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Brief Description:

Climatic Research Unit (CRU) TS (time-series) datasets are month-by-month variations in climate over the last century or so. These are calculated on high-resolution (0.5x0.5 degree) grids, which are based on an archive of monthly average daily maximum and minimum temperatures provided by more than 4000 weather stations distributed around the world. They allow variations in climate to be studied. CRU TS 3.21 variables are cloud cover, diurnal temperature range, frost day frequency, PET, precipitation, daily mean temperature, monthly average daily maximum and minimum temperature, vapour pressure and wet day frequency for the period Jan. 1901 - Dec. 2012. In addition to updating the dataset with 2012 data, the v3.21 release corrects two errors in the v3.20 dataset.

Reference:

University of East Anglia Climatic Research Unit (CRU). [Phil Jones, Ian Harris]. CRU TS3.21: Climatic Research Unit (CRU) Time-Series (TS) Version 3.21 of High Resolution Gridded Data of Month-by-month Variation in Climate (Jan. 1901 - Dec. 2012), [Internet]. NCAS British Atmospheric Data Centre.

 

Temporal Coverage:

Monthly average values for 1901/01 to 2012/12.

Spatial Coverage:

2.0 degree latitude x 2.0 degree longitude global grid (180x91).
-89.75S – 89.75N, -179.75W – 179.75E.

Levels:

Just one level.

Data Format:

NetCDF.

 

CRU

Download path: 

/archive/Reanalysis/CRU/3.21

Variable:

Label

Variable

Units

Comments

cld

Cloud Cover

Percentage (%)

 

dtr

Diurnal Temperature Range

Degrees Celcius (℃)

The diurnal temperature range is the difference between the daily minimum and maximum temperatures

frs

Frost Day Frequency

Days

Frost days are constructed synthetically from monthly TMN. The process is described in: Representing Twentieth-Century Space-Time Climate Variability.

Part II: Development of 1901-96 Monthly Grids of Terrestrial Surface Climate; New et al (2000).

A frost day is a period of 24 hours in which the minimum temperature falls below 0°C. If the temperature stays below zero all day, that's an 'ice day'.

pet

Potential Evapotranspiration

Millimeters

The method used is the FAO (Food and Agricultural Organization) grass reference evapotranspiration equation (Ekstrom et al., 2007, which is based on Allen et al., 1994). It is a variant of the Penman Monteith method using the gridded TMP, TMN, TMX, VAP and CLD.

Note that PET values are mean mm/day for each month (with a scaling factor of 10 applied to the PET ascii (*.dat) files, but NOT the PET netcdf files (*.nc). The pet values in the datafiles therefore need to be muliplied by the number of days for each month to get the mean pet for that month.

pre

Precipitation

Millimeters

 

tmp

Daily Mean Temperature

Degrees Celcius (℃)

The daily 'mean' temperature is the mid-point (median) between the daily minimum and maximum temperatures.

tmn

Monthly Average Daily Minimum Temperature

Degrees Celcius (℃)

 

tmx

Monthly Average Daily Maximum Temperature

Degrees Celcius (℃)

 

vap

Vapor Pressure

hPa

 

wet

Wet Day Frequency (Rain Days per Month)

Days

 

 

 

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