摄食水平对褐牙鲆幼鱼能量收支的影响

褐牙鲆幼鱼 (体重 0 .71～ 4 .16 g;体长 4 .4 5～ 8.14cm)在 2 4℃下保持 5个摄食水平 (0～最大 )。投喂人工配合饵料。褐牙鲆能量和干物质的吸收效率随摄食水平的增加而增加 ,平均为97.38%和 76 .73%。褐牙鲆排粪能 (F )占摄食能的比例为 0 .95 %～ 2 .83% ,随摄食水平的增加而减少 ;氮排泄 (U)占摄食能比例为 5 .5 2 %～ 6 .77% ,各摄食水平下变化不大 ;标准代谢耗能 (Rs)占摄食能比例为 1.0 5 %～ 7.82 % ,随摄食水平的增加而减少 ;在各摄食水平条件下 ,摄食代谢耗能(Rf)占摄食能比例变化不大 ,平均为 4 5 .72 % ;生长能 (G)占摄食能比例为 32 .6 7%～ 4 9.2 1%。随摄食水平增加而增加。在最大摄食水平时 ,褐牙鲆能量分配形式为 :10 0 C =0 .95 F + 5 .5 2 U +4 4.31R+ 4 9.2 1G     

Matching carbon pools and fluxes for the Southern Ocean Iron Release Experiment (SOIREE)

The Lagrangian Southern Ocean Iron Release Experiment (SOIREE) allowed study of a gradually evolving iron-mediated phytoplankton bloom in water labelled with the inert tracer sulfur hexafluoride, SF₆. This article describes a pelagic carbon budget for the mixed layer in SOIREE and assesses the extent to which closure of the budget is achieved. Net community production (NCP) converted 837 mmol m⁻² of inorganic carbon to organic carbon in 12.0 d after the first iron addition. A large fraction (41%) of NCP remained as particulate organic carbon in the mixed layer of the iron-enriched patch, while 23% was lost by horizontal dispersion and 0–29% was exported. The closure of the carbon budget is hampered by the lack of measurements of dissolved organic carbon (DOC), by a major uncertainty in carbon export, and by use of empirical conversion factors in estimates of carbon biomass and metabolic rates. Lagrangian carbon-budget studies may be improved by direct measurement of all major carbon parameters and conversion factors. Carbon cycling in the SOIREE bloom resembled that in ‘natural’ algal blooms in the open Southern Ocean in some respects, but not in all. Daily NCP in the SOIREE bloom (70 mmol m⁻² d⁻¹) was higher than in natural blooms, partly because other studies did not account for horizontal dispersion, were for longer periods or included less productive areas. The build-up of POC stock and carbon export as a fraction of NCP in SOIREE were in the lower range of observations elsewhere.     

On the radiation and diffraction of water waves by a rectangular structure with a sidewall

A radiation and diffraction boundary value problem is investigated. It arises from the interaction of linear water waves with a freely floating rectangular structure in a semi-infinite fluid domain of finite water depth with the leeward boundary being a vertical wall. Analytical expressions for the radiated potentials and the diffracted potential are obtained by use of the method of separation of variables and the eigenfunction expansion method. The added masses and damping coefficients for the structure heaving, swaying and rolling in calm water are obtained by use of the corresponding radiated potentials and the wave excitation forces are calculated by use of the diffracted potential. To verify the correctness of the method, a boundary element method is used. A comparison of the analytical results with those obtained by the boundary element method is made and good agreement is achieved, which shows that the analytical expressions for the radiated and diffracted potentials are correct. By use of the present analytical solution, the added mass, damping coefficients, wave excitation force, together with the hydrodynamic effects of the draft, width of the structure and the clearance between the structure and the sidewall are also investigated.     

几种虾、贝、藻混养模式能量收支及转化效率的研究

实验采用围隔实验方法,对凡纳滨对虾(Litopenaeus vannamei)、青蛤(Cyclina sinesis)、菊花心江蓠(Gracilarialichevoides)和活菌净水剂的不同单、混养生态系统的能量收支和转化效率进行了研究。实验结果表明,实验期间系统接受的总太阳光辐射能为1 983.2 MJ/m2。浮游植物对光能的利用效率在各处理间无差异(0.147±0.007)%,混养江蓠显著地提高了总利用效率(0.308±0.019)%。总能量的转化效率,虾藻混养(28.36%)和江蓠单养(27.65%)最高,其次是虾贝藻混养(26.70%),对虾单养(12.24%)最低。单位净产量对饲料能的消耗,对虾单养(21.24 MJ/kg)最多,虾菌、虾贝混养(18.76~18.97 MJ/kg)次之,而虾藻、虾贝藻混养(2.64~3.24 MJ/kg)则显著地降低了饲料消耗量。实验中投喂组都有较多的能量沉积,对虾单养沉积量达到1.10 MJ/m2,虾贝混养(1.30 MJ/m2)稍高,而虾贝藻、虾菌、虾藻混养平均为0.53 MJ/m2,显著地低于对照。结果表明,混养青蛤和菊花心江蓠显著地提高了对虾养殖中的光能利用率和能量转化效率,减少了能量沉积,从而大大地提高了能量的利用效率。     

海浪破碎对海洋上混合层中湍能量收支的影响

海浪破碎产生一向下输入的湍动能通量,在近海表处形成一湍流生成明显增加的次层,加强了海洋上混合层中的湍流垂向混合。为了研究海浪破碎对混合层中湍能量收支的影响,文中分析了海浪破碎对海洋上混合层中湍流生成的影响机制,采用垂向一维湍封闭混合模式,通过改变湍动能方程的上边界条件,引入了海浪破碎产生的湍动能通量,并分别对不同风速下海浪破碎的影响进行了数值研究,分析了混合层中湍能量收支的变化。当考虑海浪破碎影响时,近海表次层中的垂直扩散项和耗散项都有显著的增加,该次层中被耗散的湍动能占整个混合层中耗散的总的湍能量的92.0%,比无海浪破碎影响的结果增加了近1倍;由于平均流场切变减小,混合层中的湍流剪切生成减小了3.5%,形成一种存在于湍动能的耗散和垂直扩散之间的局部平衡关系。在该次层以下,局部平衡关系与壁层定律的结论一致,即湍动能的剪切生成与耗散相平衡。研究结果表明,海浪破碎在海表产生的湍动能通量影响了海洋上混合层中的各项湍能量收支间的局部平衡关系。     

Impact of Mid- and Upper-Level Dry Air on Tropical Cyclone Genesis and Intensification: A Modeling Study of Durian (2001)

The impact of mid- and upper-level dry air, represented by low relative humidity (RH) values, on the genesis of tropical cyclone (TC) Durian (2001) in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model. The mid-level RH was lowered in different regions relative to TC Durian (2001)'s genesis location. Results suggest that the location of dry air was important to Durian (2001)'s genesis and intensification. The rapid development of the TC was accompanied by sustained near-saturated mid- and upper-level air, whereas low humidity decelerated its development. Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms, and consumed by the condensation process. The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process. With a dryer mid- and upper-level environment, convective and stratiform precipitation were both inhibited. The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed. Generally, convection played the dominant role, since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker. The vorticity budget showed that the negative vorticity convergence term, which was closely related to the inhibited convection, caused the vorticity to decrease above the lower troposphere in a dryer environment. The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs.     

A note on India’s water budget and evapotranspiration

Some recent analyses of India’s water budget are based on information attributed to the Ministry of Water Resources. An examination of the budget components indicates that they imply an evapotranspiration estimate that is significantly lower than what one may expect based on information from other sources. If such is the case, India’s water resources situation may be more dire than is otherwise perceived. For, higher evapotranspiration implies correspondingly reduced availability of water for human use. It should be worthwhile to investigate and reconcile the apparent discrepancy between water budget and evapotranspiration, considering the importance of water in the national context.     

青藏高原OLR场的季节变化特征

该文利用1979～1991年卫星观测的OLR逐候资料，分析青藏高原OLR场的季节变化特征。结果表明:青藏高原OLR场具有显著的季节变化特点，在冬、夏两季高原OLR场表现为“缓变”态，在春、秋两过渡季节表现为“急变”态。同时发现，在春季高原西南部出现持续强的OLR候际正变化区，表明高原加热场在春季的持续加强。各年高原OLR场的季节变化有很大差异，在高原夏季来得早且季节过渡快的年份，相应印度地区的季风雨偏多；在高原夏季来得晚或正常时，印度地区的季风雨偏少或正常。     

Methane emission from rice paddies

Methane release rates from rice paddies have been measured in Andalusia, Spain, during almost a complete vegetation period in 1982 using the static box system. The release rates ranged between 2 and 14 mg/m²/h and exhibited a strong seasonal variation with low values during the tillering stage and shortly before harvest, while maximum values were observed at the end of the flowering stage. The CH₄ release rate, averaged over the complete vegetation period, accounted for 4 mg/m²/h which results in a worldwide CH₄ emission from rice paddies of 35–59×10¹² g/yr if we assume that the observed CH₄ release rates are representative of global conditions. The CH₄ release rates showed diurnal variations with higher values late in the afternoon which were most likely caused by temperature variations within the upper layers of the paddy soils. Approximately 95% of the CH₄ emitted into the atmosphere by rice paddies was due to transport through the rice plants. Transport by bubbles or diffusion through the paddy water was of minor importance. Incubation experiments showed that CH₄ was neither produced nor consumed in the paddy water. The relase of CH₄ from rice paddies caused a diurnal variation of CH₄ in ambient air within the rice-growing area with maximum values of up to 2.3 ppmv during the early morning, compared to average daytime values of 1.75 ppmv.     

Seasonal variation of the salinity in the Zuari estuary,Goa, India

The annual salt budget of the Zuari is examined. The characteristics of the estuary differ markedly from the low run off season during November–May to the heavy run off period of the southwest monsoon from June to October. During November–May the estuary is vertically mixed and the two processes controlling the transport of salt are run off induced advective transport out of the estuary, and tidally induced diffusive transport into the estuary. The magnitude of the latter is about 20% larger, leading to a salinity rise in the estuary. The diffusion coefficient has been estimated to be 233 ± 101 m²/sec. With the onset of the southwest monsoon, the run off increases dramatically, and the estuary loses about 75% of its salt during the first two months of the season. About 2/3 of this loss is recovered in the next two months when the run off decreases. Because the estuary is partially stratified during June–October, gravitational circulation is expected to play a role in addition to tidal diffusion and run off. The magnitude of its contribution has, however, not yet been determined.