GEWEX and in particular its Radiation Panel is generating climate data records concerning the Earth Energy and Water Cycle by means of dedicated reprocessing activities. Currently, a missing element is a water vapour product that can be used in a consistent way with the other products. This workshop helped to answer questions on how such a water vapour climatology should be designed to be most useful in the context of GEWEX.

The format of the workshop was a mixture of presentations and breakout groups with discussions in the plenary. The presentations covered the needs of GEWEX, the current usage of data sets in climate analysis, existing data sets and validation data and methodology.

Background

There is a clear need of a global time series of temperature and humidity profiles for studies of the 3D T, q distribution, e.g., for water vapour transport, and the use within the derivation of cloud property data sets and components of the radiation budget climatology. Such a data set should cover a period of approximately 30 years starting in the late 1970s. Taking the ISCCP data set as an example the use of T-, q-profile data from satellite data real time processing systems can easily corrupt the quality of a data set for long term climate variability analysis. Currently, no single retrieved data set or NWP model-based re-analysis is capable of completely fulfilling the needs in terms of temporal coverage, homogeneity and accuracy.

Objectives

The major objective of the workshop was to bring together the producers and users of water vapour data sets to define a useful water vapour data set for GEWEX.

• Review and assessment of the existing data sets for total column water vapour as well as temperature and water vapour profiles including an analysis of their appropriateness for long term climate applications needed by GEWEX. This includes the existing FCDRs (underlying radiance records) used for the creation of water vapour climatology as well as the variety of retrieval and mapping methods used in existing data sets;
• Critical assessment of the status of validation of the existing water vapour data sets build on satellite retrieval or model-based reanalysis;
• Development of an assessment procedure for water vapour data sets;
• Identification of critical gaps in the existing and planned data sets for climate applications; - Development of the optimal strategy for improving the data sets in view of the needs of GEWEX.

Topics

• GEWEX needs for 3D temperature and water vapour data
• Usage of radiance records and temperature/water vapour data sets in climate analysis providing feedback to the current products
• Existing temperature/water vapour data sets including radiance records and derived total column and temperature and water vapour profile data sets – current status, quality and possible improvement
• Validation methodology and data for temperature/water vapour data sets including reanalysis – existing comparison and validation results, independent reference data etc.

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