海洋昼夜碳通量激光遥感研究

doi:10.3976/j.issn.1002-4026.20240143

Abstract

Abstract:

Oceanic carbon flux constitutes a critical component of the global carbon cycle and fundamentally informs climate change modeling and prediction. The advent of light detection and ranging(LiDAR) remote sensing has gradually revolutionized oceanic carbon flux measurements by providing high spatiotemporal resolutions, precision, and real-time monitoring capabilities. This review evaluates recent advances in LiDAR-based monitoring of diurnal-nocturnal oceanic carbon flux dynamics. We examine the fundamental principles, methodological approaches, and technical challenges associated with LiDAR applications in carbon flux quantification across the air-sea interface. Additionally, we identify knowledge gaps and propose future research directions to enhance the efficacy of LiDAR technology in characterizing temporal variability in oceanic carbon sequestration.

Key words: oceanic carbon flux, LiDAR-based remote sensing, diurnal-nocturnal monitoring, carbon cycle, CO₂ flux

CLC Number:

P731

CHEN Peng, LI Yunzhou, ZHANG Siqi, ZHANG Zhenhua, PAN Delu. LiDAR-based monitoring of diurnal-nocturnal oceanic carbon flux[J].Shandong Science, 2025, 38(3): 14-24.

Figures/Tables 2

References 87

[1]	GRUBER N, BAKKER D C, DEVRIES T, et al. Trends and variability in the ocean carbon sink[J]. Nature Reviews Earth & Environment, 2023, 4(2): 119-34. DOI: 10.1038/s43017-022-00381-x.
[2]	LE QUÉRÉ C, RÖDENBECK C, BUITENHUIS E T, et al. Saturation of the Southern Ocean CO₂ sink due to recent climate change[J]. Science, 2007, 316(5832): 1735-1738. DOI: 10.1126/science.1136188.
[3]	LE QUÉRÉ C, RAUPACH M R, CANADELL J G, et al. Trends in the sources and sinks of carbon dioxide[J]. Nature geoscience, 2009, 2(12): 831-836. DOI: 10.1038/ngeo689.
[4]	WU J, GOES J I, DO ROSARIO GOMES H, et al. Estimates of diurnal and daily net primary productivity using the Geostationary Ocean Color Imager (GOCI) data[J]. Remote Sensing of Environment, 2022, 280: 113183. DOI: 10.1016/j.rse.2022.113183.
[5]	BURGER F A, JOHN J G, FRöLICHER T L. Increase in ocean acidity variability and extremes under increasing atmospheric CO₂[J]. Biogeosciences, 2020, 17(18): 4633-4662. DOI:10.5194/BG-17-4633-2020.
[6]	TORRES O, KWIATKOWSKI L, SUTTON A J, et al. Characterizing mean and extreme diurnal variability of ocean CO₂ system variables across marine environments[J]. Geophysical Research Letters, 2021, 48(5): e2020GL090228. DOI: 10.1029/2020gl090228.
[7]	MCNEIL B I, SASSE T P. Future ocean hypercapnia driven by anthropogenic amplification of the natural CO₂ cycle[J]. Nature, 2016, 529(7586): 383-386. DOI: 10.1038/nature16156.
[8]	PIERRE F, JONES MATTHEW W, MICHAEL O, et al. Global carbon budget 2021[J]. Earth System Science Data Discussions, 2021.DOI:10.5194/essd-2021-386.
[9]	FRIEDLINGSTEIN P, O'SULLIVAN M, JONES M W, et al. Global carbon budget 2020[J]. Earth System Science Data, 2020, 12(4):3269-3340.DOI:10.5194/essd-12-3269-2020.
[10]	FRIEDLINGSTEIN P, O'SULLIVAN M, JONES M W, et al. Global carbon budget 2022[J]. Earth System Science Data Discussions, 2022. DOI:10.5194/essd-14-4811-2022.
[11]	FAY A R, GREGOR L, LANDSCHüTZER P, et al. Harmonization of global surface ocean p C O 2 mapped products and their flux calculations; an improved estimate of the ocean carbon sink [J]. Earth System Science Data Discussions, 2021: 1-32.
[12]	RÖDENBECK C, BAKKER D C E, GRUBER N, et al. Data-based estimates of the ocean carbon sink variability-first results of the Surface Ocean pCO₂ Mapping intercomparison (SOCOM)[J]. Biogeosciences, 2015, 12(23): 7251-7278. DOI: 10.5194/bg-12-7251-2015.
[13]	LE QUÉRÉ C, ANDREW R M, FRIEDLINGSTEIN P, et al. Global carbon budget 2017[J]. Earth System Science Data, 2018, 10(1): 405-448. DOI: 10.5194/essd-10-405-2018
[14]	CHAU T T T, GEHLEN M, CHEVALLIER F. A seamless ensemble-based reconstruction of surface ocean pCO₂ and air-sea CO₂ fluxes over the global coastal and open oceans[J]. Biogeosciences, 2022, 19(4): 1087-1109. DOI: 10.5194/bg-19-1087-2022.
[15]	BATES N R, TAKAHASHI T, CHIPMAN D W, et al. Variability of pCO₂ on diel to seasonal timescales in the Sargasso Sea near Bermuda[J]. Journal of Geophysical Research: Oceans, 1998, 103(C8): 15567-15585. DOI: 10.1029/98jc00247.
[16]	OLSEN A, OMAR A M, STUART-MENTETH A C, et al. Diurnal variations of surface ocean pCO₂ and sea-air CO₂ flux evaluated using remotely sensed data[J]. Geophysical Research Letters, 2004, 31(20): 2004GL020583. DOI: 10.1029/2004gl020583.
[17]	ALBRIGHT R, TAKESHITA Y, KOWEEK D A, et al. Carbon dioxide addition to coral reef waters suppresses net community calcification[J]. Nature, 2018, 555(7697): 516-519. DOI: 10.1038/nature25968.
[18]	DRUPP P S, DE CARLO E H, MACKENZIE F T, et al. Comparison of CO₂ dynamics and air-sea gas exchange in differing tropical reef environments[J]. Aquatic Geochemistry, 2013, 19(5): 371-397. DOI: 10.1007/s10498-013-9214-7.
[19]	MURIE K A, BOURDEAU P E. Fragmented kelp forest canopies retain their ability to alter local seawater chemistry[J]. Scientific Reports, 2020, 10: 11939. DOI: 10.1038/s41598-020-68841-2.
[20]	BERG P, DELGARD M L, POLSENAERE P, et al. Dynamics of benthic metabolism, O₂, and pCO₂ in a temperate seagrass meadow[J]. Limnology and Oceanography, 2019, 64(6): 2586-2604. DOI: 10.1002/lno.11236.
[21]	HOFMANN G E, SMITH J E, JOHNSON K S, et al. High-frequency dynamics of ocean pH: A multi-ecosystem comparison[J]. PLoS One, 2011, 6(12): e28983. DOI: 10.1371/journal.pone.0028983.
[22]	PAGE H N, COURTNEY T A, DE CARLO E H, et al. Spatiotemporal variability in seawater carbon chemistry for a coral reef flat in Kāne'ohe Bay, Hawai'i[J]. Limnology and Oceanography, 2019, 64(3): 913-934. DOI: 10.1002/lno.11084.
[23]	JURY C, THOMAS F, ATKINSON M, et al. Buffer capacity, ecosystem feedbacks, and seawater chemistry under global change[J]. Water, 2013, 5(3): 1303-1325. DOI: 10.3390/w5031303.
[24]	DENMAN K, CHRISTIAN J R, STEINER N, et al. Potential impacts of future ocean acidification on marine ecosystems and fisheries: Current knowledge and recommendations for future research[J]. ICES Journal of Marine Science, 2011, 68(6): 1019-1029. DOI: 10.1093/icesjms/fsr074.
[25]	KRANZ S A, DIETER S, RICHTER K U, et al. Carbon acquisition by Trichodesmium: The effect of pCO₂ and diurnal changes[J]. Limnology and Oceanography, 2009, 54(2): 548-559. DOI: 10.4319/lo.2009.54.2.0548.
[26]	PETER H, SINGER G A, PREILER C, et al. Scales and drivers of temporal pCO₂ dynamics in an Alpine stream[J]. Journal of Geophysical Research: Biogeosciences, 2014, 119(6): 1078-1091. DOI: 10.1002/2013jg002552.
[27]	LACHS L, DONNER S, EDWARDS A J, et al. Higher spatial resolution is not always better: Evaluating satellite-sensed sea surface temperature products for a west Pacific coral reef system[J]. Scientific Reports, 2025, 15: 1321. DOI: 10.1038/s41598-024-84289-0.
[28]	CHEN G, TANG J W, ZHAO C F, et al. Concept design of the “guanlan” science mission: China’s novel contribution to space oceanography[J]. Frontiers in Marine Science, 2019, 6: 194. DOI: 10.3389/fmars.2019.00194.
[29]	汪自军, 张扬, 刘东, 等. 新型多波束陆海激光雷达探测卫星技术发展研究[J]. 红外与激光工程, 2021, 50(7): 20211041. DOI: 10.3788/IRLA20211041.
[30]	唐军武, 陈戈, 陈卫标, 等. 海洋三维遥感与海洋剖面激光雷达[J]. 遥感学报, 2021, 25(1): 460-500. DOI:10.11834/jrs.20210495
[31]	陈卫标, 刘东. 海洋遥感激光雷达: 原理与技术[M]. 北京: 海洋出版社, 2021.
[32]	BEHRENFELD M J, GAUBE P, DELLA PENNA A, et al. Global satellite-observed daily vertical migrations of ocean animals[J]. Nature, 2019, 576(7786): 257-261. DOI: 10.1038/s41586-019-1796-9.
[33]	HOSTETLER C A, BEHRENFELD M J, HU Y X, et al. Spaceborne lidar in the study of marine systems[J]. Annual Review of Marine Science, 2018, 10: 121-147. DOI: 10.1146/annurev-marine-121916-063335.
[34]	BEHRENFELD M J, HU Y X, O’MALLEY R T, et al. Annual boom-bust cycles of polar phytoplankton biomass revealed by space-based lidar[J]. Nature Geoscience, 2016, 10(2): 118-122. DOI: 10.1038/ngeo2861.
[35]	LU X M, HU Y X, YANG Y K, et al. Antarctic spring ice-edge blooms observed from space by ICESat-2[J]. Remote Sensing of Environment, 2020, 245: 111827. DOI: 10.1016/j.rse.2020.111827.
[36]	OVERPECK J T, MEEHL G A, BONY S, et al. Climate data challenges in the 21st century[J]. Science, 2011, 331(6018): 700-702. DOI: 10.1126/science.1197869.
[37]	MOREL A, GENTILI B. Radiation transport within oceanic (case 1) water[J]. Journal of Geophysical Research: Oceans, 2004, 109(C6): 2003JC002259. DOI: 10.1029/2003jc002259.
[38]	SCHULIEN J A, BEHRENFELD M J, HAIR J W, et al. Vertically- resolved phytoplankton carbon and net primary production from a high spectral resolution lidar[J]. Optics Express, 2017, 25(12): 13577-13587. DOI: 10.1364/OE.25.013577.
[39]	BABIN M, ARRIGO K R, BéLANGER S, et al. Ocean colour remote sensing in polar seas: report of an IOCCG working group on ocean colour remote sensing in polar seas[M]. International Ocean Colour Coordinating Group, 2015.
[40]	BHARDWAJ A, SAM L, BHARDWAJ A, et al. LiDAR remote sensing of the cryosphere: Present applications and future prospects[J]. Remote Sensing of Environment, 2016, 177: 125-143. DOI: 10.1016/j.rse.2016.02.031.
[41]	ZHANG Z H, ZHANG S Q, BEHRENFELD M J, et al. Combining deep learning with physical parameters in POC and PIC inversion from spaceborne lidar CALIOP[J]. ISPRS Journal of Photogrammetry and Remote Sensing, 2024, 212: 193-211. DOI: 10.1016/j.isprsjprs.2024.05.007.
[42]	CHEN P, JAMET C, LIU D. LiDAR remote sensing for vertical distribution of seawater optical properties and chlorophyll-a from the East China Sea to the South China Sea[J]. IEEE Transactions on Geoscience and Remote Sensing, 2022, 60: 4207321. DOI: 10.1109/TGRS.2022.3174230.
[43]	ZHANG S Q, CHEN P, HU Y X, et al. Research Report Diurnal global ocean surface pCO₂ and air-sea CO₂ flux reconstructed from spaceborne LiDAR data[J]. PNAS Nexus, 2023, 3(1): pgad432. DOI: 10.1093/pnasnexus/pgad432.
[44]	CHEN P, JAMET C, ZHANG Z H, et al. Vertical distribution of subsurface phytoplankton layer in South China Sea using airborne lidar[J]. Remote Sensing of Environment, 2021, 263: 112567. DOI: 10.1016/j.rse.2021.112567.
[45]	ZHANG S, CHEN P, ZHANG Z, et al. Carbon air-sea flux in the Arctic Ocean from CALIPSO from 2007 to 2020[J]. Remote Sensing, 2022, 14(24): 6196.
[46]	CHURNSIDE J H, SHAW J A. Lidar remote sensing of the aquatic environment: Invited[J]. Applied Optics, 2020, 59(10): C92-C99. DOI: 10.1364/AO.59.000C92.
[47]	CILLINA, ARCHAMBAULT P, LONG B. Mapping the shallowwater seabedhabitat withthe SHOALS[J]. IEEETransactions on Geoscience and Remote Sensing, 2008, 46(10): 2947-2955. DOI:10.1109/TGRS.2008.920020.
[48]	BEHRENFELD M J, HU Y X, HOSTETLER C A, et al. Space-based lidar measurements of global ocean carbon stocks[J]. Geophysical Research Letters, 2013, 40(16): 4355-4360. DOI: 10.1002/grl.50816.
[49]	KHEIREDDINE M, BREWIN R J W, OUHSSAIN M, et al. Particulate scattering and backscattering in relation to the nature of particles in the red sea[J]. Journal of Geophysical Research: Oceans, 2021, 126(4): e2020JC016610.
[50]	DIONISI D, BRANDO V E, VOLPE G, et al. Seasonal distributions of ocean particulate optical properties from spaceborne lidar measurements in Mediterranean and Black sea[J]. Remote Sensing of Environment, 2020, 247: 111889. DOI: 10.1016/j.rse.2020.111889.
[51]	LACOUR L, LAROUCHE R, BABIN M. In situ evaluation of spaceborne CALIOP lidar measurements of the upper-ocean particle backscattering coefficient[J]. Optics Express, 2020, 28(18): 26989-26999. DOI: 10.1364/OE.397126.
[52]	LEE Z P, DU K P, ARNONE R. A model for the diffuse attenuation coefficient of downwelling irradiance[J]. Journal of Geophysical Research (Oceans), 2005, 110(C2): C02016. DOI: 10.1029/2004JC002275.
[53]	KUNZ G J, DE LEEUW G. Inversion of lidar signals with the slope method[J]. Applied Optics, 1993, 32(18): 3249-3256. DOI: 10.1364/AO.32.003249.
[54]	FERNALD F G. Analysis of atmospheric lidar observations: Some comments[J]. Applied Optics, 1984, 23(5): 652. DOI: 10.1364/ao.23.000652.
[55]	BU L, HUANG X, CAO N, et al. Mie-Rayleigh-Raman lidar for measurement of atmospheric temperature and aerosol extinction[J]. Proceedings of SPIE-The International Society for Optical Engineering, 2009, 7382:73824Y-73824Y-6.DOI:10.1117/12.835730.
[56]	KLETT J D. Stable analytical inversion solution for processing lidar returns[J]. Applied Optics, 1981, 20(2): 211-220. DOI: 10.1364/AO.20.000211.
[57]	EGOROV A D, POTAPOVA I A, SHCHUKIN G G. Lidar methods for probing an atmospheric aerosol[J]. Journal of Optical Technology, 2001, 68(11): 801. DOI:10.1364/JOT.68.000801.
[58]	CHEN P, PAN D L, MAO Z H, et al. A feasible calibration method for type 1 open ocean water LiDAR data based on bio-optical models[J]. Remote Sensing, 2019, 11(2): 172. DOI: 10.3390/rs11020172.
[59]	CHURNSIDE J H, SULLIVAN J M, TWARDOWSKI M S. Lidar extinction-to-backscatter ratio of the ocean[J]. Optics Express, 2014, 22(15): 18698-18706. DOI: 10.1364/OE.22.018698.
[60]	CHURNSIDE J H. Review of profiling oceanographic lidar[J]. Optical Engineering, 2014, 53(5): 051405. DOI: 10.1117/1.oe.53.5.051405.
[61]	HOGAN R. Fast lidar and radar multiple-scattering models. part I: Small-angle scattering using the photon variance-covariance method[J]. Journal of the Atmospheric Sciences, 2008, 65(12): 3621-3635. DOI:10.1175/2008JAS2642.1.
[62]	LUCHININ A G, KIRILLIN M Y, DOLIN L S. Backscatter signals in underwater lidars: Temporal and frequency features[J]. Applied Optics, 2018, 57(4): 673-677. DOI: 10.1364/AO.57.000673.
[63]	CHEN P, PAN D L, MAO Z H, et al. Semi-analytic Monte Carlo radiative transfer model of laser propagation in inhomogeneous sea water within subsurface plankton layer[J]. Optics & Laser Technology, 2019, 111: 1-5. DOI: 10.1016/j.optlastec.2018.09.028.
[64]	LIU D, XU P T, ZHOU Y D, et al. Lidar remote sensing of seawater optical properties: Experiment and Monte Carlo simulation[J]. IEEE Transactions on Geoscience and Remote Sensing, 2019, 57(11): 9489-9498. DOI: 10.1109/TGRS.2019.2926891.
[65]	BISSONNETTE L R. Lidar and multiple scattering[M]. Lidar:Range-resolvedoptical remote sensing of the atmosphere. New York, NY: NY: Springer NewYork, 2005:43-103.
[66]	MITRA K, CHURNSIDE J H. Transient radiative transfer equation applied to oceanographic lidar[J]. Applied Optics, 1999, 38(6): 889-895. DOI: 10.1364/ao.38.000889.
[67]	RAMELLA-ROMAN J, PRAHL S, JACQUES S. Three Monte Carlo programs of polarized light transport into scattering media: Part I[J]. Optics Express, 2005, 13(12): 4420-4438. DOI: 10.1364/opex.13.004420.
[68]	GORDON H R. Interpretation of airborne oceanic lidar: Effects of multiple scattering[J]. Applied Optics, 1982, 21(16): 2996-3001. DOI: 10.1364/AO.21.002996.
[69]	STEGMANN P G, SUN B Q, DING J C, et al. Study of the effects of phytoplankton morphology and vertical profile on lidar attenuated backscatter and depolarization ratio[J]. Journal of Quantitative Spectroscopy and Radiative Transfer, 2019, 225: 1-15. DOI: 10.1016/j.jqsrt.2018.12.009.
[70]	POOLE L R, VENABLE D D, CAMPBELL J W. Semianalytic Monte Carlo radiative transfer model for oceanographic lidar systems[J]. Applied Optics, 1981, 20(20): 3653-3656. DOI: 10.1364/AO.20.003653.
[71]	LIU Q, CUI X Y, JAMET C, et al. A semianalytic Monte Carlo simulator for spaceborne oceanic lidar: Framework and preliminary results[J]. Remote Sensing, 2020, 12(17): 2820. DOI: 10.3390/rs12172820.
[72]	HU Y X, WINKER D, YANG P, et al. Identification of cloud phase from PICASSO-CENA lidar depolarization: A multiple scattering sensitivity study[J]. Journal of Quantitative Spectroscopy and Radiative Transfer, 2001, 70(4/5/6): 569-579. DOI: 10.1016/S0022-4073(01)00030-9.
[73]	HU Y X, LIU Z Y, WINKER D, et al. Simple relation between lidar multiple scattering and depolarization for water clouds[J]. Optics Letters, 2006, 31(12): 1809-1811. DOI: 10.1364/ol.31.001809.
[74]	CHURNSIDE J H. Polarization effects on oceanographic lidar[J]. Optics Express, 2008, 16(2): 1196-1207. DOI: 10.1364/oe.16.001196.
[75]	LI L X, STEGMANN P G, ROSENKRANZ S, et al. Simulation of light scattering from a colloidal droplet using a polarized Monte Carlo method: Application to the time-shift technique[J]. Optics Express, 2019, 27(25): 36388-36404. DOI: 10.1364/OE.27.036388.
[76]	ZHAI S Y, TWARDOWSKI M, HEDLEY J D, et al. Optical backscattering and linear polarization properties of the colony forming Cyanobacterium Microcystis[J]. Optics Express, 2020, 28(25): 37149-37166. DOI: 10.1364/OE.405871.
[77]	WINKER D M, COUCH R H, MCCORMICK M P. An overview of LITE: NASA’s lidar in-space technology experiment[J]. Proceedings of the IEEE, 1996, 84(2): 164-180. DOI: 10.1109/5.482227.
[78]	LANCASTER R S, SPINHIRNE J D, PALM S P. Laser pulse reflectance of the ocean surface from the GLAS satellite lidar[J]. Geophysical Research Letters, 2005, 32(22): 2005GL023732. DOI: 10.1029/2005gl023732.
[79]	WINKER D M, PELON J, COAKLEY J, et al. The CALIPSO mission: A global 3D view of aerosols and clouds[J]. Bulletin of the American Meteorological Society, 2010, 91(9): 1211-1229. DOI: 10.1175/2010BAMS3009.1.
[80]	LUX O, LEMMERZ C, WEILER F, et al. ALADIN laser frequency stability and its impact on the Aeolus wind error[J]. Atmospheric Measurement Techniques Discussions, 2021, 2021: 1-40.
[81]	PARRISH C E, MAGRUDER L A, NEUENSCHWANDER A L, et al. Validation of ICESat-2 ATLAS bathymetry and analysis of ATLAS’s bathymetric mapping performance[J]. Remote Sensing, 2019, 11(14): 1634. DOI: 10.3390/rs11141634.
[82]	PEREIRA DO CARMO J, DE VILLELE G, HELIÈRE A, et al. ATLID, ESA atmospheric backscatter LIDAR for the ESA EarthCARE mission[J]. CEAS Space Journal, 2019, 11(4): 423-435. DOI: 10.1007/s12567-019-00284-6.
[83]	郭金权, 李国元, 左志强, 等. 高分七号卫星激光测高仪全波形数据质量及特征分析[J]. 红外与激光工程, 2020, 49(S2): 20200387.DOI:10.3788/IRLA20200387.
[84]	陈卫标, 刘继桥, 侯霞, 等. 大气环境监测卫星激光雷达技术[J]. 上海航天(中英文), 2023, 40(3): 13-20. DOI: 10.19328/j.cnki.2096-8655.2023.03.002.
[85]	JAMET C, IBRAHIM A, AHMAD Z, et al. Going beyond standard ocean color observations: Lidar and polarimetry[J]. Frontiers in Marine Science, 2019, 6: 251. DOI: 10.3389/fmars.2019.00251.
[86]	STARR D. NASA’s aerosol-cloud-ecosystems (ACE) mission[C]// Imaging and Applied Optics. Toronto: OSA, 2011: HMA4. DOI: 10.1364/hise.2011.hma4.
[87]	BEHRENFELD M J, LORENZONI L, HU Y X, et al. Satellite lidar measurements as a critical new global ocean climate record[J]. Remote Sensing, 2023, 15(23): 5567. DOI: 10.3390/rs15235567.

Metrics

Comments

Recommended 0

Open Access This article is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0), which permits third parties to freely share (i.e., copy and redistribute the material in any medium or format) and adapt (i.e., remix, transform, or build upon the material) the articles published in this journal, provided that appropriate credit is given, a link to the license is provided, and any changes made are indicated. The material may not be used for commercial purposes. For details of the CC BY-NC 4.0 license, please visit: https://creativecommons.org/licenses/by-nc/4.0

LiDAR-based monitoring of diurnal-nocturnal oceanic carbon flux

RichHTML

PDF (PC)

Like

Knowledge

Abstract

Cite this article

share this article

Figures/Tables 2

References 87

Related Articles 3

Metrics

Comments

Recommended 0

[1]	SHI Zhenjia, HAO Zengzhou, LI Yunzhou, YE Feng, HUANG Haiqing, PAN Delu. Fusion of mesoscale eddy data for the South China Sea [J]. Shandong Science, 2025, 38(3): 99-108.
[2]	CUI Hao, WANG Zhong-Qiu, LIU Hui, XU Yan. Contour extraction based crest coordinate collection algorithm [J]. J4, 2014, 27(2): 25-29.
[3]	SUN Ke-Qu, XU Xian, LI Jun, GE Xiu-Jun, MA Pei-Ming, HUANG Chen-Yang, LI Chuan-Zhu. Longterm characteristics of seawater salinity change in Lianyungang coastal sea area [J]. J4, 2014, 27(2): 30-33.