Water Vapor Monitoring
using Wireless
Communication Networks
Measurements
Noam David
The Department of Geophysics & Planetary Sciences, TAU
The Research Team

Prof. Pinhas Alpert –
meteorology
Team members:
 Dr. Rana Samuels
 Artem Zinevich
 Ori Auslender

Prof. Hagit Messer –
signal processing

Noam David
Dani Charkasky
Ronen Radian
Yoni Ostromtzki



Wireless Communication Networks
User 1
User 2
Base Station 1
Base Station 2
•
•
•
These links are built close to the ground, and operate in a frequency
range of tens of GHz
In many wireless communication systems the Received Signal Level
(RSL) is measured and recorded.
In wireless communication, the RSL depends on atmospheric
conditions.
Transmission losses due to atmospheric conditions
Absorption and scattering of the radiation, at frequencies of tens of GHz,
are directly related to the atmospheric conditions, primarily precipitation,
oxygen, water vapor, mist and fog (Ulaby, 1981).
The idea: Water Vapor Monitoring
•
•
•
•
•
In typical conditions of:
1013 hPa pressure
15ºC temperature
water vapor density of 7.5
gr/m3

  0.2 (dB / km)
Part of the wireless systems have a magnitude
resolution of 0.1 dB per link.

The water vapor density can be measured !
The model: microwave propagation
in moist air
   O   w  0.1820 fN" ( f , p, T ,  )
[dB/km]
- The attenuation due to water vapor and due to dry air [dB/km]
f - The link's frequency [GHz].
N” - The imaginary part of the complex refractivity measured in N units, a
function of the frequency f [GHz], pressure p[hPa], temperature T [°C] and
the water vapor density ρ[gr/m3].
* ITU-R Recommendations P. 676-6: Attenuation by atmospheric gases, September 2005
Results
Water Vapor Monitoring
Ben Gurion
Airport
Tzrifin
Ramla
Frequency: 22.525 GHz
Surface station-link distance: ~6.5 km
Length: 4.53 km
Receiver and transmitter heights: 95, 63 [m] ASL
Water Vapor Monitoring
Water Vapor
Density (g/m^3)
Water Vapor Density- Central Israel 09/2007 (03:00 a.m .)
30
25
20
15
10
5
0
26/08/2007
31/08/2007
05/09/2007
10/09/2007
15/09/2007
20/09/2007
Date
Microw ave
Number of days: 25
Correlation: 0.89
RMSD: 3.4 [g/m3]
Hum idity Gauge (Lod Airport)
25/09/2007
30/09/2007
Water Vapor Monitoring
Kiryat Ata
Harduf
Frequency: 22.725 GHz
Surface station-link distance: ~7.5 km
Length: 3.86 km
Receiver and transmitter heights: 265, 233 [m] ASL
Water Vapor Monitoring
Water Vapor Density
[g/m^3]
Water Vapor Density- North Israel 11/2005 (03:00 a.m )
25
20
15
10
5
0
30/10/2005
04/11/2005
09/11/2005
14/11/2005
19/11/2005
24/11/2005
29/11/2005
Date
Microw ave
Hum idity Gauge (K. Ata)
Correlation: 0.9
RMSD: 1.8 [gr/m3]
2 rainy days were excluded (7 and 22 November)
04/12/2005
Summary

Our results show relatively good agreement between the
conventional way to measure water vapor and our proposed,
novel method

The technique is restricted to weather conditions which
exclude rain, fog or clouds along the propagation path

Since measurements from the microwave link are line
integrated data, where in-situ measurements are point
measurements in a humidity gauge, some disparities are
expected

The method only requires standard data (saved by the
communication system anyway), therefore the costs are
minimal