National Solar Radiation Data Base User's Manual (1961-1990)

Table of Contents

1.0 Background and Overview: The National Solar Radiation Data Base (Version 1.0)

Part 1: How to Use and Interpret Data Base Products

2.0 Data Base Product Options

Current products available for Version 1.0 of the NSRDB are briefly described here. These products are intended to fit the applications of most data base users. Detailed descriptions of these products are provided in Section 3.0; information on how the products were developed is given in Part 2.

Product options include (1) serial hourly data in two formats, (2) hourly, daily, and quality statistics for solar radiation elements, (3) daily statistics for meteorological elements, and (4) persistence statistics for daily total solar radiation energy.

2.1 Hourly Data

The serially complete hourly data provided in the data base are available in NSRDB synoptic and TD-3282 formats. Each record in the NSRDB synoptic products contains hourly sequential data for five elements of solar radiation data (three surface and two extraterrestrial above the earth's atmosphere) and 15 elements of surface meteorological data. The synoptic format also contains quality flags (source and uncertainty) following each solar radiation element and separates each element by one space for greater readability when displayed linebyline on your computer or terminal monitor. Flags for meteorological elements are not included in the synoptic format.

TD-3282 is NCDC's archive format featuring daily interleaving of each of the elements specified. Each logical record contains one station's hourly data values for a specific solar radiation or meteorological element for a period of one day. The next record contains hourly data for the same day for the next element; i.e., the elements are interleaved such that all of the elements for one day appear sequentially in a block of 6000 characters. The TD-3282 element file structure is designed to allow maximum flexibility in requesting data. You need order only those elements or groups of elements of particular interest to you. In other words, if you want only the three solar radiation elements, you do not have to purchase and store all of the meteorological elements included in the synoptic products.

More detailed information on the synoptic and TD-3282 formats can be found in Section 3.0.

2.2 Statistical Summaries

The NSRDB contains statistical summaries computed from the hourly data for the entire period of record for all stations. For the solar radiation data, these statistics include the average and standard deviation of the daily total solar energy (direct normal, diffuse horizontal, and global horizontal) for each station-year-month and each station-year. The 30-year averages and the standard deviations of monthly and annual means from 1961 through 1990 are also provided. For the meteorological elements, only monthly, annual, and 30-year averages were computed.

The hourly statistical products include monthly, annual, and 30-year averages and standard deviations for each hour of the day for global horizontal, direct normal, and diffuse horizontal solar radiation. The averages can be used to prepare average diurnal profiles of hourly solar energy. The hourly values have also been binned in twenty four 50-Wh/m2 bins from 0 to 1200 Wh/m2. The mean number of hourly values falling into each bin have been determined for each station-month for the 30-year period of record from 1961 to 1990. These statistics can be used to plot histograms and/or determine cumulative frequency distributions.

A solar radiation persistence product was created for each station-month by calculating the number of times the daily total solar radiation energy persisted above or below set thresholds for periods from 1 to 15 days. These calculations were performed for the entire 30-year period from 1961 to 1990.

Statistics on the quality of the solar radiation data were determined by calculating the percentage of the hourly values to which each source and uncertainty flag was assigned. These percentages were calculated for each station-year and for the 30-year period of record and are available as a separate product.

2.3 Media

NSRDB synoptic data are available on magnetic media (3.5-in. or 5.25-in. high-density diskettes and 9-track high-density magnetic tapes). Data for one year can be placed on one high-density (1.2 MB) diskette. All 30 years for three stations can be placed on one high-density magnetic tape. Approximately 80 tapes are required to hold the entire data base. Individual station-years or any combination of stations and years can be ordered from NCDC.

Data in TD-3282 format also are available on magnetic media (3.5-in. or 5.25-in. high-density diskettes or high-density magnetic tapes). Each 1.2-megabyte diskette can hold ten years of data for a single element. Two diskettes are needed for one year of data for all elements. All 30 years of data for two stations can be placed on one high-density magnetic tape.

Daily, hourly, persistence, and quality statistics are available on magnetic media (diskettes and tape), and printed hard copy:

When future NSRDB products are produced (e.g., CD-ROM products) they will be announced by NREL and NCDC.

2.4 Where to Order Data Base Products

All of the products from the NSRDB can be ordered from NCDC at the following address:

In addition to the products described in this manual, special products made to the user's specifications can be supplied at a cost that will be quoted by NCDC. NCDC will supply a cost sheet for standard products on request.

3.0 Reading and Understanding Data Base Products

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