Time series transformation tool: development and use in CCsP projects

Parallel to the development of the KNMI’06 climate scenarios in 2006, a tool was developed to
generate temperature and precipitation time series for the future. These time series are often
needed for climate impact and adaptation models. The aim of this time series transformation tool
is to alter a daily historical time series of precipitation or temperature in a way that corresponds to
one of the four KNMI’06 climate change scenarios for a selected time horizon.
Until now no official report was issued, describing all aspects of the KNMI transformation tool,
although an elaborate user guide is available on internet, and some popular-scientific publications
are available. Within the COM28-project (“Climate data”) this transformation tool was used
regularly. As part of this project, a scientific background report was written, that gives a description
of the tool together with an overview of the development of the program, the analyses performed
by KNMI to determine the limitations and advantages of the program.
After the first publication in 2006 the transformation tool has been further developed and
improved. This synthesis report gives an overview of the various versions of the temperature and
precipitation transformation tool, the differences between the versions and a few examples of the
analyses performed with the precipitation transformation tool (Chapter 2). The tool has been used
in a considerable number of “Climate changes Spatial Planning” projects, some with assistance of
KNMI. In Chapter 3 an overview is given of the projects that used the transformation tool, and the
versions used in each project.
Chapter 4 describes the advantages and limitations of the current time series transformation tool,
an example of the Delta-method, and it gives information on alternative methods for generating
time series for the future (Direct method and Stochastic weather generator). The chapter indicates
possible improvements and modifications in future versions of the transformation tool (e.g. more
climate variables) and whether it is useful to develop (further) other methods to generate time
series for the future. This is largely driven by user demands, which also are discussed shortly. Several
ongoing or starting projects already include several of the desired and possible developments. A few
examples are: “Theme 6: Climate projections” of the Knowledge for Climate programme, the project
“Kritische Zone” of the National Model and Data Centre, and the activities for the next generation
of the KNMI climate scenarios.