The Unidata Local Data Manager (LDM) (Unidata, 2002) distributes World Meteorological Organization (WMO) Surface Meteorological data. These data have been converted to columnar ASCII NCAR/EOL surface QC format by the National Center for Atmospheric Research/ Earth Observing Laboratory (NCAR/EOL). The "Nominal" hourly observations for the TREX domain and time period are oncluded in the dataset "LDM Surface METAR Hourly Data (NCAR/EOL surface QC format) [NCAR/EOL). Special records are located in the dataset "LDM Surface METAR Specials Data (NCAR/EOL surface QC format) [NCAR/EOL]". This documentation applies to both.
Parameters Units
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Date of Observation UTC Nominal
Time of Observation UTC Nominal
Date of Observation UTC Actual
Time of Observation UTC Actual
Network Identifier Abbreviation of platform name
Station Identifier Network Dependent
Latitude Decimal degrees, South is negative
Longitude Decimal degrees, West is negative
Station Occurrence Unitless
Station Elevation Meters
Station Pressure, QC flag Hectopascals (mb)
Reported Sea Level Pressure, QC flag Hectopascals (mb)
Computed Sea Level Pressure, QC flag Hectopascals (mb)
Dry Bulb Temperature, QC flag Celsius
Dew Point, QC flag Celsius
Wind Speed, QC flag m/s
Wind Direction, QC flag Degrees
Total Precipitation, QC flag mm
Squall/Gust Indicator Code Value
Squall/Gust Value, QC flag m/s
Present Weather, QC flag Code Value
Visibility, QC flag Meters
Ceiling Height (first layer) Hundreds of feet
Ceiling Flag (first layer), QC flag Code Value
Cloud Amount (first layer), QC flag Code Value
Ceiling Height (second layer) Hundreds of feet
Ceiling Flag (second layer), QC flag Code Value
Cloud Amount (second layer), QC flag Code Value
Ceiling Height (third layer) Hundreds of feet
Ceiling Flag (third layer), QC flag Code Value
Cloud Amount (third layer), QC flag Code Value
The list of code values for the Present Weather is too large to reproduce in this document. Refer to WMO, 1988 for a complete list of Present Weather codes.
The code values for the Squall/Gust Indicator are:
Code Definition
---- ----------
blank No Squall or Gust
S Squall
G Gust
The code values for the ceiling flag Indicator are:
Code Definition
---- ----------
0 None
1 Thin
2 Clear below 12,000 feet
3 Estimated
4 Measured
5 Indefinite
6 Balloon
7 Aircraft
8 Measured/Variable
9 Clear below 6,000 feet (AUTOB)
10 Estimated / Variable
11 Indefinite / Variable
12 12-14 reserved
15 Missing
The code values for the Cloud Amount Indicator are:
Code Definition
---- ----------
0 0 ( or clear)
1 1 okta or less, but not zero or 1/10 or less, but not zero
2 2 oktas or 2/10-3/10
3 3 oktas or 4/10
4 4 oktas or 5/10
5 5 oktas or 6/10
6 6 oktas or 7/10-8/10
7 7 oktas or more, but no 8 oktas or 9/10 or more, but not 10/10
8 8 oktas or 10/10 (or overcast)
9 Sky obscured by fog and/or other meteorological phenomena
10 Sky partially obscured by fog and/or other meteorological
phenomena
11 Scattered
12 Broken
13 13-14 Reserved
15 Cloud cover is indiscernible for reasons other than fog or
other meteorological phenomena, or observation is not made.
The "Nominal" hourly observations for the TREX domain and time period are included in the dataset " Surface Meteorological (Hourly) Multi-Network Composite [NCAR/EOL]. Special records are located in the dataset "LDM Surface METAR Specials Data (NCAR/EOL surface QC format) [NCAR/EOL]". This documentation applies to both.
Sea Level Pressure is calculated from station pressure using standard GEMPAK algorithms (Unidata, 2003).
When not present in the raw data, the dewpoint temperature was computed by UCAR/JOSS from temperature and relative humidity using the formula from Bolton (1980).
When not present in the raw data, station pressure is computed
by UCAR/JOSS from altimeter and elevation using the formula from the
Smithsonian Meteorological Tables, 1949.
Bolton, D., 1980: The computation of equivalent potential temperature.,
Mon. Wea. Rev., 108, pp 1046-1053.
Smithsonian Meteorological Tables, Table No. 65, p.269.
Smithsonian Institution Press, Washington, D.C., September, 1949.
Unidata, Cited 2002: Unidata LDM [Available online from
http://www.unidata.ucar.edu/packages/ldm/].
Unidata, Cited 2003: Unidata GEMPAK/N-AWIPS [Available online from
http://www.unidata.ucar.edu/packages/gempak/].
World Meteorological Organization (WMO), 1988: Manual on Codes
Volume I, Part B - Binary Codes. WMO, Geneva, Switzerland.
3.0 Quality Control Processing
This dataset was not quality controlled by UCAR/JOSS. Possible
quality control flags occuring in the data are:
QC Code Description
------- -----------
U Unchecked
M Normally recorded but missing.
4.0 References