GEOS-Chem Newsletter January 2009

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Dear GEOS-Chem Users,

As we begin a new year it is always a good time to start new things. In this spirit, we are pleased to bring you the first GEOS-Chem newsletter. This is a quick summary of things that are going on w/r/t the GEOS-Chem model and user community.

Happy modeling!

Bob Yantosca, Philippe Le Sager, and Claire Carouge

GEOS-Chem Model Updates

Recent model updates:

  • v8-01-03
    • includes new version of TPCORE
  • v8-01-02
    • includes nested-grid capabilities for GEOS-5 (at present only China has been implemented)

Upcoming model updates (schedule subject to change)

ESMF update

Bob and Philippe are putting the finishing touches on an ESMF-ized emissions component, which will allow us to share the same emissions that are currently in GEOS-Chem with the GEOS-5 data assimilation system at NASA/GSFC. In the philosophy of ESMF, a sub-component for each inventory has been developed, which will greatly improve code maintenance in the future.

A few technical aspects are still at present being worked out (most of that involves the switchover from ESMF 2.2 to ESMF 3.1) but the work is proceeding forward nicely. We plan on hosting GSFC personnel Tom Clune and Max Suarez at Harvard in the near future for a meeting in which future coding strategy will be discussed.

GEOS-Chem Near-Real-Time Simulation

We are happy to announce that the GEOS-Chem Near-Real-Time Simulation is once again running! The NRT had been paused in order to allow us to fix a problem with the GEOS-5 optical depth fields (see below).

The simulation is currently being spun up to real time. As of Thursday, 1/15/09, the NRT has proceeded through mid-December 2008. It should reach near-time within the next couple of days or so.

You may view the NRT output online at:

For those of you who would like to download actual output files (i.e. bpch files, timeseries files, etc) from the NRT simulation, you may access those at:

 cd /pub/geos-chem/NRT-ARCTAS

there is a README file that describes the contents of the directory structure. In order to preserve disk space, we have to remove files older than a certain date (e.g. older than 60 days).

NOTE: For those of you who need to use the FLAMBE biomass emissions, we will store those indefinitely.

GEOS-5 Optical Depth Error and Solution

As previously mentioned, we recently discovered an error with the GEOS-5 optical depth fields, as described in this Wiki post.

The "quick fix" is to just multiply the cloud fraction by the optical depth. This is described in more detail here.

However, a better solution will involve reprocessing of the GEOS-5 met data archive (see below).

GEOS-5 Met Data Reprocessing

We are planning to reprocess the entire GEOS-5 met data set for these reasons:

  1. To fix the optical depth error described above.
  2. To upgrade our 2005-2007 GEOS-5 data files from the older GEOS-5.0.1 data product with the more recent GEOS-5.1.0 data product.
  3. To extract the GEOS-5.1.0 data product for the year 2004

At present the GEOS-5 met data from August 2008-January 2009 have been reprocessed. This period was reprocessed first so that we could restart the NRT simulation (see above).

The reprocessing of Jan - Aug 2008 will have the highest priority. This will allow GEOS-Chem users to run the model with the reprocessed GEOS-5 met for the ARCTAS time periods.

After 2008 is totally processed, we will start on the other years (including 2004, which we do not have at present).


  1. The met data reprocessing is totally automated, but the limiting factor is the file transfer speeds. We therefore ask for your patience in this matter.
  2. We will inform you (vie email or wiki) as we finish each year of GEOS-5 data reprocessing.
  3. GEOS-5.1.0 data was turned off in 2008. Therefore, starting with September 2008, we will use the GEOS-5.2.0 product. For more information, please see this Wiki post.

GEOS-Chem Meeting: April 7-10, 2009!

We hope to see you at the upcoming GEOS-Chem Meeting in April 2009! Please visit the following link for more information (including hotels & ground transportation options):

Stay tuned for more information!

Bob Y's group meeting

Bob Yantosca is scheduled to present a group meeting seminar on this upcoming Wednesday, Jan 21, 2009 at 12 Noon ET. He will speak about recent updates in GEOS-Chem and ESMF code development.

We will set up the usual telecon (stay tuned for phone # details). Here is a copy of Bob's presentation in PDF format. We hope that you will be able to join us.

--Bob Y. 10:53, 16 January 2009 (EST)