[cam-users] site history capability

Mon, 03 Feb 2003 10:32:24 -0800

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Dear CAM users:
=20
For some CAM applications it is desirable to save model history at =
selected grid cells. For example, if detailed measurements are available =
only at selected sites, one would like to save detailed history only at =
grid cells corresponding to those sites. Examples of sites include the =
three DOE ARM sites, NASA AERONET sites, NOAA CMDL Baseline =
Observatories, or the locations of intensive field experiments.
=20
CAM presently requires model history to be written at all model grid =
cells. If frequent time sampling of many fields is required at selected =
grid cells, the same time sampling and fields must be applied to all =
model grid cells. This can produce very large history data volumes if =
the simulation is longer than a month.

To facilitate saving model history at selected sites, I have modified =
CAM2.0 so that auxillary history files can be written for selected =
sites. The site history file options are the same as for the normal =
gridded history files, allowing the user to save time averaged, =
instantaneous, min, or max values for any averaging period and sampling =
frequency for any set of history variables. This allows, for example, =
saving instantaneous history for each time step at each site. The user =
specifies a list of site latitudes, longitudes, and names, and =
identifies an auxillary history file as a site history file with =
selected history fields and time sampling. The history is written in =
netcdf format for the grid cells closest to the selected sites.

This capability has been introduced by modifying just a few code files. =
It has been tested on a linux workstation and on a linux cluster. I =
would be happy to share these files with interested users. More =
importantly, I would like to support this option as a permanent feature =
of the CAM history. But to do so I need to know if there is sufficient =
interest. This issue could be raised at the upcoming AMWG meeting, but =
it need not be (I will not be attending it). I just need a show of =
support for it now. If there is sufficient demand for it, I will propose =
it as a permanent feature, and produce a developmental branch that =
would, if approved by the CAM leadership, be folded into the trunk of =
CAM.

So please let me know if you would like to see this feature adopted as a =
permanent feature of CAM.

-Steve Ghan

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<DIV><SPAN class=3D710421118-03022003>Dear CAM users:</SPAN></DIV>
<DIV><SPAN class=3D710421118-03022003></SPAN>&nbsp;</DIV>
<DIV><SPAN class=3D710421118-03022003>For some CAM applications it is =
desirable to=20
save model history at selected grid cells. For example, if detailed =
measurements=20
are available only at selected sites, one would like to save detailed =
history=20
only at grid cells corresponding to those sites. Examples of sites =
include the=20
three DOE ARM sites, NASA AERONET sites, NOAA CMDL Baseline =
Observatories, or=20
the locations of intensive field experiments.</SPAN></DIV>
<DIV><SPAN class=3D710421118-03022003></SPAN>&nbsp;</DIV>
<DIV><SPAN class=3D710421118-03022003>CAM presently requires model =
history to be=20
written at all model grid cells. If frequent time sampling of many =
fields is=20
required at selected grid cells, the same time sampling and fields must =
be=20
applied to all model grid cells. This can produce very large history =
data=20
volumes if the simulation is longer than a month.</SPAN></DIV>
<DIV>
<P>To facilitate saving model history at selected sites, I have modified =
CAM2.0=20
so that auxillary history files can be written for selected sites. The =
site=20
history file options are the same as for the normal gridded history =
files,=20
allowing the user to save time averaged, instantaneous, min, or max =
values for=20
any averaging period and sampling frequency for any set of history =
variables.=20
This allows, for example, saving instantaneous history for each time =
step at=20
each site. The user specifies a list of site latitudes, longitudes, and=20
names<SPAN class=3D710421118-03022003>,</SPAN> and identifies an =
auxillary history=20
file as a site history file with selected history fields and time =
sampling. The=20
history is written in netcdf format for the grid cells closest to the =
selected=20
sites.</P>
<P>This capability has been introduced by modifying just a few code =
files. It=20
has been tested on a linux workstation and on a linux =
cluster.&nbsp;<SPAN=20
class=3D710421118-03022003>I would be happy to share these files with =
interested=20
users. More importantly, I would like to support this option as a =
permanent=20
feature of the CAM history. But to do so I need to know if there is =
sufficient=20
interest. This issue could be raised at the upcoming AMWG meeting, but =
it need=20
not be (I will not be attending it). I just need a show of support for =
it now.=20
If there is sufficient demand for it, I will propose it as a permanent =
feature,=20
and produce a developmental branch that would, if approved by the CAM=20
leadership, be folded into the trunk of CAM.</SPAN></P>
<P><SPAN class=3D710421118-03022003>So please let me know if you would =
like to see=20
this feature adopted as a permanent feature of CAM.</SPAN></P>
<P><SPAN class=3D710421118-03022003></SPAN>-Steve =
Ghan</P></DIV></BODY></HTML>

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