Origins of dry air in the Tropics and Subtropics

The humidity in the dry regions of the tropical and subtropical troposphere has a major impact on the ability of the atmosphere to radiate heat to space. The water vapour content in these regions is determined by their ``origins'', here defined as the last condensation event following air masses. Trajectory simulations are used to investigate such origins using ERA40 data for January 1993. It is shown that 96% of air parcels experience condensation within 24 days and most of the remaining 4% originate in the stratosphere. Dry air masses are shown to experience a net pressure increase since last condensation which is uniform with latitude, while the median time taken for descent is 5 days into the subtropics but exceeds 16 days into the equatorial lower troposphere. The associated rate of decrease in potential temperature is consistent with radiative cooling. The relationship between the drier regions in the tropics and subtropics and the geographical localization of their origin is investigated. Four transport processes are identified to explain these relationships.

A groove-ploughing theory for the production of mega-scale glacial lineations, and implications for ice-stream mechanics

Mega-scale glacial lineations (MSGLs) are longitudinally aligned corrugations (ridge-groove structures 6-100 km long) in sediment produced subglacially. They are indicators of fast flow and a common signature of ice-stream beds. We develop a qualitative theory that accounts for their formation, and use numerical modelling, and observations of ice-stream beds to provide supporting evidence. Ice in contact with a rough (scale of 10-10(3) m) bedrock surface will mimic the form of the bed. Because of flow acceleration and convergence in ice-stream onset zones, the ice-base roughness elements experience transverse strain, transforming them from irregular bumps into longitudinally aligned keels of ice protruding downwards. Where such keels slide across a soft sedimentary bed, they plough through the sediments, carving elongate grooves, and deforming material up into intervening ridges. This explains MSGLs and has important implications for ice-stream mechanics. Groove ploughing provides the means to acquire new lubricating sediment and to transport large volumes of it downstream. Keels may provide basal drag in the force budget of ice streams, thereby playing a role in flow regulation and stability We speculate that groove ploughing permits significant ice-stream widening, thus facilitating high-magnitude ice discharge.

Children's sociospatial (re)production of disability within primary school playgrounds

There is a contemporary shift in the institutional context of 'disabled' children's education in the United Kingdom from segregated special to mainstream schools. This change is tied to wider deinstitutionalised or reinstitutionalised geographies of disabled people, fragile globalised educational 'inclusion' agendas, and broader concerns about social cohesiveness. Although coeducating children is expected to transform negative representations of (dis)ability in future society, there are few detailed explorations of how children's everyday sociospatial practices (re)produce or transform dominant representations of (dis)ability. With this in mind, children's contextual and shifting performances of (dis)ability in two case study school playground (recreational) spaces are explored. The findings demonstrate that children with mind-body differences are variously (dis)abled, in comparison with sociospatially shifting norms of ability, which have body, learning, and emotional-social facets. The discussion therefore places an emphasis on the need to incorporate 'intellectual' and 'emotional' differences more fully into geographical studies of disability and identity. The paper has wider resonance for transformative expectations placed on colocating children with a variety of 'axes of difference' (such as gender, 'race, ethnicity, and social class) in schools.

DISTRIBUTION OF Cr, Pb, Cu, Cd AND Zn IN SEDIMENTS OF THE DOBCZYCE DAM RESERVOIR (SOUTHERN POLAND)

Sediments play a fundamental role in the behaviour of contaminants in aquatic systems. Various processes in sediments, eg adsorption-desorption, oxidation-reduction, ion exchange or biological activities, can cause accumulation or release of metals and anions from the bottom of reservoirs, and have been recently studied in Polish waters [1-3]. Sediment samples from layer A: (1 divided by 6 cm depth in direct contact with bottom water); layer B: (7 divided by 12 cm depth moderate contact); and layer C: (12+ cm depth, in theory an inactive layer) were collected in September 2007 from six sites representing different types of hydrological conditions along the Dobczyce Reservoir (Fig. l). Water depths at the sampling points varied from 3.5 to 21 m. We have focused on studying the distribution and accumulation of several heavy metals (Cr, Pb, Cd, Cu and Zn) in the sediments. The surface, bottom and pore water (extracted from sediments by centrifugation) samples were also collected. Possible relationships between the heavy-metal distribution in sediments and the sediment characteristics (mineralogy, organic matter) as well as the Fe, Mn and Ca content of sediments, have been studied. The 02 concentrations in water samples were also measured. The heavy metals in sediments ranged from 19.0 to 226.3 mg/kg of dry mass (ppm). The results show considerable variations in heavy-metal concentrations between the 6 stations, but not in the individual layers (A, B, C). These variations are related to the mineralogy and chemical composition of the sediments and their pore waters.

Production of tense marking in successive bilingual children: when do they converge with their monolingual peers?

Children with English as a second language (L2) with exposure of 18 months or less exhibit similar difficulties to children with Specific Language Impairment in tense marking, a marker of language impairment for English. This paper examines whether L2 children with longer exposure converge with their monolingual peers in the production of tense marking. 38 Turkish-English L2 children with a mean age of 7;8 and 33 monolingual age-matched controls completed the screening test of the Test of Early Grammatical Impairment (TEGI). The L2 children as a group were as accurate as the controls in the production of -ed, but performed significantly lower than the controls in the production of third person –s. Age and YoE affected the children’s performance. The highest age-expected performance on the TEGI was attested in eight and nine year-old children who had 4-6 YoE. L1 and L2 children performed better in regular compared to irregular verbs, but L2 children overregularized more than L1 children and were less sensitive to the phonological properties of verbs. The results show that tense marking and the screening test of the TEGI may be promising for differential diagnosis in eight and nine year-old L2 children with at least four YoE.

Understanding and production of prosody in children with Williams syndrome: A developmental trajectory approach

This study investigated the development of three aspects of linguistic prosody in a group of children with Williams syndrome compared to typically developing children. The prosodic abilities investigated were: (1) the ability to understand and use prosody to make specific words or syllables stand out in an utterance (focus); (2) the ability to understand and use prosody to disambiguate complex noun phrases (chunking); (3) the ability to understand and use prosody to regulate conversational behaviour (turn-end). The data were analysed using a cross-sectional developmental trajectory approach. The results showed that, relative to chronological age, there was a delayed onset in the development of the ability of children with WS to use prosody to signal the most important word in an utterance (the focus function). Delayed rate of development was found for all the other aspects of expressive and receptive prosody under investigation. However, when non-verbal mental age was taken into consideration, there were no differences between the children with WS and the controls neither with the onset nor with the rate of development for any of the prosodic skills under investigation apart from the ability to use prosody in order to regulate conversational behaviour. We conclude that prosody is not a ‘preserved’ cognitive skill in WS. The genetic factors, development in other cognitive domains and environmental influences affect developmental pathways and as a result, development proceeds along an atypical trajectory.

Impact of coronal mass ejections, interchange reconnection, and disconnection on heliospheric magnetic field strength

An update of Owens et al. (2008) shows that the relationship between the coronal mass ejection (CME) rate and the heliospheric magnetic field strength predicts a field floor of less than 4 nT at 1 AU. This implies that the record low values measured during this solar minimum do not necessarily contradict the idea that open flux is conserved. The results are consistent with the hypothesis that CMEs add flux to the heliosphere and interchange reconnection between open flux and closed CME loops subtracts flux. An existing model embracing this hypothesis, however, overestimates flux during the current minimum, even though the CME rate has been low. The discrepancy calls for reasonable changes in model assumptions.

Role of coronal mass ejections in the heliospheric Hale cycle

The 11-year solar cycle variation in the heliospheric magnetic field strength can be explained by the temporary buildup of closed flux released by coronal mass ejections (CMEs). If this explanation is correct, and the total open magnetic flux is conserved, then the interplanetary-CME closed flux must eventually open via reconnection with open flux close to the Sun. In this case each CME will move the reconnected open flux by at least the CME footpoint separation distance. Since the polarity of CME footpoints tends to follow a pattern similar to the Hale cycle of sunspot polarity, repeated CME eruption and subsequent reconnection will naturally result in latitudinal transport of open solar flux. We demonstrate how this process can reverse the coronal and heliospheric fields, and we calculate that the amount of flux involved is sufficient to accomplish the reversal within the 11 years of the solar cycle.