Dictionnaire des indices

Rain indices
Heat indices
Drought indices
Compound indices
Cold indices
Temperature indices

Cold indices

FD
● Frost days $(T N < 0 ° C)$ (Days)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ . Then counted is the number of days where:

$T N_{i j} < 0 ° C$

CFD
● Maximum number of consecutive frost days $(T N < 0 ° C)$ (Days)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ . Then counted is the largest number of consecutive days where:

$T N_{i j} < 0 ° C$

ID
● Ice days $(T X < 0 ° C)$ (Days)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ . Then counted is the number of days where:

$T X_{i j} < 0 ° C$

HD17
● Heating degree days (sum of $17 ° C - T G)$ ( $° C$ )

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ . Then the heating degree days are:

$H D 17_{j} = \sum_{i = 1}^{I} (17 ° C - T G_{i j})$

GSL
● Growing season length (days)

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ . Then counted is the number of days between the first occurrence of at least 6 consecutive days with:

$T G_{i j} > 5 ° C$

and the first occurrence after 1 July of at least 6 consecutive days with:

$T G_{i j} < 5 ° C$

TXn
● Minimum value of daily maximum temperature (°C)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ . Then the minimum of daily maximum temperature is:

$T X n_{j} = min (T X_{i j})$

TNn
● Minimum value of daily minimum temperature (°C)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ . Then the minimum of daily minimum temperature is:

$T N n_{j} = min (T N_{i j})$

TN10p
● Number of days with TN < 10th percentile of daily minimum temperature (cold nights) (days)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ and let $T N_{i n} 10$ be the calendar day 10th percentile calculated for a 5 day window centred on each calendar day in the 1961-1990 period. Then counted is the number of days where:

$T N_{i j} < T N_{i n} 10$

TG10p
● Number of days with TG < 10th percentile of daily mean temperature (cold days) (days)

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ and let $T G_{i n} 10$ be the calendar day 10th percentile calculated for a 5 day window centred on each calendar day in the 1961-1990 period. Then counted is the number of days where:

$T G_{i j} < T G_{i n} 10$

TX10p
● Number of days with TX < 10th percentile of daily maximum temperature (cold day-times) (days)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ and let $T X_{i n} 10$ be the calendar day 10th percentile calculated for a 5 day window centred on each calendar day in the 1961-1990 period. Then counted is the number of days where:

$T X_{i j} < T X_{i n} 10$

CSDI
● Cold-spell duration index (days)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ and let $T N_{i n} 10$ be the calendar day 10th percentile calculated for a 5 day window centred on each calendar day in the 1961-1990 period. Then counted is the number of days where, in intervals of at least 6 consecutive days:

$T N_{i j} < T N_{i n} 10$

GD4
● Growing Degree Days (°C)

Let $T G_{i j}$ be the daily mean temperature of day $i$ of period $j$ . Then the growing degree days are:

$G D 4_{j} = \sum_{i = 1}^{I} (T G_{i j} - 4 | T G_{i j} > 4 ° C)$

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Compound indices

HI
● Huglin Index (grape growth)

Let $T G_{i j}$ be the daily mean temperature at day $i$ and let $T X_{i}$ be the daily maximum temperature at day $i$ of the period 1 April to 30 September. Then the Huglin Index is:

$H I = \sum_{1 / 4}^{30 / 9} \frac{(T G_{i} - 10) + (T X_{i} - 10)}{2} K$

where $K$ is a coefficient for day length. See here for details.

BEDD
● Biologically Effective Degree Days

Let $T N_{i j}$ be the daily minimum temperature at day $i$ and let $T X_{i}$ be the daily maximum temperature at day $i$ of the period 1 April to 30 September. Then BEDD is a growing degree days measure for grapes:

$B E D D = \sum_{1 / 4}^{30 / 9} min ((max [(\frac{T X_{i} + T N_{i}}{2}) - b, 0]), 9)$

where $b$ is 10. See here for details.

CD
● Days with $T G <$ 25th percentile of daily mean temperature and $R R <$ 25th percentile of daily precipitation amount (cold/dry days)

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ and let $T G_{i n} 25$ be the calendar day 25th percentile calculated for a 5-day window centred on each calendar day in the 1961-1990 period. Let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1.0$ mm) of period $j$ and let $R R_{w n} 25$ be the 25th percentile of precipitation at wet days in the 1961-1990 period. Then counted is the number of days where:

$T G_{i j} < T G_{i n} 25$ and $R R_{w j} < R R_{w n} 25$

CW
● Days with $T G <$ 25th percentile of daily mean temperature and $R R >$ 75th percentile of daily precipitation amount (cold/wet days)

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ and let $T G_{i n} 25$ be the calendar day 25th percentile calculated for a 5-day window centred on each calendar day in the 1961-1990 period. Let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1.0$ mm) of period $j$ and let $R R_{w n} 75$ be the 75th percentile of precipitation at wet days in the 1961-1990 period. Then counted is the number of days where:

$T G_{i j} < T G_{i n} 25$ and $R R_{w j} > R R_{w n} 75$

WD
● Days with $T G >$ 75th percentile of daily mean temperature and $R R <$ 25th percentile of daily precipitation amount (warm/dry days)

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ and let $T G_{i n} 75$ be the calendar day 75th percentile calculated for a 5-day window centred on each calendar day in the 1961-1990 period. Let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1.0$ mm) of period $j$ and let $R R_{w n} 25$ be the 25th percentile of precipitation at wet days in the 1961-1990 period. Then counted is the number of days where:

$T G_{i j} > T G_{i n} 75$ and $R R_{w j} < R R_{w n} 25$

WW
● Days with $T G >$ 75th percentile of daily mean temperature and $R R >$ 75th percentile of daily precipitation amount (warm/wet days)

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ and let $T G_{i n} 75$ be the calendar day 75th percentile calculated for a 5-day window centred on each calendar day in the 1961-1990 period. Let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1.0$ mm) of period $j$ and let $R R_{w n} 75$ be the 75th percentile of precipitation at wet days in the 1961-1990 period. Then counted is the number of days where:

$T G_{i j} > T G_{i n} 75$ and $R R_{w j} > R R_{w n} 75$

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Drought indices

CDD
● Maximum number of consecutive dry days $(R R < 1 m m)$ (Days)

Let $R R_{i j}$ be the daily precipitation amount at day $i$ of period $j$ . Then counted is the largest number of consecutive days where:

$R R_{i j} < 1 m m$

SPI3
● 3-Month Standardized Precipitation Index

SPI is a probability index based on precipitation. It is designed to be a spatially invariant indicator of drought. SPI3 refers to precipitation in the previous 3-month period ( $+$ indicates wet; $-$ indicates dry).
See for details and the algorithm: Guttman, N.B. (1999) Accepting the standardized precipitation index: A calculation algorithm, J. Amer. Water Resources Assoc., 35 (2): 311-322.

SPI6
● 6-Month Standardized Precipitation Index

SPI is a probability index based on precipitation. It is designed to be a spatially invariant indicator of drought. SPI6 refers to precipitation in the previous 6-month period ( $+$ indicates wet; $-$ indicates dry).
See for details and the algorithm: Guttman, N.B. (1999) Accepting the standardized precipitation index: A calculation algorithm, J. Amer. Water Resources Assoc., 35 (2): 311-322.

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Heat indices

SU
● Summer days $(T X > 25 ° C)$ (days)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ . Then counted is the number of days where:

$T X_{i j} > 25 ° C$

CSU
● Maximum number of consecutive summer days $(T X > 25 ° C)$ (Days)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ . Then counted is the largest number of consecutive days where:

$T X_{i j} > 25 ° C$

TR
● Tropical nights $(T N > 20 ° C)$ (days)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ . Then counted is the number of days where:

$T N_{i j} > 20 ° C$

TXx
● Maximum value of daily maximum temperature (°C)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ . Then the maximum of daily maximum temperature is:

$T X x_{j} = max (T X_{i j})$

TNx
● Maximum value of daily minimum temperature (°C)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ . Then the maximum of daily minimum temperature is:

$T N x_{j} = max (T N_{i j})$

TN90p
● Number of days with TN > 90th percentile of daily minimum temperature (warm nights) (days)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ and let $T N_{i n} 90$ be the calendar day 90th percentile calculated for a 5 day window centred on each calendar day in the 1961-1990 period. Then counted is the number of days where:

$T N_{i j} > T N_{i n} 90$

TG90p
● Number of days with TG > 90th percentile of daily mean temperature (warm days) (days)

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ and let $T G_{i n} 90$ be the calendar day 90th percentile calculated for a 5 day window centred on each calendar day in the 1961-1990 period. Then counted is the number of days where:

$T G_{i j} > T G_{i n} 90$

TX90p
● Number of days with TX > 90th percentile of daily mean temperature (warm day-times) (days)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ and let $T X_{i n} 90$ be the calendar day 90th percentile calculated for a 5 day window centred on each calendar day in the 1961-1990 period. Then counted is the number of days where:

$T X_{i j} > T X_{i n} 90$

WSDI
● Warm-spell duration index (days)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ and let $T X_{i n} 10$ be the calendar day 90th percentile calculated for a 5 day window centred on each calendar day in the 1961-1990 period. Then counted is the number of days where, in intervals of at least 6 consecutive days:

$T X_{i j} > T X_{i n} 90$

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Rain indices

RX1day
● Highest 1-day precipitation amount (mm)

Let $R R_{i j}$ be the daily precipitation amount at day $i$ of period $j$ . Then the maximum 1-day value is:

$R X 1 d a y_{j} = max R R_{i j}$

RX5day
● Highest 5-day precipitation amount (mm)

Let $R R_{k j}$ be the precipitation amount for the five-day interval $k$ of period $j$ , where $k$ is defined by the last day. Then the maximum 5-day value is:

$R X 5 d a y_{j} = max R R_{k j}$

SDII
● Simple daily intensity index (mm/wet day)

Let $R R_{w j}$ be the daily precipitation amount for wet day $w$ ( $R R \geq 1$ mm) of period $j$ . Then the mean precipitation amount at wet days is given by:

$S D I I_{j} = \sum_{w = 1}^{W} R R_{w j} / W$

RR
● Precipitation sum (mm)

Let $R R_{i j}$ be the daily precipitation amount for day $i$ of period $j$ . Then sum values are given by:

$R R_{j} = \sum_{i = 1}^{I} R R_{i j}$

RR1
● Wet days ( $R R \geq 1$ mm) (days)

Let $R R_{i j}$ be the daily precipitation amount for day $i$ of period $j$ . Then counted is the number of days where:

$R R_{i j} \geq 1 m m$

R10mm
● Heavy precipitation days ( $R R \geq 10$ mm) (days)

Let $R R_{i j}$ be the daily precipitation amount for day $i$ of period $j$ . Then counted is the number of days where:

$R R_{i j} \geq 10 m m$

R20mm
● Very heavy precipitation days ( $R R \geq 20$ mm) (days)

Let $R R_{i j}$ be the daily precipitation amount for day $i$ of period $j$ . Then counted is the number of days where:

$R R_{i j} \geq 20 m m$

CWD
● Maximum number of consecutive wet days ( $R R \geq 1$ mm) (days)

Let $R R_{i j}$ be the daily precipitation amount for day $i$ of period $j$ . Then counted is the largest number of consecutive days where:

$R R_{i j} \geq 1 m m$

R75pTOT
● Precipitation fraction due to moderate wet days ( $R R > 75 t h$ percentile) (%)

Let $R R_{j}$ be the sum of daily precipitation amount for period $j$ and let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1$ mm) of period $j$ and $R R_{w n} 75$ the 75th percentile of precipitation at wet days in the 1961-1990 period. Then the fraction is determined as:

$R 75 p T O T_{j} = 100 * \frac{\sum_{w = 1}^{W} R R_{w j}, w h e r e R R_{w j} > R R_{w n} 75}{R R_{j}}$

R95pTOT
● Precipitation fraction due to very wet days ( $R R > 95 t h$ percentile) (%)

Let $R R_{j}$ be the sum of daily precipitation amount for period $j$ and let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1$ mm) of period $j$ and $R R_{w n} 95$ the 95th percentile of precipitation at wet days in the 1961-1990 period. Then the fraction is determined as:

$R 95 p T O T_{j} = 100 * \frac{\sum_{w = 1}^{W} R R_{w j}, w h e r e R R_{w j} > R R_{w n} 95}{R R_{j}}$

R99pTOT
● Precipitation fraction due to extremely wet days ( $R R > 99 t h$ percentile) (%)

Let $R R_{j}$ be the sum of daily precipitation amount for period $j$ and let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1$ mm) of period $j$ and $R R_{w n} 99$ the 99th percentile of precipitation at wet days in the 1961-1990 period. Then the fraction is determined as:

$R 99 p T O T_{j} = 100 * \frac{\sum_{w = 1}^{W} R R_{w j}, w h e r e R R_{w j} > R R_{w n} 99}{R R_{j}}$

R75p
● Days with ( $R R > 75 t h$ percentile of daily amounts (moderate wet days) (days)

Let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1$ mm) of period $j$ and $R R_{w n} 75$ the 75th percentile of precipitation at wet days in the 1961-1990 period. Then counted is the number of days where:

$R R_{w j} > R R_{w n} 75$

R95p
● Days with ( $R R > 95 t h$ percentile of daily amounts (very wet days) (days)

Let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1$ mm) of period $j$ and $R R_{w n} 95$ the 95th percentile of precipitation at wet days in the 1961-1990 period. Then counted is the number of days where:

$R R_{w j} > R R_{w n} 95$

R99p
● Days with ( $R R > 99 t h$ percentile of daily amounts (extremely wet days) (days)

Let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1$ mm) of period $j$ and $R R_{w n} 99$ the 99th percentile of precipitation at wet days in the 1961-1990 period. Then counted is the number of days where:

$R R_{w j} > R R_{w n} 99$

PRCPTOT
● Total precipitation in wet days ( $R R > 1$ mm) (mm)

Let $R R_{w j}$ be the daily precipitation amount at wet day $w$ ( $R R \geq 1$ mm) of period $j$ . Then the total is determined as:

$P R C P T O T_{j} = \sum_{w = 1}^{W} R R_{w j}$

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Temperature indices

TN
● Mean of daily minimum temperature (°C)

Let $T N_{i j}$ be the daily minimum temperature at day $i$ of period $j$ . Then mean values in period $j$ are given by:

$T N_{j} = \sum_{i = 1}^{I} T N_{i j} / I$

TG
● Mean of daily mean temperature (°C)

Let $T G_{i j}$ be the daily mean temperature at day $i$ of period $j$ . Then mean values in period $j$ are given by:

$T G_{j} = \sum_{i = 1}^{I} T G_{i j} / I$

TX
● Mean of daily maximum temperature (°C)

Let $T X_{i j}$ be the daily maximum temperature at day $i$ of period $j$ . Then mean values in period $j$ are given by:

$T X_{j} = \sum_{i = 1}^{I} T X_{i j} / I$

DTR
● Mean of diurnal temperature range (°C)

Let $T X_{i j}$ and $T N_{i j}$ be the daily maximum and minimum temperature at day $i$ of period $j$ . Then the mean diurnal temperature range in period $j$ is:

$D T R_{j} = \sum_{i = 1}^{I} | (T X_{i j} - T N_{i j}) | / I$

vDTR
● Mean absolute day-to-day difference in DTR (°C)

Let $T X_{i j}$ and $T N_{i j}$ be the daily maximum and minimum temperature at day $i$ of period $j$ . Then calculated is the absolute day-to-day difference in period $j$ :

$v D T R_{j} = \sum_{i = 1}^{I} | (T X_{i j} - T N_{i j}) - (T X_{i - 1, j} - T N_{i - 1, j}) | / I$

ETR
● Intra-period extreme temperature range (°C)

Let $T X_{i j}$ and $T N_{i j}$ be the daily maximum and minimum temperature at day $i$ of period $j$ . Then the extreme temperature range in period $j$ is:

$E T R_{j} = max (T X_{i j}) - min (T N_{i j})$

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Cold indices

FD

CFD

ID

HD17

GSL

TXn

TNn

TN10p

TG10p

TX10p

CSDI

GD4

Compound indices

HI

BEDD

CD

CW

WD

WW

Drought indices

CDD

SPI3

SPI6

Heat indices

SU

CSU

TR

TXx

TNx

TN90p

TG90p

TX90p

WSDI

Rain indices

RX1day

RX5day

SDII

RR

RR1

R10mm

R20mm

CWD

R75pTOT

R95pTOT

R99pTOT

R75p

R95p

R99p

PRCPTOT

Temperature indices

TN

TG

TX

DTR

vDTR

ETR