Tropospheric planetary wave dynamics and mixture modeling: Two preferred regimes and a regime shift

Investigation of preferred structures of planetary wave dynamics is addressed using multivariate Gaussian mixture models. The number of components in the mixture is obtained using order statistics of the mixing proportions, hence avoiding previous difficulties related to sample sizes and independence issues. The method is first applied to a few low-order stochastic dynamical systems and data from a general circulation model. The method is next applied to winter daily 500-hPa heights from 1949 to 2003 over the Northern Hemisphere. A spatial clustering algorithm is first applied to the leading two principal components (PCs) and shows significant clustering. The clustering is particularly robust for the first half of the record and less for the second half. The mixture model is then used to identify the clusters. Two highly significant extratropical planetary-scale preferred structures are obtained within the first two to four EOF state space. The first pattern shows a Pacific-North American (PNA) pattern and a negative North Atlantic Oscillation (NAO), and the second pattern is nearly opposite to the first one. It is also observed that some subspaces show multivariate Gaussianity, compatible with linearity, whereas others show multivariate non-Gaussianity. The same analysis is also applied to two subperiods, before and after 1978, and shows a similar regime behavior, with a slight stronger support for the first subperiod. In addition a significant regime shift is also observed between the two periods as well as a change in the shape of the distribution. The patterns associated with the regime shifts reflect essentially a PNA pattern and an NAO pattern consistent with the observed global warming effect on climate and the observed shift in sea surface temperature around the mid-1970s.

NATO, Britain, France and the FRG: Nuclear Strategies and Forces for Europe, 1949-2000

This is vol. I of my two-volume study of the nuclear strategies/strategy preferences of NATO collectively, and individually of Britain, France, and West Germany in the Cold War. It shows that NATO strategy was a fragile compromise, and that these three countries, all within range of Soviet medium/intermediate range nuclear missiles and thus with less geostrategic difference than in previous military threat contexts, had wildly divergent strategies/preferences which cannot be explained merely by geography. It raises the question of what made them so different, addressed in Volume II "Nuclear Mentalities" (q.v.)

‘What Price Solidarity? Nuclear Dependence in NATO, 1949-1967’

Archive-based study of the dependence of NATO member states on the USA as nuclear guarantor, and the problems this entailed.

Benevolence, hegemony and nationalism: fifty years of the 1949 National Parks and Access to the Countryside Act

This paper reviews the National Parks and Access to the Countryside Act 1949 fifty years since its enactment. The Act is assessed in the light of fifty years of access policy and within the present context of political debates and manoeuvres over the ‘right to roam’. It is concluded that benevolence is still the prevailing attitude towards access provision, maintaining as it does the scope for alternative freedoms and opportunities to exploit land for consumptive practices such as leisure and recreation. As such, it is argued that the notion of the gift (Mauss, 1990) continues to dominate the provision of countryside access in England and Wales.

In at the Deep End. Impressions of farming in a year gaining experience: 1952-3; 1978-85

The book describes a wide variety of students’ experiences in their practical year prior to entering University to study BSc Agriculture. Until comparatively recently it was the normal requirement for all such students, whether or not they already had home farming experience, to gain a full year’s experience of practical agriculture – and to write a report thereon. This record of 41 students’ reports of the pre-entry year begins with Paul’s own experience in the early 1950s before 41 reports from 30 or more years ago. The essays provide compelling and fascinating stories, well-articulated with clear acknowledgement for most part of the humanity and the warmth with which each student was treated by farmers and farm workers alike, despite the difference in both age and experience (considerable!). [This summary is an extract from the full overview which is archived here together with the book.]

Analysis of red pigments from the Neolithic sites of Çatalhöyük in Turkey and Sheikh-e Abad in Iran

Samples containing red pigment have been collected from two different archaeological sites dating to the Neolithic (Çatalhöyük in Turkey and Sheikh-e Abad in Iran) and have been analysed by a range of techniques. Sub-samples were examined by IR spectroscopy and X-ray diffraction, whilst thin sections were studied using optical polarising microscopy, synchrotron based IR microscopy and environmental scanning electron microscopy with energy dispersive X-ray analysis. Thin layers of red paint in a wall painting from Çatalhöyük were found to contain ochre (hematite and clay) as well as an unexpected component, grains of red and colourless obsidian, which have not been identified in any previous studies of the wall paintings at Çatalhöyük. These small grains of obsidian may have improved the reflective properties of the paint and made the artwork more vivid in the darkness of the buildings. Analysis of a roughly shaped ball of red sediment found on a possible working surface at Sheikh-e Abad revealed that the cause of the red colouring was the mineral hematite, which was probably from a source of terra rossa sediment in the local area. The results of this work suggest it is unlikely that this had been altered by the Neolithic people through mixing with other minerals.

Effect of surface restoring on subsurface variability in a climate model during 1949-2005

Initializing the ocean for decadal predictability studies is a challenge, as it requires reconstructing the little observed subsurface trajectory of ocean variability. In this study we explore to what extent surface nudging using well-observed sea surface temperature (SST) can reconstruct the deeper ocean variations for the 1949–2005 period. An ensemble made with a nudged version of the IPSLCM5A model and compared to ocean reanalyses and reconstructed datasets. The SST is restored to observations using a physically-based relaxation coefficient, in contrast to earlier studies, which use a much larger value. The assessment is restricted to the regions where the ocean reanalyses agree, i.e. in the upper 500 m of the ocean, although this can be latitude and basin dependent. Significant reconstruction of the subsurface is achieved in specific regions, namely region of subduction in the subtropical Atlantic, below the thermocline in the equatorial Pacific and, in some cases, in the North Atlantic deep convection regions. Beyond the mean correlations, ocean integrals are used to explore the time evolution of the correlation over 20-year windows. Classical fixed depth heat content diagnostics do not exhibit any significant reconstruction between the different existing observation-based references and can therefore not be used to assess global average time-varying correlations in the nudged simulations. Using the physically based average temperature above an isotherm (14 °C) alleviates this issue in the tropics and subtropics and shows significant reconstruction of these quantities in the nudged simulations for several decades. This skill is attributed to the wind stress reconstruction in the tropics, as already demonstrated in a perfect model study using the same model. Thus, we also show here the robustness of this result in an historical and observational context.