A comparison of reanalyses in the tropical stratosphere. Part 2: the quasi-biennial oscillation

 Reanalysis datasets potentially offer the opportunity to examine the tropical quasi-biennial oscillation (QBO) in greater detail than in the past, including the associated meridional circulation and the links with other parts of the atmosphere. For such studies to be useful, the QBO represented by the reanalyses should be realistic. In this work, the QBO in the ERA and NCEP reanalyses is validated against rawinsonde observations from Singapore. Monthly mean data are used. In the lower stratosphere (at 50 hPa and 30 hPa) the ERA QBO is reasonable, although the wind extrema in both phases are too weak and the vertical shear and the temperature anomalies are too small. The NCEP QBO is weaker still. At 10 hPa neither reanalysis system performs well, both systems failing to reproduce the westerlies, possibly because of the proximity of the upper boundary. The Singapore wind is representative of the zonal means in the reanalyses. The weak wind extrema in the reanalyses would not support a wave-mean flow interaction theory of the QBO, because a large portion of the gravity wave spectrum which would be absorbed in reality would be transmitted beyond 10 hPa. The stronger shear zones captured in the ERA data are associated with larger, more realistic temperature perturbations near 30 hPa. The northward velocities in the NCEP data show a more realistic structure than in the ERA reanalysis, where they are dominated by a vertical “gridpoint wave” structure in the lowermost stratosphere. Despite the shortcomings of the reanalyses, the high correlations of the wind at 30 hPa and 50 hPa with the observations at Singapore mean that the reanalyses could potentially be used to examine the effects of the QBO away from the tropical stratosphere. Future reanalyses need to take full account of the wind shears evident in the rawinsonde observations and use models with an adequate resolution to capture these vertical scales. Received: 23 June 1997/Accepted 17 December 1998     

A comparison of reanalyses in the tropical stratosphere. Part 3: inclusion of the pre-satellite data era

 In this study, previous evaluations of the monthly mean structure of the tropical lower stratosphere in reanalyzed datasets are extended to include the period 1958–1978, when no satellite-based observations were available. It is shown that a large discontinuity, in temperatures near the tropical tropopause, in the NCEP data occurred when the Tiros Operational Vertical Sounder (TOVS) became operational. When only rawinsonde data were available, the tropopause temperatures in the NCEP dataset are in better agreement with ERA data for TOVS period. Both NCEP and NASA reanalyses show similar deviations from the ERA data in the TOVS renalyses show similar deviations from the ERA data in the TOVS period. There is also a stepwise change in the lower stratospheric meridional velocity when the TOVS data were introduced into the NCEP reanalyses. This discontinuity is such that in the 1958–1978 period, the annual cycle in zonal mean meridional velocity in the NCEP data resembles that of the ERA data in the 1979–1993 period. The differences are shown to result from large changes in the local meridional flow in the Indonesian region. The temporal consistency of the QBO is examined; it is shown that the NCEP assimilation system is sensitive to the data available. There is a change in the zonally asymmetric structure of the zonal wind over time, presumably related to the changes in input data and the inability of the model to represent the three-dimensional structure of the tropical lower stratosphere. These results provide further evidence of the value of rawinsonde data in data assimilation systems as well as the need to use satellite radiance data in an appropriate manner. Received: 7 April 1997 / Accepted: 4 September 1998     

Environmental hazards and natural disasters

How can the apparently growing frequency and cost of environmental hazards be explained? Drawing on a range of examples, and especially the Canterbury earthquakes, it is argued that the creation of knowledge about these events depends on the interplay of lived and historical experience with scientific awareness. But often the vulnerability of places to particular events is obscured by popular use of the terms ‘natural hazard’ or ‘natural disaster’, as if human behaviour is absolved from any responsibility. It is shown how such thinking often increases the extent of the hazard, so that although we do not cause earthquakes, floods and bushfires, we are implicated and complicit in the outcomes.     

Giving an account of oneself: The PBRF and the neoliberal university

The New Zealand Performance Based Research Fund (PBRF) has come into being in the last decade in the wider context of the neoliberalising and corporatising of the academy. It is far more than its outward form: that is, an innocent accounting of the research‐related activities of academics for the purposes of determining institutional funding levels. But neither is it only a process that seeks (to use Judith Butler's terms) to constrain, subordinate and discipline individual academics. Drawing on her book, Giving an Account of Oneself (2005), we suggest that the PBRF can also be used to enable and sustain through creating spaces to critique neoliberalising managerialism.     

Second New Zealand record of the Holothurian giant larva Auricularia Nudibranchiata Chun

Seventy‐nine specimens of the holothurian larva Auricularia nudibranchiata from north of New Zealand are described, and relationships with previously described specimens of the same or related species are discussed.