Multi-species chemical data assimilation with the Danish Eulerian hemispheric model: system description and verification

Satellite retrievals of atmospheric composition provide a wealth of data on a global scale. These complement results from atmospheric chemistry-transport models (CTMs), and can be combined using data assimilation. We present two assimilation schemes coupled to the Danish Eulerian Hemispheric Model (DEHM), a three-dimensional, off-line CTM with full photochemistry: a variant on the ensemble Kalman filter and the three-dimensional variational scheme. The aim of this paper is to describe the two schemes and present an initial assessment of their impacts on model skill. Retrievals of multiple atmospheric trace gases are assimilated, namely: NO₂ tropospheric column densities, CH₄ total column densities, and partial column concentrations of O₃, CO and CH₄; these data are retrieved from four satellite sensors. Data for each species are assimilated independently of one another, and other species are only adjusted indirectly via the model’s chemistry and dynamics. Assimilation results are compared with measurements from surface monitoring stations and other satellite retrievals, and preliminary validation results are presented.Reference simulations (without assimilation) grossly underestimate surface CO concentrations, and both assimilation schemes eliminate this large and systematic model bias. The assimilation improves the spatial correlation of modelled CO with surface observations, and improves the spatial correlation between forecasts and retrievals for CO, NO₂ and O₃. Results for CH₄ show a loss of skill due to a mismatch in model bias between two assimilated CH₄ data-sets. Finally, we discuss differences in methodology and results between this paper and a recent study on multi-species chemical data assimilation. Joint optimisation of initial conditions and emission rates offers a promising direction for improving modelled boundary-layer concentrations.     

Quantifying the P–T–t conditions of north–south Lhasa terrane accretion: new insight into the pre‐Himalayan architecture of the Tibetan plateau

An integrated field, petrological and geochronological study of the Basong Tso region of south‐eastern Tibet has constrained the timing and P–T conditions of north–south Lhasa terrane accretion and provides new insight into the tectonothermal evolution of the Tibetan plateau. Two distinct high‐grade metamorphic belts are recognized in the region: a southern belt (the Basong Tso complex) that consists of sheared schist and orthogneiss; and a northern belt (the Zhala complex) that comprises paragneiss and granite. Combined pseudosection modelling and U–Pb geochronology of monazite and zircon indicates that the Basong Tso complex records peak metamorphic conditions of 9 ± 0.5 kbar and 690 ± 25 °C at c. 204–201 Ma, whereas the Zhala complex experienced peak metamorphic conditions of 5.0 ± 1.0 kbar and 740 ± 40 °C at c. 198–192 Ma. Microstructural analysis suggests that the two belts share a common early prograde history, after which the Basong Tso complex attained peak conditions following rapid burial, and the Zhala complex approached peak conditions along an isobaric path. Overall it is inferred that the Basong Tso and Zhala complexes represent the lower and upper structural levels of an evolving orogen that underwent Barrovian‐type metamorphism following collision (M1), followed by Buchan‐style overprinting at higher structural levels due to heat advection by syn‐tectonic granites (M2). Mylonitization (sensu lato) of the Basong Tso complex and juxtaposition of the two units occurred after attainment of peak conditions. The dominance of Mesozoic regional metamorphism across most of the Tibetan plateau indicates that Cenozoic crustal thickening processes, where present, are only manifested at depth.     

Navigating the dilemmas of climate policy in Europe: evidence from policy evaluation studies

Climate change is widely recognised as a ‘wicked’ policy problem. Agreeing and implementing governance responses is proving extremely difficult. Policy makers in many jurisdictions now emphasise their ambition to govern using the best available evidence. One obvious source of such evidence is the evaluations of the performance of existing policies. But to what extent do these evaluations provide insights into the difficult dilemmas that governors typically encounter? We address this question by reviewing the content of 262 evaluation studies of European climate policies in the light of six kinds of dilemma found in the governance literature. We are interested in what these studies say about the performance of European climate policies and in their capacity to inform evidence-based policy-making. We find that the evaluations do arrive at common findings: that climate change is framed as a problem of market and/or state failure; that voluntary measures tend to be ineffective; that market-based instruments tend to be regressive; that EU-level policies have driven climate policies in the latecomer EU Member States; and that lack of monitoring and weak enforcement are major obstacles to effective policy implementation. However, we also conclude that the evidence base these studies represent is surprisingly weak for such a high profile area. There is too little systematic climate policy evaluation work in the EU to support systematic evidence-based policy making. This reduces the scope for sound policy making in the short run and is a constraint to policy learning in the longer term.     

Oil-assisted filtration of fine coal

An influence of oil additions (0–3% w/w) on the vacuum filtration of fine coal has been investigated. The results show that an oil addition of 1% can lead to a lowering of filter-cake moisture from 26% (wet basis) to 16% (wet basis). This considerable lowering of filter-cake moisture is accompanied by an increase in both filtration rate and solids pick-up rate. The results are qualitatively interpreted in terms of a flocculation process in which oil droplets condense at the particle contact points to form pendular bridges.     

A comprehensive search for extragalactic 6.7-GHz methanol masers

We have used the Australia Telescope Compact Array (ATCA) to search for 6.7-GHz methanol maser emission towards 87 galaxies. We chose the target sources using several criteria, including far-IR luminosities and the presence of known OH megamasers. In addition, we searched for methanol masers in the nearby starburst galaxy NGC 253, making a full spectral-line synthesis image. No emission was detected in any of the galaxies, with detection limits ranging from 25 to 75 mJy. This is surprising, given the close association of OH and methanol masers in Galactic star formation regions, and significantly constrains models of OH megamaser emission. This absence of maser emission may be a result of low methanol abundances in molecular clouds in starburst galaxies.     

Archean adakites from the Ashuanipi complex,eastern Superior Province,Canada: geochemistry,geochronology and tectonic significance

Contributions to Mineralogy and Petrology - Adakitic geochemical features characterize the Desliens suite of pre-tectonic diorite to tonalite sills intruded into volcanogenic greywackes of the...     

Utility of the Hadley Centre sea ice and sea surface temperature data set (HadISST1) in two widely contrasting coral reef areas

The HadISST1 sea surface temperature data set is examined for two contrasting areas: the Chagos Archipelago, central Indian Ocean which has a small (approximately 3 degrees C) annual temperature fluctuation, and Abu Dhabi in the southern Arabian Gulf whose annual air temperature fluctuation of approximately 24 degrees C is the largest known for coral reef habitats. The HadISST1 data are shown to match air temperature records closely, both in terms of annual moving averages and residual analysis. Temperatures in 1998 caused massive mortality of corals in the Indian Ocean: sea surface temperature (SST) values causing this were 33.8 degrees C in the Arabian Gulf at a time when average daily air temperature was over 40 degrees C, while in Chagos the SST lethal to corals was 29.8-29.9 degrees C, when air temperatures peaked at about 31 degrees C. The HadISST1 record was searched back to 1870 for previous abnormal peaks: one of 29.7 degrees C was found for Chagos SST in 1972, though this did not cause coral mortality. Analysis of 12-month running means of the residuals from the annual cycle show that, between 1870 and 1999, the largest SST deviations occurred between October 1997 and May 1998 in Chagos and between August 1998 and July 1999 near Abu Dhabi. The event of 1998-1999 was the largest in these regions for at least 130 years. SSTs have risen over the last three decades at rates of about 0.22 degrees or 0.23 degrees per decade in both locations.     

The Near Infrared Spectrum of Miranda: Evidence of Crystalline Water Ice

A spectrum from 1.2 to 2.5 μm of Uranus' small satellite Miranda obtained in June 1999 reveals strong water-ice signatures. It confirms the existence of a 2.0-μm water feature previously detected on Miranda and shows a strong second broad 1.5-μm water-ice absorption feature. The spectra also reveal a weak absorption band at 1.65 μm that is indicative of crystalline water ice. Reflectance models which combine the new spectra with new photometry indicate that the spectra are characteristic of a mostly water-ice surface, with a large fraction of carbonaceous or silicate contaminates, and the possible presence of ammonia hydrate, as implied by an apparent weak feature near 2.2 μm. The possible presence of other volatiles is also investigated.     

Late Mesoproterozoic rifting in Arctic Canada during Rodinia assembly: impactogens,trans‐continental far‐field stress and zinc mineralisation

This paper challenges the conventional interpretation of a major, economically important Mesoproterozoic intracratonic rift system as a group of aulacogens, proposing instead that they are rifts that developed in response to far‐field stress caused by continent–continent collision (impactogens) during supercontinent assembly. The tectonostratigraphic evolution of the Bylot basins (Arctic Canada) records dramatic alternations between extensional and compressional stress regimes, precluding an aulacogen interpretation and favouring an impactogen interpretation. New geochronological data (U–Th–Pb whole‐rock depositional age; detrital zircon signatures) provide a record of impactogens that developed in Laurentia's interior as a result of Grenvillian (~1.1 Ga) far‐field stress during assembly of the supercontinent Rodinia. Formation of the world‐class Nanisivik zinc deposit in one of the rifts is temporally associated with the Grenvillian orogeny, and consequently represents both (i) a rare exception to the global pattern of few ore deposits forming during supercontinent episodes, and (ii) a hitherto unrecognised tectonic setting for carbonate‐hosted zinc deposits.