NOAA buoy data
From I2U2
NOAA collects weather and water condition data from buoys anchored off the U.S. coast. Historical data from these buoys can be downloaded via the internet.
Contents |
[edit] File Names
A typical URL looks like
http://www.ndbc.noaa.gov/data/historical/stdmet/46005h2004.txt.gz
The file name contains the name of the station (the buoy), and the type and year of the observations. In this example the buoy number is "46005", the "h" indicates that the file contains hourly observations, and the file contains all observations for the year 2004. The ".txt" file extentsion indicates a text file, but the additional ".gz" extenstsion indicates that the file has been compressed with the gzip program.
[edit] File Format
After they are uncompressed, each file is an ASCII text file with one observation per line. Each observation consists of the date and time of the the measurements, followed by wind, water and air measurements. A typical file looks like:
YYYY MM DD hh WD WSPD GST WVHT DPD APD MWD BAR ATMP WTMP DEWP VIS TIDE 2004 01 01 00 160 1.1 3.0 5.09 14.29 9.96 999 1006.7 4.6 9.4 999.0 99.0 99.00 2004 01 01 01 55 2.3 4.7 5.27 14.29 10.32 999 1006.6 4.4 9.4 999.0 99.0 99.00 2004 01 01 02 150 2.1 4.1 4.80 16.67 10.59 999 1005.7 4.7 9.4 999.0 99.0 99.00 2004 01 01 03 304 8.4 10.7 4.13 14.29 9.55 999 1005.5 4.2 9.4 999.0 99.0 99.00 2004 01 01 04 82 4.3 6.4 4.69 14.29 10.34 999 1005.2 2.9 9.4 999.0 99.0 99.00 2004 01 01 05 143 2.9 5.1 4.68 12.50 9.99 999 1005.1 4.0 9.4 999.0 99.0 99.00 2004 01 01 06 215 1.1 2.7 4.54 12.50 9.99 999 1004.8 4.7 9.4 999.0 99.0 99.00 2004 01 01 07 246 1.1 2.8 4.57 12.50 9.92 999 1004.3 4.8 9.4 999.0 99.0 99.00 2004 01 01 08 310 6.3 10.5 4.25 14.29 9.43 999 1003.7 5.1 9.4 999.0 99.0 99.00
The fields YYYY, MM, DD, hh specify the year, month, day and hour of the observation in UTC. After that:
- WD is wind direction, in degrees measured from True North
- WSPD is wind speed, in meters/sec
- GST reports wind gusts, in meters/sec
- WVHT is wave height, in meters
- DPD is dominant wave period, in seconds
- APD is average wave period, in seconds
- MWD is mean wave direction, measured from True North
- BAR is barometric pressure, in hPa
- ATMP is air temperature, in Celsius
- WTMP is water temperature, in Celsius
- DEWP is the dew point, in Celsius
- VIS is visibility, in statute miles
- TIDE is water level, in feet above or below the "mean lower low water" level
Values of 999.0 or 99.0 are used to indicate missing measurements. In some cases a sensor may be broken, in others the sensor necessary for a measurement is not installed on the buoy.
A more complete description of these measurements and how they are obtained may be found at http://www.ndbc.noaa.gov/measdes.shtml#stdmet
[edit] File Format Changes
The format of these data files will change on 10 April 2007. New files will use the new format, old files will remain in the old format. The primary change is in the headers. The header lines will begin with "#", and a second header line will indicates the units. For example:
#YY MM DD hh mm WDIR WSPD GST WVHT DPD APD MWD PRES ATMP WTMP DEWP VIS PTDY TIDE #yr mo dy hr mn degT m/s m/s m sec sec degT hPa degC degC degC mi hPa ft 2007 04 15 13 50 120 4.0 6.0 0.4 3 MM MM 1023.4 20.6 22.5 10.8 MM +1.7 MM 2007 04 15 12 50 140 4.0 5.0 0.4 4 MM MM 1023.0 20.4 22.4 10.3 MM +1.7 MM 2007 04 15 11 50 120 5.0 6.0 0.4 3 MM MM 1022.1 20.0 22.4 10.9 MM +0.6 MM
Missing values are now indicated by "MM".
The additional quantity PTDY is the "Pressure Tendency", which measures how the pressure has increased or decreased in the previous 3 hours. It may appear in the older data format.
