2.1 Description of the maps, graphs and tables

This section presents – in graphical form – climatological information for the whole of the UK, including long-term average climates and changes and trends. It was suggested as an extension to the whole of the UK of the sort of information presented for Scotland in the SNIFFER report (Barnett et al. 2006), and hence we have followed the methods used in that report. We have modified the list of variables and derived quantities shown (Table 2.1) to be more in line with those planned to be available in the UKCP09 projections, where possible. Similar information on some additional climate variables is given in Perry (2006).

The climatological information shown in this section for the whole of the UK is as follows:

• Maps of the long-term averages (LTA) for the 30-year period 1961–1990 (the UKCP09 baseline period), by season and for the whole year.

• Maps of the long-term averages for the 30-year period 1971–2000, by season and for the whole year.

• Maps showing the differences (or percentage changes) between the above two long-term averages, that is (1971–2000) minus (1961–1990), by season and for the whole year.

• Maps showing the change between 1961 and 2006, based on a linear trend over that period, for each season and the whole year.

• Graphs of the smoothed time-series for 14 regions, from 1961–2006 (and from1914–2006 for temperature and precipitation) presented by season and for the whole year, smoothed to show decadal variations.

• Tables of changes (based on trends) for 14 regions from 1961–2006 (and from 1914–2006 for temperature and precipitation) presented by season and for the whole year. Linear regression was used to calculate the trend in each variable.

Eleven variables are considered in this report and the climatological information given for each is shown in Table 2.1. Standard meteorological seasons are used: December, January and February (Winter); March, April and May (Spring); June, July and August (Summer); and September, October and November (Autumn).

Most of the variables are self-explanatory; the definitions of the two quantities which are derived from temperature are given in Table A1.2. The degree day quantities are weighted temperature summations and include Heating Degree Days (HDD) and Cooling Degree Days (CDD). A detailed explanation of how HDD and CDD are calcuated is given in the Index.

For most of the variables all the information is given. The inhomogeneous nature of station data for wind speed, together with a relatively sparse (and changing) observational network, result in estimates of change and trends which are not robust, and so only the latest long-term average is shown. HDD, CDD and days of air frost, being annual totals, have no seasonal information.

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