These three zip files are half_degree monthly and annual growing season average
PDSI from 1979 to the previous year.

The method of how PDSI is calculated is detailed in the Supporitng Online
Material (SOM) for the 2010 Science paper (Zhao and Running, 2010).

The data are stored in HDFEOS format with Geographic map projection.  For the
masked file, I use fill-value for these half-degree cells with MODIS
non-vegetated land cover.

Note that I have solved the spin-up issue by first running 1979 PDSI for 1,000
years so that soil water reach equalibrium with the 1979 monthly climate data
(temperature and precipiation).  Therefore, there is no such problem of initial
status as mentioned in the SOM for the Science paper.

Also note that when you calculate regional average, you must use area-weighted
average since Geographic map projection is not an equal-area map projection, a
mistake commonly made even by some top geo-scientists.

You may use C, Python (PyNIO) or ENVI to read the data.

I may update the data yearly.

Dr. Maosheng Zhao

Below is the head information of the HDFEOS

For Monthly HDFEOS
*******************************************************
 field name: PDSI
 field rank: 3
 field dimensional infomation:
 bands:PDSI 420
 YDim:PDSI 360
 XDim:PDSI 720
 420 360 720 
 data type: float32
 defined array in C: float32 data[420][360][720]
 scale_factor:    1.000000
 scale_factor_err:    0.000000
 add_offset:    0.000000
 add_offset_err:    0.000000
 calibrated_nt:    5
 valid_range:    -900.000000  900.000000
 _FillValue:    -999.000000
 long_name:  monthly PDSI from 1979 to 2013
 units:  none
*******************************************************


For annual growing season average
*******************************************************
field name: PDSI
field rank: 3
field dimensional infomation:
Bands:PDSI 35
YDim:PDSI 360
XDim:PDSI 720
35 360 720 
data type: float32
defined array in C: float32 data[35][360][720]
scale_factor:    1.000000
scale_factor_err:    0.000000
add_offset:    0.000000
add_offset_err:    0.000000
calibrated_nt:    5
valid_range:    -900.000000  900.000000
_FillValue:    -999.000000
long_name:  growing season mean PDSI from 1979 to 2013
units:  none
*******************************************************