Self-service unpacking
Contents
Correction
An error in the worked example (-37.2 should have read +16.3) was corrected on 2.2.04. Thanks to Peter Droogers.
Introduction
The scenario data-sets (TYN SC 1.0 and TYN SC 2.0) are very large. To reduce data transfer volumes, the data-set is supplied in the form of a set of raw ASCII files. The user must download the raw files and then unpack them into the scenario data-sets. There are three ways in which the unpacking can be achieved:
Download
The raw files are supplied only via ftp. For access to the raw files, you must go through the data-set request procedure.
When you have obtained access to the raw files, you will find all the raw data files in the data subdirectory. At this point, if you have access to a Unix system, you may find it easier to download the archived version of the raw files, rather than each individual raw file. If you follow the archive route, all you need to download is:
If you do not follow the archive route, you will need to download everything in the data subdirectory except the archive* files. For either route, you only need to be download the files for the climate variables of interest to you.
If you have downloaded any archives, the raw files must be unarchived at the Unix prompt:
Whether you have followed the archive or non-archive route, many of the raw files will be in a compressed form. They will require decompression with 'uncompress'.
Ingredients
Definition
xvgsiym = ovim + o'viym + ( pvgsim * tgsy )
The calculated value must be checked to ensure that it lies within the permissible range. If the value is out-of-range, it must be corrected to the minimum or maximum permissible value, as appropriate.
The symbols used in the above equation are given in the two tables below: main characters in the first table, subscript characters in the second table. The 'units' given in the first table presume that the climate variable is precipitation; for other climate variables substitute the relevant unit wherever 'mm' appear. The 'file type' given in the first table is a backwards reference to the 'Ingredients' table.
Procedure
The sequence of operations that might be performed in carrying out the unpacking is summarised below. This is given as an example, and is not prescriptive: the user is at liberty to use any sequence that satisfies the above equation. As an example we show how to obtain, for the 0.5° grid-box (363, 286) containing Norwich (52° 38' N, 1° 19' E), the projection of precipitation in July 2081 under the scenario given by using the climate model HadCM3 to represent the A2 emissions scenario.
To follow this example through, use the relevant files. Most of the files are standard grids. The 'global warming' files are in a self-explanatory columnar format. The 'scenario selector' file was designed to inform my own fortran software, and contains:
The 'minimum' and 'maximum' files were included in order to simplify the additions that had to be made to an existing code base. They are not likely to be convenient if you are writing your own software. You can achieve the same effect by applying the values in the table below to every grid-box:
Please bear in mind that I do not offer any support for software design, coding, debugging, or execution. Your software is your responsibility! If you have any further questions, please read the data-set documentation and the Frequently Asked Questions (FAQ).
The raw files used as the ingredients in creating the scenario data-sets are given in the table below:
file type
contents
format
TYN SC 1.0
TYN SC 2.0
scenario selector
key values for individual scenarios
ASCII ordered list
scenarios.txt
scenarios.txt
response pattern
GCM patterns of change from 2070-2099
standard grid
*.2080s.ateam.*
hd*
global warming
time-series of global temperature change (2001-2100)
ASCII columns with headers
*-*.ann
*-*.ann
residual
detrended inter-annual variability from 1901-2000
standard grid
ateam.iavar*
iavar*
climatology
1961-1990 average climate
standard grid
obs*
obs*
minimum
minimum permissible value
standard grid
min.???.ann
min.???.ann
maximum
maximum permissible value
standard grid
max.???.ann
max.???.ann
Each datum (x) in any scenario is defined by the following equation:
symbol
variable
units
file
x
scenario datum
mm
-
o
(observed) climatology
mm
'climatology'
o'
(observed) residual
mm
'residual'
p
response pattern
mm °C-1
'response pattern', modified by 'scenario selector'
t
global warming
°C
'global warming'
symbol
variable
v
climate variable
g
climate model (GCM)
s
SRES emissions scenario
i
grid-box
y
year
m
month
The unpacking of the raw files into the scenario data-set comprises:
°C
PCM
CGCM2
CSIRO2
HadCM3
ECHam4
A1FI
3.045
4.382
4.855
4.863
1.000 (use A2)
A2
2.462
3.548
3.938
3.931
1.000
B2
1.894
2.462
3.139
3.070
1.000
B1
1.541
2.023
2.592
2.521
1.000 (use B2)
climate variable
units
minimum
maximum
temperature
°C
none (in theory -273.15)
none
precipitation
mm
0.0
none
diurnal temperature range
°C
0.1
none
vapour pressure
hPa
0.0
none
cloud cover
%
0.0
100.0