在波罗的海不同的气候条件下模拟的海面温度和热通量

本文使用由不同的全球模拟所产生的区域性耦合海洋-大气模型,通过数值模型试验探讨了波罗的海气候未来可能的物理状况.将一些情景以及近来的一些气候模拟情况作了比较,以估计气候变化.海面温度总体平均明显地增高2.9℃.平均年平均增温的水平模式主要可由冰盖的减少解释.由大气向波罗的海的热输送表现出季节性变化周期秋季热损失减少,春季热吸收增加,夏季热吸收减少.年际间海面温度的变化一般是在增加.这与北部一些中平滑的频率分布有关.全部热收支表示出海面太阳辐射在增加,而太阳辐射增加由热通量其他组成成分的变化所平衡.     

Optimising the environmental benefits of emission reductions from UK coal- and oil-fired power stations: a critical loads approach

This paper describes a method for determining reductions of SO₂ emissions from coal- and oil-fired power stations, oil refineries and large industrial units in the UK taking into account their pollution potential. The method is based on the use of two gridded data sets: critical loads, which represent the sensitivity of the environment to acid deposition and modelled estimates of total (wet + dry) sulphur deposition for 646 point sources within the UK. An iterative method is used to identify and subsequently reduce emissions from point sources that contribute most to areas of critical loads exceedance. This paper demonstrates how the method may be used to determine an optimal allocation of emissions across the UK which yields the maximum amount of environmental protection per unit of emission.The paper then goes on to consider the changes that will have to take place within the UK power generation industry in order to meet the revised EC Large Combustion Plant Directive which comes into force on 1 January 2008. Particular emphasis is placed upon proposed emissions trading schemes and the environmental implications of allowing trading between stations with high and low pollution potentials. The paper concludes by suggesting that the emissions trading process should take into account the pollution potential of each source, irrespective of whether the proposed emission is within the plant's agreed emission limit. An approach based entirely on minimizing environmental damage rather than one which takes cost into account, as in current integrated assessment modelling, could provide an interesting approach across the rest of Europe.     

模拟消落带水华暴发行为的数值沙堆模型

以长江最大支流汉江近年来水华污染的现场资料为例,通过氮磷浓度、水温、流速和光照等实测数据构建了消落带开放水域环境体系的数值沙堆模型,描述了藻类生长及水华暴发的动力学机制;利用数值沙堆系统崩塌行为反映出的频率-尺度幂律关系作为判断消落带水域是否暴发水华以及规模大小的依据,采用有限尺度标度分析从不同侧面验证了水华暴发系统的自组织临界性,并揭示出各种拟合参数与水华暴发规模之间的定量关系.研究表明,沙堆模型如果存在良好的幂律关系,相应的消落带水域将暴发水华,且幂律指数越大,水华污染程度越严重.     

Sustainable resource management coupled to resilient germplasm to provide new intensive cereal–grain–legume–livestock systems in the dry savanna

Sustainable resource management is the critical agricultural research and development challenge in sub-Saharan Africa. The accumulated knowledge on soil management gathered over the last 10 years, combined with solid crop improvement and plant health research at farmers’ level, has brought us to a stage where we can now address with confidence the intensification of cereal–grain–legume-based cropping systems in the dry savanna of West Africa in a sustainable and environmentally positive manner.Two sustainable farming systems that greatly enhance the productivity and sustainability of integrated livestock systems have been developed and implemented in the dry savanna of Nigeria. These are: (i) maize (Zea mays L.)–promiscuous soybean [Glycine max (L.) Merr.] rotations that combine high nitrogen fixation and the ability to kill large numbers of Striga hermonthica seeds in the soil; and (ii) miflet [Eleusine coracana (L.) Gaerth] and dual-purpose cowpea [Vigna unguiculata (L.) Walp.]. Improvement of the cropping systems in the dry savanna has been driven by the adoption of promiscuously nodulating soybean varieties (in particular TGx 1448-2E) and dual-purpose cowpea. The rate of adoption is very high, even in the absence of an efficient seed distribution system. The number of farmers cultivating the improved varieties increased by 228% during the last 3 years. Increased production of promiscuous soybean has been stimulated by increased demand from industries and home utilization. Production in Nigeria was estimated at 405,000 t in 1999 compared to less than 60,000 t in 1984. Economic analysis of these systems shows already an increase of 50–70% in the gross incomes of adopting farmers compared to those still following the current practices, mainly continuous maize cultivation. Furthermore, increases in legume areas of 10% in Nigeria (about 30,000 ha in the northern Guinea savanna) and increases of 20% in yield have translated into additional fixed nitrogen valued annually at US$ 44 million. This reflects, at the same time, an equivalent increase in land-use productivity, and with further spread of the improved crops, there are excellent prospects for additional economic and environmental benefits from a very large recommendation domain across West Africa.