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About the GSOD Data Set
The data summaries provided here are based on data exchanged under the World Meteorological Organization (WMO) World Weather Watch Program according to WMO Resolution 40 (Cg-XII). This allows WMO member countries to place restrictions on the use or re-export of their data for commercial purposes outside of the receiving country. Data for
selected countries may, at times, not be available through this system.
Those countries' data summaries and products which are available
here are intended for free and unrestricted use in research,
education, and other non-commercial activities. However, for
non-U.S. locations' data, the data or any derived product shall
not be provided to other users or be used for the re-export ofcommercial services. To determine off-line availability of anycountry's data, please contact NCDC: ncdc.orders@noaa.gov, 828-271-4800. Please email ncdc.info@noaa.gov if you haveany other questions.
As described below, the data are available via:
- WWW -- http://www.ncdc.noaa.gov/cgi-bin/res40.pl?page=gsod.htmland
- FTP -- ftp://ftp.ncdc.noaa.gov/pub/data/gsod
and...the WWW system includes graphing and selection of data by station and element.
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OVERVIEW
The following is a description of the global surface summary of day product produced by the National Climatic Data Center (NCDC)
in Asheville, NC. The input data used in building these daily summaries are the Integrated Surface Data (ISD), which includes global data obtained from the USAF Climatology Center, located in the Federal Climate Complex with NCDC. The latest daily summary
data are normally available 1-2 days after the date-time of the observations used in the daily summaries. The online data files begin with 1929, and are now at the Version 7 software level. Over 9000 stations' data are typically available.
The daily elements included in the dataset (as available from each station) are:
- Mean temperature (.1 Fahrenheit)
- Mean dew point (.1 Fahrenheit)
- Mean sea level pressure (.1 mb)
- Mean station pressure (.1 mb)
- Mean visibility (.1 miles)
- Mean wind speed (.1 knots)
- Maximum sustained wind speed (.1 knots)
- Maximum wind gust (.1 knots)
- Maximum temperature (.1 Fahrenheit)
- Minimum temperature (.1 Fahrenheit)
- Precipitation amount (.01 inches)
- Snow depth (.1 inches)
- Indicator for occurrence of:
- Fog
- Rain or Drizzel
- Snow or Ice Pellets
- Hail
- Thunder
- Tornado/Funnel Cloud
For details on the contents of the dataset, see the format documentation shown below.
The data are available via:
1) WWW -- http://www.ncdc.noaa.gov/cgi-bin/res40.pl?page=gsod.html
2) FTP -- ftp://ftp.ncdc.noaa.gov/pub/data/gsod via browser
3) Command line ftp:
a) Enter: open ftp.ncdc.noaa.gov
b) Login is: ftp
c) Password is: your email address
d) To move to the correct subdirectory, enter:
cd /pub/data/gsod
The files included in this subdirectory are:
Data Files--
Annual files:
eg, gsod_2006.tar - All 2006 files (compressed) by station, in one tar file.
etc, etc - For each annual volume.
Note: Each year's data are contained in subdirectories/folders by year.
Station files:
eg, 010010-99999-2006.op.gz - Files by station year, identified by WMO number, WBAN number (if appropriate), and year. For a cross reference of the filenames with location, see:ish-history.txt
Informational/Utility Files--
country-list.txt - A list showing the station number range for each country.
ish-history.txt -- A station list to be used with the data files, showing the names and locations for each station.
Note: Global summary of day contains a subset of the stations listed in this station history.
readme.txt - A description of the data and its format.
e) To get a copy of the data description, enter:
get readme.txt destination (destination is your
output location and name)...e.g.--
get readme.txt c:readme.txt - copies to hard drive c:
f) Then, to get a copy of any of the other files, use
the same procedure, such as--
get gsod_2006.tar c:data.txt
g) To logoff the system when finished, enter:
bye
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DETAILS/FORMAT
Global summary of day data for 18 surface meteorological elements are derived from the synoptic/hourly observations contained in USAF DATSAV3 Surface data and Federal Climate Complex Integrated Surface Data (ISD). Historical data are generally available for 1929 to the present, with data from 1973 to the present being the most complete. For some periods, one or more countries' data may not be available due to data restrictions or communications problems. In deriving the summary of day data, a minimum of 4 observations for the day must be present (allows for stations which report 4 synoptic observations/day). Since the data are converted to constant units (e.g, knots), slight rounding error from the originally reported values may occur (e.g, 9.9 instead of 10.0).
The mean daily values described below are based on the hours of operation for the station. For some stations/countries, the visibility will sometimes 'cluster' around a value (such as 10 miles) due to the practice of not reporting visibilities greater than certain distances. The daily extremes and totals--maximum wind gust, precipitation amount, and snow depth--will only appear if the station reports the data sufficiently to provide a valid value. Therefore, these three elements will appear less frequently than other values. Also, these elements are derived from the stations' reports during the day, and may comprise a 24-hour period which includes a portion of the previous day. The data are reported and summarized based on Greenwich Mean Time (GMT, 0000Z - 2359Z) since the original synoptic/hourly data are reported and based on GMT.
As for quality control (QC), the input data undergo extensive automated QC to correctly 'decode' as much of the synoptic data as
possible, and to eliminate many of the random errors found in the original data. Then, these data are QC'ed further as the summary of day data are derived. However, we expect that a very small % of the errors will remain in the summary of day data.
The data are strictly ASCII, with a mixture of character data, real values, and integer values.
Following is the data format:
First record--header record.
All ensuing records--data records as described below.
All 9's in a field (e.g., 99.99 for PRCP) indicates no report or insufficient data.
FIELD POSITION TYPE DESCRIPTION
STN--- 1-6 Int. Station number (WMO/DATSAV3 number)
for the location.
WBAN 8-12 Int. WBAN number where applicable--this is the
historical "Weather Bureau Air Force Navy"
number - with WBAN being the acronym.
YEAR 15-18 Int. The year.
MODA 19-22 Int. The month and day.
TEMP 25-30 Real Mean temperature for the day in degrees
Fahrenheit to tenths. Missing = 9999.9
(Celsius to tenths for metric version.)
Count 32-33 Int. Number of observations used in
calculating mean temperature.
DEWP 36-41 Real Mean dew point for the day in degrees
Fahrenheit to tenths. Missing = 9999.9
(Celsius to tenths for metric version.)
Count 43-44 Int. Number of observations used in
calculating mean dew point.
SLP 47-52 Real Mean sea level pressure for the day
in millibars to tenths. Missing =
9999.9
Count 54-55 Int. Number of observations used in
calculating mean sea level pressure.
STP 58-63 Real Mean station pressure for the day
in millibars to tenths. Missing =
9999.9
Count 65-66 Int. Number of observations used in
calculating mean station pressure.
VISIB 69-73 Real Mean visibility for the day in miles
to tenths. Missing = 999.9
(Kilometers to tenths for metric version.)
Count 75-76 Int. Number of observations used in
calculating mean visibility.
WDSP 79-83 Real Mean wind speed for the day in knots
to tenths. Missing = 999.9
(Meters/second to tenths for metric version.)
Count 85-86 Int. Number of observations used in
calculating mean wind speed.
MXSPD 89-93 Real Maximum sustained wind speed reported
for the day in knots to tenths.
Missing = 999.9
(Meters/second to tenths for metric version.)
GUST 96-100 Real Maximum wind gust reported for the day
in knots to tenths. Missing = 999.9
(Meters/second to tenths for metric version.)
MAX 103-108 Real Maximum temperature reported during the
day in Fahrenheit to tenths--time of max
temp report varies by country and
region, so this will sometimes not be
the max for the calendar day. Missing =
9999.9
(Celsius to tenths for metric version.)
Flag 109-109 Char Blank indicates max temp was taken from the
explicit max temp report and not from the
'hourly' data. * indicates max temp was
derived from the hourly data (i.e., highest
hourly or synoptic-reported temperature).
MIN 111-116 Real Minimum temperature reported during the
day in Fahrenheit to tenths--time of min
temp report varies by country and
region, so this will sometimes not be
the min for the calendar day. Missing =
9999.9
(Celsius to tenths for metric version.)
Flag 117-117 Char Blank indicates min temp was taken from the
explicit min temp report and not from the
'hourly' data. * indicates min temp was
derived from the hourly data (i.e., lowest
hourly or synoptic-reported temperature).
PRCP 119-123 Real Total precipitation (rain and/or melted
snow) reported during the day in inches
and hundredths; will usually not end
with the midnight observation--i.e.,
may include latter part of previous day.
.00 indicates no measurable
precipitation (includes a trace).
Missing = 99.99
(For metric version, units = millimeters
to tenths & missing = 999.9.)
Note: Many stations do not report '0' on
days with no precipitation--therefore,
'99.99' will often appear on these days.
Also, for example, a station may only
report a 6-hour amount for the period
during which rain fell.
See Flag field for source of data.
Flag 124-124 Char A = 1 report of 6-hour precipitation
amount.
B = Summation of 2 reports of 6-hour
precipitation amount.
C = Summation of 3 reports of 6-hour
precipitation amount.
D = Summation of 4 reports of 6-hour
precipitation amount.
E = 1 report of 12-hour precipitation
amount.
F = Summation of 2 reports of 12-hour
precipitation amount.
G = 1 report of 24-hour precipitation
amount.
H = Station reported '0' as the amount
for the day (eg, from 6-hour reports),
but also reported at least one
occurrence of precipitation in hourly
observations--this could indicate a
trace occurred, but should be considered
as incomplete data for the day.
I = Station did not report any precip data
for the day and did not report any
occurrences of precipitation in its hourly
observations--it's still possible that
precip occurred but was not reported.
SNDP 126-130 Real Snow depth in inches to tenths--last
report for the day if reported more than
once. Missing = 999.9
(Centimeters to tenths for metric version.)
Note: Most stations do not report '0' on
days with no snow on the ground--therefore,
'999.9' will often appear on these days.
FRSHTT 133-138 Int. Indicators (1 = yes, 0 = no/not
reported) for the occurrence during the
day of:
Fog ('F' - 1st digit).
Rain or Drizzle ('R' - 2nd digit).
Snow or Ice Pellets ('S' - 3rd digit).
Hail ('H' - 4th digit).
Thunder ('T' - 5th digit).
Tornado or Funnel Cloud ('T' - 6th
digit).
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REFERENCE
The NCDC Climate Services Branch (CSB) is responsible for
distribution of NCDC products to users. NCDC's CSB can be
contacted via the following phone number, internet address, or
fax number.
Telephone Number: 828-271-4800
Fax Number: 828-271-4876
Internet Address: ncdc.orders@noaa.gov
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