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About the Weather Generator
About the Weather Generator
Weather Generator version 2.0 released, February 2011 – for an overview of changes, go to About the Weather Generator version 2.0 section.
It is a downscaling tool that can be used to generate statistically plausible daily and hourly time series. These time series comprise a set of climate variables at a 5 km resolution that are consistent with the underlying 25 km resolution climate projections.
Vulnerability, impacts and adaptation assessments often require higher temporal and spatial resolution climate information than are available from the probabilistic projections ( and 25 km grid squares respectively). Recognising this need, a decision was taken to include a weather generator tool that could be used within the context of the available probabilistic projections.
Use the links below to jump to headliines for each section, or the links to the left for more details.
The UKCP09 Weather Generator builds on a well-established method. It begins by developing statistical relationships among daily climate variables using a baseline period climate, and then introduces the UKCP09 projections to produce possible daily (and if required hourly) time series for future time periods. Generating time series that are consistent with the underlying probabilistic projections has necessitated the introduction of several innovations that are described in the Weather Generator report.
The UKCP09 Weather Generator provides:
Plausible multiple daily and hourly time series from 30 to 1000 years in length (length specified by user, with different options available for daily and hourly outputs), which are statistically equivalent and stationary. See the Online Weather Generator report.
- For one location ( square) or one location representative of an area up to a maximum of 40 contiguous 5 km grid squares (1,000 km2)
- For one 30-year time period
- For one UKCP09 emission scenario
Users will receive the following set of outputs:
- Control run – 100 time series of 30 years for the baseline period.
- Future climate runs – minimum of 100 time series of user-defined runs perturbed using a given future climate. The number and length of the time series can be set within specified limits by the user when configuring the Weather Generator request within the UKCP09 User Interface (the default is 30 years and 100 time series).
- Metadata – includes information on the request parameters selected, internal Weather Generator settings, seed values, model variant IDs used, etc.
- A column headers file – Climate variable column headers for the control and scenario runs. These are not included in the control and scenario files so that they can be automatically read into computer programmes.
- To investigate more local scale climate impacts.
- To explore some types of extreme events.
- To explore a sub-sample of the selected probabilistic projections’ distribution.
- To investigate the risk of threshold being exceeded.
- To obtain a representative daily climate sequence.
- Based on a well established methodology.
- Suitable for use with the UKCP09 probabilistic projections.
- Long time series.
- Outputs that can be used to generate derived climate indices.
- That rainfall and wet-dry sequences can be used to estimate other variables.
- That observed relationships between daily variables are not allowed to change over time.
- That hourly values can be disaggregated from daily values.
- That time series generated are for a point representative of the climate for the chosen grid square or area.
- It is not a physically-based climate model
- Quality of ouput depends on quality of input data
- Translating climate projections into time series introduces an additional source of uncertainty
- Potentially large resource requirement
- Validation is crucial
- Outputs are not spatially consistent
- Estimation of some types of extreme events not necessarily possible
- Weather generator output is not a weather forecast!
- Poor representation of large scale climate processes
- Last updated: Sunday, 11 March 2012