SEACOOS CDL v2.0 December 9, 2004 1 1. Introduction This document describes a set of conventions adopted by the SouthEast Atlantic Coastal Ocean Observing System (SEACOOS) to promote sharing and exchange of data from disparate ocean observing and remote-sensing data sources.  These data include observations from buoys, offshore towers, ships, tide- and stream-gauging stations, acoustic profilers, radar, aircraft, satellites and other remote mapping sensors. SEACOOS is a regional partnership that has initiated an integrated coastal ocean observing system for a four-state (North Carolina, South Carolina, Georgia and Florida) region of the southeast coastal U.S. (Seim, et al., 2003, Seim, et al, 2002). SEACOOS partners publish near real-time data in  netCDF (network Common Data Form) format and make it available on the Internet through OPeNDAP (Open source Project for a Network Data Access Protocol) Servers. This document details the agreed upon netCDF format categories, required variables, and required and recommended attributes.  The name of this standard is “SE ACOOS CDL”.  CDL stands for Common Data Language. The current accepted version is 2.0.   SEACOOS CDL provides conformity to develop automated search and aggregation tools. It is also flexible to allow SEACOOS to coordinate many different sources of data into a merged dataset and provide unique graphical displays of these merged data in near real- time.  SEACOOS CDL provides an unambiguous output format for SEACOOS partners.  It allows anyone to incorporate their observational data into powerful displays with similar data. 2. General Background 2.1 Data Management Coordinating Committee (DMCC) The Data Management Coordinating Committee (DMCC) of SEACOOS establishes hardware, software, data format, and metadata conventions in order to help partners make data distribution systems operational. This committee is made up of data management personnel from each of the SEACOOS partner institutions.  The DMCC is responsible for developing and documenting SEACOOS CDL. One main goal of the DMCC is “to provide access via a web interface to SEACOOS-supported, quality controlled data and associated metadata and derived products.” Another goal of this committee is “to implement the OPeNDAP software solution as a form of data sharing.”  The OPeNDAP protocol ha s been designated by Ocean.US as a component for the delivery of data in a sustainable Integrated Ocean Observing System (IOOS).   The main obstacles that the DMCC overcame in drafting the SEACOOS CDL standard were how to unambiguously describe the time and vertical coordinates.  A number of choices had to be made to provide consistency but remain flexible for the different sources of data that observational data presents. The first choice was that each partner would provide data in netCDF files and share their data in a distributed forum by using OPeNDAP. NetCDF is the most tested and supported file formats under OPeNDAP. Other data formats such as XML, HDF, and RDBMS will probably be investigated by the DMCC in the future.