The response of the South Asian Summer Monsoon circulation to intensified irrigation in global climate model simulations

Agricultural intensification in South Asia has resulted in the expansion and intensification of surface irrigation over the twentieth century. The resulting changes to the surface energy balance could affect the temperature contrasts between the South Asian land surface and the equatorial Indian Ocean, potentially altering the South Asian Summer Monsoon (SASM) circulation. Prior studies have noted apparent declines in the monsoon intensity over the twentieth century and have focused on how altered surface energy balances impact the SASM rainfall distribution. Here, we use the coupled Goddard Institute for Space Studies ModelE-R general circulation model to investigate the impact of intensifying irrigation on the large-scale SASM circulation over the twentieth century, including how the effect of irrigation compares to the impact of increasing greenhouse gas (GHG) forcing. We force our simulations with time-varying, historical estimates of irrigation, both alone and with twentieth century GHGs and other forcings. In the irrigation only experiment, irrigation rates correlate strongly with lower and upper level temperature contrasts between the Indian sub-continent and the Indian Ocean (Pearson’s r = ?0.66 and r = ?0.46, respectively), important quantities that control the strength of the SASM circulation. When GHG forcing is included, these correlations strengthen: r = ?0.72 and r = ?0.47 for lower and upper level temperature contrasts, respectively. Under irrigated conditions, the mean SASM intensity in the model decreases only slightly and insignificantly. However, in the simulation with irrigation and GHG forcing, inter-annual variability of the SASM circulation decreases by ~40 %, consistent with trends in the reanalysis products. This suggests that the inclusion of irrigation may be necessary to accurately simulate the historical trends and variability of the SASM system over the last 50 years. These findings suggest that intensifying irrigation, in concert with increased GHG forcing, is capable of reducing the variability of the simulated SASM circulation and altering the regional moisture transport by limiting the surface warming and reducing land–sea temperature gradients.     

Simulation of the annual and diurnal cycles of rainfall over South Africa by a regional climate model

The capability of a current state-of-the-art regional climate model for simulating the diurnal and annual cycles of rainfall over a complex subtropical region is documented here. Hourly rainfall is simulated over Southern Africa for 1998–2006 by the non-hydrostatic model weather research and forecasting (WRF), and compared to a network of 103 stations covering South Africa. We used five simulations, four of which consist of different parameterizations for atmospheric convection at a 0.5 × 0.5° resolution, performed to test the physic-dependency of the results. The fifth experiment uses explicit convection over tropical South Africa at a 1/30° resolution. WRF simulates realistic mean rainfall fields, albeit wet biases over tropical Africa. The model mean biases are strongly modulated by the convective scheme used for the simulations. The annual cycle of rainfall is well simulated over South Africa, mostly influenced by tropical summer rainfall except in the Western Cape region experiencing winter rainfall. The diurnal cycle shows a timing bias, with atmospheric convection occurring too early in the afternoon, and causing too abundant rainfall. This result, particularly true in summer over the northeastern part of the country, is weakly physic-dependent. Cloud-resolving simulations do not clearly reduce the diurnal cycle biases. In the end, the rainfall overestimations appear to be mostly imputable to the afternoon hours of the austral summer rainy season, i.e., the periods during which convective activity is intense over the region.     

Enhancing the relevance of Shared Socioeconomic Pathways for climate change impacts,adaptation and vulnerability research

This paper discusses the role and relevance of the shared socioeconomic pathways (SSPs) and the new scenarios that combine SSPs with representative concentration pathways (RCPs) for climate change impacts, adaptation, and vulnerability (IAV) research. It first provides an overview of uses of social–environmental scenarios in IAV studies and identifies the main shortcomings of earlier such scenarios. Second, the paper elaborates on two aspects of the SSPs and new scenarios that would improve their usefulness for IAV studies compared to earlier scenario sets: (i) enhancing their applicability while retaining coherence across spatial scales, and (ii) adding indicators of importance for projecting vulnerability. The paper therefore presents an agenda for future research, recommending that SSPs incorporate not only the standard variables of population and gross domestic product, but also indicators such as income distribution, spatial population, human health and governance.     

Calcium,Na, K and Mg Concentrations in Seawater by Inductively Coupled Plasma‐Atomic Emission Spectrometry: Applications to IAPSO Seawater Reference Material,Hydrothermal Fluids and Synthetic Seawater Solutions

We report a measurement procedure to determine simultaneously the major cation concentrations (Na, Ca, K and Mg) of seawater‐derived solutions by inductively coupled plasma‐atomic emission spectrometry. The best results were obtained when the IAPSO (‘standard’) seawater reference material was diluted by thirty times with Milli‐Q^® water. We obtained an average reference value r_K (the ratio of the mass fraction of potassium to that of chlorine, i.e., (g kg^?1)/(g kg^?1)) for IAPSO seawater of 0.0205 ± 0.0006 (2.9% RSD), not significantly different from 0.0206 ± 0.0005 (2.4% RSD) for seawater composition reported in the literature. The measured Na, Ca and Mg concentrations correspond to r_Na, r_Ca and r_Mg values of 0.5406 ± 0.0026 (0.5% RSD), 0.02192 ± 0.00048 (2.2% RSD) and 0.06830 ± 0.00047 (0.7% RSD), respectively, in line with previous values measured by wet‐chemistry and atomic absorption spectrophotometry or wet‐chemical titration. Our measurement procedure was used successfully on synthetic seawater solutions and high‐temperature hydrothermal fluids.     

Overstepping the garnet isograd: a comparison of QuiG barometry and thermodynamic modeling

The consequences of overstepping the garnet isograd reaction have been investigated by comparing the composition of garnet formed at overstepped P–T conditions (the overstep or “OS” model) with the P–T conditions that would be inferred by assuming garnet nucleated in equilibrium with the matrix assemblage at the isograd (the equilibrium or “EQ” model). The garnet nucleus composition formed at overstepped conditions is calculated as the composition that produces the maximum decrease in Gibbs free energy from the equilibrated, garnet-absent, matrix assemblage for the bulk composition under study. Isopleths were then calculated for this garnet nucleus composition assuming equilibrium with the matrix assemblage (the EQ model). Comparison of the actual P–T conditions of nucleation (the OS model) with those inferred from the EQ model reveals considerable discrepancy between the two. In general, the inferred garnet nucleation P–T conditions (the EQ model) are at a lower temperature and higher or lower pressure (depending on the coexisting calcic phase(s)) than the actual (OS model) nucleation conditions. Moreover, the degree of discrepancy increases with the degree of overstepping. Independent estimates of the pressure of nucleation of garnet were made using the Raman shift of quartz inclusions in garnet (quartz-in-garnet or QuiG barometry). To test the validity of this method, an experimental synthesis of garnet containing quartz inclusions was made at 800 °C, 20 kbar, and the measured Raman shift reproduced the synthesis conditions to within 120 bars. Raman band shifts from three natural samples were then used to calculate an isochore along which garnet was presumed to have nucleated. Model calculations were made at several temperatures along this isochore (the OS model), and these P–T conditions were compared to those computed assuming equilibrium nucleation (the EQ model) to estimate the degree of overstepping displayed by these samples. A sample from the garnet isograd in eastern Vermont is consistent with overstepping of around 10 degrees and 0.6 kbar (affinities of around 2 kJ/mole garnet). A sample from the staurolite–kyanite zone in the same terrane requires overstepping of around 50 °C and 2–5 kbar (affinities of around 10–18 kJ/mole garnet). A similar amount of overstepping was inferred for a blueschist sample from Sifnos, Greece. These results indicate that overstepping of garnet nucleation reactions may be common and pronounced in regionally metamorphosed terranes, and that the P–T conditions and paths inferred from garnet zoning studies may be egregiously in error.     

Thermal and rheological controls on the formation of mafic enclaves or banded pumice

Magma mixing can occur in a fluid manner to produce banded pumice or in a brittle manner to form enclaves. We propose that the critical control on mixing style is a competition between developing networks of crystals in the intruding magma that impart a strength to the magma and melting and disrupting those networks in the host. X-ray computed tomography analysis demonstrates that banded pumice from the 1915 Mt. Lassen eruption lacks crystal networks. In contrast, rhyodacite hosts with mafic enclaves from Chaos Crags contain well-developed networks of large crystals. We present a one-dimensional conductive cooling model that predicts mixing style, either ductile or brittle, as a function of magma compositions, temperatures, and the size of the intruding dike. Our model relies on three assumptions: (1) Mixing is initiated by the injection of a hot dike into a cooler magma body with a yield strength; (2) when magma crystallinity exceeds a critical value, 13 vol% plagioclase, the magma develops a yield strength; and (3) when total crystallinity exceeds 40 vol%, the magma has a penetrative crystal network and is effectively solid. Importantly, because the two magmas are of different compositions, their crystallinities and viscosities do not have the same variations with temperature. As the intruding magma cools, it crystallizes from the outside in, while simultaneously, host magma temperature near the intruder rises. Mixing of the two magmas begins when the host magma is heated sufficiently to (1) disrupt the crystal network and (2) initiate convection. If the shear stress exerted by the convecting host magma on the dike is greater than the yield strength of the dike margin (and dike crystallinity does not exceed 40 %), then fluid mixing occurs, otherwise enclaves form by brittle deformation of the dike. Application of the model to magma compositions representative of Lassen and Chaos Crags shows that emplacement of dikes <1 m thick should produce enclaves, whereas thicker dikes should generate fluid mixing and form banded pumice within days to weeks of emplacement. Similar relationships apply to other modeled magmatic systems, including Pinatubo, Unzen, and Ksudach/Shtuybel’ volcanoes. For all studied systems, the absolute size of the intruding dike, not just its proportion relative to the host, influences mixing style.     

Guiding ecological principles for marine spatial planning

The declining health of marine ecosystems around the world is evidence that current piecemeal governance is inadequate to successfully support healthy coastal and ocean ecosystems and sustain human uses of the ocean. One proposed solution to this problem is ecosystem-based marine spatial planning (MSP), which is a process that informs the spatial distribution of activities in the ocean so that existing and emerging uses can be maintained, use conflicts reduced, and ecosystem health and services protected and sustained for future generations. Because a key goal of ecosystem-based MSP is to maintain the delivery of ecosystem services that humans want and need, it must be based on ecological principles that articulate the scientifically recognized attributes of healthy, functioning ecosystems. These principles should be incorporated into a decision-making framework with clearly defined targets for these ecological attributes. This paper identifies ecological principles for MSP based on a synthesis of previously suggested and/or operationalized principles, along with recommendations generated by a group of twenty ecologists and marine scientists with diverse backgrounds and perspectives on MSP. The proposed four main ecological principles to guide MSP—maintaining or restoring: native species diversity, habitat diversity and heterogeneity, key species, and connectivity—and two additional guidelines, the need to account for context and uncertainty, must be explicitly taken into account in the planning process. When applied in concert with social, economic, and governance principles, these ecological principles can inform the designation and siting of ocean uses and the management of activities in the ocean to maintain or restore healthy ecosystems, allow delivery of marine ecosystem services, and ensure sustainable economic and social benefits.     

Orbit Determination of Binary Asteroids

In addition to the detection of an asteroid moon or a binary asteroid, the knowledge of the satellite’s true orbit is of high importance to derive fundamental physical parameters of the binary system such as its mass and to shed light on its possible formation history and dynamical evolution (prograde/retrograde orbit, large/small eccentricity or inclination, etc.). A new methodology for preliminary orbit determination of binary asteroids – and visual binaries in general – is proposed. It is based on Thiele–Innes method combined with a ‘trial and error’ Monte-Carlo technique. This method provides the full set of solutions (bundle of orbits, with the 7 orbital elements) even for a reduced number of observations. The mass is a direct by-product of this orbit determination, from which one can next infer the bulk-density and porosity. In addition to the bundle of orbits, the method provides the marginal probability densities of the foreseen parameters. Such error analysis – since it avoids linear approximation – can be of importance for the prediction of the satellite’s position in the plane-of-sky during future stellar occultations or subsequent observations, but also for the analysis of the orbit’s secular evolution. After briefly describing the method, we present the algorithm and its application to some practical cases, with particular emphasis on asteroids binaries and applications on orbital evolution.     

Evaluation of policy options for the live reef food fish trade in the province of Palawan,Western Philippines

The live reef food fish (LRFF) trade has an estimated annual retail value of US$1 billion in the Asia-Pacific region and at least US$30 million in the Philippines. Palawan Province is the trade's center accounting for as much as 55% of the commodity's total export. Concern about the LRFF trade has caused the Palawan Provincial government to take action to regulate the trade. Four key policy options to address the short-term policy objective of developing a sustainable LRFF industry through the reduction of threats associated with destructive fishing and overfishing were proposed. These four policy options and associated analyses were presented to stakeholders at three separate policy consultations. The stakeholders reached a consensus that a regulated LRFF trade was the most sensible option. As a result, the Provincial Government of Palawan took action to enact “The Palawan Live Reef Fish Ordinance of 2006”, which provides for the sustainable and integrated regulation of the LRFF industry. This provincial ordinance will assist in crafting a national policy for the LRFF trade and may also be useful in revising the 1998 Philippine Fisheries Code. The key challenge is how to translate the ordinance provisions into effective on-the-ground actions.