Transpose-AMIP II and ACCESS: Introduction

Transpose-AMIP II is a WMO Working Group on Numerical Experiments (WGNE) and Working Group on Coupled Models (WGCM) endorsed activity to run climate models in weather forecast (hindcast) mode. The premise for these experiments is that centres which run climate and NWP models in a unified system frequently find that model errors are common across timescales. Transpose-AMIP (T-AMIP) type experiments can provide: Process evaluation and insights into bias development through comparison with observations; and, insight into fast processes (e.g. clouds) which are the principal sources of model spread in terms of simulating climate and climate change. Thus running realistically initialized climate models in forecast mode can be used to determine their initial drift from the NWP analyses and/or from the available field data, thereby gaining insights on model parameterization deficiencies.

The Transpose-AMIP II website can be found at ( and the experimental design detailed there requires that 64 global hindcasts are to be produced with an Atmospheric General Circulation Model (AGCM), with each hindcast being 5 days in length. In fact 4 sets of 16 hindcasts are to be run, the first in each set starting at 00UTC on the 15th of the following months and then subsequently at 30 hour intervals: October 2008, January 2009, April 2009 and July 2009. This ensures sampling throughout the annual and diurnal cycles for each grid-point for a given lead time. These periods have been chosen to tie in with the Year of Tropical Convection (YOTC ) and various Intense Observational Periods (IOPs).

We will refer to this experimental design as T-AMIP for convenience, even though it is actually Transpose-AMIP II.

Hence, the T-AMIP start dates are:

00Z 15th Oct 2008 00Z 15th Jan 2009 00Z 15th Apr 2009 00Z 15th Jul 2009
06Z 16th Oct 2008 06Z 16th Jan 2009 06Z 16th Apr 2009 06Z 16th Jul 2009
12Z 17th Oct 2008 12Z 17th Jan 2009 12Z 17th Apr 2009 12Z 17th Jul 2009
18Z 18th Oct 2008 18Z 18th Jan 2009 18Z 18th Apr 2009 18Z 18th Jul 2009
00Z 20th Oct 2008 00Z 20th Jan 2009 00Z 20th Apr 2009 00Z 20th Jul 2009
06Z 21st Oct 2008 06Z 21st Jan 2009 06Z 21st Apr 2009 06Z 21st Jul 2009
12Z 22nd Oct 2008 12Z 22nd Jan 2009 12Z 22nd Apr 2009 12Z 22nd Jul 2009
18Z 23rd Oct 2008 18Z 23rd Jan 2009 18Z 23rd Apr 2009 18Z 23rd Jul 2009
00Z 25th Oct 2008 00Z 25th Jan 2009 00Z 25th Apr 2009 00Z 25th Jul 2009
06Z 26th Oct 2008 06Z 26th Jan 2009 06Z 26th Apr 2009 06Z 26th Jul 2009
12Z 27th Oct 2008 12Z 27th Jan 2009 12Z 27th Apr 2009 12Z 27th Jul 2009
18Z 28th Oct 2008 18Z 28th Jan 2009 18Z 28th Apr 2009 18Z 28th Jul 2009
00Z 30th Oct 2008 00Z 30th Jan 2009 00Z 30th Apr 2009 00Z 30th Jul 2009
06Z 31st Oct 2008 06Z 31st Jan 2009 06Z 1st May 2009 06Z 31st Jul 2009
12Z 1st Nov 2008 12Z 1st Feb 2009 12Z 2nd May 2009 12Z 1st Aug 2009
18Z 2nd Nov 2008 18Z 2nd Feb 2009 18Z 3rd May 2009 18Z 2nd Aug 2009

Note that the same procedures as we use in T-AMIP could be applied to other dates using the ERA-40 and ERA-Interim reanalyses as initial conditions.

Elements of the experimental design that were required to setup T-AMIP for ACCESS were:

  • Model state variables are to be initialised from ECMWF YOTC analyses available from Guidance on carrying out the interpolation can be found in the ECMWF IFS documentation.
  • Atmospheric composition, solar forcing and land use should be as the final year of the CMIP5 AMIP experiment (2008).
  • SSTs from ECMWF YOTC should be used in the hindcasts.
  • Land surface models should be initialised using one of the following methods:
    • Initialise from fields produced by a land surface assimilation system (e.g. ECMWF or GLDAS)
    • Initialise using a suitable climatology: e.g. from GSWP2 or derived from the model’s AMIP simulation.
    • Initialised with a nudging method as described by Boyle et al. (2005).
  • Aerosols concentrations should either be initialised using a climatology calculated from the model’s AMIP simulation, or initialised using the nudging method of Boyle et al. (2005).
  • Non-state variable prognostics which spin-up quickly (such as cloud fraction for models with a prognostic scheme) can either be initialised from zero, or initialised using the nudging method of Boyle et al. (2005).
  • The AGCMs submitted should be the same (both in terms of physics and resolution) as those used for the CMIP5 AMIP experiment in order to compare model biases across timescales.

The following section details the T-AMIP experimental design steps taken to setup the ACCESS 1.3 T-AMIP procedure. All the scripts and jobs used, examples of the files produced and the location of all the final datasets can be found on

 raijin at /g/data/p66/glr548/tamip_sam/access1.3

More details on the Transpose-AMIP II experimental design and its application to the ACCESS 1.3 model can be found in "ACCESS Transpose-AMIP: Experimental Procedure and Preliminary Results", Greg Roff (accepted CAWCR Res.Let., Oct 2014) and a companion README file, copies of which can also be found as pdf's on the above site.

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[19/11/2014] Review and updates by Greg Roff

For further support on this suite, please contact g.roff@…

Last modified 4 years ago Last modified on Feb 3, 2015 4:34:49 PM