THE NOAA OPERATIONAL MODEL ARCHIVE AND DISTRIBUTION SYSTEM (NOMADS)

G. K. RUTLEDGE[^1]

*National Climatic Data Center*

*151 Patton Ave,*

*Asheville, NC 28801, USA*

*E-mail: Glenn.Rutledge@noaa.gov*

J. Alpert

National Centers for Environmental Prediction

Camp Springs, MD 20736, USA\
E-mail: Jordan.Alpert@noaa.gov

R. STOUFFER

Geophysical Fluid Dynamics Laboratory

Princeton, NJ 08542, USA\
E-mail: Ronald.Stouffer@noaa.gov

B. Lawrence

British Atmospheric Data Centre

Chilton, Didcot, OX11 0QX, U.K.\
E-mail: b.n.lawrence@rl.ac.uk

Abstract

An international collaborative project to address a growing need for
remote access to real-time and retrospective high volume numerical
weather prediction and global climate model data sets (Atmosphere-Ocean
General Circulation Models) is described. This paper describes the
framework, the goals, benefits, and collaborators of the NOAA
Operational Model Archive and Distribution System (NOMADS) pilot
project. The National Climatic Data Center (NCDC) initiated NOMADS,
along with the National Centers for Environmental Prediction (NCEP) and
the Geophysical Fluid Dynamics Laboratory (GFDL). A description of
operational and research data access needs as outlined in the U.S.
Weather Research Program (USWRP) Implementation Plan for Research in
Quantitative Precipitation Forecasting and Data Assimilation to "redeem
practical value of research findings and facilitate their transfer into
operations."

# 1.0 Introduction  {#introduction .unnumbered}

To address a growing need for real-time and retrospective General
Circulation Model (GCM) and Numerical Weather Prediction (NWP) data, the
National Climatic Data Center (NCDC) along with the National Centers for
Environmental Prediction (NCEP) and the Geophysical Fluid Dynamics
Laboratory (GFDL) have initiated the collaborative NOAA Operational
Model Archive and Distribution System (NOMADS) (Rutledge, et. al.,
2002). A new paradigm for sharing data among climate and weather
modelers is evolving. It takes advantage of the Internet and relatively
inexpensive computer hardware. In this new framework, scientists put
their data unto a computer on the Internet. Software running on the
computer allows outside users to see not only their local data but also
data on other computers running this same software. This framework is
also known as "Grid Computing". NOMADS uses this framework and is a
network of data servers using established and emerging technologies to
access and integrate model and other data stored in geographically
distributed repositories in heterogeneous formats. NOMADS enables the
sharing and inter‑comparing of model results and the comparing of model
results with observations. It is a major collaborative effort, spanning
multiple government agencies and academic institutions. The data
available under the NOMADS framework include model input and NWP gridded
output from NCEP, and GCM and simulations from GFDL, NCAR, and other
leading institutions from around the world. The effort has gained many
international partners, as the need for a convergence of emerging yet
similar distributed data efforts become implemented. The goals of NOMADS
are:

-   Provide access to NWP (weather) and GCM (climate, including ocean
    related) models.

-   Provide the observational and model data assimilation products for
    Regional model initialization and forecast verification for use in
    both weather and climate applications.

-   Develop linkages between the research and operational modeling
    communities and foster collaborations between the climate (including
    ocean) and weather modeling communities.

-   Promote product development and collaborations within the
    geo-science communities (ocean, weather, and climate) to improve
    operational weather and climate forecasts by allowing more users to
    interact with the model data.

-   Foster inter-disciplinary research to study multiple earth systems
    using collections of distributed data under sustainable system
    architectures.

-   Ensure permanent stewardship of select agreed upon model data sets.

NOMADS provides retrospective access to model and observational data by
a wide variety of users via the Internet and eventually the Next
Generation Internet (NGI) or Internet -2. NOMADS is an inter-operable
network architecture with fully integrated data access and manipulation
tools using a distributed, format independent client‑server methodology.
NOMADS benefits from existing and emerging technologies to provide
distributed access to models and data.

To enable universal user access and system inter-operability, NOMADS has
four primary data servers: 1) Climate Data Analysis Tools (CDAT),
(Williams, et al., 2002); 2) the Open source Project for a Network Data
Access Protocol (OPeNDAP), (formally called the Distributed
Oceanographic Distribution System (DODS)), (Davis, et al., 1999); 3) the
GrADS Data Server (GDS); (Doty, et al., 2001); and 4) the Live Access
Server (LAS), (Hankin, et al., 2001). Traditional on‑line data services
through standard Web-based File Transport Protocol (FTP) will also be
available. Users with commonly available desktop data manipulation tools
such as Ferret, MatLAB, IDL, GrADS and even typical Web browsers can
access data in their preferred format. To provide for this format
neutral data access, NOMADS uses the EXtensible Markup Language (XML)
(Bray, et al., 1998).

Both researchers and policy‑makers now expect national data assets to be
easily accessible and interoperable with each other, regardless of their
physical location. As a result, an effective interagency distributed
data service requires the coordination of data infrastructure and
management extending beyond traditional organizational boundaries. With
NOMADS and its collaborators, users at any skill level will be able to
obtain weather and climate information. This will allow the users to
make better, informed decisions about how nature will impact their
future, either in their life, or business decisions.

**2.0 Background**

A major transition in weather and climate prediction is now occurring,
one in which real‑time and retrospective NWP and GCM research is
spreading from a handful of national centers to dozens of groups across
the country. This growth of global and regional scale NWP and GCM model
development is in part, now possible due to:

-   The availability of low-cost multiprocessor workstations.

-   The availability of regional scale models that run on these
    workstations (e.g., MM5).

-   The availability of climate simulations, analysis and forecast grids
    from NCEP, GFDL, NCAR and other institutions.

NOMADS addresses model data access needs as outlined in the U.S. Weather
Research Program (USWRP) [Implementation Plan for Research in
Quantitative Precipitation Forecasting and Data
Assimilation]{.underline} to "redeem practical value of research
findings and facilitate their transfer into operations." The NOMADS
framework was also developed to facilitate climate model and
observational data inter-comparison issues as discussed in documents
such as the Intergovernmental Panel on Climate Change (IPCC 1990, 1995,
2001) and the U.S. National Assessment (2000). NOMADS is being developed
as a unified climate and weather archive so that users can make
decisions about their specific needs on time scales from days (weather),
to months (El Nino), to decades (global warming). Currently, NCEP NWP
output are available in real‑time through a number of different
channels, although they are available using traditional high volume
methods (push, ftp etc.). Historical data, the data needed for research
and collaboration, are more difficult to obtain and the variety of
products are much more limited. There is no single repository or
effective distribution method for both NWP and GCM data. Local piecemeal
approaches at government laboratories, data centers, and universities
fall short of filling the need for retrospective model data. Even in
cases where the data are available, there exists no mechanism to redeem
practical value of research findings and facilitate these findings back
into operations.

The primary U.S. National responsibility for the archive and service of
weather and climate data rests with the NCDC. However, as the temporal
and spatial resolution of models increase, the volume and varied formats
of data presented for archive at NCDC using current communications
technologies and data management techniques are inadequate. The
scientific modeling community is a vast intellectual resource. This
community is extremely interested in obtaining both weather and climate
products for historical cases, and for operational and research
purposes.

The NOMADS is actively partnering with existing and development
activities including the Comprehensive Large Array Stewardship System
(CLASS); the National Oceanographic Partnership Program's (NOPP)
National Virtual Ocean Data System (NVODS); the Department of Energy's
Earth System Grid (ESG); and the Thematic Real-time Environmental Data
Distributed Services (THREDDS) project being developed through the
National Science Foundation and Unidata. To ensure that agency and
institutional requirements are being met, the NOMADS collaborators have
established science and technical expert teams. These newly established
teams, comprised of NOMADS members will ensure system and data
inter-operability; and develop data archive requirement recommendations
to NOAA.

**3.0 Benefits**

NOMADS fosters system inter-operability by integrating legacy systems
with existing and emerging technologies and metadata conventions. NOMADS
relies on local decisions about data holdings by combining legacy
systems, while developing new ways to support data access. Distributed
or "Grid" computing allows NOMADS to work on the cutting edge of data
access methods. In this effort, no one institution carries the weight of
data delivery since data are distributed across the network, and served
by the institutions that developed the data. The responsibility for
documentation falls on the data generator; with the NOMADS expert teams
ensuring inter-operability, accuracy and precision of the data. Further,
NOMADS in no way precludes the need for national centers to maintain and
support long-term archives. In fact, NOMADS and secure data archives are
mutually supportive and necessary for long-term access and research. A
primary science benefit of the NOMADS framework is that it enables a
feedback mechanism to tie Government and university research back to the
modeling community.

Under the NOMADS framework improvements to NWP models will lead to
longer lead times and improved accuracy for forecasts over all time
scales. This results in fewer lives lost and reductions in property
damage. The NOMADS will allow researchers to more easily access and
understand data thereby increasing scientific productivity.

NOMADS provides a capability for scientists to assess the potential
impact of long term climate change on the Nation using increasingly
detailed and complex models since various models will be more readily
available for inter-comparison. Climate model development and
diagnostics will also be enhanced since NOMADS provides access to GFDL
and other climate model results through collaborating institutions, and
provides the tools to inter-compare these models and observations.
NOMADS will allow for various model diagnostics and the coordination of
multi-institutional model development such as forcings, feedbacks and
uncertainty analysis as recommended by the IPCC Chapter 8 "[Climate
Change 2001: The Scientific Basis]{.underline}" IPCC Working Group I
(2001). GFDL and NCAR models are already available under the NOMADS
framework and described under sections 5.3 and 5.4. In addition, the
Atmospheric Model Intercomparison Project (AMIP), and the Coupled Model
Intercomparison Project (CMIP) model results are available via NOMADS at
the Department of Energy (DOE) Lawrence Livermore National Laboratory
(LLNL), Program for Climate Model Diagnosis and Intercomparison (PCMDI).

A significant benefit of the NOMADS framework is that it will reduce
data center costs by integrating local efforts to archive and gain
access to real-time and retrospective climate and weather models and
data. The sheer number of institutions collaborating under the NOMADS
framework helps to develop new collaborations and ensures for the
long-term viability of the project itself. The NOMADS project leverages
off many person-years of software development within NOAA and elsewhere.
Heavy dependence is made upon technology transfer and re‑use of
previously developed and successful web portal technologies.

NOMADS allows an option for the integration of large data sets by
performing data aggregation, manipulation, sub-setting, and compression
on the servicing hosts rather then transmitting large amounts of data
across the Internet at relatively slow speed. NOMADS available data sets
can be expanded to include other data sets such as satellite and radar
using XML to describe the data using NOMADS sub-setting capabilities for
efficient distribution of these high volume data.

## 4.0 System Architecture {#system-architecture .unnumbered}

The concept of distributed computing is not new. During the 1970's,
AT&T's Bell Laboratories and the UNIX operating system championed
capabilities for distributed computing with multi-system
inter-operability. Later, Sun Microsystems Inc., corporate slogan
included the phrase "\...the network is the computer". Indeed for simple
text based retrieval, the concept finally escalated with the Internet
and a protocol called HTTP. Distributed computing had taken center stage
for the search and retrieval of text-based documents and images.
Distributed scientific data access is the next step in this progression
and allows browsing, obtaining, and manipulating scientific data on
geographically distributed data as easily as Internet Web browsing of
today.

To provide inter-operability across multiple operating systems and known
user formats, NOMADS currently provides several client-server data
servers. Currently available NOMADS core servers include the OPeNDAP,
the GDS, the CDAT, and the LAS. These servers provide access to
collections of data. A DODS client requests data from the servers using
URL's to describe the desired data and data location. DODS servers
translate data into format neutral network objects, allowing
participating modelers to serve data in their native file formats.
Clients once re‑linked with DODS can access these format neutral objects
through standard Applications Program Interfaces (APIs). Client
connectivity is built upon multiple API's, including standards such as
netCDF and HDF, the Binary Universal Form for the Representation of
meteorological data (BUFR), and the GRIdded Binary (GRIB) format,
enabling NOMADS to integrate with standard desktop tools, custom models,
GrADS, Matlab, IDL, idv, Ferret, and other desktop display and analysis
applications.

The NOMADS framework can support the following data transport protocols:

-   Open source Project for a Network Data Access Protocol (OpenDAP)
    formally known as the DODS protocol

-   Common Object Request Broker Architecture (CORBA)

-   Java^TM^ Remote Method Invocation (Java/RMI)

-   Internet Inter-Orb Protocol (IIOP)

-   Hypertext transport protocol (HTTP)

-   FTP

-   TCP/IP

NOMADS users can use and exchange the following data formats and desktop
applications:

-   COARDS

-   Cf

-   FGDC

-   ASCII

-   BUFR

-   Consolidated PREODB (ECMWF version)

-   ECMWF NetCDF in METVIEW

-   ESML data forms

-   Ferret/IDL/MatLAB/GrADS

-   GrIB / GRIB (2)

-   HDF

-   Prepda (NCEP BUFR for data assimilation)

-   Naval Research Laboratory METQC

-   NetCDF

-   Various spreadsheets, Web browsers

-   XML

-   any OPeNDAP enabled client

The NOMADS allows DODS enabled transactions but also has the capability
for enhanced server side data manipulation using CDAT, GDS, or LAS. In
GDS, GrADS expressions can be provided in the body of the URL request to
manipulate data on the server providing only the resultant back to the
user. History has shown that network connectivity continually lags
behind desktop processing speeds. NOMADS will allow Internet users
access to information they would not normally consider possible.

Since most weather model data are stored in the GRIB and BUFR data
formats and most climate model data are stored in the NetCDF data
format, NOMADS will provide for the comparison between these two
formats. Converting between these two data formats has been a very
difficult task in the past. The NOMADS software allows users to work in
whatever data format is the most advantageous to them. The combination
of quality control routines, and independent data format will, for the
first time, provide users with a seamless interface to models and
associated data. Climate modelers could access weather models, and
weather modelers could access climate models. Never before has this
capability existed outside a given institution.

NOMADS allows for growth of data sets and for changing data formats. If
the current list of applicable formats no longer applies or is no longer
in use, the NOMADS framework allows the XML to conform to the new data
"standard." Although XML is supposed to be a generic and general
language, in real life it requires the prior agreement on a vocabulary
by all parties. Thus, full coordination is required for a successful
inter-operability of systems for data sharing. This coordination already
exists among the NOMADS collaborators as is evident by the sheer number
of collaborating institutions contributing their expertise and
collections under the NOMADS framework. The NOMADS distributed
client-server architecture has the potential to bridge the gaps of
inter-operability between systems and thus provide users with a metadata
of geo-sciences information, visualization and analysis tools, and
research opportunities- potentially reaching beyond the physical
sciences.

## 4.1 Open source Project for a Network Data Access Protocol: OPeNDAP  {#open-source-project-for-a-network-data-access-protocol-opendap .unnumbered}

The Open source Project for a Network Data Access Protocol (OPeNDAP-
formally known as the Distributed Oceanographic Data System (DODS))
began as a joint effort between staff and scientists at the University
of Rhode Island, Graduate School of Oceanography and at the
Massachusetts Institute of Technology, Department of Earth Atmospheric
and Planetary Science. DODS is a software framework that simplifies all
aspects of scientific data networking, allowing simple access to remote
data. Local data can be made accessible to remote locations regardless
of local storage format by using DODS servers. Existing, familiar data
analysis and visualization applications can be transformed into DODS
clients, i.e., applications able to access remote DODS served data. DODS
provides a protocol for requesting and transporting data across the web.
The current DODS Data Access Protocol (DAP) uses HTTP to frame the
requests and responses. For details on the DODS DAP, see DODS Data
Access Protocol (DAP 2.0):
[www.unidata.ucar.edu/packages/dods/design/dap‑rfc‑html.]{.underline}

The DODS involves a community of users working together to use, improve,
and extend the DODS protocol and software. The DODS design principles
are based on two considerations:

-   data are often most appropriately distributed by the individual or
    group that has developed them;

-   the user will in general like to access data from the application
    software with which s/he is most familiar.

This has resulted in a highly distributed system that allows users to
control the distribution of their own data and the way they access data
from remote sites. The currently available DODS/OPeNDAP servers include
data formats for:

-   DODS/OPeNDAP

-   FreeForm

-   GDS (GrADS-DODS Server)

-   HDF 4

-   JGOFS

-   Matlab

-   NetCDF and

-   DODS Aggregation Server (AS)

The DODS AS, is part of the Java/DODS Servlet library, allowing physical
files to be logically aggregated and served as a single DODS dataset The
AS also presents all available datasets in an integrated THREDDS
Catalog, and is also a netCDF file server. The AS is currently in beta
testing. For more information on the DODS AS see

[www.unidata.ucar.edu/projects/THREDDS/tech/DODSAggServer.html.]{.underline}

For more information on DODS see:
[www.unidata.ucar.edu/packages/dods]{.underline}.

.

**4.2 The Live Access Server**

The Live Access Server (LAS) is a highly configurable Web server
designed to provide flexible access to geo‑referenced scientific data.
It can present distributed data sets as a unified virtual database
through the use of DODS networking. Ferret is the default visualization
application used by LAS, though other applications (Matlab, IDL, IDV,
GrADS) can also be used. LAS was developed at NOAA's Pacific Marine
Environmental Laboratory (PMEL). LAS enables the Web user to visualize
data with on‑the‑fly graphics and users can request custom subsets of
variables in a choice of file formats. LAS can access background
reference material about the data (metadata) and compare (difference)
variables from distributed locations. LAS enable the data provider to
unify access to multiple types of data in a single interface and create
thematic data servers from distributed data sources. LAS also offers
derived product generation "on-the-fly", and has the capability to
remedy metadata inadequacies, e.g., poorly self‑describing data. LAS
also offer the ability to produce unique products, e.g. visualization
styles specialized for the data, for scientific exploration. For more
information on LAS see:
h[ttp://ferretwrc.noaa.gov/Ferret/LAS/ferret_LAS.html.]{.underline}

## 4.3 GrADS-Data Server {#grads-data-server .unnumbered}

The Grid Analysis and Display System (GrADS) Data Server (GDS) was
developed at the IGES/COLA. GDS is a data server that provides
sub-setting and analysis services across the Internet These services can
be provided for any GrADS‑readable dataset The sub-setting capability
allows users to retrieve a specified temporal and/or spatial sub-domain
from a large dataset, eliminating the need to download everything simply
to access a small relevant portion of a dataset The analysis capability
allows users to retrieve the results of an operation applied to one or
more datasets on the server. Examples of analysis operations include
basic math functions, averages, smoothing, differencing, correlation,
and regression. The GDS supports operations that can be expressed in a
single GrADS expression. Figure 1 provides an example of the processes
initiated during a typical GDS user request under the GDS NOMADS
framework. There is currently an extensive GDS user base using GrADS as
its primary data manipulation client. It is expected that many users of
NWP and model input data will access NWP data via NOMADS using GrADS.
For further information on GDS see: http://www.iges.org/grads/gds.

GDS allows for variable comparison. For example, a GDS running at NCAR
([http://motherlode.ucar.edu:9090](http://motherlode.ucar.edu:9090/)) is
distributing a set of ensemble members from the "Climate of the 20^th^
Century" runs of the COLA atmospheric general circulation model. One can
easily compare the relative humidity "rh" from the first two datasets,
namely "C20C_A" and "C20C_B". If one wants to find a global time-average
of the difference at the 1000 mb level in 1960 GrADS can be used as the
client to open the following URL as follows

ga-\> sdfopen
[http://motherlode.ucar.edu:9090/dods/\_expr\_{C20C_A,C20C_B](http://motherlode.ucar.edu:9090/dods/_expr_{C20C_A,C20C_B)}
{ave((rh.1-rh.2),time=1jan1960,time=1dec1960)}

{0:360,-90:90,1000:1000,1nov1976:1nov1976}

ga-\> display result

![](media/image1.png){width="5.0in" height="4.375in"}

###  {#section .unnumbered}

###  **Figure 1. Example path of a GDS user request.** {#figure-1.-example-path-of-a-gds-user-request. .unnumbered}

The analysis results are returned in the variable "result" in the opened
dataset Note that the world coordinate boundaries specified in the third
set of curly braces fix the time to 1Nov1976. This can be set to any
arbitrary time because the time dimension specification is overridden by
the GrADS expression that tells the server to average over the period
from January 1960 to December 1960. In order to facilitate the use of
these various servers, a library of GrADS scripts have been developed
and are available at the COLA site.

Among many other US sites, NCDC and NCEP have GDS servers running under
the NOMADS project, and are serving both reat-time and retrospective NWP
models and data. The NCDC GDS site is found under the "gds" heading at:
http://nomads.ncdc.noaa.gov/ncdc-ui/ncdc.html. NCEP's GDS server can be
found at: http://nomad1.ncep.noaa.gov/. For NOMADS Program and other
information see the main NCDC NOMADS site at:
http://www.ncdc.noaa.gov/oa/climate/nomads/nomads.html.

**4.4 LLNL's Climate Data Analysis Tool**

Under the NOMADS framework, and a collaboration between PCMDI, GFDL, and
PMEL, the LLNL has developed a new web access capability that merged the
LAS with the CDAT (Williams, et al., 2002) suite of access and quality
control programs. The URL to view CDAT‑LAS is
[http://esg.llnl.gov/las]{.underline}. Currently, CDAT‑LAS is serving up
AMIP, CMIP, and NCAR's Parallel Climate Model (PCM) data sets. CMIP and
PCM data sets are restricted and only accessed with the proper user name
and password. The AMIP data sets are unrestricted and can be accessed by
the general public. For more information of the PCMDI effort see
[www‑pcmdi.llnl.gov]{.underline}.

The open nature of the CDAT system will permit any member of the climate
community to contribute to the system on an equal footing with the
members of PCMDI. With this philosophy, the general goal is to develop a
consistent and flexible tool for everyone. NCDC will implement this
package during 2002. The collaborations under NOMADS, such as THREDDS
and PCMDI with other on-line packages (GDS, LAS, DODS), are to increase
collaboration among climate and weather research scientists. NOMADS will
also act as the technology that will allow NOAA to collaborate under the
Earth System Grid (ESG) project. CDAT is:

-   portable open source software (free)

-   incorporates modules

-   exceptions and error‑handling

-   dynamic typing (for very fast prototyping)

-   supports classes; very clear syntax

-   extensible in C or C++ and other languages (i.e., FORTRAN)

-   access local or remote databases and files in various formats

-   data extraction, grid transformation, and computation support

-   quick and easy way to browse through terabytes of data.

    For more information on CDAT or ESG see
    [http://esg.llnl.gov/cdat.]{.underline}

##  {#section-1 .unnumbered}

## 4.5 The Thematic Real-time Environmental Data Distributed Services Project-( THREDDS) {#the-thematic-real-time-environmental-data-distributed-services-project--thredds .unnumbered}

The Thematic Real-time Environmental Data Distributed Services (THREDDS)
project is a system to make it possible for educators and researchers to
publish, locate, analyze, and visualize a wide variety of environmental
data in both their classrooms and laboratories. Just as the World Wide
Web and digital‑library technologies have simplified the process of
publishing and accessing multimedia documents, THREDDS will provide
needed infrastructure for publishing and accessing scientific data in a
similarly convenient fashion.

THREDDS will establish both an organizational infrastructure and a
software infrastructure. A team of data providers, software tool
developers, and metadata experts will work together to develop a
software framework that allows users to publish, find, analyze, and
display data residing on remote servers.

The THREDDS software framework, based on a concept of publishable data
inventories and catalogs, will tie together a set of technologies
already in use in existing, extensive collections of environmental data:
client/server data‑access protocols from the University of Rhode Island
and the University of Wisconsin‑Madison; Unidata's real‑time Internet
Data Distribution system; the discovery system at the Digital Library
for Earth System Education (DLESE); and an extensive set of client
visualization tools. For more information regarding the THREDDS see
[www.unidata.ucar.edu/projects/THREDDS.]{.underline}

The newly established National Science Digital Library (NSDL) will focus
on "Womb to Tomb" education via the Internet, expand data distribution
and sharing, aggregation, and cataloging‑ across many sciences
(biologic, physical, math, etc.). NSDL has a direct link to THREDDS, and
THREDDS to NOMADS since NOMADS will function as one of the THREDDS data
sources.

## Distributed Metadata Server 

Under the NOMADS and THREDDS partnership, various database search
engines are being explored to locate the many distributed collections of
data across the Internet. One such effort is being developed by the
George Mason University and is called the Distributed Metadata Server
(DIMES) (Yang et al., 2002). In contrast to most other standard metadata
systems, DIMES employs a flexible metadata structure, linked data
providers (nodes), and supports a wide variety of metadata forms with a
minimum of semantic rules. DIMES also provides a software framework to
search and browse the metadata. DIMES has been integrated with GDS to
create a scientific data information "super-server" to support both data
and metadata access consistently. One such example is running at GMU.
For more information see:

http:// spring.scs.gmu.edu:8099/servlet/SiesipDataTree.

**5.0 NOMADS Data Availability**

The distributed NOMADS framework will provide data manipulation
capabilities and real-time and retrospective access to NWP model input
and output, ensembles, reanalysis, GCM's and observational data both
upper-air and surface based, including oceanographic measurements being
served by OPeNDAP enabled hosts. NCEP model output will be ingested at
NCDC though NCDC's NOAAPort Data Access and Retrieval System (NDARS,
Rutledge, et al., 2000) in real-time. These data have been archived at
NCDC since October 1999. Real-time NWP data will also be available
through NCEP's real-time NOMADS data services effort (Alpert, et al.,
2002).

NCEP model output grids that are currently available include the Global
Forecast Model (GFM, formally called AVN and MRF), the Rapid Update
Cycle (RUC), Eta, mesoEta, and the Weather Research Forecast (WRF) model
when fully developed at NCEP. Also available under NOMADS will be NCEP's
model input data and "run history" information including model spectral
coefficients. GFDL, NCAR, and other climate simulations and diagnostics
will also be available. For realtime NWP data see
http://nomad1.ncep.noaa.gov/ for realtime and retrospective NWP data see
the NCDC NOMADS: http://www.ncdc.noaa.gov/oa/climate/nomads/nomads.html
and for various climate and in-situ data see the PMEL NOMADS site at:
[http://ferret.pmel.noaa.gov/NOMADS/servlets/dataset]{.underline}. For
GCM data see the GFDL NOMADS site at:
[http://nomads.gfdl.noaa.gov.]{.underline} Near real-time GDAS model
input data will be available for testing and limited user access by the
Fall of 2003.

### **5.1 NCEP Model Input Data** {#ncep-model-input-data .unnumbered}

The NCEP Global Data Assimilation System (GDAS) analysis files will be
ingested through NCDC Load Balanced System and will be available under
NOMADS from the NCDC archive. Data are currently documented in Federal
Geographic Data Committee (FGDC) format as NOAA required. This
documentation can be accessed at NCDC under Tape Deck (TD) No. 6172 at:
[www4.ncdc.noaa.gov/ol/documentlibrary/datasets.html]{.underline}.

The GDAS dataset consists of the minimum set necessary to re-generate
NCEP analysis and forecast products (model re-start and initialization
files). GDAS includes the Global Spectral Forecast Model (GSM), and the
Spectral Statistical Interpolation (SSI) Cycling Analysis System (CAS)
with triangular truncation (T) 170 and 28 sigma levels. To start the
CAS, model spectral coefficients are provided on gaussian grid in a
sigma vertical coordinate system. These data represent the model's
"ground truth", and the best estimate- in terms of analyzed fields- for
scientific study. Data that are restricted may not be available.

"Post" is a FORTRAN program is available from NCEP that will convert
spectral coefficients to gaussian grid, sigma to pressure, and gaussian
to latitude and longitude. Work continues to couple Post to the NOMADS
user interface for source and executable downloads. The GDAS dataset
under NOMADS will include the Global Spectral Forecast Model (GSM) and
the Spectral Statistical Interpolation Cycling Analysis System (SSI-CAS)
binary files and contains \~2.5Gb per day (4 cycles/day: 00Z, 06Z, 12Z,
and 18Z). The binary files are raw data, which are acted on by NOMADS
servers to produce useful grids. The archived analysis data sets serve
as model verification as well as the source for model reruns and
retrospectives. Including the observations allows for cycling analysis
systems to re-analyze the observations. Never before has this model
input data and information been available to the public. A partial list
of NOMADS planned available observations (with associated data format)
include:

Analysis Bias Corrected Information (ASCII)

Ship / Buoy Observations (BUFR)

Guess prep / guess output (BUFR)

Observational Toss List (ASCII)

Bogus Observations (BUFR)

ACARS and Aircraft (BUFR)

Wind Observations (BUFR)

Analysis Ready Obs. (prepBUFR)

Surface Analysis Restart Files (BUFR)

Surface and Upper-Air observations (BUFR)

Fixed Snow Field (GRIB)

Previous 6 hour forecast (BUFR)

"Post" Guess Output (spectral binary)

Profiler (BUFR) / SST's (GRIB)

MSU 14 and HIRS 14/15/16 (IEEE)

SSMI Satellite obs (BUFR)

NOAA (satellite) 15/16 AMSU - A/B

TOVS 1B Radiances (IEEE)

TOVS Satellite Obs (BUFR) / GOES Satellite Obs (BUFR)

O3 Sat Obs (binary) and ERS Sat obs

SBUV: Satellite Wind Observations

Radar VAD Winds (BUFR)

The formats of these data sets are generally dictated by the necessity
to run models efficiently on modern computers. NOMADS converts the
formats and structure to the users requested form but also allows the
raw data to be directly accessed. It is expected that NOMADS distributed
access to NCEP GDAS will be available by the Fall of 2003.

**5.2 The Weather Research and Forecast Model**

NOMADS is a technology for collaboration and model development as
exemplified by the Weather Research and Forecast (WRF) model. The
contribution of the scientific community to the WRF development effort
requires the transfer of data sets of model retrospective results for
testing and comparison. NOMADS enables both retrospective and real time
access to the suite of digital products from reanalysis and operational
results to give a range of users, from commercial to university
scientist, model comparison access and supply operational grade
initialization for forecast model study. For more information regarding
the emerging WRF model see
[www.wrf-model.org/documentation_main.html]{.underline}

### **5.3 GFDL GCM Data Availability**  {#gfdl-gcm-data-availability .unnumbered}

General Circulation Models available under the NOMADS framework include
the GFDL R-30 climate model. R-30 is a coupled Atmosphere‑Ocean General
Circulation Model (AOGCM). Its four major components are an atmospheric
spectral GCM, and ocean GCM, and relatively simple models of sea ice and
land surface processes. The name "R30" is derived from the resolution of
the atmospheric spectral model (rhomboidal truncation at wave number
30). The R30 model is identified as GFDL_R30c in the Third Assessment
Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC).
See Chapter 9, Table 9.1 of "[Climate Change 2001: The Scientific
Basis]{.underline}" IPCC Working Group I (2001).

The model output that is stored on the GFDL NOMADS server are taken from
six experiments conducted at GFDL using the GFDL_R30c model. Data files
produced by one long‑running control integration (one with no changes in
external forcings, e.g., constant CO~2~) and five climate change
scenario experiments have been made accessible to interested
researchers. More information regarding the individual experiments is
found in the Control & Transient Forcing Experiments section of the GFDL
NOMADS Web site. The GFDL R-30 numerical model was developed and the
experiments conducted by members of the Climate Dynamics and Prediction
Group at the GFDL in Princeton, New Jersey. For further information on
current available GCM data see the NOMADS site at GFDL at
http://data1.gfdl.noaa.gov/.

**5.4 NCAR Data Availability**

NCAR also has a distributed computing effort collaborating under NOMADS.
Working with UCAR and NCAR, NOMADS will partner with the forward-looking
pilot project called the Community Data Portal (CDP). The CDP is
targeted directly at elevating NCAR's collective ability to function as
a data provider with a coherent web-based presence. Under the CDP it is
expected that portions of Community Climate System Model (CCSM), and
Parallel Climate Model (PCM), NCEP reanalysis and other data will be
available under the NOMADS framework. A NOMADS GDS server has been
established at NCAR and can be reached at

http://dataportal.ucar.edu:8080/dodsC/;
http://dataportal.ucar.edu/las5/badVersion.html;
http://dataportal.ucar.edu:9090/index.html; or
http://dataserver.ucar.edu/.

### **5.5 Climate Diagnostic Center**  {#climate-diagnostic-center .unnumbered}

NOAA's Climate Diagnostic Center (CDC) a NOMADS collaborator with an
extensive array of distributed data sets for Web access. CDC is
currently has one of the largest inventories of client-server listing in
the country. CDC is well known for "one-stop shopping" for NCEP
reanalysis, and many other data sets and observations. For more
information on the CDC data sets see http://www.cdc.noaa.gov/dods/; and
http://www.cdc.noaa.gov/cgi-bin/nph-nc/Datasets/

Additionally, CDC continues to advance NOMADS capabilities through user
support services on the GrADS list server. CDC serves as a role model
for distributed data access by fulfilling their own unique data access
needs while permitting external user access to their holdings under the
NOMADS distributed processing philosophy.

### **5.6 NASA's Global Change Master Directory** {#nasas-global-change-master-directory .unnumbered}

NASA's Global Change Master Directory (GCMD) is a NOMADS collaborator
and provides descriptions of Earth science data sets and services
relevant to global change research. The GCMD database includes
descriptions of data sets covering agriculture, the atmosphere,
biosphere, hydrosphere and oceans, snow and ice, geology and geophysics,
paleoclimatology, and human dimensions of global change. The DODS portal
at the GCMD can be reached at
http://gcmd.gsfc.nasa.gov/Data/portals/dods/index.html.

The GCMD through the PCMDI, GFDL, and PMEL collaboration has agreed to
develop an XML-based database search engine for NOMADS implementation.

### **6.0 The Collaborators** {#the-collaborators .unnumbered}

The current participating collaborators under the NOMADS framework now
include:

-   NOAA National Climatic Data Center (Project Lead)

-   National Weather Service, National Centers for Environmental
    Prediction

-   NOAA Geophysical Fluid Dynamics Laboratory

-   National Center for Atmospheric Research

-   NOAA-CIRES Climate Diagnostics Center

-   NOAA Forecast Systems Laboratory

-   NOAA Pacific Marine Environmental Laboratory

-   Center for Ocean-Land-Atmosphere Studies

-   University Consortium for Atmospheric Research Unidata Program

-   National Severe Storms Laboratory (collaborating with the University
    of Wisconsin, Space Science Engineer Center). Data User.

-   NASA Global Change Master Directory

-   NASA Seasonal-to-Interannual Earth Sciences Information Partner

-   LLNL Program for Climate Model Diagnosis and Intercomparison

-   DOE Accelerated Climate Prediction Initiative

-   DOE Earth System Grid

-   George Mason University

-   University of Alabama, Huntsville

-   University of Washington

-   Committee for Earth Observing Satellites

The University of Alabama is leading a collaborative effort that shares
distributed data using similar and NOMADS compatible XML based metadata
scheme called the Earth Science Markup Language (ESML), (Ramachandran,
et al., 2001). For more information on ESML see
[http://esml.itsc.uah.edu/index2.html]{.underline}. It is expected that
satellite and Radar and Geographical Information System (GIS) capable
applications will be incorporated into the NOMADS framework using this
schema in the near future.

**6.1 Other Resources and Collaborator's**

A related and much larger effort is the DOE Earth System Grid, and the
Globus project. Working with Argonne National Laboratory, Lawrence
Livermore National Laboratory, the University of Southern California,
Oak Ridge National Laboratory, and Lawrence Berkeley National
Laboratory, NOMADS will deploy an operational component in support of
terascale/petascale climate research. These projects are a significant
opportunity to advance research and collaboration in the scientific
community, and it has already drawn substantial interest that extends
into the international community. The ESG project can be found at

http://www.earthsystemgrid.org and the grid computing GLOBUS project is
at

http://www.globus.org.

As so many established U.S. based institutions are collaborating under
the NOMADS framework, both U.S National and International interest in
the collaboration have rapidly expanded. International NOMADS
collaborators now include:

-   The British Atmospheric Data Center (BADC)

-   E‑Science: ClimatePrediction.net

-   E‑Science: NERC DataGrid

-   Hadley Centre

NOMADS has been selected as one of five programs that are being
implemented as coordinated through the Departments of Commerce, State,
Energy and the Environmental Protection Agency (EPA) for a new U.S. --
Australia "Climate Action Partnership" (CAP). For further information on
this partnership see: http://www.state.gov/r/pa/prs/ps/2002/8545.htm.

**6.1.1 Grid Computing**

The "Grid" refers to the expanding network of computational and physical
scientists and leading organizations (business, government, and
academia) from around the world that have agreed to pursue large-scale
distributed processing and access across the Internet and Next
Generation Internet (NGI) or Internet-2. A feature of such collaborative
scientific enterprises is that they will require access to very large
data collections, very large scale computing resources and high
performance visualization back to the individual user scientists.

The Grid, and NOMADS is an architecture proposed to bring all these
issues together and make a reality of such a vision. There are many
developing grid technology projects. The Globus Project (Foster, et al.,
2001), approach to the Grid defines the Grid as "*an enabler for Virtual
Organizations: an infrastructure that enables flexible, secure,
coordinated resource sharing among dynamic collections of individuals,
institutions and resources*."

Collaborations under the NOMADS umbrella have been reached with several
Grid computing projects including:

-   The Earth System Grid (ESG) project http://www.earthsystemgrid.org

-   Natural Environment Research Council Datagrid:

```{=html}
<!-- -->
```
-   The Committee for Earth Observation Satellites (CEOS) Data Grid

-   The Globus Project

For detailed information on Grid technologies see

http://www.globus.org/research/papers/anatomy.pdf.

**7.0 The Users**

Currently, GFDL has one of the larger NOMADS sites for climate data. On
the GFDL NOMADS server there is model data available from various
climate studies, from the seasonal-interannual to decadal and longer
time scales. There are more than 700 GB of model data available in more
than 4,000 files. From October, 2000 to August 2002, there was more than
480 GB of data downloaded by users. There are about 75 registered users,
80% are from the United States and 20% are international users. Of the
75 users, about half are from private groups and corporations, with
about a 25% from universities and about 15% from government users. Most
of these users are scientists interested in obtaining GFDL model data.

The users of the GFDL data range from people interested in performing
studies of how the climate of Arctic region changes due to changes in
the greenhouse gases to the IPCC Data Distribution Center. A typical
user finds the model data via "word of mouth". The user then searches
the GFDL site, for the data needed. At present, this process is rather
difficult and is representative of an area of active software
development for NOMADS. The user then downloads the model data via ftp
to a local computer where the user performs some analysis using the
model data. The model data is stored in a netCDF data format, so the
analysis process is normally straightforward if the user has experience
using netCDF data.

NCDC has just completed an on-line user access and plot (browse)
capability for gridded (GRIB), NWP data sets from NCEP. NCDC has
archived operational NCEP NWP models since 1999 and is available from
the NCDC Web site at
http://www.ncdc.noaa.gov/oa/climate/nomads/nomads.html, This web
interface is user friendly, and we expect students and policymakers to
be able to use the NOMADS servers.

### **8.0 Future Requirements** {#future-requirements .unnumbered}

Even with the emergence of new web based services, the comparison of GCM
results with the observational climate record is still difficult for
several reasons. One limitation is the global distributions of a number
of basic climate quantities, such as precipitation or clouds, are not
well known. Similarly, observational limitations exist with model
re-analysis data. Both the NCEP/NCAR (Kistler, Collins, Kalnay, et al.,
2001) and the ECMWF (Gibson, et al., 1997) re-analysis eliminate the
problems of changing model analysis systems but observational data also
contain time-dependant biases by changing observational networks,
station moves, and the assimilation of various remotely sensed data
(Rutledge, et al., 1991) using differing sensor instruments, or
calibrations. These changes in input data are blended with the natural
variability making estimates of true variability uncertain. The need for
data homogeneity is critical to study questions related to the ability
to evaluate simulation of past climate. One approach to correct for
time-dependant biases and data sparse regions is the development and use
of high quality "reference" data sets (Karl, et al., 2000).

Beyond the ingest and access capability being implemented with NOMADS
are the challenges of algorithm development for the inter-comparison of
large-array data (e.g., satellite and radar) with surface, upper-air,
and sub-surface ocean observational data. The implementation of NOMADS
will foster the development of new quality control processes by taking
advantage of distributed data access. One major challenge facing the
scientific community is the development of methodologies for the
inter-comparison of large-array observational data sets with model
simulations. In the near future, NOMADS would include the development of
algorithms to blend remotely sensed data with in-situ surface and
upper-air data, then to use these blended fields for verification and
validation of both weather prediction and climate models in both time
and space (Rutledge, et al., 2001).

Finally, the interface between the NOMADS spinning disks, and
hierarchical tape archive systems such as NCDC's mass storage systems,
will be developed during 2003 so users may obtain access to data sets
destined for long-term storage.

**8.1 U.S. National Model "HelpDesk"**

Under President Bush's new Climate Change Research Initiative (CCRI),
access to and understanding of climate models and data is a high
priority. Several Agencies including the U.S. Departments of
Agriculture, Commerce, Energy, and the EPA and NOAA, are currently
collaborating to monitor emissions, foster international partnerships
for research, uncertainty reduction in climate models, and develop
technologies for access to climate models for large-scale systematic
approaches to model evaluation. A large and growing number of impacts
groups and carbon cycle researchers will require access to, and
understanding of these models and data. NCDC is charged with the archive
of these data, however users at all skill levels will require on-line
assistance with easy to navigate Web interfaces to model data. There is
a danger that if users are not properly educated on the science or use
of a specific model, it may be interpreted incorrectly, or users may use
a model in a way that is inappropriate. Users must not only have access
to data but the science and information behind the models, and how to
properly use these complex data sets.

In support of these activities and the NOMADS project itself, NCDC has
proposed the formation of a "U.S. National Climate and Weather Model
*HelpDesk*" to assist these model users. The *Helpdesk* will:

-   Provide a tailored Web interface to NCDC's archives of climate and
    weather models.

-   A capability to service users with the information they need, not
    just model output and data.

-   Develop distributed database search engines.

-   Provide for the long-term stewardship of these high volume and
    complex data and metadata at NCDC and elsewhere in a distributed
    framework.

**9.0 Acknowledgments**

The authors gratefully acknowledge the combined efforts of all the
NOMADS Team members for the growing success of NOMADS. Thanks also to
NOMADS PI's Dean Williams, Steve Hankin, Lawrence Buja, Ben Domenico,
Brian Doty, and to Ethan Davis, Don Hooper, Jennifer Adams, Jerry
Potter, Don Middleton, and Howard Diamond. Pilot funding has been
provided by ESDIM 02-444E.

# 10.0 Appendix A. Acronyms {#appendix-a.-acronyms .unnumbered}

ACARS Aircraft Communications and Reporting System

AOGCM Atmospheric-Ocean General Circulation Model

API Application Program Interface

AMIP Atmospheric Model Intercomparison Project

AS DODS Aggregation Server

ASCII American Standard Code for Information Interchange

AVN NCEP Aviation Model (now GFS)

AWIPS NWS Advanced Weather Interactive Processing System

BADC British Atmospheric Data Center

BUFR Binary Universal Form for the Representation of meteorological data

CAS NCEP Cycling Analysis System

CCRI US Climate Change Research Initiative

CCSM NCAR Community Climate System Model

CDAT PCMDI Climate Data Analysis Tools

CDC NOAA Climate Diagnostics Center

CDP NCAR Community Data Portal

CGI Common Gateway Interface

CLASS NESDIS Comprehensive Large Array Stewardship System

CMIP Coupled Model Intercomparison Project

COARDS Cooperative Ocean-Atmosphere Research Data Standard

COLA Center for Ocean-Land-Atmosphere Studies

CORBA Common Object Request Broker Architecture

DAP Data Access Protocol

DIMES Distributed Metadata Server

DOA U.S. Department of Agriculture

DOC U.S. Department of Commerce

DOE U.S. Department of Energy

DODS Distributed Oceanographic Data System

ECMWF European Center for Medium-Range Weather Forecasting

EOS Earth Observing System

EPA Environmental Protection Agency

ETA NCEP Eta Model

ERS European Remote Sensing Satellite

ESG DOE Earth System Grid

ESML Earth Science Markup Language

FGDC Federal Geographic Data Committee

FTP File Transport Protocol

GCM General Circulation Model

GCMD Global Change Master Directory

GDAS Global Data Assimilation System

GDS GrADS Data Server

GFDL Geophysical Fluid Dynamics Laboratory

GIS Geographical Information System

GOES Geostationary Operational Environmental Satellite

GrADS Grid Analysis and Display System

GRIB GRIdded Binary

GSFC Goddard Space Flight Center

GSM Global Spectral Forecast Model

GUI Graphical User Interface

HDF Hierarchical Data Format

HDF-EOS Hierarchical Data Format - EOS

HIRS High-Resolution Infrared Radiation Sounder

HTML Hyper Text Markup Language

HTTP Hypertext transport protocol

IDL Interactive Display Language

IEEE Institute of Electrical and Electronics Engineers

IIOP Internet Inter-Orb Protocol

IPCC Intergovernmental Panel on Climate Change

JGOFS Joint Global Ocean Flux Experiment

LAS Live Access Server

LLNL Lawrence Livermore National Laboratory

MIT Massachusetts Institute of Technology

MSU Microwave Sounding Unit

NASA National Aeronautics and Space Administration

NCAR National Center for Atmospheric Research

NCDC National Climatic Data Center

NCEP National Centers for Environmental Prediction

NDARS NOAAPort Data Access and Retrieval System

NERC Natural Environment Research Council

NetCDF NETwork Common Data Format Data Access Protocol

NGI Next Generation Internet

NGM NCEP Nested Grid Model

NOAA National Oceanic and Atmospheric Administration

NOPP National Oceanographic Partnership Program

NSDL National Science Digital Library

NSF National Science Foundation

NVODS NOAA Virtual Ocean Data System

NWP Numerical Weather Prediction

NWS National Weather Service

OPeNDAP Open source Project for a Network Data Access Protocol

PCM NCAR Parallel Climate Model

PCMDI Program for Climate Model Diagnosis and Intercomparison

PMEL Pacific Marine Environmental Laboratory

RUC NCEP Rapid Update Cycle Model

SSI Spectral Statistical Interpolation

SSMI Special Sensor Microwave Instrument

SST Sea Surface Temperature

TCP/IP Transmission Control Protocol/Internet Protocol

THREDDS Thematic Real-time Environmental Data Distributed Services

TIROS Television Infrared Observation Satellite

TOVS TIROS Operational Vertical Sounder

UCAR University Corporation for Atmospheric Research

URI University of Rhode Island

URL Uniform Resource Locator

USWRP U.S. Weather Research Program

WRF Weather Research Model

WWW World Wide Web

XML Extensible Markup Language

References

Alpert, J.C., 2002, Rutledge, G.K., Williams, D., Stouffer, R., Buja,
L., Doty, B, Hankin, S., Domenico, B., Kafatos, M., 2002, "The Plan to
Access Real-Time NWP Operational Model Data Sets using NOMADS",
Proceedings of the 18^th^ International Conference on Interactive
Information and Processing Systems (IIPS) for Meteorology, Oceanography,
and Hydrology, American Meteorological Society, Orlando FL. 73 pp.

Bray, T., Paoli, J., Sperberg-McQueen, C.M., 1998, "Extensible Markup
Language (XML) 1.0 Specification", W3C REC-xml-19980210:
[www.w3.org/TR/1998/REC-xml-19980210](http://www.w3.org/TR/1998/REC-xml-19980210).

Davis, E. R., J. Gallagher, J., 1999, "Using DODS to Access and Deliver
Remote Data", Proceedings of the 15^th^ International Conference on
Interactive Information and Processing Systems (IIPS) for Meteorology,
Oceanography, and Hydrology, American Meteorological Society, Dallas,
TX. 571 pp.

Doty, B.E., Wielgosz, J., Gallagher, J., Holloway, D., 2001, "GrADS and
DODS", Proceedings of the 17^th^ International Conference on Interactive
Information and Processing Systems (IIPS) for Meteorology, Oceanography,
and Hydrology, American Meteorological Society Albuquerque, NM. 385 pp.

Foster, I., Kesselman, C. and Tuecke, S. 2001, "The Anatomy of the Grid:
Enabling Scalable Virtual Organizations", International Journal of

High Performance Computing Applications, 15 (3). 200-222.

Gibson, J. K., P. Kallberg, S. Uppala, A. Noumura, A. Hernandez, and E.
Serrano, 1997, "ERA Description. ECMWF Re‑Analysis Project Report",
Series 1, ECMWF, Reading, UK, 77 pp.

Hankin, S., J. Callahan, and J. Sirott, 2001, "The Live Access Server
and DODS: Web visualization and data fusion for distributed holdings",
17^th^ Conference on Interactive Information and Processing Systems
(IIPS) for Meteorology, Oceanography, and Hydrology, American
Meteorological Society, Albuquerque, NM. 380 pp.

Karl, T., D. Easterling, P. Groisman, et al., March 2000, "Observed
Variability and Trends in Extreme Climate Events: A Brief Review",
Bulletin of the American Meteorological Society, 81, 417 pp.

Kistler, R., W. Collins, E. Kalnay, R. Reynolds, S. Saha, G. White, J.
Woollen, Y. Zhu, M. Chelliah, W. Ebisuzaki, J. Janowiak, M. Kanamitsu,
K. Mo, C. Ropelewski, R. Jenne, D. Joseph and M. Fiorino, 2001: The
NCEP/NCAR 50‑year Reanalysis: Monthly‑means CD‑ROM and Documentation.
Bulletin of the American Meteorological Society, 92, 247 pp.

Ramachandran R., M. Alshayeb, B. Beaumont, H. Conover, S. Graves, X. Li,
S. Movva, A. McDowell and M. Smith, 2001: "Earth Science Markup
Language: A Solution for Generic Access to Heterogeneous Data Sets,"
Earth Science Technology Conference, Maryland

Rutledge, G.K., E. Legg, and P. Menzel, 1991, "Operational Production of
Winds from Cloud Motions", Palaeogeography, Palaeoclimaotology,
Palaeoecology, Vol. 90 No. 1-3 (Global and Planetary Change Section),
141 pp.

Rutledge, G.K., A. Stanley, E. Page, L. Spayd, and J. Brundage, 2000,
"Implementation of the NOAAPort Data Archive and Retrieval System
(NDARS) at the National Climatic Data Center", Proceedings 16^th^
Conference on Interactive Information and Processing Systems (IIPS) for
Meteorology, Oceanography, and Hydrology, Long Beach, American
Meteorological Society, 492 pp.

Rutledge, G.K., T. Karl, D. Easterling, L. Buja, R. Stouffer, 2001
"Evaluating Transient Global and Regional Model Simulations: Bridging
the Model/Observations Information Gap", (Invited), American Geophysical
Union, Spring Meeting Boston MA S35 pp.

Rutledge, G.K., D. Williams, R. Stouffer, J. Alpert, L. Buja, B. Doty,
S. Hankin, B. Domenico, M. Kafatos, 2002, "The NOAA Operational Model
Archive and Distribution System (NOMADS)", Proceedings 13^th^ Symposium
on Global Change and Climate Variations, American Meteorological
Society, Orlando FL. J76 pp.

Williams, D.N., R.S. Drach, P.F. Dubois, C. Doutriaux, C.J. O'Connor,
K.M. AchutaRao, and M. Fiorino, 2002: Climate Data Analysis Tool: An
open software system approach. 13^th^ Symposium on Global Change and
Climate Variations, American Meteorological Society extended abstract
volume, Orlando, Florida, J71pp.

Yang, R., X. Deng, M. Kafatos, C. Wang and X. Wang, 2001, "An XML-Based
Distributed Metadata Server (DIMES) Supporting Earth Science Metadata",
Proceedings of the 13^th^ International Conference on Scientific and
Statistical Database Management, Institute of Electrical and Electronics
Engineers, Computer Society, Fairfax VA. 251 pp.

[^1]: ^†^ Work partially supported by grant NES-444E (ESDIM) of the
    National Oceanic and Atmospheric Administration (NOAA).