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Introduction to Regional Earth System Model (RegESM) ���

���Ufuk Turuncoglu ���

Istanbul Technical University���Informatics Institute���

14/05/2014, 7th ICTP Workshop on the Theory and Use of Regional Climate Models

Outline •  Earth System and Modeling (AOGCMs to ESMs) •  RegESM

–  Components –  Design –  Run Sequence –  Concurrent vs. Sequential

•  Project Home and Documentation •  Simplified Test Case (“a new toy”)

Earth System •  It is interactively coupled system

http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/103088557/1_2.jpg

Earth System … •  Spatial and temporal (response time) scales differ among the

components

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Earth System Models •  There is a shift from AOGCM or regional coupled AO model to

fully integrated ESMs (see IPCC, AR5, WG1)

Components •  Currently, it has three different component: ATM/OCN/RTM

ATM: RegCM OCN: ROMS / MITgcm RTM: HD DRIVER: RegESM

What is driver / coupler ? •  The driver can be defined as a “glue” •  It merges the different components of the modeling system •  In general, the modeling system might be designed to have

–  Single executable –  Multiple executable

•  In the multiple executable case, the usage of the modeling system might be difficult

•  The driver is generally responsible for –  Interaction among the components: ���

exchange boundary data between the components, regridding etc. –  Synchronization: ���

to coordinate the time evolution of the physical models

Driver Design •  The driver is designed as generic as possible to allow plugging

new components easily •  It uses ESMF (Earth System Modeling Framework) and NUOPC

(National Unified Operational Prediction Capability) layer

•  The driver is responsible for plugging components, orchestration and data exchange

•  It is the key part of the���“puzzle”

•  It has an generic interface

for the model components

Driver Design … •  The current driver uses only “connector” component

•  The driver defines; –  The model components (i.e. RegCM, ROMS) – grid, fields, states etc. –  Coupler component (connector) –  Global clock and calendar

•  and synchronizes the sequence of actions

Driver Design … •  Different designs are possible with NUOPC layer •  The mediator approach is much more efficient when the

number of components increase

Simple Coupling ���with Connectors

ATM+OCN

Coupling through a Mediator

Run Sequence •  The NUOPC Layer is capable of implementing many different

coupling schemes –  Explicit (exchange data in same time) – two connector (i.e.

backward and forward) –  Explicit with slow and fast clock support (different interaction time

among the components) –  Semi-implicit (leap-frog style interaction)

Run Sequence … •  The RegESM uses explicit coupling schemes along with the

support of fast and slow time steps. –  Fast interaction between ATM and OCN –  Slow interaction between ATM and RTM, RTM-OCN

Sequential vs. Concurrent •  The modeling system supports two different approach to run

the model components.

•  In sequential mode: model components are run in order •  In concurrent mode: all models are active at same time (it does

not allow overlapping of the used PETs – cores / CPUs)

Repository and Project Home •  The RegESM project is hosted by GitHub

–  https://github.com/uturuncoglu/RegESM •  The project home page

Implemented by using CoG1

http://cess.be.itu.edu.tr/projects/regesm/

I) https://www.earthsystemcog.org/projects/cog/

Documentation •  Initial version of user guide is ready

–  Basic model design –  Installation of libraries, components ���

and RegESM model –  Definition of configuration files���

(exchange fields and model) –  Known bugs and limitations

•  Send any comments by e-mail –  Experience about installation in ���

different computing system –  Bugs

•  Unfortunately, there is no support ���ticket handling system yet!

–  Results of your applications ���(tested domains, detail about configuration etc.)

Test Application •  Simple MED application (50km in ATM) along with a toy ocean

model (flat bathymetry, no complex masking, wall along E/W/N and S sides, 40 vertical z-layer) underneath

•  Components: –  RegCM –  MITgcm

•  Setup: –  Coupling interval is 1-hour (for data exchange between

components) –  Exchange fields:

•  ATM to OCN – wind components, surface pressure, net heat flux (short-long-latent-sensible) and net freshwater flux (E-P)

•  OCN to ATM – sea surface temperature

Domain Decomposition •  The domain decomposition is used to distribute the work to

the set of processors (or PETs in ESMF)

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RegCM Tiling 4x5

Domain Decomposition … •  It could be one (i.e. slices along latitude or longitude) or two

dimensional (both latitude and longitude) – ghost points !!!

MITgcm Tiling 4x5

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Questions!

Contact:

u.utku.turuncoglu@be.itu.edu.tr

Acknowledgements    The development of RegESM has been supported by a research grant (113Y108)

provided by The Scientific and Technological Research Council of Turkey (TUBITAK) and The Abdus Salam International Centre for Theoretical Physics (ICTP).