Recent observations and theoretical work suggest that the 2 day planetary wave in the summertime mesosphere is composed of multiple superposed zonal wave numbers. Here we use EOS Aura Microwave Limb Sounder (MLS) temperature data to determine the component zonal wave numbers of the 2 day wave in the mesosphere at latitudes of 70°S to 70°N from 2004 to 2009. We consider the effect of aliasing between different wave numbers and note that significant aliasing can occur and result in spurious signals, particularly at high latitudes in winter. The seasonal evolution of the different wave numbers is investigated and found to be very different between the Northern and Southern Hemispheres. In both hemispheres the wave is dominated by westward traveling waves of zonal wave number 3 and 4 (W3 and W4). However, in the Southern Hemisphere the wave is dominated by the W3 component, but in the Northern Hemisphere the W3 component is smaller and the W4 component is often of similar or larger amplitude. A small‐amplitude westward traveling zonal wave number 2 (W2) wave is also evident in both hemispheres. In the Northern Hemisphere, the W2 amplitudes never exceed 3 K, the W3 amplitudes can reach 3.5 K, and the W4 can be the largest component, reaching amplitudes of 4 K. In the Southern Hemisphere, the W2 amplitudes can reach up to 3.5 K, the W3 amplitudes can be much larger, reaching 12 K, and the W4 amplitudes are smaller than in the Northern Hemisphere, in 4 out of 5 years not exceeding 3 K. The Northern Hemisphere W4 can reach large amplitudes in August when the W3 is small, which means that the late summer Northern Hemisphere quasi‐2 day wave is usually a W4 oscillation rather than the familiar W3. In contrast, in the Southern Hemisphere, the W3 is often larger than the W4 around the summer solstice, and there are no episodes observed where the wave becomes dominated by the W4 for an extended period of time. A high degree of interannual variability is evident, particularly in the Southern Hemisphere, where the W3 peak amplitudes vary from 12 K in January 2006 to 3 K in January 2009. The height‐latitude structure of the W4 suggests that this wave is a (4, 0) Rossby‐gravity wave.

In 1997, drawing on methods to assess risk in institutional settings developed by McDougall and colleagues (Clark et al.have also been developed in the psychodynamic literature (e.g. Malan's (1999) 'triangle of persons' where three-way links are made between what happens in the session, what happened in past relationships and what is happening with signifi cant others. Most recently, Jones defi ned OPB as: ' Any form of offence related behavioural (or fantasized behaviour) pattern that emerges at any point before or after an offence. It does not have to result in an offence; it simply needs to resemble, in some signifi cant respect, the sequence of behaviours leading up to the offence' (2004, p. 38). Unlike the risk assessment model developed by McDougall and colleagues, Jones (2004) identifi ed OPB as a developmental sequence of behaviour akin to the notion of an offence chain that is understood in terms of function not morphology. He also, and perhaps more critically, advocated the OPB framework as a strategy for identifying intervention opportunities, monitoring treatment progress and supplementing risk-related decision-making in custodial settings.Since it was offered, interest in the framework, at least within the United Kingdom, has developed, perhaps because of its clinical utility, intuitive appeal and face validity. Interest is particularly evident in institutional staff as it gives Daffern et al. 272 fi ed in the defi nition provided here may improve reliability. However, there are presently few such methods available to forensic clinicians. A research agenda to evaluate the framework is under development, as is work on its application in various settings and methods for developing OPB formulations. Contribution and collaboration by others interested in this fi eld is invited.

[1] Upper mesosphere OH temperature measurements are compared at the stations of Wuppertal (51°N, 7°E) and Hohenpeißenberg (48°N, 11°E) for [2004][2005][2006][2007][2008][2009] in order to form a combined data set which considerably improves the measurement statistics. This allows time analyses near the Nyquist frequency (2 days) which is used for a study of the quasi 2 day wave (QTDW) in summer. The well-known maximum near solstice is observed. In addition, there are two unexpected side maxima about 45-60 days before and after the center peak. A similar triplet is seen in the QTDW analysis of Microwave Limb Sounder temperature data. The triple structure is also found in a very similar form 15 years earlier in the interval 1988-1993 in early Wuppertal data. In these 15 years the time distance between the first and last triple peak has increased by about 22 days. Amplitudes of the QTDW correspond to the meridional gradient of the quasi-geostrophic potential vorticity (from MLS data) and baroclinic instabilities (bc) from radar winds (at Juliusruh, 55°N, 13°E). Parameter bc also shows a triple structure, when mean values 2003-2008 are calculated. The QTDW triplet results from the combination of atmospheric (in)stability and critical wind speed. The widening of the QTDW triple structure suggests a long-term change of mesospheric stability and wind structure. This is found, indeed, in the bc and zonal wind data. The changes likely reflect a long-term circulation change in the middle atmosphere extending up to the mesopause.

Abstract. There have been comparatively few studies reported of the 2-day planetary wave in the middle atmosphere at polar latitudes. Here we report studies made using high-latitude meteor radars at Rothera in the Antarctic (68° S, 68° W) and Esrange in Arctic Sweden (68° N, 21° E). Observations from 2005–2008 are used for Rothera and from 1999–2008 for Esrange. Data were recorded for heights of 80–100 km. The radar data reveal distinct summertime and wintertime 2-day waves. The Antarctic summertime wave occurs with significant amplitudes in January–February at heights between about 88–100 km. Horizontal wind monthly variances associated with the wave exceed 160 m2 s−2 and the zonal component has larger amplitudes than the meridional. In contrast, the Arctic summertime wave occurs for a longer duration, June–August and has meridional amplitudes larger than zonal. The Arctic summertime wave is weaker than that in the Antarctic and maximum monthly variances are typically 60 m2 s−2. In both hemispheres the summertime wave reaches largest amplitudes in the strongly sheared eastward zonal flow above the zero wind line and is largely absent in the westward flow below. The observed differences in the summertime wave is probably due to the differences in the background zonal winds in the two hemispheres. The Antarctic and Arctic wintertime waves have very similar behavior. The Antarctic wave has significant amplitudes in May–August and the Arctic wave in November–February. Both are evident across the full height range observed.

Abstract. There have been comparatively few studies