Accuracy of grid precipitation data for Brazil: application in river discharge modelling of the Tocantins catchment

Here, we compared grid precipitation data — Climate Forecast System Reanalysis (CFSR) and WATCH Forcing Data methodology applied to ERA‐Interim (WFDEI) data — with Brazilian Weather Bureau (INMET) and Brazilian Water Agency (ANA) rain gauge data (n = 2027) for the period 1980–2010 in order to evaluate which grid data set better represents precipitation, and is thus more suitable for hydrological modelling of Brazilian water resources. We found that WFDEI outperformed CFSR according to three statistical indicators. We then applied and interpolated a simple bias correction to further improve WFDEI data before we used these data to model river discharge of the Tocantins catchment with the Soil and Water Assessment Tool (SWAT). Calibration (validation in parentheses; weighted averages of all gauges) had satisfactory statistical metrics: p‐factor = 0.52 (0.47); r‐factor = 0.84 (0.99); R² = 0.78 (0.71); bR² = 0.68 (0.47); NS = 0.70 (0.66); Pbias = ?4.5 (4.0). Finally, the calibrated SWAT model was used to assess the spatial distribution of the catchment's water resources. Annual green water flow (evapotranspiration) increased from the south‐east (640–840 mm yr^?1) to north‐west (1140–1440 mm) of the Tocantins catchment, while green water storage (soil water content) increased from south (330–1070 mm) to north (2180–3290 mm). Blue water (water yield) had a less clear pattern, with lower values in the south and the central borders of the catchment (20–560 mm) and higher values along the central axis and the north (920–1460 mm). Our analysis suggested that WFDEI was an accurate representation of Brazilian precipitation. For large catchments, we therefore recommend the use of WFDEI instead of sparse and often missing rain gauge data in modelling Brazilian water resources. Copyright © 2015 John Wiley & Sons, Ltd.     

Advancing isotope-enabled hydrological modelling for ungauged calibration of data-scarce humid tropical catchments

Realistic projections of the future climate and how this translates to water availability is crucial for sustainable water resource management. However, data availability constrains the capacity to simulate streamflow and corresponding hydrological processes. Developing more robust hydrological models and methods that can circumvent the need for large amounts of hydro-climatic data is crucial to support water-related decisions, particularly in developing countries. In this study, we use natural isotope tracers in addition to hydro-climate data within a newly developed version of the spatially-distributed J2000iso as an isotope-enabled rainfall-runoff model simulating both water and stable isotope (δ²H) fluxes. We pilot the model for the humid tropical San Carlos catchment (2500 km²) in northeastern Costa Rica, which has limited time series, but spatially distributed data. The added benefit of simulating stable isotopes was assessed by comparing different amounts of observation data using three model calibration strategies (i) three streamflow gauges, (ii) three gauges with stream isotopes and (iii) isotopes only. The J2000iso achieved a streamflow Kling–Gupta efficiency (KGE) of 0.55–0.70 across all the models and gauges, but differences in hydrological process simulations emerged when including stable water isotopes in the rainfall-runoff calibration. Hydrological process simulation varied between the standard J2000 rainfall-runoff model with a high simulated surface runoff proportion of 37% as opposed to the isotope version with 84%–89% simulated baseflow or interflow. The model solutions that used only isotope data for calibration exhibited differences in simulated interflow, baseflow and model performance but captured bulk water balances with a reasonable match between the simulated and observed hydrographs. We conclude that J2000iso has shown the potential to support water balance modelling for ungauged catchments using stable isotope, satellite and global reanalysis data sets.     

Carbonyl sulfide emissions from biomass burning in the tropics

Carbonyl sulfide emissions from biomass burning have been studied during field experiments conducted both in an African savanna area (Ivory Coast) and rice fields, central highland pine forest and savanna areas in Viet-Nam. During these experiments CO₂, CO and C₂H₂ or CH₄ have also been also monitored. COS values range from 0.6 ppbv outside the fires to 73 ppbv in the plumes. Significant correlations have been observed between concentrations of COS and CO (R ²=0.92,n=25) and COS and C₂H₂ (R ²=0.79,n=26) indicating a COS production during the smoldering combustion. COS/CO₂ emission factors (COS/CO₂) during field experiments ranged from 1.2 to 61×10^–6 (11.4×10^–6 mean value). COS emission by biomass burning was estimated to be up to 0.05 Tg S/yr in tropics and up to 0.07 Tg S/yr on a global basis, contributing thus about 10% to the global COS flux. Based on the S/C ratio measured in the dry plant biomass and the COS/CO₂ emission factor, COS can account for only about 7% of the sulfur emitted in the atmosphere by biomass burning.     

Creative industries in the tropics: Reflections on creativity and northeastern Australia as place

This paper explores the concept of creativity and place as relevant to Cairns and Townsville in northeastern Australia. These two provincial cities are key to the economic and population growth of northern Australia and as such are the focus of renewed interest from all levels of government. While the creative industries sector in each location is significant, to date there has been no research specifically exploring the views of industry participants in terms of the creative strengths, impediments and opportunities across the region. Interviews with 38 creative industries participants were completed, revealing the significant benefits and challenges associated with being located in a remote tropical environment where the concept of place is strong. The interviews also reveal a number of potential growth strategies for the sector in each location that have the potential to inform policy and urban development approaches not only in the tropical north of Australia but also more broadly across the country. That is, the findings provide further evidence in support of the need for ongoing research into the particular contributions of regional and rural cities to the global creative economy.     

End member and Bayesian mixing models consistently indicate near-surface flowpath dominance in a pristine humid tropical rainforest

The impacts of forest conversion on runoff generation in the tropics have received much interest, but scientific progress is still hampered by challenging fieldwork conditions and limited knowledge about runoff mechanisms. Here, we assessed the runoff generation, flow paths and water source dynamics of a pristine rainforest catchment in Costa Rica using end member mixing analysis (EMMA) and a Bayesian mixing model (MixSIAR). Geochemical tracer data collected over a 4-week field campaign were combined with tritium data used to assess potential deeper groundwater flow pathways to the perennial stream. The streamflow composition was best captured using three end-members, namely throughfall, shallow (5–15 cm) and deeper (15–50 cm) soil water. We estimated the end-member contributions to the main stream and two tributaries using the two mixing approaches and found good agreement between results obtained from EMMA and MixSIAR. The system was overwhelmingly dominated by near-surface sources, with little evidence for deeper and older groundwater as tritium-derived baseflow mean transit time was between 2.0 and 4.4 years. The shallow soil flow pathway dominated streamflow contributions in the main stream (median 39% and 49% based on EMMA and MixSIAR, respectively), followed by the deeper soil (32% and 31%) and throughfall (25% and 19%). The two tributaries had even greater shallow soil water contributions relative to the main stream (83% and 74% for tributary A and 42% and 63% for tributary B). Tributary B had no detectable deep soil water contribution, reflecting the morphology of the hillslope (steeper slopes, shallower soils and lower vegetation density compared to hillslope A). Despite the short sampling campaign and associated uncertainties, this study allowed to thoroughly assess runoff generation mechanisms in a humid tropical catchment. Our results also provide a first comparison of two increasingly used mixing models and suggest that EMMA and MixSIAR yield comparable estimates of water source partitioning in this tropical, volcanic rainforest environment.     

The relative stability of prehistorical geographic environment in China’s tropics on the basis of archaeology

According to archaeological data from about sixty samples the relative stability of physical and human geographical environment in the tropical zone of China is discussed in this paper. Because of the superior natural environment, sufficient food resources and a sparse population resulting in the absence of social requirement to transform the productive forces, the advancement of economy and society was stagnated during prehistorical period in China’s tropics. Compared with northern China, the appearance of ground stone tool stagnated about 3,000 years, the beginning of Bronze Age, about 1,000 years, and the agriculture, 2,500–3,000 years. The no ceramics age continued till the early Neolithic Age and the appearance of colour or white ceramics was 2,000 years later than that in northern China. The life form of migration to gather and to hunt continued till the middle Neolithic Age, and the fixed settlement based on agriculture 1,000–2,000 years stagnated. The clan commune just appeared at the end of the Neolithic Age which was 2, 000–3,000 years later than that in northern China.     

热带MJO对2009年11月我国东部大范围雨雪天气的可能影响

结合对历史资料的分析,研究了2009年11月热带地区一次强的热带大气季节内振荡（MJO）过程与11月我国东部大范围雨雪天气的可能联系,结果表明2009年11月强的MJO过程是我国东部大范围雨雪天气的一个重要的影响因子。MJO对流11月上中旬在印度洋地区异常活跃,尤其是MJO对流中心在第3位相（印度洋中东部）维持了9天（7—16日）,对应了11月两次最强的降水（雪）过程。对MJO历史事件的合成分析显示,当MJO对流位于印度洋时,我国东部大部地区降水概率明显增加,温度偏低,与2009年11月的实况一致。中高纬地区大气环流的异常有可能受到热带MJO对流强迫的影响,这种影响可能通过遥相关的方式来实现。当MJO对流位于印度洋时,有利于欧亚中高纬环流维持两脊一槽的分布,同时西太平洋副热带高压偏强偏西,东亚东部地区维持一条显著的对流活跃带,这些环流异常形势与2009年11月的实况也较一致,体现了MJO对热带外地区环流异常影响的一般特征。热带地区MJO对流的异常通过对流加热强迫,除引起大尺度纬向环流异常外,同样会引起经向环流异常,从而影响热带外地区环流。当MJO对流位于印度洋时,西太平洋地区为异常的下沉运动控制,东亚东部辐合上升,在热带和中纬度地区之间形成一个异常的经向环流圈,经向环流的存在进一步有利于低层低纬度水汽的向北输送,造成东部降水偏多。利用MJO的发展和演变,对于把握类似2009年11月这样的大范围雨雪气候异常很有帮助。      

Patterns of development of lavaka,Madagascar's unusual gullies

Lavaka (Madagascar's abundant gullies) show a complex pattern of development. Fourteen independent measures of size and shape in 93 lavaka were investigated by principal components analysis and discriminant function analysis. Typical lavaka start either as wounds and raw patches on mid-hillside that develop step-like head scarps, or as toe slopes collapsed by seepage, slumping, or undercutting. They become deep, raw, vertical-sided, teardrop- to heart-shaped gashes that may be deepest and broadest uphill. As the walls retreat, slump, and become overgrown, lavaka become longer, broader, gentler, and partly filled concavities. They can grow to reach from the valley floor to the hill crest (or even beyond the crest) before healing over. Unless excessive erosion creates tors and inselbergs, they heal over and end up as unremarkable hillside reentrants and side-valleys.     

中国热带第四纪板块运动的地貌效应

The eastern and western fronts of plate movement in Taiwan Island and Tibetan Plateau respectively are the two major sources of tectonic force for the morphogensis during Quaternary in China′s tropics. Seven examples of geomorphological effects of plate movement are enumerated to discuss the differentiation of tectonic landforms in space and time during Quaternary. The tectonic movement tends to be more active since middle Pleistocene. Some phenomena such as the arc-shape mountain systems, volcanism and crustal deformation imply that the juncture zone of eastern and western tectonic forces is located at about 1 1O°E.     

Organic carbon export in the form of wood during an extreme tropical storm,Upper Rio Chagres,Panama

Widespread, intense rainfall over the Upper Rio Chagres watershed (414 km²) in central Panama during December 2010 triggered numerous landslides that introduced large numbers of trees to the river network. We flew by helicopter along the mainstem Upper Chagres and the adjacent margins of Lake Alhajuela, into which the Upper Chagres flows, in February and June 2011. We used low‐elevation video photography from these flights to tally the number of wood pieces stored along the lake margin and within the channel, and the number of landslides reaching the mainstem. We used these tallies with ground‐verified estimates of average wood piece size and landslide surface area, and assumptions about wood density, carbon content, and aboveground biomass, to develop a first‐order estimate of carbon export in the form of wood from the Upper Chagres following the 2010 storms. Based on the wood tally, we estimate 9 · 6 to 16 Mg C/km² export, and from the landslide tally we estimate 24 Mg C/km². We believe the landslide tally provides a more accurate minimum estimate of carbon export from the Upper Chagres during the December 2010 storms. These values are an order of magnitude higher than limited data for average or background rates of wood‐based carbon export from other catchments, but two orders of magnitude lower than wood‐based carbon export during extreme storms in Taiwan. The findings suggest that duration of flood flow above a threshold for mobilizing wood within the channel network exerts a more important control on wood export from the Upper Chagres than magnitude of flood peak. Copyright © 2013 John Wiley & Sons, Ltd.