Table 1.

CRU TS variables, showing codes, units, correlation decay distances (CDDs) and precursors.

Variables	Code	Units	CDD (km)	Precursors
Variables - primary
Mean 2 m temperature	TMP	degrees Celsius	1200	None
Diurnal 2 m temperature range	DTR	degrees Celsius	750	TMN, TMX databases
Precipitation rate	PRE	mm/month	450	None
Variables - secondary
Vapour pressure	VAP	hPa	1000	TMP, DTR
Wet days (Notes 1, 2)	WET	days	450	PRE
Cloud cover	CLD	percentage	600	DTR
Variables - derived
Frost days (Note 3)	FRS	days per month	750	TMN
Minimum 2 m temperature (Note 4)	TMN	degrees Celsius	1200	TMP, DTR
Maximum 2 m temperature (Note 4)	TMX	degrees Celsius	1200	TMP, DTR
Potential evapo-transpiration (Note 5)	PET	mm/day	n/a	TMP, TMX, TMN, VAP, CLD

Note 1: A wet day is one receiving ≥0.1 mm precipitation.

Note 2: Used in diverse areas, including evaluation of satellite observations³² and evaluation of potential evapotranspiration equations³⁶.

Note 3: Also used in many areas, including dendroclimatology³⁷ and health³⁸.

Note 4: Used to calculate scPDSI for monitoring drought³⁹, and in areas including regional agronomic production⁴⁰ and river basin vegetation⁴¹.

Note 5: minimum and maximum temperatures are the monthly means of the individual daily minimum and maximum temperatures; they are not the overall minimum or maximum temperature recorded in each month.