+----------------------------------------------------+-----------------+
|                                                    |                 |
|                                                    |                 |
| The IPCC Data Distribution Centre                  |                 |
|                                                    |                 |
| Data File Format                                   |                 |
+----------------------------------------------------+-----------------+

**Nomenclature**

The files have been given an eight letter prefix and three letter suffix
to make them compatible with all computers and media, thus the filename
structure is:

**cxxxyyyy.dat**

+---------------+--------------------------+--------------------------+
| yyyy =        | e.g. 6190 = 1961-1990;   |                          |
| Timeslice     | 0110=1901-1910; etc.     |                          |
+---------------+--------------------------+--------------------------+
| xxx= Variable | Variable                 | Units                    |
| Code          |                          |                          |
+---------------+--------------------------+--------------------------+
| cld           | Cloud Cover              | Percent                  |
|               |                          |                          |
| dtr           | Diurnal Temperature      | Deg. C \* 10             |
|               | Range                    |                          |
| frs           |                          | Days \*10                |
|               | Ground-frost Frequency   |                          |
| pre           |                          | (millimetres/day) \*10   |
|               | Precipitation            |                          |
| rad           |                          | W/sq.metre               |
|               | Radiation                |                          |
| wet           |                          | Days \*10                |
|               | Wet Day Frequency        |                          |
| tmp           |                          | Deg. C \* 10             |
|               | Mean Temperature         |                          |
| tmx           |                          | Deg. C \* 10             |
|               | Maximum Temperature      |                          |
| tmn           |                          | Deg. C \* 10             |
|               | Minimum Temperaure       |                          |
| vap           |                          | hPa \* 10                |
|               | Vapour Pressure          |                          |
| wnd           |                          | (met                     |
|               | Wind                     | re/se\<!\--SELECTION\--\ |
|               |                          | >\<!\--/SELECTION\--\>c) |
|               |                          | \* 10                    |
+---------------+--------------------------+--------------------------+

An example, therefore, is \"cpre1120.dat\": which contains mean monthly
1911-1920 precipitation.

**Data Format**

The format of the Observed Climate Download files is as follows.

Format (ASCII)

One file per year per variable.

The first and second lines of the file contain information on the grid
size, for example:

 

grd_sz xmin ymin xmax ymax n_cols n_rows n_months missing

0.5 0.25 -89.75 359.75 89.75 720 360 12 -9999

 

This is followed by 12 monthly grids that are n_cols by n_rows in size.
Each record contains n_cols (=720) columns longitude values, format
720i5, starting at xmin (= 0.25 deg East) and ending at xmax (=0.25 deg
West) The first record starts at January, ymax (=89.75 deg North) and
the last record is the row for December, ymin (=-89.75 deg South).
Co-ordinates represent the centre of each grid cell. Missing values
(Antarctica, oceans and major inland water bodies) are assigned integer
values of -9999.

 

To read in one year of data the following program should work:

 

program rd_ascii

c f90 program to read in an integer ascii grid with

c variable dimensions into a global grid (720x360x12)

c

parameter (n_cols=720,n_rows=360)

integer\*2 grid(n_cols,n_rows,12)

character infl\*72,fmt\*20

call getarg(1,infl)

if(infl.eq.\' \')then

write(\*,\*) \'Enter ascii grid file name\'

read(\*,\'(a72)\')infl

endif

open(1,file=infl,status=\'old\')

read(1,\*)

read(1,\*)xmin,ymin,xmax,ymax,ncols,nrows,nmonths,missing

grid=missing

fmt=\'( i5)\'

write(fmt(2:4),\'(i3)\')n_cols

do im=1,nmonths

do lat=1,n_rows

read(1,fmt)(grid(lon,lat,im),lon=1,n_cols)

enddo

enddo

end