Source:         Princeton University
Name:           Princeton Global Forcings V2 (March 2014)
Period:         Jan-1901 - Dec-2012
Times:          3-hourly, daily, monthly
Coverage:       Global
Resolution:     1.0-degree, 0.5-degree
Grid:           Latitude-longitude
Type:           Observational-Reanalysis hybrid
Related Sites:	http://hydrology.princeton.edu/data/index.html
Publications:   Sheffield, J., G. Goteti, and E. F. Wood, Development of a
		50-yr high-resolution global dataset of meteorological forcings for land
		surface modeling, J. Climate, 19 (13), 3088-3111.
Timestamp:	All data are averages over the timestep, starting at the timestamp of the record (e.g. 3-hourly precipitation at 0hr is the average precipitation from 0-3hr) 
Variables:	Precipitation (prcp) [kg m-2 s-1] equivalent to [mm/s]
		Air temperature at 2m above ground (tas) [K]
		Downward longwave at surface (dlwrf) [W m-2]
		Downward shortwave at surface (dswrf) [W m-2]
		Surface pressure (pres) [Pa]
		Specific humidity (shum) [kg kg-1]
		Windspeed (wind) [m s-1]
Formats:        NetCDF V4 compressed
History:	Original data	
Volume:         1.0deg	3hourly: 722 - 724 MB/year/variable; daily: 90 MB/year/variable; monthly: 3 MB/year/variable 
		0.5deg	3hourly: 1.7 - 2.1 GB/year/variable; daily: 90 - 280 MB/year/variable; monthly: 12 MB/year/variable 
Date Created:   Mar 24 2014
Change Log:     

4) 8 Feb 2015
Some of the 0.5-deg daily files (1914, 1919, 1923) had a few missing temperature 
related values (tas, shum, tmax, tmin) because of the DTR problem (Oct 2014). All 
0.5-deg (3-hourly, daily, monthly) files for tas, shum , tmax, tmin files for 
1901-1947 were updated.

3) 15 June 2015
Large inconsistencies (up to a few K) were found in the monthly 0.5deg tas data when
compared to the CRU monthly data, which are used for scaling the 3-hourly and
daily data. This problem also affected files for shum, tmax and tmin. The 
scripts were re-run for 1901-1947 and the problem fixed. All files for 0.5deg 
(3-hourly, daily, monthly) for tas, shum, tmax, tmin files for 1901-1947 were updated.

2) 15 Oct 2014
Very low (or zero) values of DTR in the CRU dataset, especially over central
Europe in a few years, resulted in missing values in the daily Tmin and Tmax. 
DTR was set to a minimum value and all 3-hourly, daily and monthly Tas, Tmin, 
Tmax and Shum files have been updated. Monthly files for all variables
recalculated.
 
1) Mar 24 2014
Version 2 of the PGF created and uploaded to website.
This version extends the original version (V1) to 1901-2012, and includes 
improvements to the downscaling and bias-correction methods, and updated 
versions of the monthly observational datasets.