Development of regional future climate change scenarios in South America using the Eta CPTEC/HadCM3 climate change projections: climatology and regional analyses for the Amazon, S?o Francisco and the Paraná River basins

The objective of this study is to assess the climate projections over South America using the Eta-CPTEC regional model driven by four members of an ensemble of the Met Office Hadley Centre Global Coupled climate model HadCM3. The global model ensemble was run over the twenty-first century according to the SRES A1B emissions scenario, but with each member having a different climate sensitivity. The four members selected to drive the Eta-CPTEC model span the sensitivity range in the global model ensemble. The Eta-CPTEC model nested in these lateral boundary conditions was configured with a 40-km grid size and was run over 1961–1990 to represent baseline climate, and 2011–2100 to simulate possible future changes. Results presented here focus on austral summer and winter climate of 2011–2040, 2041–2070 and 2071–2100 periods, for South America and for three major river basins in Brazil. Projections of changes in upper and low-level circulation and the mean sea level pressure (SLP) fields simulate a pattern of weakening of the tropical circulation and strengthening of the subtropical circulation, marked by intensification at the surface of the Chaco Low and the subtropical highs. Strong warming (4–6°C) of continental South America increases the temperature gradient between continental South America and the South Atlantic. This leads to stronger SLP gradients between continent and oceans, and to changes in moisture transport and rainfall. Large rainfall reductions are simulated in Amazonia and Northeast Brazil (reaching up to 40%), and rainfall increases around the northern coast of Peru and Ecuador and in southeastern South America, reaching up to 30% in northern Argentina. All changes are more intense after 2040. The Precipitation–Evaporation (P–E) difference in the A1B downscaled scenario suggest water deficits and river runoff reductions in the eastern Amazon and S?o Francisco Basin, making these regions susceptible to drier conditions and droughts in the future.     

The influence of light on nitrogen cycling and the primary nitrite maximum in a seasonally stratified sea

In the seasonally stratified Gulf of Aqaba Red Sea, both release by phytoplankton and oxidation by nitrifying microbes contributed to the formation of a primary nitrite maximum (PNM) over different seasons and depths in the water column. In the winter and during the days immediately following spring stratification, formation was strongly correlated (R² = 0.99) with decreasing irradiance and chlorophyll, suggesting that incomplete reduction by light limited phytoplankton was a major source of . However, as stratification progressed, continued to be generated below the euphotic depth by microbial oxidation, likely due to differential photoinhibition of and oxidizing populations. Natural abundance stable nitrogen isotope analyses revealed a decoupling of the δ¹⁵N and δ¹⁸O in the combined and pool, suggesting that assimilation and nitrification were co-occurring in surface waters. As stratification progressed, the δ¹⁵N of particulate N below the euphotic depth increased from −5‰ to up to +20‰.N uptake rates were also influenced by light; based on ¹⁵N tracer experiments, assimilation of , , and urea was more rapid in the light (434 ± 24, 94 ± 17, and 1194 ± 48 nmol N L⁻¹ day⁻¹ respectively) than in the dark (58 ± 14, 29 ± 14, and 476 ± 31 nmol N L⁻¹ day⁻¹ respectively). Dark assimilation was 314 ± 31 nmol N L⁻¹ day⁻¹, while light assimilation was much faster, resulting in complete consumption of the ¹⁵N spike in less than 7 h from spike addition. The overall rate of coupled urea mineralization and oxidation (14.1 ± 7.6 nmol N L⁻¹ day⁻¹) was similar to that of oxidation alone (16.4 ± 8.1 nmol N L⁻¹ day⁻¹), suggesting that mineralization of labile dissolved organic N compounds like urea was not a rate limiting step for nitrification. Our results suggest that assimilation and nitrification compete for and that N transformation rates throughout the water column are influenced by light over diel and seasonal cycles, allowing phytoplankton and nitrifying microbes to contribute jointly to PNM formation. We identify important factors that influence the N cycle throughout the year, including light intensity, substrate availability, and microbial community structure. These processes could be relevant to other regions worldwide where seasonal variability in mixing depth and stratification influence the contributions of phytoplankton and non-photosynthetic microbes to the N cycle.     

Ambient and cold‐temperature infrared spectra and XRD patterns of ammoniated phyllosilicates and carbonaceous chondrite meteorites relevant to Ceres and other solar system bodies

Mg‐phyllosilicate‐bearing, dark surface materials on the dwarf planet Ceres have NH₄‐bearing materials, indicated by a distinctive 3.06 μm absorption feature. To constrain the identity of the Ceres NH₄‐carrier phase(s), we ammoniated ground particulates of candidate materials to compare their spectral properties to infrared data acquired by Dawn's Visible and Infrared (VIR) imaging spectrometer. We treated Mg‐, Fe‐, and Al‐smectite clay minerals; Mg‐serpentines; Mg‐chlorite; and a suite of carbonaceous meteorites with NH₄‐acetate to exchange ammonium. Serpentines and chlorites showed no evidence for ammoniation, as expected due to their lack of exchangeable interlayer sites. Most smectites showed evidence for ammoniation by incorporation of NH₄⁺ into their interlayers, resulting in the appearance of absorptions from 3.02 to 3.08 μm. Meteorite samples tested had weak absorptions between 3.0 and 3.1 μm but showed little clear evidence for enhancement upon ammoniation, likely due to the high proportion of serpentine and other minerals relative to expandable smectite phases or to NH₄⁺ complexing with organics or other constituents. The wavelength position of the smectite NH₄ absorption showed no variation between IR spectra acquired under dry‐air purge at 25 °C and under vacuum at 25 °C to ?180 °C. Collectively, data from the smectite samples show that the precise center wavelength of the characteristic ~3.05 μm v₃ absorption in NH₄ is variable and is likely related to the degree of hydrogen bonding of NH₄‐H₂O complexes. Comparison with Dawn VIR spectra indicates that the hypothesis of Mg‐saponite as the ammonium carrier phase is the simplest explanation for observed data, and that Ceres dark materials may be like Cold Bokkeveld or Tagish Lake but with proportionally more Mg‐smectite.     

A computer-controlled geochemical analysis system for use with existing Perkin Elmer double-beam atomic absorption spectrophotometers

A system is described for the automated analysis of trace and major elements in geochemical samples. The signal at the photomultiplier tube of a Perkin Elmer model 303 double-beam atomic absorption spectrophotometer is decoded and digitized in a locally designed interface unit and input to a Texas Instruments model 960A minicomputer. This controls an automatic sampler and provides a computer compatible tape and printout of analytical data in concentration units for up to 200 samples in a run.     

CUBES: cassegrain U-band Brazil-ESO spectrograph

CUBES is a high-efficiency, medium-resolution (R～20,000) ground based UV (300–400 nm) spectrograph, to be installed in the cassegrain focus of one of ESO’s VLT unit telescopes in 2017/18. The CUBES project is a joint venture between ESO and IAG/USP, and LNA/MCTI. CUBES will provide access to a wealth of new and relevant information for stellar as well as extragalactic sources. Main science cases include the study of beryllium and heavy elements in metal-poor stars, the direct determination of carbon, nitrogen and oxygen abundances by study of molecular bands in the UV range, as well as the study of active galactic nuclei and the quasar absorption lines. With a streamlined modern instrument design, high efficiency dispersing elements and UV-sensitive detectors, it will give a significant gain in sensitivity over existing ground based medium-high resolution spectrographs, enabling vastly increased sample sizes accessible to the astronomical community. We present here a brief overview of the project including the status, science cases and a discussion of the design options.     

Using on‐nadir spectral reflectance to detect soil surface changes induced by simulated rainfall and wind tunnel abrasion

The surface susceptibility to erosion (erodibility) is an important component of soil erosion models. Many studies of wind erosion have shown that even relatively small changes in surface conditions can have a considerable effect on the temporal and spatial variability of dust emissions. One of the main difficulties in measuring erodibility is that it is controlled by a number of highly variable soil factors. Collection of these data is often limited in scale because in situ measurements are labour‐intensive and very time‐consuming. To improve wind erosion model predictions over several spatial and temporal scales simultaneously, there is a requirement for a non‐invasive approach that can be used to rapidly assess changes in the compositional and structural nature of a soil surface in time and space. Spectral reflectance of the soil surface appears to meet these desirable requirements and it is controlled by properties that affect the soil erodibility. Three soil surfaces were modified using rainfall simulation and wind tunnel abrasion experiments. Observations of those changes were made and recorded using digital images and on‐nadir spectral reflectance. The results showed clear evidence of the information content in the spectral domain that was otherwise difficult to interpret given the complicated interrelationships between soil composition and structure. Changes detected at the soil surface included the presence of a crust produced by rainsplash, the production of loose erodible material covering a rain crust and the selective erosion of the soil surface. The effect of rainsplash and aeolian abrasion was different for each soil tested and crust abrasion was shown to decrease as rainfall intensity increased. The relative contributions of the eroded material from each soil surface to trapped mixtures of material assisted the erodibility assessment. Ordination analyses within each of two important soil types explained significant amounts of the variation in the reflectance of all wavebands by treatments of the soil and hence changes in the soil surface. The results show that soil surface conditions within a soil type are an underestimated source of variation in the characterization of soil surface erodibility and in the remote sensing of soil. Copyright © 2005 John Wiley & Sons, Ltd.