Over 40 climate extreme indices

The ETCCDI indices refer to a standardised set of climate extremes indices developed by the Expert Team on Climate Change Detection and Indices (ETCCDI). This initiative was sunset in 2018 but these indices and their variants are still widely used by scientists and adaptation practitioners to quantify and analyse changes in climate extremes such as heat waves, cold spells, heavy rainfall, droughts, and more, based on daily temperature and precipitation data. The ETCCDI set of indices is listed below based on the underlying weather variable.

ETCCDI indices based on daily precipitation (18 indices)

• Precipitation days Index: Number of days with precipitation exceeding 5 mm/day
• Heavy precipitation days Index: number of days with precipitation exceeding 10 mm/day
• Very heavy precipitation days Index: number of days with precipitation exceeding 20 mm/day
• Dry days Index: number of consecutive days with no precipitation (< 1 mm)
• Consecutive Dry days Index: largest number of consecutive Dry days
• Number of consecutive Dry days periods: number of 5-consecutive Dry days periods
• Wet Days Index: number of days with precipitation (> 1 mm)
• Consecutive wet days Index: largest number of consecutive Wet days
• Number of consecutive wet days periods: number of 5-consecutive Wet days period
• Moderate wet days: Percentage of Moderate Wet Days (precipitation > 75th percentile) during Wet days
• Wet days: Percentage of Wet Days (precipitation > 90th percentile) during Wet days
• Very wet days: Percentage of Very Wet Days (precipitation > 95th percentile) during Wet days
• Precipitation fraction due to moderate wet days
• Precipitation fraction due to wet days
• Precipitation fraction due to very wet days
• Highest one day precipitation amount
• Highest 5 days precipitation amount
• Mean precipitation amount at wet days

ETCCDI indices based on daily mean temperature (7 indices)

• Cold days Index: Percentage of days, centred on a five-day window, with temperature below the 10th percentile
• Warm days Index: Percentage of days, centred on a five-day window, with temperature above the 90th percentile
• Cold-spell days Index: Days in intervals of at least 6 days with temperature < 10th percentile
• Cold-spell days periods: periods in intervals of at least 6 days with temperature < 10th percentile
• Warm-spell days Index: days in intervals of at least 6 days with temperature > 90th percentile
• Warm-spell days periods: periods in intervals of at least 6 days with temperature > 90th percentile
• Heating degree days: sum of degrees below 18°C.

ETCCDI indices based on daily maximum temperature (8 indices)

• Very cold days: Percentage of days, centred on a five-day window, with temperature below the 10th percentile
• Very warm days: Percentage of days, centred on a five-day window, with temperature above the 90th percentile
• Ice days Index: number of days with temperature below 0°C
• Summer days Index: number of days with temperature above 25°C
• Consecutive summer days Index: largest number of consecutive Summer days
• Consecutive summer days periods: number of 5-consecutive Summer days periods
• Heat wave duration Index: largest number of consecutive days with temperature at least 5°C above the average
• Heat wave duration periods: number of 6 consecutive days periods with temperature at least 5°C above the average

ETCCDI indices based on daily minimum temperature (8 indices)

• Cold nights (TN10p): percentage of days with a daily minimum temperature below the 10th percentile, centred on a five-day window
• Warm nights (TN90p): percentage of days with a daily minimum temperature above the 90th percentile, centred on a five-day window
• Tropical nights (TR): number of days with a daily minimum temperature above 20°C
• Frost days Index (< 0°C): number of days with temperature below 0°C
• Consecutive frost days Index: largest number of consecutive Frost days
• Consecutive frost days periods: number of periods of five consecutive days with temperature below 0°C
• Cold wave duration Index: largest number of consecutive days with temperature at least 5°C below the average
• Cold wave duration periods: number of 6 consecutive days periods with temperature at least 5°C below the average