esci/cmip5 tools - jeudi 2 octobre 2008 1 cmip5 tools earth system grid-netcdf4-...

ESCI/CMIP5 Tools - Jeudi 2 octobre 2008

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CMIP5 ToolsEarth System Grid-NetCDF4-CMOR2.0-Gridspec-Hyrax …


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Fédération de sites Earth System Grid


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Earth System Grid en 3 Tiers.


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Architecture Earth System Grid


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Authorization Use Case 1: BADC User


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Authorization Use Case 1: CCSM Admin


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Authorization Use Case 1: BADC User


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Metadata and query

http://dycore.ucar.edu/query/modelComparison.htm


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NetCDF 3 Classic Model

11/6/2007HDF and HDF-EOS Workshop XI, Landover,

MD


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Enhanced data model for netCDF4

A file has a top-level unnamed group. Each group may contain one or more named subgroups, user-defined types, variables, dimensions, and attributes. Variables also have attributes. Variables may share dimensions, indicating a common grid. One or more dimensions may be of

unlimited length.

Dimension name: String

length: int

isUnlimited( )

Attribute name: String

type: DataType

values: 1D array

Variable name: String

shape: Dimension[ ]

type: DataType

array: read( ), …

Group name: String

File location: Filename

create( ), open( ), …

Variables and attributes have one of twelve primitive data types or one of

four user-defined types.DataType

PrimitiveTypecharbyte

short int

int64float

doubleunsigned byte unsigned short

unsigned intunsigned int64

string

UserDefinedType

typename: String

Compound

VariableLength

Enum

Opaque


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Why CMOR-2 ?

• Original CMOR accommodated only data stored on Cartesian longitude-latitude

grids. Written in FORTRAN 95 mainly by a climate scientist with limited

time to maintain and extend it.

• CMOR-2 Can write Output on model “native" grids that are not Cartesian

longitude-latitude. Station data (needed, for example, by the HTAP project),

including metadata for station names and station locations Written in C (with optional FORTRAN 95 interface) by a computer

scientist with ongoing commitment to support it. The calls to CMOR-2 are identical to those in CMOR except as

needed to make use of the new extended capabilities. NetCDF4 for compression recompile all clients


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Horizontal grids in use in ESMs


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Dependencies across data from many models Model intercomparisons have

become a primary research avenue for consensus and uncertainty estimates of anthropogenic climate change. This plot is a composite across the entire AR4 archive.

Model chaining: output from one model used as forcing for another “downstream”.


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Grid metadataTo be of use by models as well as for interpreting model output, the

standard must enable vector calculus and conservative regridding.

The following aspects of a grid must be included in the specification:

distances between gridpoints, to allow differential operations; angles of grid lines with respect to a reference, usually geographic

East and North, to enable vector operations. One may also choose to include an arc type (e.g “great circle”), which specifies families of curves to follow while integrating a grid line along a surface.

areas and volumes for integral operations. This is generally done by defining the boundaries of a grid cell represented by a point value. Below we will also consider fractional areas and volumes in the presence of a mask, which defines the sharing of cell between two or more components.


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Projections

polar_stereographic, lambert_conformal, mercator, none, etc. May need auxiliary information: e.g north_pole attribute that is

not the geographic North Pole. (a “rotated pole” is not a mapping or a projection but an attribute!)

Sometimes stored under grid_mapping.

The tripolar grid of Murray (1996) is composedof tiles with different projections: two polarstereographic projections with different poles,and a spherical coordinate system below thepolar latitude.


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AR5 open issues and questions

What are the set of runs to be done and derived from that the expected data volumes we can expect?

Expected participants – where will data be hosted? (Who is going to step up and host the data nodes, and provide the level of support expect in terms of manpower and hardware capability.) minimum software and hardware data holding site requirement (e.g., ftp

access and ESG authentication and authorization) skilled staff help desk

AR5 archive to be globally distributed with support for WG1, WG2, and WG3. Will there be a need for a central (or core) archive and what will it look like?

Replication of holdings - disaster protection, a desire to have a replica of the core data archive on every continent, etc.

Number of users and level of access – scientist, policy makers, economists, health officials, etc.

esci/cmip5 tools - jeudi 2 octobre 2008 1 cmip5 tools earth system grid-netcdf4-...

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