Title:
GPS SuomiNet Precipitable Water (30-min) Data [UCAR/UNAVCO]
Authors:
John Braun, Teresa Van Hove, Chris Rocken
braunj@ucar.edu
P.O. Box 3000
Boulder, CO 80307
303.497.8018 (phone)
303.497.2610 (fax)
Joel Van Baelen
CNRS - CNRM/GAME Tel: +33 - (0)5 - 61 07 96 07
42 avenue G. Coriolis Fax: +33 - (0)5 - 61 07 96 27
31057 Toulouse E-mail: joel.van-baelen@meteo.fr
France
1.0 Data Set Overview
This data set consists of 30 minute estimates of Precipitable Water Vapor (PW)
from GPS data collected during IHOP. The network of sites includes networks
operated by NOAA/FSL, SuomiNet, and CNRS/INSU from France. A map of the stations can
be found at the following URL: http://www.gst.ucar.edu/~braunj/ihop.html
The time window for the data set is essentially the entire IHOP experiment
(May 12 - April 29, 2002).
2.0 Instrument Description
Please see the following URLs:
http://www.gst.ucar.edu/gpsrg/realtime
http://gpsmet.fsl.noaa.gov/jsp/index.jsp
3.0 Data Collection and Processing
All data were analyzed using the Bernese V4.3 GPS Software. An elevation
mask of 7 degrees was used with Niell mapping functions. Data were processed
in 24 hour time windows using the IGS final orbit products. Normal equations
were used to combine each 24 hour data set with the previous day of data in
an effort to reduce day boundary jumps in the PW time series.
4.0 Data Format
The following naming convention was used: ihop_SSSS_YYYYMMDD_nc
Where:
SSSS is the four character abreviation for each station
YYYY is the year number (2002)
MM is the month number (05 or 06)
DD is the day of month
Each file contains the following netCDF records:
char station(station, station_name_length) ;
station:long_name = "GPS station name" ;
double time_offset(time_offset) ;
time_offset:long_name = "Time delta from start_time" ;
time_offset:units = "seconds" ;
time_offset:missing_value = "-999" ;
double lat(station) ;
lat:long_name = "Station latitude" ;
lat:units = "Degrees North(-90 to 90)" ;
lat:missing_value = "-999" ;
double lon(station) ;
lon:long_name = "Station longitude" ;
lon:units = "Degrees East(-180 to 180)" ;
lon:missing_value = "-999" ;
double height(station) ;
height:long_name = "Station Height above mean sea level (JGM2 geoid)" ;
height:units = "meters" ;
height:missing_value = "-999" ;
double network_id(station) ;
network_id:long_name = "Network ID: \n",
"0 = unknown, \n",
"1 = suominet, \n",
"2 = Forecast Systems Lab, NOAA, \n",
"3 = US Dept. of Transportation, \n",
"4 = US Coast guard/Army Corps of Engineers\n",
"" ;
float duration(station, time_offset) ;
duration:long_name = "Duration of validity of measurement" ;
duration:units = "minutes" ;
duration:missing_value = "-999" ;
float pwv(station, time_offset) ;
pwv:long_name = "Precipitable Water Vapor" ;
pwv:units = "millimeters" ;
pwv:missing_value = "-999" ;
float pwv_err(station, time_offset) ;
pwv_err:long_name = "Precipitable Water Vapor format error" ;
pwv_err:units = "millimeters" ;
pwv_err:missing_value = "-999" ;
float wet_delay(station, time_offset) ;
wet_delay:long_name = "Wet Delay" ;
wet_delay:units = "millimeters" ;
wet_delay:missing_value = "-999" ;
float model_dry_delay(station, time_offset) ;
model_dry_delay:long_name = "Dry Delay from model" ;
model_dry_delay:units = "millimeters" ;
model_dry_delay:missing_value = "-999" ;
float total_delay(station, time_offset) ;
total_delay:long_name = "Total Delay" ;
total_delay:units = "millimeters" ;
total_delay:missing_value = "-999" ;
float pifact(station, time_offset) ;
pifact:long_name = "Pi factor (conversion between wet delay and PWV)" ;
pifact:units = "millimeters" ;
pifact:missing_value = "-999" ;
float pres(station, time_offset) ;
pres:long_name = "Surface atmospheric pressure" ;
pres:units = "millibars" ;
pres:missing_value = "-999" ;
float temperature(station, time_offset) ;
temperature:long_name = "Surface temperature" ;
temperature:units = "degrees C" ;
temperature:missing_value = "-999" ;
float rh(station, time_offset) ;
rh:long_name = "Surface relative humidity" ;
rh:units = "percent" ;
rh:missing_value = "-999" ;
float final_dry_delay(station, time_offset) ;
final_dry_delay:long_name = "Final dry delay" ;
final_dry_delay:units = "millimeters" ;
final_dry_delay:missing_value = "-999" ;
char met_flag(station, time_offset) ;
met_flag:long_name = "MET Flag (A = actual MET values used, I = Interpoled values used)" ;
met_flag:missing_value = "X" ;
char pifact_type(station, time_offset) ;
pifact_type:long_name = "PI factor type (S = surface temp. coefficients used)" ;
pifact_type:missing_value = "X" ;
5.0 Data Remarks
All available GPS data within the IHOP region were analyzed. Some of the data
streams did not have ancillary met records to derive PW from the total zenith delay.
In the instances where met records were not available, the netCDF files contain
only the total zenith delay (and missing record flags for all other fields). If
met records (pressure and temperature) become available for these stations, we would
willing to compute PW fields from these total zenith delays.
All rh values were set to 0.0 within the met records, without regard to whether
they existed in the associated met stream or not.
6.0 References
The following URLs may be useful:
http://www.gst.ucar.edu/~braunj/ihop.html
http://www.gst.ucar.edu/gpsrg/realtime/
http://www.gst.ucar.edu/gpsrg/realtime/references.html