The basic ingredients of the North Atlantic storm track. Part I: land-sea contrast and orography

Understanding and predicting changes in storm tracks over longer time scales is a challenging problem, particularly in the North Atlantic. This is due in part to the complex range of forcings (land–sea contrast, orography, sea surface temperatures, etc.) that combine to produce the structure of the storm track. The impact of land–sea contrast and midlatitude orography on the North Atlantic storm track is investigated through a hierarchy of GCM simulations using idealized and “semirealistic” boundary conditions in a high-resolution version of the Hadley Centre atmosphere model (HadAM3). This framework captures the large-scale essence of features such as the North and South American continents, Eurasia, and the Rocky Mountains, enabling the results to be applied more directly to realistic modeling situations than was possible with previous idealized studies. The physical processes by which the forcing mechanisms impact the large-scale flow and the midlatitude storm tracks are discussed. The characteristics of the North American continent are found to be very important in generating the structure of the North Atlantic storm track. In particular, the southwest–northeast tilt in the upper tropospheric jet produced by southward deflection of the westerly flow incident on the Rocky Mountains leads to enhanced storm development along an axis close to that of the continent’s eastern coastline. The approximately triangular shape of North America also enables a cold pool of air to develop in the northeast, intensifying the surface temperature contrast across the eastern coastline, consistent with further enhancements of baroclinicity and storm growth along the same axis.

The zonal asymmetry of the Southern Hemisphere storm-track

Atmospheric general circulation model experiments have been performed to investigate how the significant zonal asymmetry in the Southern Hemisphere (SH) winter storm track is forced by sea surface temperature (SST) and orography. An experiment with zonally symmetric tropical SSTs expands the SH upper-tropospheric storm track poleward and eastward and destroys its spiral structure. Diagnosis suggests that these aspects of the observed storm track result from Rossby wave propagation from a wave source in the Indian Ocean region associated with the monsoon there. The lower-tropospheric storm track is not sensitive to this forcing. However, an experiment with zonally symmetric midlatitude SSTs exhibits a marked reduction in the magnitude of the maximum intensity of the lower-tropospheric storm track associated with reduced SST gradients in the western Indian Ocean. Experiments without the elevation of the South African Plateau or the Andes show reductions in the intensity of the major storm track downstream of them due to reduced cyclogenesis associated with the topography. These results suggest that the zonal asymmetry of the SH winter storm track is mainly established by stationary waves excited by zonal asymmetry in tropical SST in the upper troposphere and by local SST gradients in the lower troposphere, and that it is modified through cyclogenesis associated with the topography of South Africa and South America.

Developments in the Doha Round and WTO dispute settlement: some implications for EU agricultural policy

Progress in the Doha Round is assessed against the changes to the common agricultural policy (CAP) brought about by the Fischler reforms of 2003-2004, and that proposed for sugar. An elimination of export subsidies could place EU exports of processed foods at a competitive disadvantage because of high sugar and milk prices. Provided the single payment scheme falls within the green box, the likely new limits on domestic support should not be problematic for the post-Fischler CAP. However, an ambitious market access package could open up EU markets and bring pressure for further reform. If there is no Doha agreement, existing provisions will continue to apply, but without the protection of the Peace Clause; and increased litigation is likely. Further CAP reform is to be expected.

Post-partum depression and infant growth in a South African peri-urban settlement

Aim: To examine the association between maternal post-natal depression and infant growth. Background: Infant growth has recently been shown, in two studies from South Asia, to be adversely affected by maternal depression in the early post-partum period. It is uncertain whether a similar association obtains in developing countries outside Asia. Method: A sample of 147 mother–infant dyads was recruited from a peri-urban settlement outside Cape Town and seen at 2 and 18 months post partum. Results: No clear effect of post-partum depression on infant growth was found. Although maternal depression at 2 months was found to be associated with lower infant weight at 18 months, when birthweight was considered this effect disappeared. Conclusions: Possible explanations for the non-replication of the South Asian findings are considered.

The mother-infant relationship and infant attachment in a south African peri-urban settlement

A sample of 147 mother-infant dyads was recruited from a peri-urban settlement outside Cape Town and seen at 2- and 18-months postpartum. At 18 months, 61.9% of the infants were rated as securely attached (B); 4.1% as avoidant (A); 8.2% as resistant (C); and 25.8% disorganized (D). Postpartum depression at 2 months, and indices of poor parenting at both 2 and 18 months, were associated with insecure infant attachment. The critical 2-month predictor variables for insecure infant attachment were maternal intrusiveness and maternal remoteness, and early maternal depression. When concurrent maternal sensitivity was considered, the quality of the early mother-infant relationship remained important, but maternal depression was no longer predictive. Cross-cultural differences and consistencies in the development of attachment are discussed.

The factor structure of the Edinburgh postnatal depression scale in a South African peri-urban settlement

The factor structure of the Edinburgh Postnatal Depression scale (EPDS) and similar instruments have received little attention in the literature. The researchers set out to investigate the construct validity and reliability of the EPDS amongst impoverished South African women. The EPDS was translated into isiXhosa (using Brislin's back translation method) and administered by trained interviewers to 147 women in Khayelitsha, South Africa. Responses were subjected to maximum likelihood confirmatory factor analysis. A single factor structure was found, consistent with the theory on which the EPDS was based. Internal consistency was satisfactory (a = 0.89).

Infrared filters and dichroics for the advanced along track scanning radiometer

The design and manufacture of the band-defining filters and their associated dichroic beam splitter for the 11- and the 12-µm infrared channels of the advanced along-track scanning radiometer are described. The filter requirements that have led to the choice of coating designs, coating materials, disposition of coatings, and effects of polarization are discussed. Overall spectral throughputs of the filter and dichroic interaction for the two channels are also presented.

The later Anglo-Saxon settlement at Bishopstone. A downland manor in the making

This volume reports on the excavations from 2002 to 2005 designed to investigate this transition, with the focus on the origins of Bishopstone village. Excavations adjacent to St Andrew’s churchyard revealed a dense swathe of later Anglo-Saxon (8th- to late 10th-/early 11th-century) habitation, including a planned complex of ‘timber halls’, and a unique cellared tower. The occupation encroached upon a pre-Conquest cemetery of 43 inhumations. The report provides a comprehensive analysis, interpretation and academic contextualisation of the archaeological discoveries brought to light by these excavations, the first to sample a later Anglo-Saxon rural settlement in East Sussex on an extensive scale. The inter-disciplinary approach appraises the historical and topographical evidence alongside that recovered during the excavations.

The basic ingredients of the North Atlantic Storm Track. Part II: Sea surface temperatures

The impact of North Atlantic SST patterns on the storm track is investigated using a hierarchy of GCM simulations using idealized (aquaplanet) and “semirealistic” boundary conditions in the atmospheric component (HadAM3) of the third climate configuration of the Met Office Unified Model (HadCM3). This framework enables the mechanisms determining the tropospheric response to North Atlantic SST patterns to be examined, both in isolation and in combination with continental-scale landmasses and orography. In isolation, a “Gulf Stream” SST pattern acts to strengthen the downstream storm track while a “North Atlantic Drift” SST pattern weakens it. These changes are consistent with changes in the extratropical SST gradient and near-surface baroclinicity, and each storm-track response is associated with a consistent change in the tropospheric jet structure. Locally enhanced near-surface horizontal wind convergence is found over the warm side of strengthened SST gradients associated with ascending air and increased precipitation, consistent with previous studies. When the combined SST pattern is introduced into the semirealistic framework (including the “North American” continent and the “Rocky Mountains”), the results suggest that the topographically generated southwest–northeast tilt in the North Atlantic storm track is enhanced. In particular, the Gulf Stream shifts the storm track south in the western Atlantic whereas the strong high-latitude SST gradient in the northeastern Atlantic enhances the storm track there.