Water vapour (I)

Considering the fundamental role of water vapour in climate, and the scarcity of information concerning its distribution, variability and long-term evolution, the SPARC Scientific Steering Group recognised the need for a critical review of the 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. The lack of knowledge on water vapour also led to a large uncertainty in the prediction of climate change. Phase 1 of the SPARC Water Vapour Assessment (WAVAS-I) had been launched in 1998 with the objective to consolidate and review our understanding of the role of water vapour in the climate system and to make this assessment available to support the 2001 IPCC Third Assessment Report on Climate Change (TAR).

The WAVAS Report was published in 2000 as SPARC Report No. 2. In preparation for this report, 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 and to the wider community for independent verification of the results (find the data set at the SPARC Data Centre). 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.

Phase 2 of WAVAS (WAVAS II) will provide an update to this first assessment.

Activity Leaders:

Dieter Kley, Forschungszentrum, Germany
James M. Russell III, Hampton University, USA

Published results:

SPARC report:

SPARC Report No. 2 (2000) Upper Tropospheric and Stratospheric Water Vapour. D. Kley, J.M. Russell III, and C. Philips (eds.). WCRP-113, WMO/TD – No. 1043.

Journal publications:

Rosenlof, K.H., S.J. Oltmans, D. Kley, J.M. Russell III, E.-W. Chiou, W.P. Chu, D.G. Johnson, K.K. Kelly, H.A. Michelsen, G.E. Nedoluha, E.E. Remsberg, G.C. Toon, M.P. McCormick (2001) Stratospheric water vapour increases over the past half-century. Geophysical Research Letters 28(7), pp. 1195-1198, DOI: 10.1029/2000GL012502

Ozone profile (I)

Phase 1 of the SPARC ozone profile activity (ozone profile I) was launched in 1994 to critically examine the underlying research in the existing ozone trends assessment, and to look at plans for the monitoring of ozone (space- and ground-based) to see if the gaps are filled and calibrations ensured. This scientific assessment was carried out jointly by SPARC and the International Ozone Commission (IOC), in close co-operation with WMO’s Global Atmospheric Watch programme (GAW). The assessment led to SPARC Report No. 1 (1998).

The objective of this report was to review critically the measurements and trends of the vertical distribution of ozone and to assess associated uncertainties. Recently revised data were used where appropriate and the time period covered was extended into mid-1996.

This is the first assessment of its kind carried out by SPARC and the IOC. It was stimulated by the WMO/UNEP Scientific Assessment of Ozone Depletion (1994), which found large discrepancies between ozone trends in the lower stratosphere. One of the objectives of this assessment was to ensure continuity in the international effort necessary to prepare the WMO/UNEP Assessments, and the SPARC contribution has been since heavily relied upon in the production of the subsequent ozone  assessment. It was also being used in the preparation of the Special IPCC Report on Aviation and the Global Atmosphere (1999). In addition, this first SPARC-IOC-GAW assessment anticipated the need for precise updated observations of the vertical distribution of stratospheric ozone depletion to be used to assess the impact on climate in the 2001 Third IPCC Assessment Report on Climate Change (TAR).

Phase 2 of the ozone profile activity (Ozone profile II) will provide an update to this first assessment.

Activity leaders:

Neil Harris, European Ozone Research Coordinating Unit, Centre for Atmospheric Science, University of Cambridge, UK
Bob Hudson, Department of Meteorology, University of Maryland, USA

Published results:

SPARC report:

  • SPARC Report No. 1 (1998) SPARC/IOC/GAW Assessment of Trends in the Vertical Distribution of Ozone. By N. Harris, R. Hudson and C. Phillips (eds). WMO Ozone Research and Monitoring Project Report No. 43.