Definitions of the core climate extreme indices
There are 27 core climate extreme indices^{Footnote 1}
Index | Definition | Variable |
---|---|---|
Number of frost days (FD) |
Annual count of days when daily minimum temperature is less than 0°C. Let TN_{ij} be daily minimum temperature on day i in year j. Count the number of days where: TN_{ij} < 0°C |
minimum temperature |
Number of summer days (SU) |
Annual count of days when daily maximum temperature is greater than 25°C. Let TX_{ij} be daily maximum temperature on day i in year j. Count the number of days where: TX_{ij} > 25°C |
maximum temperature |
Number of icing days (ID) |
Annual count of days when daily maximum temperature is less than 0°C. Let TX_{ij} be daily maximum temperature on day i in year j. Count the number of days where: TX_{ij} < 0°C |
maximum temperature |
Number of tropical nights (TR) |
Annual count of days when daily minimum temperature is greater than 20°C. Let TN_{ij} be daily minimum temperature on day i in year j. Count the number of days where: TN_{ij} > 20°C |
minimum temperature |
Growing season length (GSL) |
Annual (January 1 to December 31 in Northern Hemisphere (NH), July 1 to June 30 in Southern Hemisphere (SH)) count between first span of at least 6 days with daily mean temperature greater than 5°C and first span after July 1 (January 1 in SH) of 6 days with daily mean temperature less than 5°C. Let TG_{ij} be daily mean temperature on day i in year j. Count the number of days between the first occurrence of at least 6 consecutive days with: TG_{ij} > 5°C and the first occurrence after July 1 (January 1 in SH) of at least 6 consecutive days with: TG_{ij} < 5°C. |
mean temperature |
Monthly maximum value of daily maximum temperature (TX_{x}) |
Let TX_{x} be the daily maximum temperatures in month k, period j. The maximum daily maximum temperature each month is then: TX_{xkj} = max(TX_{xkj}) |
maximum temperature |
Monthly maximum value of daily minimum temperature (TN_{x}) |
Let TN_{x} be the daily minimum temperatures in month k, period j. The maximum daily minimum temperature each month is then: TN_{xkj} = max(TN_{xkj}) |
maximum temperature |
Monthly minimum value of daily maximum temperature (TX_{n}) |
Let TX_{n} be the daily maximum temperatures in month k, period j. The minimum daily maximum temperature each month is then: TX_{nkj} = min(TX_{nkj}) |
minimum temperature |
Monthly minimum value of daily minimum temperature (TN_{n}) |
Let TN_{n} be the daily minimum temperatures in month k, period j. The minimum daily minimum temperature each month is then: TN_{nkj} = min(TN_{nkj}) |
minimum temperature |
Percentage of days when daily minimum temperature is less than the 10th percentile (TN10p) |
Let TN_{ij} be the daily minimum temperature on day i in period j and let TN_{in}10 be the calendar day 10th percentile centred on a 5-day window for the base period 1961-1990. The percentage of time for the base period is determined where: TN_{ij} = TN_{in}10. To avoid possible inhomogeneity across the in-base and out-base periods, the calculation for the base period (1961-1990) requires the use of a bootstrap procedure. Details are described in Zhang et al. (2005). |
minimum temperature |
Percentage of days when daily maximum temperature is less than the 10th percentile (TX10p) |
Let TX_{ij} be the daily maximum temperature on day i in period j and let TX_{in}10 be the calendar day 10th percentile centred on a 5-day window for the base period 1961-1990. The percentage of time for the base period is determined where: TX_{ij} < TX_{in}10. To avoid possible inhomogeneity across the in-base and out-base periods, the calculation for the base period (1961-1990) requires the use of a bootstrap procedure. Details are described in Zhang et al. (2005). |
maximum temperature |
Percentage of days when daily minimum temperature is greater than the 90th percentile (TN90p) |
Let TN_{ij} be the daily minimum temperature on day i in period j and let TN_{in}90 be the calendar day 90th percentile centred on a 5-day window for the base period 1961-1990. The percentage of time for the base period is determined where: TN_{ij} > TN_{in}90. To avoid possible inhomogeneity across the in-base and out-base periods, the calculation for the base period (1961-1990) requires the use of a bootstrap processure. Details are described in Zhang et al. (2005). |
minimum temperature |
Percentage of days when daily maximum temperature is greater than the 90th percentile (TX90p) |
Let TX_{ij} be the daily maximum temperature on day i in period j and let TX_{in}90 be the calendar day 90th percentile centred on a 5-day window for the base period 1961-1990. The percentage of time for the base period is determined where: TX_{ij} > TX_{in}90. To avoid possible inhomogeneity across the in-base and out-base periods, the calculation for the base period (1961-1990) requires the use of a bootstrap processure. Details are described in Zhang et al. (2005). |
maximum temperature |
Warm spell duration index (WSDI) |
Annual count of days with at least 6 consecutive days when daily maximum temperature is greater than the 90th percentile. Let TX_{ij} be the daily maximum temperature on day i in period j and let TX_{in}90 be the calendar day 90th percentile centred on a 5-day window for the base period 1961-1990. Then the number of days per period is summed where, in intervals of at least 6 consecutive days: TX_{ij} > TX_{in}90 |
maximum temperature |
Cold spell duration index (CSDI) |
Annual count of days with at least 6 consecutive days when daily minimum temperature is less than the 10th percentile. Let TN_{ij} be the daily minimum temperature on day i in period j and let TN_{in}10 be the calendar day 10th percentile centred on a 5-day window for the base period 1961-1990. Then the number of days per period is summed where, in intervals of at least 6 consecutive days: TN_{ij} < TN_{in}10 |
minimum temperature |
Daily temperature range (DTR) |
Monthly mean difference between daily maximum and minimum temperature Let TX_{ij} and TN_{ij} be the daily maximum and minimum temperature, respectively, on day i in period j. If I represents the number of days in j, then: DTR_{j} = $\frac{\sum _{i=1}^{I}(T{X}_{ij}-T{N}_{ij})}{I}$ |
minimum temperature maximum temperature |
Monthly maximum 1-day precipitation (Rx1day) |
Let RR_{ij} be the daily precipitation amount on day i in period j. The maximum 1-day value for period j are: Rx1day_{j} = max(RR_{ij}) |
precipitation |
Monthly maximum consecutive 5-day precipitation (Rx5day) |
Let RR_{kj} be the precipitation amount for the 5-day interval ending k, period j. Then maximum 5-day values for period j are: Rx5day_{j} = max(RR_{kj}) |
precipitation |
Annual count of days when precipitation is greater than or equal to 10mm (R10mm) |
Let RR_{ij} be the daily precipitation amount on day i in period j. Count the number of days where: RR_{ij} ≥ 10mm |
precipitation |
Simple precipitation intensity index (SDII) |
Let RR_{wj} be the daily precipitation amount on wet days, w (RR ≥ 1mm) in period j. If W represents number of wet days in j, then: SDII_{j} = $\frac{\sum _{w=1}^{W}R{R}_{wj}}{W}$ |
precipitation |
Annual count of days when precipitation is greater than or equal to 20mm (R20mm) |
Let RR_{ij} be the daily precipitation amount on day i in period j. Count the number of days where: RR_{ij} ≥ 20mm |
precipitation |
Annual count of days when precipitation is greater than or equal to "nnmm", nn is a user defined threshold (Rnnmm) |
Let RR_{ij} be the daily precipitation amount on day i in period j. Count the number of days where: RR_{ij} ≥ nnmm |
precipitation |
Maximum length of dry spell, maximum number of consecutive days with daily precipitation less than 1mm (CDD) |
Let RR_{ij} be the daily precipitation amount on day i in period j. Count the largest number of consecutive days where: RR_{ij} < 1mm |
precipitation |
Maximum length of wet spell, maximum number of consecutive days with daily precipitation greater than or equal to 1mm (CWD) |
Let RR_{ij} be the daily precipitation amount on day i in period j. Count the largest number of consecutive days where: RR_{ij} ≥ 1mm |
precipitation |
Annual total precipitation when daily precipitation is greater than the 95th percentile (R95pTOT) |
Let RR_{wj} be the daily precipitation amount on a wet day, 'w', (RR ≥ 1.0mm) in period i and let RR_{wn}95 be the 95th percentile of precipitation on wet days in the 1961-1990 period. If W represents the number of wet days in the period, then: R95p_{j} = $\sum _{w=1}^{W}$RR_{wj} where RR_{wj} > RR_{wn}95 |
precipitation |
Annual total precipitation when daily precipitation is greater than the 99th percentile (R99pTOT) |
Let RR_{wj} be the daily precipitation amount on a wet day, 'w', (RR ≥ 1.0mm) in period i and let RR_{wn}99 be the 99th percentile of precipitation on wet days in the 1961-1990 period. If W represents the number of wet days in the period, then: R99p_{j} = $\sum _{w=1}^{W}$RR_{wj} where RR_{wj} > RR_{wn}99 |
precipitation |
Annual total precipitation in wet days (PRCPTOT) |
Annual total precipitation in wet days: Let RR_{ij} be the daily precipitation amount on day i in period j. If I represents the number of days in j , then: PRCPTOT_{j} = $\sum _{i=1}^{I}$RR_{ij} |
precipitation |