruise from 3 to 11 May 2014. The study also attempts to modify the aerosol correction bands used in SeaDAS to prevent saturation of these bands. The modified algorithms showed an R-Square value of 0.7289 for Chl a fitting, and 0.7338 for CDOM fitting, and corrected overestimation of Chl a concentration in the Pearl River estuary.

关键词： optical remote sensing algorithm Pearl River Estuary

Remote sensing study of wetlands in the Pearl River Delta during 1995-2015 with the support vector machine method

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Frontiers of Earth Science 2018年第3期12卷 521-531页

作者： Xiaosong HAN jiayi pan Adam T. DEVLIN Institute of Space and Earth Information Science The Chinese University of Hong Kong Hong Kong China

In recent years, experienced rapid economic the Pearl River Delta has growth which may create a substantial burden to its ecology. In this study, the wetlands of the Pearl River Delta are investigated. Through the use of remote sensing methods, we analyze spatial and temporal variations of wetlands in this area over the past twenty years. The support vector machine （SVM） method is proven to be an effective approach for classifying the wetlands of the Pearl River Delta, and the total classifica- tion resolution reaches 94.94% with a Kappa coefficient exceeding 0.94, higher than other comparable analysis methods. Our results show that wetland areas were reduced by 36.9% during the past twenty years. The change detection analysis method shows that there was a 95.58% intertidal zone change to other land-use types, most of which （57.12%） was converted to construction land. In addition, farmland was reduced by 54.89% during the past twenty years, 47.19% of which was changed to construction land use. The inland water area increased 19.02%, but most of this growth （18.77%） was converted from the intertidal zone.

关键词： wetland Pearl River Delta support vector machine method Landsat images

The spatiotemporal variation of the wind-induced near-inertial energy flux in the mixed layer of the South China Sea

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Acta Oceanologica Sinica 2015年第1期34卷 66-72页

作者： LI Juan LIU Junliang CAI Shuqun pan jiayi State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of Sciences University of Chinese Academy of Sciences Institute of Earth and Space Information Science Chinese University of Hong Kong

On the basis of the QSCAT/NCEP blended wind data and simple ocean data assimilation(SODA), the wind-induced near-inertial energy flux(NIEF) in the mixed layer of the South China Sea(SCS) is estimated by a slab model, and the model results are verified by observational data near the Xisha Islands in the SCS. Then, the spatial and temporal variations of the NIEF in the SCS are analyzed. It is found that, the monthly mean NIEF exhibits obvious spatial and temporal variabilities, i.e., it is large west of Luzon Island all the year, east of the Indo-China Peninsula all the year except in spring, and in the northern SCS from May to September. The large monthly mean NIEF in the first two zones may be affected by the large local wind stress curl whilst that in the last zone is probably due to the shallow mixed layer depth. Moreover, the monthly mean NIEF is relatively large in summer and autumn due to the passage of typhoons. The spatial mean NIEF in the mixed layer of the SCS is estimated to be about 1.25 m W/m2 and the total wind energy input from wind is approximately 4.4 GW. Furthermore, the interannual variability of the spatial monthly mean NIEF and the Ni?o3.4 index are negatively correlated.

关键词： near-inertial energy flux mixed layer spatiotemporal variation slab model South China Sea

Influence of the upper mixed layer depth on Langmuir turbulence characteristics

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Journal of Oceanology and Limnology 2023年第1期41卷 17-37页

作者： Guojing LI Changming DONG jiayi pan Adam T.DEVLIN Dongxiao WANG State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Nanjing University of Information Science and Technology Nanjing 210044China Institute of Space and Earth Information Science the Chinese University of Hong KongHong Kong 999077China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 510301China

The upper mixed layer depth(h)has a significant seasonal variation in the real ocean and the low-order statistics of Langmuir turbulence are dramatically influenced by the upper mixed layer *** explore the influence of the upper mixed layer depth on Langmuir turbulence under the condition of the wind and wave equilibrium,the changes of Langmuir turbulence characteristics with the idealized variation of the upper mixed layer depth from very shallow(h=5 m)to deep enough(h=40 m)are studied using a non-hydrostatic large eddy simulation *** simulation results show that there is a direct entrainment depth induced by Langmuir turbulence(h_(LT))within the *** normalized depthaveraged vertical velocity variance is smaller and larger than the downwind velocity variance for the ratio of the upper mixed layer to a direct entrainment depth induced by Langmuir turbulence h/h_(LT)1,respectively,indicating that turbulence characteristics have the essential change(i.e.,depth-averaged vertical velocity variance(DAVV)DADV for Langmuir turbulence)between h/h_(LT)*** rate of change of the normalized depth-averaged low-order statistics for h/h_(LT)*** reason is that the downward pressure perturbation induced by Langmuir cells is strongly inhibited by the upward reactive force of the strong stratified thermocline for h/h_(LT)***,the upper mixed layer depth has significant influences on Langmuir turbulence characteristics.

关键词： the upper mixed layer depth Langmuir turbulence turbulent characteristics large eddy simulation

Frontogenesis and Frontolysis of a Cold Filament Driven by the Cross-Filament Wind and Wave Fields Simulated by a Large Eddy Simulation

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Advances in Atmospheric Sciences 2024年第3期41卷 509-528页

作者： Guojing LI Dongxiao WANG Changming DONG jiayi pan Yeqiang SHU Zhenqiu ZHANG State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Shool of Marine Sciences Nanjing University of Information Science and TechnologyNanjing 210044China School of Geography and Environment Jiangxi Normal UniversityNanchang 330022China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China

The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and wave fields are *** results show that the intense wind and wave fields further break the symmetries of submesoscale flow fields and suppress the levels of filament frontogenesis. The changes of secondary circulation directions—that is, the conversion between the convergence and divergence of the surface cross-filament currents with the downwelling and upwelling jets in the filament center—are associated with the inertial oscillation. The filament frontogenesis and frontolysis caused by the changes of secondary circulation directions may periodically sharpen and smooth the gradient of submesoscale flow *** lifecycle of the cold filament may include multiple stages of filament frontogenesis and frontolysis.

关键词： cold filament frontogenesis frontolysis large eddy simulation

Observation of ocean current response to 1998 Hurricane Georges in the Gulf of Mexico

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Acta Oceanologica Sinica 2006年第1期25卷 1-14页

作者： ZHENG Quanan LAI Ronald J HUANG Nortlen E pan jiayi LIU W Timothy Department of Atmospheric and Oceanic Science University of Maryland College Park Maryland 20742 USA Minerals Management Service U S Department of the Interior Hemdon Virginia 20170 USA Ocean and Ice Branch NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA Department of Environmental and Biomolecular Systems Oregon Graduate Institute Beaverton Oregon 97006 USA Jet Propulsion Laboratory California Institute of Technology Pasadena California 91109 USA

The ocean current response to a hurricane on the shelf-break is examined. The study area is the DeSoto Canyon in the northeast Gulf of Mexico, and the event is the passage of 1998 Hurricane Georges with a maximum wind speed of 49 m/s. The data sets used for analysis consist of the mooring data taken by the Field Program of the DeSoto Canyon Eddy Intrusion Study, and simultaneous winds observed by NOAA （National Oceanic and Atmospheric Administration） Moored Buoy 42040. Time-depth ocean current energy density images derived from the observed data show that the ocean currents respond almost immediately to the hurricane with important differences on and offthe shelf. On the shelf, in the shallow water of 100 m, the disturbance penetrates rapidly downward to the bottom and forms two energy peaks, the major peak is located in the mixed layer and the secondary one in the lower layer. The response dissipates quickly after external forcing disappears. Offthe shelf, in the deep water, the major disturbance energy seems to be trapped in the mixed layer with a trailing oscillation; although the disturbance signals may still be observed at the depths of 500 and 1 290 m. Vertical dispersion analysis reveals that the near-initial wave packet generated offthe shelf consists of two modes. One is a barotropic wave mode characterized by a fast decay rate of velocity amplitude of 0.020 s^-, and the other is baroclinic wave mode characterized by a slow decay rate of 0.006 9 s^-1. The band-pass-filtering and empirical function techniques are employed to the frequency analysis. The results indicate that ialf frequencies shift above the local inertial frequency. On the shelf, the average frequency is 1.04fin the mixed layer, close to the diagnosed frequency of the first baroclinic mode, and the average frequency increases to 1.07fin the thermocline. Offthe shelf, all frequencies are a little smaller than the diagnosed frequency of the first mode. The average frequency decreases from 1.035

关键词： shelf dynamics hurricane ocean current air-sea interaction

Remote sensing observations of phytoplankton increases triggered by successive typhoons

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Frontiers of Structural and Civil Engineering 2017年第4期11卷 601-608页

作者： Lei HUANG Hui ZHAO jiayi pan Adam DEVLIN College of Ocean and Meteorology Guangdong Ocean University Zhanjiang 524088 China Institute of Space and Earth Information Science The Chinese University of Hong Kong Hong Kong China Shenzhen Research Institute The Chinese University of Hong Kong Shenzhen 518057 China College of Marine Science Nanjing University of Information Science and Technology Nanjing 210044 China Department of Civil and Environmental Engineering Portland State University Portland OR 97207 USA

Phytoplankton blooms in the Western North Pacific, triggered by two successive typhoons with different intensities and translation speeds under different pre-existing oceanic conditions, were observed and analyzed using remotely sensed chlorophyll-a （Chl-a）, sea surface temperature （SST）, and sea surface height anomaly （SSHA） data, as well as typhoon parameters and CTD （conductivity, temperature, and depth） profiles. Typhoon Sinlaku, with relatively weaker intensity and slower translation speed, induced a stronger phytoplankton bloom than Jangrni with stronger intensity and faster translation speed （Chl-a〉0.18 mg-m-3 versus Chl- a〈 0.15 mg.m-3） east of Taiwan Island. Translation speed may be one of the important mechanisms that affect phytoplankton blooms in the study area. Pre-existing cyclonic circulations provided a relatively unstable thermodynamic structure for Sinlaku, and therefore cold water with rich nutrients could be brought up easily. The mixed-layer deepening caused by Typhoon Sinlaku, which occurred first, could have triggered an unfavorable condition for the phytoplankton bloom induced by Typhoon Jangmi which followed afterwards. The sea surface temperature cooling by Jangmi was suppressed due to the presence of the thick upper-ocean mixed-layer, which prevented the deeper cold water from being entrained into the upper-ocean mixed layer, leading to a weaker phytoplankton augment. The present study sug- gests that both wind （including typhoon translation speed and intensity） and pre-existing conditions （e.g., mixed- layer depths, eddies, and nutrients） play important roles in the strong phytoplankton bloom, and are responsible for the stronger phytoplankton bloom after Sinlaku＇s passage than that after Jangmi＇s passage. A new typhoon- influencing parameter is introduced that combines the effects of the typhoon forcing （including the typhoon intensity and translation speed） and the oceanic pre- condition. This parameter shows that the forcing effect of

关键词： typhoon mixed-layer depth phytoplanktonbloom Northwest Pacific Ocean upwelling