On the features of the SST annual cycle and surface heat budget in the South China Sea

The annual cycle in the ocean and atmosPhere system 15 the important signal of the climatic variabilities.Observed studies had indicated that the seasonal feature of the climatic system which 15 of an annual period 15 due to the seasonal variation of the solar radiation.Funher researches has shown that the formation and maintenance of the annual cycle of the thermal condition(situation)in the upper oceans are the results of both dynamical and thermal processes which both are involved in air-sea interaction.Since researches on the large-scale air-sea interaction were Propoed,sea surface temperature(SST)has always been the primary object to observe,study and predict by the scientists.     

Analysis on the annual variation characteristics of heat exchange on the atmosphere-sea interface over the tropical Pacific

The tropical ocean is the area where the interaction process between atmosphere and sea is most active.To analyze the sensible and latent heat flux (abridged as SHF and LHF hereafter) over the tropical ocean and their spatial and temporal variation as well as the relationship between them and other factors are all essential in understanding the thermo-dynamic interaction mecha nism between atmosphere and sea.These are also useful in the further study on the unusual oceanic and atmospheric circulation and on the climate modelling.By using EOF method,we have discussed the LFH and SFH over the tropical Pacific and the causality factors of the heat flux,the main purpose is to initialize some new approaches with climatic significance.     

Evolutions of flow field and heat exchange on equatorial Pacific surface in El Nino-La Nina cycle

Abstract-In this paper, the monthly averages and deviations of temperature, pressure, tonal wind, specific humidity, cloud rover and the components of heat budget have been remputed on the equatorial (5°S-3°N) Pacific surface (EPS) based on the 2^*×2^* grid data of CORDS from 1950 to 1987 and the evolutions of tt0ese elements have been provided. Two feedback mechanisms of El Nino-La Nina cycle which include the dynamic, thermal and hydrological processes in the coupled air-sea system are verified. During El Nino, the pressure gradient and trade wind decreased on the EPS, the sensible and latent heat exchanges enlarged on the central-eastern EPS, the water vapor and cloud cover rose in the atmo sphere, the net longwave radiation and incident solar radiation decreased and the net gain (loss) of the heat reduced (increased) on the central and eastern EPS:During La Nina the circumstances were opposite     

Sensitivity of amplitude-phase characteristics of the surface air temperature annual cycle to variations in annual mean temperature

The ERA40 and NCEP/NCAR data over 1958–1998 were used to estimate the sensitivity of amplitude-phase characteristics (APCs) of the annual cycle (AC) of the surface air temperature (SAT) T _s. The results were compared with outputs of the ECHAM4/OPYC3, HadCM3, and INM RAS general circulation models and the IAP RAS climate model of intermediate complexity, which were run with variations in greenhouse gases and sulfate aerosol specified over 1860–2100. The analysis was performed in terms of the linear regression coefficients b of SAT AC APCs on the local annual mean temperature and in terms of the sensitivity characteristic D = br ², which takes into account not only the linear regression coefficient but also its statistical significance (via the correlation coefficient r). The reanalysis data were used to reveal the features of the tendencies of change in the SAT AC APCs in various regions, including areas near the snow-ice boundary, storm-track ocean regions, large desert areas, and the tropical Pacific. These results agree with earlier observations. The model computations are in fairly good agreement with the reanalysis data in regions of statistically significant variations in SAT AC APCs. The differences between individual models and the reanalysis data can be explained, in particular, in terms of the features of the sea-ice schemes used in the models. Over the land in the middle and high latitudes of the Northern Hemisphere, the absolute values of D for the fall phase time and the interval of exceeding exhibit a positive intermodel correlation with the absolute value of D for the annual-harmonic amplitude. Over the ocean, the models reproducing larger (in modulus) sensitivity parameters of the SAT annual-harmonic amplitude are generally characterized by larger (in modulus) negative sensitivity values of the semiannual-harmonic amplitude T _{s, 2}, especially at latitudes characteristic of the sea-ice boundary. In contrast to the averaged fields of AC APCs and their interannual standard deviations, the sensitivity parameters of the SAT AC APCs on a regional scale vary noticeably for various types of anthropogenic forcing.     

Wind sensitivity of the inter-ocean heat exchange

An idealised two-basin model is used to investigate the impact of the wind field on the heat exchange between the ocean basins. The scalar potential of the divergent component of the horizontal heat flux is computed, which gives a 'coarse-grained' image of the surface heat flux that captures the large-scale structure of the horizontal heat transport. Further the non-divergent component is examined, as well as the meridional heat transport and the temperature–latitude overturning stream function. A sensitivity analysis examines the heat transport response to changes in wind stress at different latitudes. The results are compared with results from an eddy-permitting global circulation model. The westerly wind stress over the Southern Ocean has two effects: a local reduction of the surface heat loss in response to the equatorward surface Ekman drift, and a global re-routing of the heat export from the Indo-Pacific. Without wind forcing, the Indo-Pacific heat export is released to the atmosphere in the Southern Ocean, and the net heat transport in the southern Atlantic is southward. With wind forcing, the Indo-Pacific export enters the Atlantic through the Aghulas and is released in the Northern Hemisphere. The easterlies enhance the poleward heat transport in both basins.     

The annual silica cycle of the North Pacific subtropical gyre

Silica cycling in the upper 175 m of the North Pacific Subtropical Gyre was examined over a two year period (January 2008-December 2009) at the Hawaii Ocean Time-series (HOT) station ALOHA. Silicic acid concentrations in surface waters ranged from 0.6 to 1.6 ??M, exhibiting no clear seasonal trends. Biogenic silica concentrations and silica production rates increased by an order of magnitude each summer following stratification of the upper 50 m reaching values of 157 nmol Si L⁻¹ and 81 nmol Si L⁻¹ d⁻¹, in 2008 and 2009, respectively. Sea surface height anomalies together with analyses of variability in isothermal surfaces at 150-175 m indicated that the summer periods of elevated biogenic silica were associated with anticyclonic mesoscale features during both years. Lithogenic silica concentrations increased in the spring during the known period of maximum atmospheric dust concentrations with maximum values of 36 nmol Si L⁻¹ in the upper 10 m. Dust deposition would enhance levels of dissolved iron in surface waters, but there was no response of diatom biomass or silica production to increases in near-surface ocean lithogenic silica concentrations suggesting iron sufficiency of diatom silica production rates.Low ambient silicic acid concentrations restricted silica production rates to an average of 43% of maximum potential rates. Si sufficiency only occurred during the summer period when diatom biomass was elevated suggesting that bloom diatoms are adapted to exploit low silicic acid concentrations. Annual silica production at HOT is estimated to be 63 mmol Si m⁻² a⁻¹ with summer blooms contributing 29% of the annual total. Diatoms are estimated to account for 3-7% of total phytoplankton primary productivity, but 9-20% of organic carbon export confirming past suggestions that diatoms are relatively minor contributors to primary productivity and autotrophic biomass, but important contributors to new and export production in oligotrophic open-ocean ecosystems.Annual silica production at HOT is nearly 4-fold lower than estimates at the Bermuda Atlantic Time-series Study (BATS) site in the Sargasso Sea from the 1990s, but annual silica export at the base of the euphotic zone is similar between the two gyres indicating very different balances between silica production and its loss in surface waters. On a relative basis, BATS is a more productive system with respect to silica, where biogenic silica is recycled with high efficiency in surface waters; in contrast the NPSG is a lower productivity system with respect to silica, but where lower recycling efficiency leads to a much higher fraction of new silica production. The two gyres show contrasting long-term trends in diatom biomass as biogenic silica concentrations at HOT have been increasing since 1997, but they have been decreasing at BATS suggesting very different forcing of decadal trends in the contribution of diatoms in carbon cycling between these gyres. Combining the data from both gyres indicates that globally subtropical gyres produce 13 Tmol Si a⁻¹, which is only 51% of previous estimates reducing the contribution of subtropical gyres to 5-7% of global annual marine silica production.     

Photosynthate allocation in a temperate sea over an annual cycle: the relationship between protein synthesis and phytoplankton physiological state

The seasonal and vertical variations in the patterns of photosynthate allocation into biomolecules by natural phytoplankton assemblages were determined, together with their species composition, in a coastal station of the central Cantabrian Sea (southern Bay of Biscay). Chlorophyll-a concentration ranged from values below 20 mg m⁻² in winter to values above 80 mg m⁻² during spring and during an upwelling event in summer. Low primary production rates (<300 mgC m⁻² d^-1) were measured during winter and during summer stratification periods. The rate of C fixation during summer upwelling conditions exceeded 3500 mgC m⁻² d⁻¹. In terms of photosynthate partitioning, proteins were the dominant fraction, as they typically accounted for >30% of total photo-assimilated C, with polysaccharides and low molecular weight metabolites showing incorporation percentages around 10–30%. Relative C incorporation into lipids was generally <15%. Recurrent patterns of vertical variability in photosynthate partitioning were observed: the relative synthesis of proteins increased toward the bottom of the euphotic zone, whereas the relative C incorporation into polysaccharides and lipids tended to be higher near the surface. When primary production decreased, the synthesis of proteins was maintained more than that of other molecules. Throughout the year, the relative synthesis of proteins was inversely correlated with phytoplankton biomass, production and growth rate. The conservation of protein synthesis under growth-limiting conditions and the enhancement of lipid and polysaccharide synthesis when irradiance is high seem to constitute general patterns of photosynthate partitioning in marine phytoplankton. In our study, these patterns represented metabolic strategies of phytoplankton in response to changing environmental factors, rather than the effect of variations in the species composition of the community.     

东南极中山站陆缘固定冰2011/2012年度的时空变化

Annual observations of first-year ice(FYI) and second-year ice(SYI) near Zhongshan Station, East Antarctica,were conducted for the first time from December 2011 to December 2012. Melt ponds appeared from early December 2011. Landfast ice partly broke in late January, 2012 after a strong cyclone. Open water was refrozen to form new ice cover in mid-February, and then FYI and SYI co-existed in March with a growth rate of 0.8 cm/d for FYI and a melting rate of 2.7 cm/d for SYI. This difference was due to the oceanic heat flux and the thickness of ice,with weaker heat flux through thicker ice. From May onward, FYI and SYI showed a similar growth by 0.5 cm/d.Their maximum thickness reached 160.5 cm and 167.0 cm, respectively, in late October. Drillings showed variations of FYI thickness to be generally less than 1.0 cm, but variations were up to 33.0 cm for SYI in March,suggesting that the SYI bottom was particularly uneven. Snow distribution was strongly affected by wind and surface roughness, leading to large thickness differences in the different sites. Snow and ice thickness in Nella Fjord had a similar "east thicker, west thinner" spatial distribution. Easterly prevailing wind and local topography led to this snow pattern. Superimposed ice induced by snow cover melting in summer thickened multi-year ice,causing it to be thicker than the snow-free SYI. The estimated monthly oceanic heat flux was ～30.0 W/m2 in March–May, reducing to ～10.0 W/m2 during July–October, and increasing to ～15.0 W/m2 in November. The seasonal change and mean value of 15.6 W/m2 was similar to the findings of previous research. The results can be used to further our understanding of landfast ice for climate change study and Chinese Antarctic Expedition services.     

南昆嵩地区断裂?构造演化特征及其控制因素

南昆嵩地区是万安盆地西部负向构造单元,其中部N–S向断裂贯穿南北,独特的构造特征使其成为研究万安盆地西部构造演化与区域断裂走滑活动的窗口。将研究区沉积地层划分为3套构造层,通过回剥法绘制南昆嵩地区构造–沉积充填剖面,并计算南昆嵩地区构造沉降量以及构造沉降速率,论述南昆嵩地区构造演化史与沉降过程以及控制因素。研究结果表明:下部构造层和中部构造层中断裂组合样式主要为卷心型断层、“Y”型断层、阶梯状断层和高角度花状构造等,断裂延伸方向大致可分为:N–S向、W–E向和NE–SW向3种;上部构造层断裂不发育,为稳定沉积;在区域走滑断裂以及南海扩张运动的控制下,南昆嵩地区始新世以来构造演化经历4个阶段:初始裂谷期、伸展断拗期、走滑改造期和热沉降期,新生代地层构造性质也表现为以伸展与走滑作用为主–走滑断裂控制–热沉降的三段式转变。     

安达曼海的热收支分析及其水交换研究

The characteristics of the T/S structures, water mass exchange and deep circulation in the Andaman Sea are investigated based on the simulation from a high-resolution general circulation model(MITgcm). The results show that, below 1 000 m, the water mass is saltier, warmer and more homogeneous in the Andaman Sea than that in the Bay of Bengal, attributing to the strong vertical mixing at the depth of ～1 800 m. The water mass exchange between the Andaman Sea and the Bay of Bengal goes through three major channels, which manifests itself as follows: the northern channel(Preparis Channel) is the main passage of water mass transport from the Bay of Bengal to the Andaman Sea, whereas the Middle Channel(the south of Andaman Islands and the north of Nicobar Islands) has an opposite transport; the southern channel(Great Channel) features with a four-layer water exchange which results in the least net transport among the three channels; all the transports through the three channels have an intra-annual variation with a period of half a year. At 1 000-m depth, the entire Andaman Sea is occupied by a cyclonic circulation in January and July while by an anticyclonic one in April and October. The semiannual cycle found in both the deep circulation and water mass exchange is likely associated with the downwelling eastward-propagating Kelvin waves induced by the semiannual westerly component in the equatorial Indian Ocean during intermonsoon seasons.     

Local phase relationship between sea surface temperature and net heat flux over weekly to annual periods in the extratropical North Pacific

The relationship between sea surface temperature (SST) and net heat flux (NHF) in the North Pacific over weekly to annual period bands was investigated using gridded datasets of SST obtained by the Advanced Microwave Scanning Radiometer for the Earth Observing System, and flux data produced by the Modern-era Retrospective-analysis for Research and Applications Reanalysis. This study focused on the phase difference between the SST and NHF, which can suggest the driving force between two co-varying parameters. The SST delay behind the NHF, with phase differences from π/4 to π/2, which suggests that the SST change would be controlled by the NHF, was commonly found over all periods. In the intra-annual (100- to 200-day periods) band, part of the coherent variations showed negative phase differences (around ?π to ?π/3), which were found in the western North Pacific and along ～30°N in the central North Pacific. The spatial scales of SST variability in the shorter band (weekly to intraseasonal: less than 100-day periods) are dominantly over 200?km. In contrast, the scales in the intra-annual band were in the range 50–150?km, where the negative phase differences were frequently found.     

Nematode community dynamics over an annual production cycle in the central North Sea

Nematode species composition, trophic structure and body size distributions were followed over an annual production cycle in the central North Sea; to test responses to temporally changing food quality and quantity in the sediment. Changes in the phytoplankton concentration in the water column were quantitatively reflected in the concentration of chlorophyll a and breakdown products in the sediment, with higher concentrations in spring and autumn following blooms, and lower concentrations in summer and winter. The taxonomic and trophic structure of nematode communities differed significantly among stations over relatively short distances, potentially masking some of the temporal dynamics. Spatio-temporal differences in nematode species composition were linked to changes in the quality and quantity of organic material reaching the seabed, reflecting a species-specific response to the nutritional quality of sedimenting organic material and the biochemical changes in the sediment associated with its decomposition. The size distributions of selected nematode species indicated that most species bred continuously throughout the sampling period, although one species, the epigrowth feeder Spilophorella paradoxa, had periods of increased growth following the deposition of the spring phytoplankton bloom. There was no consistent temporal relationship between the trophic composition of nematode communities and spring chlorophyll a or carbon sedimentation, most likely a result of the trophic plasticity of most feeding types and the capacity of the community to use both freshly sedimented material as well as the subsequent breakdown products and refractory organic matter. Community metrics implied that there were small responses to the seasonal production cycle, but these belied strong responses of a few species with life histories that allowed them to track the availability of suitable food resources.     

Nematode community dynamics over an annual production cycle in the central North Sea

Nematode species composition, trophic structure and body size distributions were followed over an annual production cycle in the central North Sea; to test responses to temporally changing food quality and quantity in the sediment. Changes in the phytoplankton concentration in the water column were quantitatively reflected in the concentration of chlorophyll a and breakdown products in the sediment, with higher concentrations in spring and autumn following blooms, and lower concentrations in summer and winter. The taxonomic and trophic structure of nematode communities differed significantly among stations over relatively short distances, potentially masking some of the temporal dynamics. Spatio-temporal differences in nematode species composition were linked to changes in the quality and quantity of organic material reaching the seabed, reflecting a species-specific response to the nutritional quality of sedimenting organic material and the biochemical changes in the sediment associated with its decomposition. The size distributions of selected nematode species indicated that most species bred continuously throughout the sampling period, although one species, the epigrowth feeder Spilophorella paradoxa, had periods of increased growth following the deposition of the spring phytoplankton bloom. There was no consistent temporal relationship between the trophic composition of nematode communities and spring chlorophyll a or carbon sedimentation, most likely a result of the trophic plasticity of most feeding types and the capacity of the community to use both freshly sedimented material as well as the subsequent breakdown products and refractory organic matter. Community metrics implied that there were small responses to the seasonal production cycle, but these belied strong responses of a few species with life histories that allowed them to track the availability of suitable food resources.     

冬季大风影响下的渤黄海水交换特征

利用 ROMS海洋数值模式对 2006年冬季渤黄海的海洋动力环境进行模拟,基于温度、盐度模拟结果,使用谱混合 模型进行水团分析,定义了渤海海峡地区的水交换区。并进一步讨论了冬季大风事件对水交换区的影响,给出了冬季大风影 响下的渤黄海水交换特征。研究得出,冬季的黄海水团以“舌”形分布于渤海海峡地区,水交换区则表现为沿" 舌" 形边缘 呈带状分布,具有西北--东南的走向趋势,并且在“舌”尖处的水交换面积最大。通过缩小研究范围,发现位于黄海最北部 的沿岸海域并不参与渤黄海之间的水体交换。最后研究发现,冬季大风事件对渤海水交换具有促进作用,具体表现为：大风 过程使黄海暖流对渤海的入侵更加深入,水交换区向渤海方向伸展,南部的水交换带变宽,河流径流进入渤海后与渤海水的 混合区加大,并发生北移。     

南海表层水温年循环的数值模拟

本文采用一个非线性约化重力海洋模式对南海表层水温(SST)年循环过程进行了数值研究,探讨了南海表层水温年循环形成和维持的动力学和热力学机制·模拟结果表现出与观测分析相一致的年循环变化阶段性和空间结构,并发现南海SST年循环的阶段性是海面动力强迫和热力强迫共同作用的结果;南海上层海洋的热力平衡有着明显的季节特征.     

Amplification mechanism for the amplitude of the annual cycle of continental-scale tropospheric temperature anomalies

Physical mechanisms for the annual evolution of special continental-scale seasonal anomalies in the tropospheric temperature and the general atmospheric circulation are described. The relationship between large negative tropospheric temperature anomalies over the continents in winter and positive temperature anomalies in the subsequent summer is explained. It is shown that large winter negative anomalies over the continents can possibly stabilize the climatic annual cycle. A general process that can trigger the mechanism regulating the annual cycle by means of continental-scale tropospheric temperature anomalies is the equalizing of the temperature anomalies over the continents and the oceans. In turn, the latter phenomenon can happen when the low-frequency variability of intensifying planetary waves generates extreme events on a hemispheric scale.     

Modeling of vertical heat and moisture transfer and carbon exchange in the soil-vegetation-atmosphere system

A physical and mathematical model of the vertical heat and moisture transfer and the carbon exchange in the soil-vegetation-atmosphere system is proposed that includes the interaction between these processes. The model describes the interception of precipitation by plants and its further evaporation, transpiration, evaporation from a soil surface as well as vertical moisture transfer, photosynthesis, and plant and soil respiration. The model has been verified against data from observations of heat, moisture, and carbon dioxide fluxes at a grassland site (international FIFE experiment, Kansas, United States), in a pine forest (BOREAS, Saskatoon, Canada), and in a broad-leaved mixed forest (FLUXNET measurements in the southeastern United States). Numerical experiments with the models have been conducted to estimate the influence of soil moisture and atmospheric CO₂ concentration on transpiration and carbon exchange of the vegetation cover.