Sea surface height variations in the South China Sea from satellite altimetry     

《Oceanologica Acta》1999,22(1):1-17

Sea surface elevation in the South China Sea is examined in the Topex/Poseidon altimeter data from 1992 to 1995. Sea level anomalies are smoothed along satellite tracks and in time with tidal errors reduced by harmonic analysis. The smoothed data are sampled every ten days with an along-track separation of about 40 km. The data reveal significant annual variations in sea level. In winter, low sea level is over the entire deep basin with two local lows centred off Luzon and the Sunda Shelf. In summer, sea level is high off Luzon and off the Sunda Shelf, and a low off Vietnam separates the two highs. The boundary between the Vietnam low and Sunda high coincides with the location of a jet leaving the coast of Vietnam described in earlier studies. Principal component analysis shows that the sea level variation consists mainly of two modes, corresponding well to the first two modes of the wind stress curl. Mode 1 represents the oscillation in the southern basin and shows little inter-annual variation. The mode 2 oscillation is weak in the southern basin and is strongest off central Vietnam. During the winters of 1992–1993 and 1994–1995 and the following summers, the wind stress curl is weak, and the mode 2 sea level variation in the northern basin is reduced, resulting in weaker winter and summer gyres. Weakening of the Vietnam low in summer implies diminishing of the eastward jet leaving the coast of Vietnam. The results are consistent with model simulations.  相似文献   

European Forum on Integrated Environmental Assessment (EFIEA)     

《Global Environmental Change》1999,9(1):1-3

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新疆博斯腾湖水体颗粒和溶解有机碳的季节变化及其来源初探   总被引：5，自引：2，他引：3  

王秀君  房传苓  于志同  王家平  彭冬梅  康静静 《湖泊科学》2014,26(4):552-558

在博斯腾湖选取了13个点位,于2012年5、8、10月测定表层和底层水体中的颗粒有机碳、溶解有机碳、颗粒有机氮和叶绿素a含量.结果显示颗粒和溶解有机碳在表层水体中的浓度与底层相近.博斯腾湖水体中颗粒有机碳的季节变化十分明显,其平均浓度从春季(0.64 mg/L)到夏季(0.71 mg/L)变化不大,但在秋季变化十分显著(浓度达1.58 mg/L).其中西北湖区和湖心区颗粒有机碳的季节变化最明显,东部湖区颗粒有机碳的季节变化相对较小.博斯腾湖水体的颗粒有机碳在春、秋两季主要来自外源输入,在夏季受水体中浮游生物的影响较大.博斯腾湖水体中溶解有机碳也具有一定的季节变化,夏季浓度(平均为9.3 mg/L)略低于春、秋两季(平均为10.3 mg/L).溶解有机碳在河口区的季节变化最强,其夏季浓度明显偏低,主要是由于开都河河水的稀释作用.总体上,博斯腾湖水体中溶解有机碳浓度的变化主要受外部因素的影响.  相似文献   

A non-breaking-wave-generated turbulence mixing scheme for a global ocean general circulation model     

Zhuang  Zhanpeng  Zheng  Quanan  Yuan  Yeli  Yang  Guangbing  Zhao  Xinhua 《Ocean Dynamics》2020,70(3):293-305

Ocean Dynamics - A novel vertical mixing scheme to describe the influence of the non-breaking surface waves in ocean general circulation models is proposed based on the second-order turbulence...  相似文献   

Vaporization in comets; Outbursts from comet Schwassmann-Wachmann 1     

John J. Cowan  Michael F. A&#x;Hearn 《Icarus》1982,50(1):53-62

We propose that the outbursts frequently observed from Comet P/Schwassmann-Wachmann 1 do not require storage of energy as suggested by many authors. We present revised estimates to show that the total mass and kinetic energy in a typical outburst are lower than previously estimated and we show that this mass is comparable to the mass of gas vaporized as inferred from recent observations of CO⁺ in this comet. We propose simple equilibrium vaporization of CO₂ or CO which is suddenly exposed on a nucleus which is otherwise composed primarily of H₂O. Calculations of the variation of vaporization with rotational phase under these conditions indicate that quantitatively the mechanism can produce outbursts of the size observed.  相似文献   

Sedimentary nutrient dynamics in a tropical estuarine mangrove ecosystem     

M. Bala Krishna Prasad  A.L. Ramanathan 《Estuarine, Coastal and Shelf Science》2008

Mangrove sediments play a pivotal role in the nutrient biogeochemical processes by behaving as both source and sink for nutrients and other materials. Surface and core sediments were collected from various locations of the Pichavaram mangrove (India) and analyzed for grain size distribution, nutrients and stable N isotope (δ¹⁵N) signatures in order to understand the spatial and vertical distribution of nutrients and biogeochemical processes of the C, N, P and S in this ecosystem. Sand is the dominant fraction followed by silt and clay. Spatial distribution of nutrients is controlled by the external and internal loadings, whereas vertical distribution is largely driven by the in situ microbial activities. Interior mangrove sediments contain higher concentrations of organic carbon (OC) than the estuarine sediments reflecting high rates of organic matter retention. Finer fractions of sediment hold ∼60% OC due to high surface area. At some sampling points, moderately high δ¹⁵N signatures were observed and this may be because of agricultural runoff and aquaculture effluents.  相似文献   

A study of the predictability of sea surface temperature over the tropics     

Mingyue Chen  Arun Kumar  Wanqiu Wang 《Climate Dynamics》2015,44(7-8):1767-1776

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Preface to CFSv2 topical collection     

Jin Huang  Annarita Mariotti  Jim Kinter  Arun Kumar 《Climate Dynamics》2014,43(7-8):2309-2309

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Measured and remotely sensed estimates of primary production in the Atlantic Ocean from 1998 to 2005     

《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(15):918-930

Primary production (PP) was determined using ¹⁴C uptake at 117 stations in the Atlantic Ocean to validate three PP satellite algorithms of varying complexity. An empirical satellite algorithm based on log chlorophyll-a had the highest bias and root-mean square error compared with measured ¹⁴C PP and tended to under-estimate PP. The vertical generalised production model improved PP estimates and was the most accurate algorithm in the Eastern Tropical Atlantic (ETRA) and Western Tropical Atlantic (WTRA), but tended to over-estimate PP in eutrophic provinces. A photosynthesis-light wavelength-resolved model was the most accurate over the Atlantic basin, having the lowest mean log-difference error, root-mean square error and bias, and exhibited a superior performance in six out of the nine ecological provinces surveyed. Using this algorithm and mean monthly SeaWiFS fields, a PP time series was generated for the Atlantic Ocean from 1998 to 2005 which was compared with Advanced Very High Resolution Radiometer (AVHRR) sea-surface temperature (SST) data. There was a significant negative correlation between SST and PP in the North Atlantic Subtropical Gyre Province (NAST), North Atlantic Tropical Gyre (NATR), and WTRA suggesting that recent warming trends in these provinces are coupled with a decrease in phytoplankton production.  相似文献   

Estimation of net primary productivity using a process-based model in Gansu Province, Northwest China     

Peijuan Wang  Donghui Xie  Yuyu Zhou  Youhao E  Qijiang Zhu 《Environmental Earth Sciences》2014,71(2):647-658

The ecological structure in the arid and semi-arid region of Northwest China with forest, grassland, agriculture, Gobi, and desert, is complex, vulnerable, and unstable. It is a challenging and sustaining job to keep the ecological structure and improve its ecological function. Net primary productivity (NPP) modeling can help to improve the understanding of the ecosystem, and therefore, improve ecological efficiency. The boreal ecosystem productivity simulator (BEPS) model provides the possibility of NPP modeling in terrestrial ecosystem, but it has some limitations for application in arid and semi-arid regions. In this paper, we improve the BEPS model, in terms of its water cycle by adding the processes of infiltration and surface runoff, to be applicable in arid and semi-arid regions. We model the NPP of forest, grass, and crop in Gansu Province as an experimental area in Northwest China in 2003 using the improved BEPS model, parameterized with moderate resolution remote sensing imageries and meteorological data. The modeled NPP using improved BEPS agrees better with the ground measurements in Qilian Mountain than that with original BEPS, with a higher R ² of 0.746 and lower root mean square error (RMSE) of 46.53 gC m^?2 compared to R ² of 0.662 and RMSE of 60.19 gC m^?2 from original BEPS. The modeled NPP of three vegetation types using improved BEPS shows evident differences compared to that using original BEPS, with the highest difference ratio of 9.21 % in forest and the lowest value of 4.29 % in crop. The difference ratios between different vegetation types lie on the dependence on natural water sources. The modeled NPP in five geographic zones using improved BEPS is higher than those with original BEPS, with higher difference ratio in dry zones and lower value in wet zones.  相似文献