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Posts Tagged ‘climate models’

van Hateren 2012: May the Schwartz be with you

2012 May 17 2 comments

Figure 6. Isomorphism between resistance-capacitance circuit and two-compartment energy balance climate model. Differential equations on right can be solved to give time dependence for arbitrary applied time-dependent forcing (current). Dashed boxes enclose corresponding one-compartment systems. The figure is modified from the Reply to Comments on my 2007 paper and an in-press paper (Spring, 2012) that interprets the observed increase in GMST over the latter part of the twentieth century in terms of the two-compartment model.

Stephen E. Schwartz Home Page
http://www.ecd.bnl.gov/steve/schwartz.html

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Call for PCCM2.1 / CCM2 T21L18 Double Precision Data Sets

2012 March 9 Comments off

Digging into Drake, et al, (1999), I noted that the model had been run for performance benchmarking at lower resolution. Digging back into the code, I found that the parameter that set the spectral power truncation was also used to reset lat/lon resolution. It was easy to recompile PCCM2.1 to a T21L18 resolution with a 4-fold reduction in cells (128×64 grid to 64×32 grid). That was the good news.

The bad news is that the freshly compiled program does not read the data sets for the T42 resolution model. I did find some data files for CCM2 on the UCAR ftp server, but they do not seem to be compatible with PCCM2.

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PCCM2.1 Performance Implementations

2012 March 6 2 comments

PCCM2.1 Performance Implementations of PCCM2 are now available on the Intel Paragon, the IBM SP2, the CRAY T3D and the CRAY C90. The performance of of the code on these platforms gives an indication of relative machine performance and indicates the usefullness of the MPP platforms for climate research. Two horizontal resolutions are compared The performance is given in the number of seconds it takes to simulate one day on the computer. Two resolutions are shown. The T42 resolution corresponds to a 2.8 degree grid while T170 is a 0.7 degree grid. The higher resolution represents the what might be required for regional scale modeling of climate impacts.

http://www.csm.ornl.gov/chammp/highlights.html
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PCCM2.1: The Parallelized Port of CCM2

2012 March 4 2 comments

I found the PCCM2.1 source while following up on the mostly whimsical idea last week of running a Beowulf cluster of Raspberry Pis. I speculated that UVic_ESCM might be a candidate climate model for running on a cluster, but according to some very kind email responses, I see that I have misread the tea-leaves. So that sent me on a quick search for climate models better suited for parallel environments. PCCM2 caught my eye. This model is a fork of the UCAR CCM2, recoded for parallel computing. It supports a variety of parallel architectures and hardware and, as seen below, can be configured to run on a Linux 64 bit x86 platform running OpenMPI. Not bad for a nearly 20 year old piece of archived code designed for rather particular (peculiar?) environments.

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IPCC AR4 WG1 TS5.1 Fig TS.26 Six Year Review

2012 March 1 5 comments

This is a composite chart showing a range of estimates around the “projected trends” of surface temperature anomalies. This chart appears to be popular given that my link in a comment in Real Climate has already been propagated to comments in Stokes’ Moyhu blog and Watts’ WUWT blog. The recent observations in red are from HadCRUTv3 and are only hand-fitted to the chart. I believe the original observations charted were HadCRUT of one variant or another. Quoting IPCC AR4 WG1: “Projections for 1990 to 2005 carried out for the FAR and the SAR suggested global mean temperature increases of about 0.3°C and 0.15°C per decade, respectively. The difference between the two was due primarily to the inclusion of aerosol cooling effects in the SAR, whereas there was no quantitative basis for doing so in the FAR. Projections given in the TAR were similar to those of the SAR.” I look forward to similar projections in IPCC AR5 WG1.
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/tssts-5-1.html
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IPCC AR4 WG1 Earth System Models of Intermediate Complexity

2012 February 21 Comments off

STUDENT: Which climate models should the student seek out?
Which papers are good at outlining the points of failure?
Beside ‘institutional knowledge’, where are the strengths and weaknesses of various models catalogued?

PROFESSOR: All those answers await, and many more, once you deposit $25000 in an educational institution near you.

STUDENT:

A first small step can be found in the IPCC AR4 WG1 in its table of Earth Models of Intermediate Complexity (table 8.3). EMICs are the models of my current interest. The UVIC_ESCM is an EMIC.

There are eight models listed with some high level summaries of their atmosphere, ocean, land, ice, and flux characteristics.

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UVIC_ESCM: Main Flow Chart

2012 February 18 3 comments

“Begin at the beginning,”, the King said, very gravely, “and go on till you come to the end: then stop”
-Lewis Carroll

Last week’s dump of the entire calling structure was an interesting exercise, but didn’t go very far in revealing the structure of UVic_ESCM. This week I focus on just the major components of the “main” routine. The graphic to the left is my first pass at a high-level summary.

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