An increasingly significant use of meteorological data is the monitoring of the climate of our planet, which undergoes considerable changes. Just twenty years ago the study of climate was not a high research priority. Now climate issues are prominent; some of the nation's top scientists specialize in climate study, and policymakers actively seek information on what climatic conditions we might expect in the future. The importance of old atmospheric data thus has come to the forefront. Analyses of these old data in search of trends have often found them inadequate and poorly documented. Furthermore, this recent usage was not anticipated. The growing interest in global climate change and the difficulties with historic data that it helped uncover have been perhaps the strongest motivators for earth scientists to take a serious interest in the long-term preservation of atmospheric and other environmental data. Studies of long-term water and land usage need time series of at least many decades. Similar data needs apply to planning aquifer usage, and studies on deforestation and desertification.

Some historians examine connections between environmental conditions and human events. The time scales studied can range from the acute, such as the influence of weather on battles, to the long term, such as the rise or decline of a civilization affected by water availability. Workers in this field often search through the oldest existing data and have even provided meteorological information to atmospheric scientists from unconventional sources such as diaries and agricultural records.

4 ARRANGEMENTS FOR STORAGE AND ARCHIVING

The arrangements for the storage and archiving of atmospheric data are diverse and complex, and present many problems. Some of these arrangements could be improved. Atmospheric data can be found in many locations and have a broad range of differing life cycles. Difficult problems are raised in the preparation of metadata, packaging data for extended archiving, motivating researchers to prepare their data for use by others, and the very large size of some atmospheric data sets. Criteria for deciding which data sets should be saved indefinitely are not obvious. Finally, any proposed solutions must come up against limits on budgets and other resources. In this section, the panel provides some analyses of and suggestions for improvements in the archiving of atmospheric data.

Where the Data Are

The largest atmospheric science data holdings in the United States are those of the federal government. However, significant amounts of material are available only from state or private sources. Some U.S. data are archived primarily at foreign locations in the World Data Centers, while some World Data Centers are in the United States.

For much meteorological and climate research and for many applications, it is essential to have archives of data from around the globe. This has been achieved largely in the United States. Collectively, U.S. archives have the best sets of global data of any nation. There are still many valuable data stored in other nations, however, that our scientists cannot access (and sometimes are inaccessible to that nation's own scientists as well). The principal holdings of atmospheric data in the United States are reviewed below.

National Climatic Data Center

The largest holdings of atmospheric data are at the NCDC in Asheville, North Carolina. At the end of 1993 NCDC maintained roughly 450 data sets, with 210 million paper records, 1.2 million microfiche, and over 200 thousand magnetic tapes and cartridges (containing about 100 terabytes of data). By a combination of federal statute and interagency agreement, NCDC has been designated the official repository for all federally owned weather and climate data. NCDC is also World Data Center-A for meteorology.

The NCDC collection contains records for most of the traditional meteorological observations listed in Table III.2. NCDC also serves as home to most U.S. radar data and will soon be accepting the bulk of the NEXRAD data tapes. Extensive satellite data holdings can be found at NCDC, but these data are distributed in many other locations as well.

Though domestic data dominate the collections at NCDC, there are also significant foreign data. NCDC has a long-established international exchange of surface marine weather data. Monthly foreign data publications were maintained by NCDC in the 1960s and early 1970s. This program largely disintegrated in the 1980s, but is now being revived and enhanced; basic information will be entered into a library-type on-line database. NCDC also has



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