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Each sounding in the archive consists of a header record, followed by a number of data records. Typically 20 to 40 levels are available in each sounding. Appendix 2 includes an example of a sounding. The database is archived on CD-ROM.
We recognize that users usually desire a database of this type to be sorted in one of two ways:
As a compromise, the following file structure is used: One file contains a one-year time series of soundings for one station. Users requiring station-ordered data can append individual one-year files to obtain a station history of a length that is suitable to their needs. Users requiring synoptic-ordered data may extract files for several stations corresponding to a particular year, then extract from them the necessary dates and times.
The variables and formats of the individual soundings are as follows:
1. STATION
World Meteorological Organization (WMO) station identification number. All stations are ascribed a WMO number with the exception of "SHIP M" (Figure 1; Appendix 1). This was arbitrarily assigned a station code of 80000.
2. LATITUDE
Latitude of the station in degrees and hundredths of a degree (N).
3. LONGITUDE
Longitude from 0 to 360 degrees, in degrees and hundredths of a degree, measured counterclockwise from the Greenwich Meridian as viewed from the pole.
4. YEAR
Year of sounding.
5. MONTH
Month of sounding.
6. DAY
Day of sounding.
7. HOUR
Hour of sounding. This is usually 0000 GMT, 0600 GMT, 1200 GMT or 1800 GMT. Prior to 1952, however, soundings reported at 0800 GMT and 1400 GMT.
8.-10. PROC1, PROC2, PROC3
Special processing codes. These are only available for sounding type ID=1. They provide information on special processing, and whether soundings were manually or automatically processing (see Appendix 4). For all other sounding types (ID=2, 3, 4 or 5), PROC1, PROC2, and PROC3 are assigned blanks. Pages 6 and 7 of Office Note 29 (Mulder, 1977), which describe these codes for the ID=1 data, are given in Appendix 5.
11. REP
Report type. This will always be assigned the value of 011 or 0. It denotes that the sounding was taken at a fixed land station.
12. ELEVATION
Station elevation in meters above mean sea level. Missing values are 99999.
13. INSTRUMENT
Instrument type used in sounding (e.g., Vaisala, Metox). This information is only available for ID=1 soundings. Page 9 of Office Note 29 (Mulder, 1977), describing the instruments for ID=1 soundings, is included in Appendix 5. For all other sounding types, this variable is assigned a value of 0.
14. NLEVELS
The number of levels reported in the sounding; i.e., the number of data records following the header record.
15. ID
An identification code indicating which original source the sounding came from. Values correspond to the listing in Section 2. These identification values are important because the quality codes vary with each sounding type (Appendix 4).
The FORTRAN format of the header record (15 variables) is as follows: FORMAT (A5, 2I5, 1X, 4I2, 1X, 3A1, I3, I5, I2, 1X, I3, 1X, I1).
The variables are as follows:
1. PRESSURE
Pressure in tenths of millibars. Data from most stations are rounded to the nearest 1 mb. Missing values are 99999.
2. GEOPOTENTIAL HEIGHT
Geopotential height of the pressure level in whole meters. Missing values are 99999.
3. TEMPERATURE
Temperature in tenths of a degree (degrees C). Missing values are 9999.
4. DEWPOINT DEPRESSION
Dewpoint depression in tenths of a degree (degrees C). Missing values are 999.
5. WIND DIRECTION
Wind direction, 0-360 degrees, measured clockwise from north (e.g., 90 degrees is east). Missing values are 999.
6. WIND SPEED
Wind speed in whole meters per second. Missing values are 999.
7.-15. QG, QG1, QT, QT1, QD, QD1, QW, QW1, QP
Quality control flags for geopotential height (QG, QG1), temperature (QT, QT1), dewpoint depression (QD, QD1), winds (QW, QW1), and pressure (QP). The values of QG, QT, QD, QW, and QP depend on the sources of the sounding as identified by the value of ID (see Appendix 4). These vary considerably among the sources of the original soundings, and on whether the original processing was accomplished automatically (via computer) or manually (designated by "auto" or "man" in Appendix 4).
QG1, QT1, QD1, and QW1 are additional quality code flags for geopotential height, temperature, dewpoint depression, and winds, based on additional error-checking procedures. Values are either 'P' (passed limits check) or 'F' (failed limits check). No limits check quality flag is given for pressure, as we used pressure as the test variable in the limits check. (These additional codes are not available on Volume 5. Please see Revision below.)
16. LEVCK
A quality control flag set to 'P' if there were no errors detected in the level for any variable based on the limits check described above. If any errors were detected in the limits check, it is set to 'F'. *(This variable is not available on Volume 5. Please see Revision below.)
17. LTYPE
Code for level type (surface, significant, or mandatory). Only relevant for soundings of type ID=4 (see Appendix 4). For sounding types other than ID=4, the value is assigned a blank. *(This variable is not available on Volume 5. Please see Revision below.)
18. LQUAL
Flag for quality of level. Only relevant for soundings of type ID=4 (see Appendix 4). *(This variable is not available on Volume 5. Please see Revision below.)
The FORTRAN format of the data records (18 variables) are as follows: FORMAT (2(I5, 1X), I4, 1X, 3(I3, 1X), 2A1, 1X, 2A1, 1X, 2A1, 1X, 2A1, 1X, 4A1).
*Revision
Experience has shown that the additional quality codes have limited value to the user. Starting with Volume 5, these codes are no longer provided. The columns corresponding to these codes simply appear as blanks. FORTRAN code that performs more comprehensive error-checking is available from M. Serreze.
