ALBERT

Description / Table of Contents: Contents: 1 Introduction ; 2 Floods on the rise? Review of literature on detection and attribution ; 3 Detection of change in annual maximum flow ; 4 Concluding remarks

Description / Table of Contents: This scientific assessment has been carried out by the WCRP project on Stratospheric Processes and their Role in Climate (SPARC). The objective of the report is to critically review measurements of water vapour in the stratosphere and upper troposphere, in order to consolidate our knowledge and understanding of the distribution of water vapour and its variability on time scales ranging from the seasonal to the long-term inter-annual. Considering the fundamental role of water vapour in climate, and the scarcity of information concerning its distribution, variability and long-term evolution, the need for such an assessment was recognised by the SPARC Scientific Steering Group. The lack of knowledge on water vapour also leads to a large uncertainty in the prediction of climate change. One of the objectives of the assessment was therefore to support the Third IPCC Assessment Report on Climate Change due to be published in 2001. Great effort has been made to prepare the best data sets possible, to retrieve historical data sets, and to make them all available to the assessment team. This report contains an extensive description of the measurements and their associated uncertainties, an assessment of data quality based on comparison studies of the various data sets, and a description of the understanding of the distribution and variability of water vapour in the stratosphere and upper troposphere which ensues from the data. Finally, recommendations are made to ensure that the difficulties met during this work are overcome in order that the remaining uncertainties in our knowledge and understanding can be resolved. The preceding summary also appears in SPARC Newsletter number 16 (January 2001). The outline of the assessment was determined during an international workshop held at NCAR, Boulder, Colorado, USA, 26-28 August 1998. The drafts of the chapters were prepared in the following year and a number of new data sets were produced. The first draft report was examined by an international panel of reviewers both by mail peer review and at a meeting in Paris, France in January 2000. During the review meeting the responses to the mail review comments were proposed by the authors and discussed by the participants. This rigorous review greatly improved the report, the contribution of the reviewers being significant. A second draft report was reviewed by mail review in August 2000. The success in producing the Report is the result of the intensive work and enthusiastic cooperation of a large number of scientists world-wide who have worked towards improving the quality of the measurements and our understanding of the observations. The work of the contributors and reviewers was generously supported by many organisations and agencies including WMO, WCRP, SPARC, DG Research of the European Commission, NASA, NOAA, NCAR, CNRS, CNES, Forschungszentrum Jülich, Imperial College and other national research programmes and institutions. We take this opportunity to express our gratitude to all the scientists (authors, contributors and reviewers) who helped in the preparation of this assessment and to the SPARC scientific steering group who have been supportive since its inception. Our special gratitude is due to the lead authors of the chapters. Particular thanks must be given to: Petra Udelhofen at the SPARC Data Center for setting up the data archive, Sam Oltmans who organised the workshop at NCAR, Boulder, Colorado; Computational Physics Inc., for hosting the workshop in Washington D.C.; François Dulac from the CNES for hosting the review meeting in Paris, and Céline Phillips for her co-editorship. We also thank Marie-Christine Gaucher at the SPARC office for her help in the organisation of the review meeting in Paris and in the final editing of the report and Catherine Michaut at the SPARC office for her help in editing the second peerreview draft and the final draft of the report.

Description / Table of Contents: SPARC has from its outset been concerned with “Stratospheric Indicators of Climate Change,” “Stratospheric Processes,” and “Troposphere/Stratosphere Modelling.” The SPARC project GRIPS (GCM Reality Intercomparison Project) has focused on comparing troposphere/stratosphere general circulation models with one another, both in terms of their technical formulations and in their results. Of course, another aspect of GRIPS is to examine how well model results compare to observations. Direct model/data comparisons are not so straightforward, however. For instance, the stratosphere displays a great deal of interannual variability, so that model-data comparisons necessarily include statistics of both means and variances over comparable time periods. Additionally, stratospheric data are obtained from complicated inversions of radiances derived from satellite measurements, from direct but sparse balloon or rocket measurements, from time continuous but geographically sparse ground-based remote sensing instruments, and finally from analysis of stratospheric measurements either by statistical techniques or from data assimilation methods. The climatologies derived by these different methods do not agree in all respects. Finally, the entire concept of stratospheric trends means that stratospheric climatology is itself time varying. The SPARC Reference Climatology Group was established to update and evaluate existing middle atmosphere climatologies for use in GRIPS, and in other SPARC activities. Rather than create a single new “super climatology,” it was decided that a valuable contribution would be to (1) compile existing climatologies and make them easily available to the research community, and (2) carefully compare and evaluate the existing climatologies. The SPARC Data Center was established (in part) as a response to item (1), and this Report is a response to item (2). Here we present detailed intercomparisons of climatological wind and temperature data sets that are currently used in the research community, which are derived from a variety of meteorological analyses and satellite data sets. Special attention is focused on tropical winds and temperatures, where large differences exist among separate analyses. We also include comparisons between the global climatologies and historical rocketsonde temperature and wind measurements, and also with more recent lidar temperature data. These comparisons highlight differences and uncertainties in contemporary middle atmosphere data sets, and allow biases in particular analyses to be isolated. In addition, a brief atlas of zonal mean wind and temperature statistics is provided to highlight data availability and as a quick-look reference. This Report is intended as a companion to the climatological data sets held in archive at the SPARC Data Center (http://www.sparc.sunysb.edu).