: Model Data
: HadCM3 Data
SO&P: HadCM3 Geographic pattern of sea level anomalies
control : 1243-2252 constant forcings
Important notes regarding the HadCM3 data:
- Do not redistribute data to others outside the SO&P project.
- Hadley Centre will require co-authorship and need to know from the start
what analyses you are using the HadCM3 data for. Please contact
Simon Tett (see SO&P
participants table) and keep him informed.
- To ensure collaboration between SO&P partners, please refer to the
list of ongoing/planned model-data
comparisons. Please contact
others who have listed an interest in the same area, to initiate
collaboration. To add your planned areas of model-data work to the list,
email Tim Osborn.
- A small climate drift, unrelated to the external forcings, is present
in the HadCM3 simulations. It's significance depends on the region and
variable being considered. Simon Tett describes how this should be dealt
with, by reference to the HadCM3 control simulation, in this report (not yet
available). The HadCM3 control simulation data is not yet available.
- Please inform Tim Osborn
of any errors that you find in the data.
For important notes regarding the
For important notes regarding the
Obtaining fields of model data
Fields of model data, covering the entire globe, are available in netCDF
format only (please email Tim Osborn
if you cannot use netCDF files). For monthly and seasonal-mean data, there
is usually one file for each decade (though not always and the filenames or
headers will make it clear when this is not the case). For annual data
there are usually separate files for each year.
The netCDF header contains all the information
about coordinates and units that you need.
You have two options for downloading the files:
Note that the data files use the HadCM3 variable name instead of the
variable name used on the SO&P website. Instead of
sealv, the files are named
- Use wget with the command listed below
to obtain the wget software, to understand its options and for an explanation of its advantages):
wget --mirror --no-parent --no-directories --accept=nc --http-user=soaphad --http-passwd=xe2005 http://www.cru.uea.ac.uk/cru/projects/soap/pw/data/model/hadcm3/soaparchive/control/nc/surface.y/
- Click here
to see a listing of all files, and right-click each one that you want to download/save.
Note also that the units used in the data files may be different to those given
in the time series plots/data, because I converted some variables to more common units.
Refer to the netCDF file headers for the units used (and any notes below regarding
errors in this information).
For this variable, I multiplied the data files by 0.1
to convert the data to mm.
Select alternative simulation for this variable:
Select alternative variable from this simulation:
Important notes regarding the 'control' simulation:
- The 'control' simulation has constant external forcings, representative
of (approximately) pre-industrial conditions (though, for example, the
vegetation cover is set to present day).
- In the SO&P web archive we have 1010 years of data from the 'control'
simulation. The 'control' simulation actually began 750 years earlier, so
essentially we have years 751 to 1760 of the simulation (these are
not calendar years!). Even at this stage in the simulation, there are
some residual climate drifts (trends) in certain variables.
- What does the "year" in the control simulation mean? In the
actual netCDF data files provided by the Hadley Centre, the first year of
the 'control' run was given the year nominal year "1530", and so the years
751 to 1760 that we have are given nominal years "2280" to "3289". The
'nat' simulation was started from the 1000th year of the 'control'
simulation (nominal year "2529" in the netCDF files). The 'nat'
simulation is associated with specific calendar years (because the
time series of external forcings represents calendar years 1492-1999).
Therefore, to compare the 'nat' run with the 'control'
run, we need to compare calendar years 1492-1999 with 'control' run
nominal years "2529"-"3036" (in fact, in SO&P we are using calendar years 1500-1999,
which can be compared with 'control' run nominal years "2537"-"3036").
The 'all' simulation begins in calendar year 1750, and because it starts from
the calendar year 1750 conditions of the 'nat' run, its relationship with the control run is the
same (i.e., calendar years 1750-1999 should be compared with 'control' run
nominal years "2787"-"3036"). The following table may help:
|Year conversions||nominal year in netCDF files||year of the control run||corresponding calendar year of nat/all runs
|start of control run||"1530"||1||N/A
|start of control run data held by SO&P||"2280"||751||1243 AD
|start of nat run||"2529"||1000||1492 AD
|start of nat run data used by SO&P||"2537"||1008||1500 AD
|start of all run||"2787"||1258||1750 AD
|end of nat and all runs||"3036"||1507||1999 AD
|end of control run data held by SO&P||"3289"||1760||2252 AD
- To simplify things, just subtract 1037 from the nominal year stored in the 'control'
run data files to convert it to a calendar year for comparison with the 'nat' and
'all' simulations. In the time series files this has already been done.
Important notes regarding the
- It is extremely important to realise that the sealv variable does not
contain the correct global-mean changes.
- The global-mean of the sealv data from any one year
should be calculated (using area-weighting of each grid cell, which is proportional
to the cosine of the latitude of the cell) and subtracted from the sea level at
every individual grid cell for the same year.
This will yield patterns of local sea level deviations from the global-mean for that
- To obtain the actual simulated local sea levels, the correct global-mean value of sea level
for the year (see HadCM3 global-mean sea level)
should be added to the pattern of local sea level deviations.
- By adding the sum of (1) the global ocean expansion and (2) the global glacier/small-ice-cap
melt component, then the local sea levels will capture both components plus the local deviations
- Note also that the absolute values are arbitrary (there is no definition of "zero" sea level)
and so some adjustment to a common baseline period is necessary before comparing different
regions and/or different model simulations.
- A suggested adjustment is this: after combining the local and global changes as
described above, subsequently add a constant to each grid cell's sea level time series so that
it has zero mean over the 1500-1549 period in the 'nat' simulation. For the 'all' simulation,
add a constant to each grid cell's sea level time series so that it has the same mean as
the adjusted 'nat' series over the 1750-1799 period.
Last updated: August 2004, Tim Osborn