Increasing
the Interoperability of an Earth System Model:
Atmospheric-Ocean Dynamics and Tracer Transports
NCC4-624
Milestone B: FY02 Annual Report
January 2002 – January 2003
1. Objectives
The objectives of this project are twofold:
1.1 Demonstrate interoperability at the model level using the ESM (Earth System
Model) Framework (ESMF). Build demonstration ESM using the AGCM/OGCM and/or
components developed by other modeling teams supported by this CAN.
1.2 Estimate the sensitivity of simulated Southern Oscillation structures to
different background states of the coupled ocean-atmosphere
system, including testing the impact of NASA data in improving El Niño
predictions.
2. Approach
For
Objective 1.1, the approach is based on designing interfaces between the ESMF
and an expanded version of the UCLA ESM, including components developed by other
groups. Towards this objective, C. Roberto Mechoso (PI), John Farrara and Joseph
Spahr attended the ESMF Team Meeting, September 24th-26th 2002 at NCAR, Boulder,
CO. Also, Cecelia Deluca (ESMF Development Team) visited UCLA on January 13,
2003. Shujia Zhou, Brice Womack (both NASA GSFC) and Phil Merkey (Univ. of Michigan)
visited UCLA on Oct. 14-15 to discuss issues related to the ESM codes and their
future interface to the ESMF. Mechoso, Farrara and Spahr reviewed the ESMF Architecture
document.
The sensitivity study referred to in Objective
1.2 will be performed with the UCLA AGCM/LANL POP combination, and the testing
with UCLA AGCM/MIT OGCM combination. The latter will build on work at the JPL
Ocean Data Assimilation Project.
John Baumgardner (co-PI) is in the process of
coupling the AGCM to the global version of POP. The ENSO prediction work in
our project will be carried out primarily with the Tropical Pacific version
of the ocean model. Nevertheless, it is of great scientific interest to validate
the coupled model performance when the high latitudes are interactive, particularly
in view of the importance for climate of feedbacks associated with variations
in the sea-ice. Dimitris Menemenlis (Co-PI) collaborating with Joe Spahr succeeded
in coupling low-resolution versions of the models with encouraging results.
Similar work with the high-resolution versions is in progress.
3. Scientific Accomplishments
The
current UCLA Earth System Model (ESM) comprises four models representing the
coupled dynamics, physics and chemistry of the global atmosphere and world oceans:
1) an atmospheric general circulation model (UCLA AGCM), 2) an oceanic general
circulation model (Parallel Ocean Model: POP), 3) an atmospheric chemistry and
transport model (UCLA ACTM), and 4) a JPL Ocean Chemical Transport Model (OCTM).
Data exchanges are carried out through a novel Distributed Data Broker (DDB).
Our Round 3 project is based on the AGCM, POP (also in a version with a hybrid
vertical coordinate or HYPOP), and the DDB. The ocean general circulation model
developed at MIT will be incorporated as an option. The report for Milestone
A includes a detailed description of the ESM components. Our project will demonstrate
the ESMF functionality by analyzing the El Niño prediction capability
of the UCLA AGCM coupled to a POP version with a hybrid vertical coordinate
(HYPOP) and the MIT OGCM, in combination with NASA/JPL ocean data and optimization
products. The AGCM had not been coupled to the MIT OGCM before.
At the start of the funding period we were using
the version 7.1 of the AGCM coupled to the version the Tropical Pacific U2 version
of POP (see www.atmos.ucla.edu/~mechoso/esm for definition of model versions).
Inspection of the results produced by this coupled model showed a significant
climate drift characterized by warm bias in the equatorial sea surface temperatures
(SSTs). This deficiency motivated work on the parameterization of cloud-radiative
interactions. A notable improvement in the realism of the simulations was obtained
by changing the definition of cloudiness in convectively active regions. These
changes resulted in the AGCM version 7.2. The climate drift problem was not
solved completely, but its manifestation was delayed in such a way that it is
not significant during model integrations of the length to be used for ENSO
predictions.
4. Technology Accomplishments
4.1 Porting of codes to computers in Round 3 Testbeds
The
AGCM, POP and MIT OGCM codes have been ported to the SGI Origin 3000 at NASA
ARC (Ames). The AGCM/POP combination is being installed in the Compaq System
at NASA GSFC.
4.2 The DDB
The DDB, which was developed in Round 2, is a
general-purpose tool for coupling multiple, possibly heterogeneous, parallel
models. Using the DDB, each producer sends data directly to each consume. This
strategy conserves bandwidth, reduces memory requirements, and minimizes the
delay that would otherwise occur if a centralized element were to reassemble
each of the fields and retransmit them.
Work on a major upgrade of the DDB has started.
Currently, the DDB is a mix of MPI and PVM. It's started with MPI run, but most
of the internal communications are still in PVM. Daniel Katz (NASA JPL) has
begun converting the code from PVM to MPI. Completion of the conversion is expected
in March 2003. Future work will include improvements in DDB performance, diagnostic
and error handling, and user interface.
4.3 Model Timings
Several model timings were performed as part of
the Milestone E work using the baseline (Round 2) coupled AGCM/OGCM code implemented
on the NASA ARC testbed. The performance was better and the scaling was comparable
to that at the end of Round 2. Tables showing the timings are included in the
Milestone E report.
4.4 Software Management
The ESM software is now managed using the tool
Concurrent Versions System (CVS). Versions 7.1 and 7.2 of the UCLA AGCM code
and version U2 of the POP code are currently installed in CVS repositories at
UCLA. The MIT GCM, including the modifications for coupling it to the UCLA atmosphere
model, is also being maintained on CVS servers, both at JPL and at MIT. The
MIT server (http://mitgcm.org/cgi-bin/cvsweb.cgi/MITgcm/)
is configured as an anonymous CVS server, hence making the code modifications
and updates publicly available in real time.
4.5 Project website
A revised and upgraded project website was developed
and is frequently updated (www.atmos.ucla.edu/~mechoso/esm). Milestone reports
are posted in the website. The proposal text for Round 1 is already there and
those for Rounds 2 and 3 will be incorporated soon.
5. Status/Plans
The parameterization of the planetary boundary
layer (PBL) used in the AGCM will be upgraded to a version with multiple layers
as part of the work for Milestone F. This development is considered to be crucial
for a better representation of low-level cloudiness in the tropics. A researcher
familiar with the AGCM (Gabriel Cazes) has been hired for this task. Cazes joined
UCLA on January 1, 2003.
Multiple-decade long simulations will be performed
with the UCLA AGCM coupled to the MIT OGCM in order to validate the model climatology
and interannual variability. Similar runs are planned with the global version
of POP.
6. Point of contact
C. Roberto Mechoso
Department of Atmospheric Sciences
UCLA Mail Code 156505
405 Hilgard Avenue
Los Angeles, California 90095
7. Caption for the Graphic
Monthly mean sea surface temperature fields simulated by the UCLA AGCM v7.2
coupled to the low-resolution MIT ECCO/JPL OGCM.
8. Publications
None
9. Conference Presentations
Mechoso, C. R., J. D. Farrara, 2002: The UCLA Earth System Model: Development
and Application. Earth Science Technology Conference, 11-13 June 2002, Pasadena,
California. Available at http://esto.nasa.gov/conferences/estc-2002/
10. Graduate Students and Post Docs
Gabriel Cazes – Graduate Researcher
Heng Xiao – Graduate Student