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seasonal variability of the Kuroshio Current at the PN Section in the East China Sea based on in-situ observation from 1987 to 2010

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Acta Oceanologica Sinica 2015年第5期34卷 12-21页

作者： WEI Yanzhou PEI Yuhua ZHANG Rong-Hua Key Laboratory of Ocean Circulation and Wave Institute of OceanologyChinese Academy of Sciences University of the Chinese Academy of Sciences State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyState Oceanic Administration College of Physical and Environmental Oceanography Ocean University of China

As the spatio-temporal variability of the Kuroshio is highly influenced by mesoscale eddies, representing its seasonal variability characteristics requires sufficiently long term observations to reduce the uncertainties. Geostrophic velocity data estimated from hydrographic observation from 1987 to 2010 and the shipboard ADCP velocity data from 1993 to 2008 at the PN Section in the central East China Sea are collected to view the seasonal variability objectively. From both types of observation, it is found that the seasonal climatology mean of the Kuroshio Current exhibits significant difference in three areas, which are located at the Kuroshio Current core and its two flanks in a shallow layer less than 300 m, with the weakest northeast current at the core in autumn, the strongest counter current on the right flank in spring, and the strongest northeast current on the left flank in autumn, respectively. The seasonal variance of the Kuroshio Current also exhibits significant difference on the off- shore side of the Kuroshio, with larger variance in spring and summer while smaller variance in autumn and winter. For the current parallel to the PN Section, the ratio of the seasonal variability component to the intraseasonal variability component is relatively smaller than that for the current perpendicular to the PN Section. Further analyses indicate that the seasonal variability at the PN Section is tightly linked to the upstream and downstream current variability.

关键词： Kuroshio Current seasonal variability East China Sea significance test

seasonal variability OF THE INDONESIAN THROUGHFLOW FROM A VARIABLE-GRID GLOBAL OCEAN MODEL

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Journal of Hydrodynamics 2004年第5期16卷 525-532页

作者： WANGYong-gang FANGGuo-hong WEIZe-xun CHENHai-ying WANGXin-yi KeyLaboratoryofMarineScienceandNumericalModeling TheFirstInstituteofOceanographyStateOceanicAdministrationQingdao266061China InstituteofOceanology ChineseAcademyofSciencesQingdao266071China

The objective of this study is to model the mean and seasonal mass transportof the Pacific to Indian O-cean throughflow using variable-grid global Ocean General CirculationModel (OGCM) with fine grid (1°/6) covering the area from 20°S to 60°N and from 98°E to 156°*** computations show that Indonesian Throughflow (ITF) mass transport, computed as a sum ofthrough-strait transport, has maximum transport in Sept. (17. 5Sv) and minimum transport in Jan. (9.5Sv). The annual mean ITF transport amounts to 14. 5Sv. Twenty-two percent of this transport passesthrough Lombok Strait. Sixty-five percent of this transport passes through Timor ***-annual variability is apparent in Lombok and Ombai Straits while annual variability is apparentin Timor Passage.

关键词： indonesian throughflow seasonal variability global ocean circulation model

seasonal variability in dissolved oxygen in the Bohai Sea,China

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Journal of Oceanology and Limnology 2022年第1期40卷 78-92页

作者： Yaozu CHEN Fangguo ZHAI Yanzhen GU Jing CAO Cong LIU Xingchuan LIU Zizhou LIU Peiliang LI School of Marine Sciences Sun Yat-Sen UniversityZhuhai 519082China College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao 266100China North China Sea Environmental Monitoring Center State Oceanic AdministrationQingdao 266000China Institute of Physical Oceanography and Remote Sensing Ocean CollegeZhejiang UniversityZhoushan 316021China Hainan Institute of Zhejiang University Sanya 572024China

Deoxygenation has frequently appeared in coastal ecosystems over the past century due to the joint infl uence of increasing anthropogenically induced nutrient inputs and global *** semi-enclosed Bohai Sea is a typical system that is prone to deoxygenation,with regular hypoxia events consistently recorded in recent *** on in-situ observation data collected in large-scale voyage surveys in the Bohai Sea during 2008-2017,the seasonal variability in dissolved oxygen(DO)and its controlling mechanisms were *** results indicated that in spring and autumn,the DO distributions exhibited similar spatial patterns in the surface and bottom layers,while in summer,its spatial distribution was characterized by large-scale oxygen-poor zones distributed off the Qinhuangdao Coast and the central southern Bohai Sea in the bottom *** controlling mechanisms of the DO distribution varied from season to *** and autumn DO distributions were dominated by the seawater *** the combined eff ects of stratifi cation and decomposition,the summer bottom DO exhibited dual-core *** the one hand,stratifi cation could greatly impede vertical mixing,resulting in reduced bottom DO *** the other hand,the increased bottom organic matter intensifi ed the decomposition processes,inducing massive DO consumption and elevated dissolved inorganic nitrogen *** addition,the stronger stratifi cation might be the reason for the more severe deoxygenation in the southern oxygen-poor zones in *** study provides guidance for an in-depth understanding of the DO seasonality in the Bohai Sea and the mechanisms that modulate it and for the improvement of hypoxia forecasts in ocean models.

关键词： dissolved oxygen seasonal variability mechanism the Bohai Sea

seasonal variability in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon

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Science China Earth Sciences 2011年第10期54卷 1595-1603页

作者： HU Liang LI YaoDong SONG Yang DENG DiFei National Satellite Meteorological Center China Meteorological Administration Beijing 100081 China Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Beijing Aviation Meteorological Institute Beijing 100085 China L M. Systems Group Satellite Meteorology and Climatology Division National Oceanic andAtmospheric Administration Washington D C USA

seasonal variations in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon are analyzed using 10-year (1998-2007) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) rain products (2A25). Datasets from the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) 24 general circulation models (GCMs) are evaluated using TRMM PR rain products in terms of their ability to simulate convective and stratiform precipitation and their deficiencies. The results show that Asian monsoon convective and stratiform precipitation increases significantly after onset of the summer monsoon, but the percentage of convective precipitation clearly decreases over tropical areas while it increases in subtropical regions. The GCMs simulate well the seasonal variation in the contribution of Asian monsoon subtropical convective precipitation to the total rainfall; however, the simulated convective precipitation amount is high while the simulated stratiform precipitation amount is low relative to TRMM measurements, especially over the Asian monsoon tropical region. There is simultaneous TRMM-observed convective and stratiform precipitation in space and time, but GCMs cannot simulate this relationship between convective and stratiform precipitation, resulting in the deficiency of stratiform precipitation simulations.

关键词： convective precipitation stratiform precipitation Asian monsoon seasonal variability

seasonal variability of tropical cyclones generated over the South China Sea

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Acta Oceanologica Sinica 2007年第4期26卷 20-28页

作者： WANG Guihua WANG Hui QI Yiquan State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography State Oceanic Administration Hangzhou 310012 China Chinese Academy of Meteorology Sciences China Administration of Meteorology Beijing 100081 China Key Laboratory of Tropical Marine and Environmental Dynamics South China Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou 510301 China

The seasonal variability of tropical cyclones （CTCs） generated over the South China Sea （SCS） from 1948 to 2003 is analyzed. It peaks in occurrence in August and few generate in late winter （from January to March）. The seasonal activity is attributed to the variability of atmosphere and ocean environments associated with the monsoon system. It is found that the monsoonal characteristics of the SCS basically determine the region of tropical cyclone （TC） genesis in each month.

关键词： seasonal variability South China Sea tropical cyclone

seasonal variability in the thermohaline structure of the Western Pacific Warm Pool

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Acta Oceanologica Sinica 2015年第7期34卷 44-53页

作者： QIN Sisi ZHANG Qilong YIN Baoshu Key Laboratory of Ocean Circulation and Waves Institute of Oceanology Chinese Academy of Sciences University of Chinese Academy of Sciences

Using the 28℃ isotherm to define the Western Pacific Warm Pool （WPWP）, this study analyzes the seasonal variability of the WPWP thermohaline structure on the basis of the monthly-averaged sea temperature and salinity data from 1950 to 2011, and the dynamic and thermodynamic mechanisms based on the monthly-averaged wind, precipitation, net heat fluxes and current velocity data. A△T=-0.4℃ is more suitable than other temperature criterion for determining the mixed layer （ML） and barrier layer （BL） over the WPWP using monthly-averaged temperature and salinity data. The WPWP has a particular thermohaline structure and can be vertically divided into three layers, i.e., the ML, BL, and deep layer （DL）. The BL thickness （BLT） is the thickest, while the ML thickness （MLT） is the thinnest. The MLT has a similar seasonal variation to the DL thickness （DLT） and BLT. They are all thicker in spring and fall but thinner in summer. The temperatures of the ML and BL are both higher in spring and autumn but lower in winter and summer with an annual amplitude of 0.15℃, while the temperature of the DL is higher in May and lower in August. The averaged salinities at these three layers are all higher in March but lower in September, with annual ranges of 0.41-0.45. Zonal currents, i.e., the South Equatorial Current （SEC） and North Equatorial Counter Current （NECC）, and winds may be the main dynamic factors driving the seasonal variability in the WPWP thermohaline structure, while precipitation and net heat fluxes are both important thermodynamic factors. Higher （lower） winds cause both the MLT and BLT to thicken （thin）, a stronger （weaker） NECC induces MLT, BLT, and DLT to thin （thicken）, and a stronger （weaker） SEC causes both the MLT and BLT to thicken （thin） and the DLT to thin （thicken）. An increase （decrease） in the net heat fluxes causes the MLT and BLT to thicken （thin） but the DLT to thin （thicken）, while a stronger （weaker） precipitation favors thinner （thicker） MLT but thicker

关键词： Western Pacific Warm Pool thermohaline structure barrier layer mixed layer seasonal variability

seasonal variability of salinity budget and water exchange in the northern Indian Ocean from HYCOM assimilation

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Chinese Journal of Oceanology and Limnology 2012年第6期30卷 1082-1092页

作者：张玉红杜岩 State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of Sciences

Based on HYbrid Coordinate Ocean Model (HYCOM) assimilation and observations, we analyzed seasonal variability of the salinity budget in the southeastern Arabian Sea (AS) and the southern part of the Bay of Bengal (BOB), as well as water exchange between the two basins. Results show that fresh water flux cannot explain salinity changes in salinity budget of both regions. Oceanic advection decreases salinity in the southeastern AS during the winter monsoon season and increases salinity in the southern BOB during the summer monsoon season. In winter, the Northeast Monsoon Current (NMC) carries fresher water from the BOB westward into the southern AS; this westward advection is confined to 4°-6°N and the upper 180 m south of the Indian peninsula. Part of the less saline water then turns northward, decreasing salinity in the southeastern AS. In summer, the Southwest Monsoon Current (SMC) advects high-salinity water from the AS eastward into the BOB, increasing salinity along its path. This eastward advection of high-salinity water south of the India Peninsula extends southward to 2°N, and the layer becomes shallower than in winter. In addition to the monsoon current, the salinity difference between the two basins is important for salinity advection.

关键词： seasonal variability salinity budget Arabian Sea Bay of Bengal zonal water exchange HYbridCoordinate Ocean Model (HYCOM) assimilation

seasonal variability of the North Equatorial Current transport in the western Pacific Ocean

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Chinese Journal of Oceanology and Limnology 2014年第1期32卷 223-237页

作者：闫庆勋胡敦欣翟方国 Key Laboratory of Ocean Circulation and Waves Chinese Academy of Sciences Institute of Oceanology Chinese Academy of Sciences University of Chinese Academy of Sciences Third Institute of Oceanography State Oceanic Administration

seasonal variability of the North Equatorial Current （NEC） transport in the western Pacific Ocean is investigated with ECMWF Ocean Analysis/Reanalysis System 3 （eRA-S3）. The result shows that NEC transport （NT） across different longitudes in the research area shows a similar double-peak structure, with two maxima （in summer and winter）, and two minima （in spring and autumn）. This kind of structure can also be found in NEC geostrophic transport （NGT）, but in a different magnitude and phase. These differences are attributable to Ekman transport induced by the local meridional wind and transport caused by nonzero velocity at the reference level, which is assumed to be zero in the NGT calculation. In the present work, a linear vorticity equation governing a 1.5-layer reduced gravity model is adopted to examine the dynamics of the seasonal variability of NGT. It is found that the annual cycle of NGT is mainly controlled by Ekman pumping induced by local wind, and westward-propagating Rossby waves induced by remote wind. Further research demonstrates that the maximum in winter and minimum in spring are mostly attributed to wind east of the dateline, whilst the maximum in summer and minimum in autumn are largely attributed to that west of the dateline.

关键词： North Equatorial Current (NEC) transport seasonal variability linear vorticity equation

Tea Production Response to seasonal Rainfall variability: Evidence from Rwanda

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Agricultural Sciences 2024年第8期15卷 909-938页

作者： Joseph Ndagijimana Athanase Hafashimana Department of Economics College of Business and Economics University of Rwanda Rwanda The African Centre of Excellence in Data Science University of Rwanda Rwanda

Tea is a very important cash crop in Rwanda, as it provides crucial income and employment for farmers in poor rural areas. From 2017 to 2020, this study was intended to determine the impact of seasonal rainfall on tea output in Rwanda while still considering temperature, plot size (land), and fertiliser for tea plantations in three of Rwanda’s western, southern, and northern provinces, western province with “Gisovu” and “Nyabihu”, southern with “Kitabi”, and northern with “Mulindi” tea company. The study tested the level of statistical significance of all considered variables in different formulation of panel data models to assess individual behaviour of independent variables that would affect tea production. According to this study, a positive change in rainfall of 1 mm will increase tea production by 0.215 percentage points of tons of fresh leaves. Rainfall is a statistically significant variable among all variables with a positive impact on tea output Qitin Rwanda’s Western, Southern, and Northern provinces. Rainfall availability favourably affects tea output and supports our claim. Therefore, there is a need for collaboration efforts towards developing sustainable adaptation and mitigation options against climate change, targeting tea farming and the government to ensure that tea policy reforms are targeted towards raising the competitiveness of Rwandan tea at local and global market.

关键词： Tea Production Climate Change Production Technology seasonal variability Panel Data Models