Using GPS to Measure Precipitable Water Vapor in Antarctica
1. Using Global Positioning System to Measure
Precipitable Water Vapor in Antarctica
Amanda Murray, Mike Willis and Terry Wilson
School of Earth Sciences and Byrd Polar Research Center, Ohio State University,
Columbus, Ohio 43210; murray.501@osu.edu
Background: Formulas: Southern Victoria Land; Jan 21, 2005
• The GPS signal is broadcast on two frequencies (L1 and L2). ZHD = 2.2779*(Ps/(1-0.00266*COS(2λ)- Moisture (mm) Pressure (hPa) Temperature (k)
• Precipitable Water Vapor can be extracted from delay of radio signals
as they pass through the atmosphere. 0.00028*H))
• Delay can be broken into Zenith Path Delay (ZPD), Zenith Hydrostatic Where Ps = surface pressure, λ = latitude and
"Dry" Delay (ZHD) and Zenith Wet Delay (ZWD).
•ZWD is caused by the water vapor
H = height above ellipsoid in km
in the troposphere.
• ZPD is from GPS, ZHD from Precipitable Water = ∏ * ZWD
atmospheric model and formula ∏^-1 = 10^-6ρRv[(k3/Tm)+K'2]
leaving ZWD. k'2 = k2 -mk1
• ZWD is converted to PWD. Tm = ∫((Pv/T)dz)/((Pv/T2)dz) ≈ ∑^N
•Z HD error is nearly eliminated
((Pvi/Ti)∆zi)/∑^N((Pvi/Ti^2)∆zi)
because the L1 and L2 signals are
ρ = density of liquid water, Rv = specific gas constant, m = ratio
spaced apart and can be combined.
• Model data downloaded from the of molar constants, Pv = partial pressure of water, T =
Antarctic Mesoscale Prediction System (AMPS) is compared to GPS data. temperature in Kelvin, i= each discrete level, N = number of
•The resulting improvement in our knowledge of water vapor layers, Z = height in m
distribution will enable more accurate weather forecasts and will contribute
to studies of climate change (Bevis et al. 1994).
Location of GPS Sites in Southern
Manipulating the Data: Victoria Land, Antarctica
•AMPS model data were downloaded into directories in Linux.
•Surface pressure (hPa), 2-meter temperature (K), and moisture (mm) data
were all examined for the year 2005. Interpolation: Work in Progress:
•All were geocoded to a 30km by 30km grid across Antarctica in order to Coordinates for GPS sites (stars – above • ZHDs are still being calculated.
produce maps of these variables. and below) were interpolated. • ZWDs have yet to be calculated.
• There were 31 GPS sites examined for this study and the values from the
• ZNDs for more GPS sites were
variables were interpolated for each GPS station.
This below was one acquired than anticipated.
• The coordinates of the GPS sites are used as interpolation points from the
of the first maps. • More charts and maps are to
AMPS 30km by 30km gridded data.
come!
• Time series of moisture (see below) were created for each GPS site from
the interpolation.
• AMPS model pressure data were used to calculate the ZHDs for GPS sites.
References:
• ZNDs from each GPS site were given to us for this study. Bevis, M., S. Businger, S. Chishwell, T. A.
Moisture Time Series for 4 GPS Sites Herring, R. A. Anthes, C. Rocken and R. H.
Ware, 1994: GPS meteorology: mapping
zenith wet delays onto precipitable
water. Journal of Applied Meteorology.
Comparisons: Vol. 33, 379-386.
• AMPS is at present a reliable source for prediction of
pressure and temperature.
Acknowledgements:
A. Murray thanks Kelly Carroll for the
• Model predictions may be inaccurate if the model data is support and for this research
different from the GPS data. opportunity, Dr. Diem and Dr. Crampton
for the references, everyone involved in
• Any patterns and correlations between the GPS data and the OSU SROP program and especially
model output will be analyzed. NSF (grant 60008970) and POLENET for
• For the ZNDs from each GPS site, there are days with no making this opportunity available.
data and it is different for each site.
![Using Global Positioning System to Measure
Precipitable Water Vapor in Antarctica
Amanda Murray, Mike Willis and Terry Wilson
School of Earth Sciences and Byrd Polar Research Center, Ohio State University,
Columbus, Ohio 43210; murray.501@osu.edu
Background: Formulas: Southern Victoria Land; Jan 21, 2005
• The GPS signal is broadcast on two frequencies (L1 and L2). ZHD = 2.2779*(Ps/(1-0.00266*COS(2λ)- Moisture (mm) Pressure (hPa) Temperature (k)
• Precipitable Water Vapor can be extracted from delay of radio signals
as they pass through the atmosphere. 0.00028*H))
• Delay can be broken into Zenith Path Delay (ZPD), Zenith Hydrostatic Where Ps = surface pressure, λ = latitude and
"Dry" Delay (ZHD) and Zenith Wet Delay (ZWD).
•ZWD is caused by the water vapor
H = height above ellipsoid in km
in the troposphere.
• ZPD is from GPS, ZHD from Precipitable Water = ∏ * ZWD
atmospheric model and formula ∏^-1 = 10^-6ρRv[(k3/Tm)+K'2]
leaving ZWD. k'2 = k2 -mk1
• ZWD is converted to PWD. Tm = ∫((Pv/T)dz)/((Pv/T2)dz) ≈ ∑^N
•Z HD error is nearly eliminated
((Pvi/Ti)∆zi)/∑^N((Pvi/Ti^2)∆zi)
because the L1 and L2 signals are
ρ = density of liquid water, Rv = specific gas constant, m = ratio
spaced apart and can be combined.
• Model data downloaded from the of molar constants, Pv = partial pressure of water, T =
Antarctic Mesoscale Prediction System (AMPS) is compared to GPS data. temperature in Kelvin, i= each discrete level, N = number of
•The resulting improvement in our knowledge of water vapor layers, Z = height in m
distribution will enable more accurate weather forecasts and will contribute
to studies of climate change (Bevis et al. 1994).
Location of GPS Sites in Southern
Manipulating the Data: Victoria Land, Antarctica
•AMPS model data were downloaded into directories in Linux.
•Surface pressure (hPa), 2-meter temperature (K), and moisture (mm) data
were all examined for the year 2005. Interpolation: Work in Progress:
•All were geocoded to a 30km by 30km grid across Antarctica in order to Coordinates for GPS sites (stars – above • ZHDs are still being calculated.
produce maps of these variables. and below) were interpolated. • ZWDs have yet to be calculated.
• There were 31 GPS sites examined for this study and the values from the
• ZNDs for more GPS sites were
variables were interpolated for each GPS station.
This below was one acquired than anticipated.
• The coordinates of the GPS sites are used as interpolation points from the
of the first maps. • More charts and maps are to
AMPS 30km by 30km gridded data.
come!
• Time series of moisture (see below) were created for each GPS site from
the interpolation.
• AMPS model pressure data were used to calculate the ZHDs for GPS sites.
References:
• ZNDs from each GPS site were given to us for this study. Bevis, M., S. Businger, S. Chishwell, T. A.
Moisture Time Series for 4 GPS Sites Herring, R. A. Anthes, C. Rocken and R. H.
Ware, 1994: GPS meteorology: mapping
zenith wet delays onto precipitable
water. Journal of Applied Meteorology.
Comparisons: Vol. 33, 379-386.
• AMPS is at present a reliable source for prediction of
pressure and temperature.
Acknowledgements:
A. Murray thanks Kelly Carroll for the
• Model predictions may be inaccurate if the model data is support and for this research
different from the GPS data. opportunity, Dr. Diem and Dr. Crampton
for the references, everyone involved in
• Any patterns and correlations between the GPS data and the OSU SROP program and especially
model output will be analyzed. NSF (grant 60008970) and POLENET for
• For the ZNDs from each GPS site, there are days with no making this opportunity available.
data and it is different for each site.](https://image.slidesharecdn.com/amandasposter-12528974843938-phpapp02/85/Using-GPS-to-Measure-Precipitable-Water-Vapor-in-Antarctica-1-320.jpg)
