The ensemble of 11 simulations using the Hadley Centre regional climate model (RCM) has some benefits over UKCP09 products when used in certain circumstances. These benefits include:
1. An improved representation of regional climate extremes
The higher spatial resolution of the 11-member RCM ensemble than that of global climate models means that the representation of small-scale meteorological processes is improved. This leads to better representation of regional weather and climate extremes (such as regional precipitation events). However, the RCM ensemble members inherit biases at larger scales from the global climate models used to drive them, which contribute to limitations in their ability to represent regional extremes. (See Box 2 of the Briefing Report, in the Reports & guidance section, for further information on this point).
2. Continuous (transient) climate projections
The 11-member RCM provides continuous (or transient) projections from 1950 right through to 2099 while the UKCP09 probabilistic projections provide projections of 30-year climate averages for a set of overlapping period. Because of this, you are able to investigate variability in the projections from year-to-year, alongside the emergence of climate change signals over multiple decades.
3. Daily data
In addition to providing information for individual months and seasons (see above), the 11-member RCM data also provides daily information for a large number of variables for all 25 km grid boxes, adding to its flexibility. Daily information can also be gained from the UKCP09 Weather Generator. Unlike the RCM data, the Weather Generator can provide a set of daily time series consistent with the full range of long-term climate changes represented in the probabilistic projections. However, the RCM data can provide spatially coherent time series for a wider range of variables (see below).
4. Projections that are spatially and temporally coherent
The 11-member RCM ensemble provides projections with full spatial and temporal coherence. This means that you are able to aggregate daily data from a number of grid squares to produce averages over a larger area. Spatial coherence also means that users can assess impacts of weather events or climate changes that occur simultaneously in several different places. Temporal coherence means that each RCM member provides an evolution of variability and change that is fully consistent over the entire 21st century.
5. A larger number of variables
The 11-member RCM data provides a wider range of variables than the UKCP09 Weather Generator - which is the other source of daily information.