Climate Indicator Parameters¶
These are the definitions of the climate indicator parameters, as defined by the World Meteorological Organization Expert Team on Climate Change Detection and Indices (ETCCDI), now the Expert Team on Sector-specific Climate Indices.
Temperature¶
FD - Frost Days¶
Annual count of days when TN (daily minimum temperature) < 0°C. Let TNij be daily minimum temperature on day i in year j. Count the number of days where TNij < 0°C.
CFD - Consecutive Frost Days¶
Longest run of days in a year where the daily minimum temperature is less than 0°C.
SU - Summer Days¶
Annual count of days when TX (daily maximum temperature) > 25°C. Let TXij be daily maximum temperature on day i in year j. Count the number of days where TXij > 25 °C.
CSU - Consecutive Summer Days¶
Longest run of days in a year where the daily maximum temperature is greater than 25°C.
HD17 - Heating Degree Days (17 degrees Celsius threshold)¶
Annual sum of n - TM, where n is a base temperature and TM < n. In this case n = 17 degrees Celsius. A measure of the energy demand needed to heat a building.
ID - Ice Days¶
Annual count of days when TX (daily maximum temperature) < 0 °C. Let TXij be daily maximum temperature on day i in year j. Count the number of days where TXij < 0 °C.
TR - Tropical Nights¶
Annual count of days when TN (daily minimum temperature) > 20 °C. Let TNij be daily minimum temperature on day i in year j. Count the number of days where TNij > 20 °C.
TN10p/1X10p - Cold Days/Nights¶
Annual count of days where both daily maximum and minimum are below the 10th percentile.
TG10p - Cold Days¶
Annual count of days where the daily mean temperature is below the 10th percentile.
TN90p/TX90p Warm Days/Nights¶
Annual count of days where both daily maximum and minimum are above the 90th percentile.
TG90p - Warm Days¶
Annual count of days where the daily mean temperature is above the 90th percentile.
HWDI/CWDI - Heat/Cold Wave Duration Index¶
The longest length of heat wave or cold wave observed within a particular year. A heat (cold) wave is defined as a period with at least five consecutive days where daily maximum (minimum) temperatures exceed (are below) the local climatological normal by 5 °C (9 °F) or more.
HWFI/CWFI - Heat/Cold Wave Frequency Index¶
The total number of days that contribute to heat or cold waves. Heat and cold waves are defined with the same definition as the in the duration index: a period with at least five consecutive days where daily maximum (minimum) temperatures exceed (are below) the local climatological normal by 5 °C (9 °F) or more.
ETR - Extreme Temperature Range¶
The difference between the highest maximum temperature and lowest minimum temperature range observed in a particular month.
GSL - Growing Season Length¶
Annual count between the first span of at least 6 days with daily mean temperature TG >5 °C and the first span after July 1st (Jan 1st in SH) of 6 days with TG <5 °C.
Let TGij 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 TGij > 5 °C and the first occurrence after 1st July (Jan 1st in SH) of at least 6 consecutive days with TGij < 5 °C.
Annual means Jan 1st to Dec 31st in the Northern Hemisphere (NH); July 1st to June 30th in the Southern Hemisphere (SH).
Precipitation¶
R10mm/R20mm - Heavy and Very Heavy Precipitation Days¶
The number of days in a year when daily precipitation amount is above 10 mm (heavy) or 20 mm (very heavy).
Let RRij be the daily precipitation amount on day i in period j. Count the number of days where RRij ≥ 10 mm.
RX1day/RX5day - Max 1-day/5-day precipitation¶
The maximum precipitation total amount that occurs in 1-day or 5-day period.
CDD/CWD - Consecutive Dry/Wet Days¶
The maximum number of consecutive days with total daily precipitation of less than 1 mm.
Let RRij be the daily precipitation amount on day i in period j. Count the largest number of consecutive days where RRij < 1mm.
R75p/R95p - Moderate/Very Wet Days¶
The sum of the total precipitation on days when the daily total precipiation is at or above the 75th (moderate wet) and 95th (very wet) percentile.
R99p - Extremely Wet Days¶
The sum of the total precipitation in days when the daily total precipitation is at or above the 99th percentile.
R90N - Number of Events Greater than Long-Term 90th Percentile¶
The number of days with daily precipitation ≥ 90th percentile
R75pTOT and R99pTOT - Fraction Due to 75th and 99th Percentile Days¶
Fraction of the total annual precipitation that is a result of precipitation on days with daily amount above the 75th and 99th percentiles in the long-term distribution
R95T and R90T¶
Percent of the total annual precipitation days that have daily precipitation amounts above the 90th or 95th percentiles.
SDII - Simple Daily Intensity Index¶
The average daily precipitation amount on all wet days within a year.
Let RRwj 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 = (Sum of daily precipitation on wet days)/(number of wet days)
Prec90p - 90th percentile of rainday amounts¶
The value of daily rainfall amounts at the 90th percentile in the distribution over specified time window of observation