Primary production in the eastern tropical Pacific: A review

The eastern tropical Pacific includes 28 million km² of ocean between 23.5°N and S and Central/South America and 140°W, and contains the eastern and equatorial branches of the north and South Pacific subtropical gyres plus two equatorial and two coastal countercurrents. Spatial patterns of primary production are in general determined by supply of macronutrients (nitrate, phosphate) from below the thermocline. Where the thermocline is shallow and intersects the lighted euphotic zone, biological production is enhanced. In the eastern tropical Pacific thermocline depth is controlled by three interrelated processes: a basin-scale east/west thermocline tilt, a basin-scale thermocline shoaling at the gyre margins, and local wind-driven upwelling. These processes regulate supply of nutrient-rich subsurface waters to the euphotic zone, and on their basis we have divided the eastern tropical Pacific into seven main regions. Primary production and its physical and chemical controls are described for each.Enhanced rates of macronutrient supply maintains levels of primary production in the eastern tropical Pacific above those of the oligotrophic subtropical gyres to the north and south. On the other hand lack of the micronutrient iron limits phytoplankton growth (and nitrogen fixation) over large portions of the open-ocean eastern tropical Pacific, depressing rates of primary production and resulting in the so-called high nitrate-low chlorophyll condition. Very high rates of primary production can occur in those coastal areas where both macronutrients and iron are supplied in abundance to surface waters. In these eutrophic coastal areas large phytoplankton cells dominate; conversely, in the open-ocean small cells are dominant. In a ‘shadow zone’ between the subtropical gyres with limited subsurface ventilation, enough production sinks and decays to produce anoxic and denitrified waters which spread beneath very large parts of the eastern tropical Pacific.Seasonal cycles are weak over much of the open-ocean eastern tropical Pacific, although several eutrophic coastal areas do exhibit substantial seasonality. The ENSO fluctuation, however, is an exceedingly important source of interannual variability in this region. El Niño in general results in a depressed thermocline and thus reduced rates of macronutrient supply and primary production. The multi-decadal PDO is likely also an important source of variability, with the ‘El Viejo’ phase of the PDO resulting in warmer and lower nutrient and productivity conditions similar to El Niño.On average the eastern tropical Pacific is moderately productive and, relative to Pacific and global means, its productivity and area are roughly equivalent. For example, it occupies about 18% of the Pacific Ocean by area and accounts for 22–23% of its productivity. Similarly, it occupies about 9% of the global ocean and accounts for 10% of its productivity. While representative, these average values obscure very substantial spatial and temporal variability that characterizes the dynamics of this tropical ocean.     

Spatial Patterns in Nutrient and In Vivo Fluorescence Distributions in the Marginal Ice Zone and the Seasonally Open Oceanic Zone in the Indian Sector of the Antarctic Ocean, in Austral Summer

Surface temperature, salinity, concentrations of silicate (Si) and nitrate + nitrite (N), and in vivo fluorescence (Fluor) were investigated in the marginal ice zone (MIZ) and the seasonally open oceanic zone (SOOZ) (32–40°E, 64–69°S) from February 23 to 28 1992. In the MIZ the mean Si and N were 67.8 ± 2.2 M and 32.5 ± 1.7 M, respectively. There was a trend that low N values coincided with high Fluor values. Observation conducted at one point (64°S, 38°E) revealed a diel variation pattern in Fluor. Applying this pattern of deviation from noon value, all Fluor data were normalized to value at local noon. In the MIZ a significant negative correlation was observed between the normalized Fluor and N but not Si. On the other hand, Si decreased continuously from south to north in the SOOZ and was negatively correlated with the normalized Fluor. Difference in Si concentration was about 30 M between the sea around 64°S and the MIZ, while the difference in N concentration was estimated as less than 10 M. If diatoms take up silicate and nitrogen at an approximate ratio of 1:1, additional nitrogenous nutrients other than nitrate and nitrite (e.g. ammonia, urea etc.) would be required. In this case, an f-ratio of lower than 33% is obtained. It is suggested that in the MIZ abundance of phytoplankton community dominated by non-diatom increases utilizing nitrate while in the SOOZ abundance of phytoplankton community dominated by diatoms increases consuming Si and regenerated nitrogen.     

The Mobile Street Food Service Practice in the Urban Economy of Kumba, Cameroon

The mobile food service practice is one of multiple survival strategies adopted by poor urban households in Cameroon to maintain and expand the base of subsistence incomes, especially in the current surge of economic crisis. Though a fast-growing informal sector enterprise, it is still at an artisanal stage in urban Cameroon, creating an urgent need for a supportive policy environment that could have measurable positive impacts on improving the productivity, welfare and income levels of the micro-entrepreneurs. This study looks at the mobile food service practice in Kumba, Cameroon, in terms of its basic characteristics, the locational factors influencing its socio-spatial distribution, the critical success factors (CSFs) determining customer choices, and its impacts on the local environmental resources and quality of urban life. The mobile food service practice creates employment, generates income, and acts as a food energy-support instrument to the urban poor and local economic activities operating in Kumba. The vendors, who are mostly women, can make incomes that are 405 per cent of the national minimum wage and, thus, contribute financially towards the education, health and survival of their families. The paper provides some recommendations on ways to improve the efficiency of this sector so as to achieve sustainable economic and social development and to enhance empowerment thereof.     

Chasing a 'loose and baggy monster': almshouses and the geography of charity

This paper goes some way towards redressing the lack of geographical literature on charity through exploring the geography of the British domestic charitable sector. The size and geography of the third sector is outlined, followed by an analysis of how almshouses can be understood as inherently geographical and deeply embedded in local social networks of inclusion as well as exclusion.     

青藏公路铁路沿线生态系统特征及道路修建对其影响

根据2001—08和2002—08月野外调查数据及2001年1：100万中国植被图、1996年1：400万青藏高原植被区划图和2000年青藏铁路沿线自然保护区分布及功能区界调整图，以青藏公路铁路沿线植被生态系统为研究对象，运用ARCVIEW和ARC／INFO软件研究青藏公路铁路建设对沿线生态系统结构的影响，结论如下：①青藏公路铁路南北跨越9个纬度，东西跨越12个经度，共穿越青东祁连山地草原地带、柴达木山地荒漠地带、青南高寒草甸草原地带、羌塘高寒草原地带、果洛那曲高寒灌丛草甸地带和藏南山地灌丛草原地带6个自然区，对植被类型的统计结果显示了地带性。②青藏公路铁路的建设对生态系统产生直接的切割，使景观更加破碎。③青藏公路铁路的建设直接破坏沿线植被生态系统(主要为50m缓冲区内)，年损失总净初级生产量为30504．62t，损失总生物量432919．25～1436104．3t／a。损失总净初级生产量占1km缓冲区年净初级生产量535005．07～535740．11t／a的百分比为5．70％，占10km缓冲区年净初级生产量3408950．45～3810480．92t／a的0．80～0．89％；损失生物量占1km缓冲区生物总量7502971．85～25488342．71t／a的5．70％，占10km缓冲区总生物量43615065．35～164150665．37t／a的0．80％～0．89％。     

主键约束在数字化前兆数据服务软件中的关键运用

数字化前兆数据库是一个分布式网络数据库SQLServer,数据库的建成运用为预报人员的日常数据分析提供了一个准确的、完整的资源平台。为考虑数据库设计完整性规则 ,本文着重讲述建立两套前兆数据库的过程中 ,主键约束在数字化前兆数据服务软件EPDS的建库及入库中起的重要作用。     

Determination of Lithium, Beryllium and Boron at Trace Levels by Laser Ablation-Inductively Coupled Plasma-Sector Field Mass Spectrometry

The analytical capabilities of laser ablation (LA)-ICP-MS in determining Li, Be and B at trace levels in geological samples have been tested on a series of glass reference materials and natural samples. The LA-ICP-MS instrument used consisted of a sector-field ICP-MS coupled with a laser ablation microprobe operating at either 266 or 213 nm wavelength. Reference glasses from NIST (SRM 612, 614 and 616) and MPI-DING (KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, T1-G and ATHO-G) were selected to develop the analytical method and to assess the best instrumental configuration. A series of calcic amphiboles with different Li, Be and B concentrations were also analysed using both LA-ICP-MS and SIMS to test the applicability of the method to natural minerals. Results indicated that with a spot size of 40 μm the agreement between measured and reference values of Li, Be and B is generally better than 10% for NIST SRM 612 and 20% for NIST SRM 614. Average reproducibility at the 2s level was 10% for Li, 20% for Be and 15% for B. Limits of detection were approximately 100 ng g^-1 for Be and B and 200 ng g^-1 for Li. These results were confirmed by analyses carried out on natural amphiboles and compared well in terms of precision and accuracy with those commonly achieved by SIMS.     

长江中下游地区暖区暴雨特征分析

利用2007到2013年5-9月间常规和非常规资料以及6 h一次的NCEP 1°×1°再分析资料,将长江中下游地区暖区暴雨按天气形势划分为冷锋前暖区暴雨、暖切变暖区暴雨以及副热带高压边缘暖区暴雨三种类型。统计表明暖区暴雨一般发生在距离切变线(锋线)100~300 km的暖区内。主要结论包括:(1)冷锋型降水强度偏弱且分布均匀,集中在5、6月;暖切变型发生次数最多且强度大,主要发生在6、7月长江中下游地区的偏南部;副热带高压边缘型发生次数最少但强度较大,发生在7、8月。暖区暴雨的发生次数及强度在大别山、皖南山区较为集中。(2)暖区暴雨中短时强降水贡献大。(3)冷锋背景下的暖区暴雨一般产生在锋前低压槽中,暴雨落区与高低空急流耦合有紧密联系;暖切变型以低层暖切变线为主要天气背景,地面常有弱静止锋,暖区对流活动与中尺度急流结构、地形强迫等因素存在较高的相关性;副热带高压边缘暖区暴雨与局地的水汽积累和对流不稳定条件的发展有密切关系。据此建立三类暖区暴雨的概念模型。     

Neotectonics of the Kharaulakh sector of the Laptev Shelf

Seismotectonic deformation and crustal stress pattern have been studied comprehensively in major seismogenic structures of the Kharaulakh sector of the Verkhoyansk fold system and adjacent parts of the Chersky seismotectonic zone. The study focuses on neotectonic structures, deep structure, and systems of active faults, as well as tectonic stress fields inferred by tectonophysical analysis of Late Cenozoic faults and folds. The results, along with geological and geophysical data, reveal main strain directions and structural patterns of crustal stress and strain in the Arctic segment of the Eurasia-North America plate boundary. The area is a junction of mid-ocean and continental structures evolving in a mixed setting of extension, compression, and their various combinations. The rotation pole of the two plates is presumably located near Buor-Khaya Bay. In this case, extension is expected to act currently upon the neotectonic structures north of the bay and compression to control those in the south and southeast. This inference is consistent with the identified zoning of stress and strain in the Kharaulakh sector.     

Reducing wind power curtailment in China: comparing the roles of coal power flexibility and improved dispatch

Renewable energy curtailment is a critical issue in China, impeding the country’s transition to clean energy and its ability to meet its climate goals. This paper analyzes the impacts of more flexible coal-fired power generation and improved power dispatch towards reducing wind power curtailment. A unit commitment model for power dispatch is used to conduct the analysis, with different scenarios demonstrating the relative impacts of more flexible coal-fired generation and improved power dispatch. Overall, while we find both options are effective in reducing wind power curtailment, we find that improved power dispatch is more effective: (1) the effect of ramping down coal-fired generators to reduce wind power curtailment lessens as the minimum output of coal-fired generation is decreased; and (2) as a result, at higher wind capacity levels, wind curtailment is much more significantly reduced with improved power dispatch than with decreased minimum output of coal-fired generation.

Key policy insights

• China should emphasize both coal power flexibility and dispatch in its policies to minimize renewable power curtailment and promote clean energy transition.

• China should accelerate the process of implementing spot market and marginal cost-based economic dispatch, while making incremental improvements to the existing equal share dispatch in places not ready for spot market.

• A key step in improving of dispatch is incorporating renewable power forecasts into the unit commitment process and updating the daily unit commitment based on the latest forecast result.

• China should expand the coal power flexibility retrofit programme and promote the further development of the ancillary service market to encourage more flexibility from coal-fired generation.