Temperature related variables

Introduction

 
 

This section presents the analysis for:

 

 

Records of temperature are probably the most frequently analysed of all information linked to meteorology. A Met Office gridded dataset covers the period 1914 to 2004 and includes average, maximum and minimum daily temperatures. Figure 2 shows where the temperature recording stations are in Scotland.

 

Calculated temperature variables We can work out a number of other measures from the information we have on temperature. These measures are particularly significant for several sectors and can be better related to direct impacts of climate.

 

  • Heating degree days (HDD). This is an indicator of how much heat energy households use and represents the energy needed to keep a building at a constant temperature. The base temperature for working out a heating degree day is 15.5ºC. This means that if the average temperature is below 15.5ºC, the value of the HDD for that day would be 15.5ºC minus the average temperature. For example, if a day has an average temperature of 13.5ºC, this is equal to 2 heating degree-days (15.5-13.5). Typical figures at the start of the 1961 to 2004 period were 3200 HDD a year for North and East Scotland, and 2900 HDD a year for West Scotland.
  • Growing degree days (GDD). This is the sum of daily average temperatures above 5ºC. This represents the temperature above which grass grows. Typical values in the early 1960s were 950 GDD a year in North Scotland, 1000 GDD a year in East Scotland and 1150 GDD a year in West Scotland.
  • Growing season length (GSL). This is the number of days between the start and end of the growing season (GSE-GSS). In the early 1960s typical values for the length of the growing season were 213 days in East Scotland, 217 days in North Scotland and 237 days in West Scotland.
  • Growing season start date (GSS). This is the start date for the growing season (calculated from 1 January). We assume that the growing season starts on the fifth day in a row which has an average daily temperature of 5ºC or greater. During the 1960s the typical start date for the growing season was 12 April in EastmScotland, 10 April in North Scotland and 29 March in West Scotland.
  • Growing season end date (GSE). This is the end date for the growing season (calculate from 1 January). We assume that the growing season ends on the fifth day in a row with an average temperature of 5ºC or less. During the 1960s the typical end date for the growing season was 10 November in East Scotland, 12 November in North Scotland and 20 November in West Scotland.
  • Extreme temperature range (ETR) is the range between the highest maximum and lowest minimum temperature within a year.
  • We work out cold spells for the winter half-year (October to March). In this study we define it as the total length of any period, lasting six days or more, where the minimum temperature each day is at least 3ºC lower than the 1961 to 1990 average temperature for those days.