scholarly journals Atmospheric observations with E-band microwave links – challenges and opportunities

2020 ◽  
Author(s):  
Martin Fencl ◽  
Michal Dohnal ◽  
Pavel Valtr ◽  
Martin Grabner ◽  
Vojtěch Bareš
Keyword(s):  
Water Vapor ◽  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Distribution Data ◽  
Vapor Sensing ◽  
Challenges And Opportunities ◽  
Atmospheric Observations ◽  
Order Of Magnitude ◽  
Microwave Link

Abstract. Opportunistic sensing of rainfall and water vapor using commercial microwave links operated within cellular networks was conceived more than a decade ago. It has since been further investigated in numerous studies predominantly concentrating on the frequency region of 15–40 GHz. This manuscript provides the first evaluation of rainfall and water vapor sensing with microwave links operating at an E band (specifically, 71–76 GHz and 81–86 GHz), which are increasingly updating, and frequently replacing, older communication infrastructure. Attenuation-rainfall relations are investigated theoretically on drop size distribution data. Furthermore, quantitative rainfall estimates from six microwave links, operated within cellular backhaul, are compared with observed rainfall intensities. Finally, the capability to detect water vapor is demonstrated on the longest microwave link measuring 4.86 km in path length. The results show that E-band microwave links are by one order of magnitude more sensitive to rainfall than devices operating in the 15–40 GHz range and are thus able to observe even light rainfalls, a feat practically impossible to achieve previously. The E-band links are, however, substantially more affected by errors related to variable drop size distribution. Water vapor retrieval might be possible from long E band microwave links, nevertheless, the efficient separation of gaseous attenuation from other signal losses will be challenging in practice.

scholarly journals Atmospheric observations with E-band microwave links – challenges and opportunities

2020 ◽  
Vol 13 (12) ◽  
pp. 6559-6578
Author(s):  
Martin Fencl ◽  
Michal Dohnal ◽  
Pavel Valtr ◽  
Martin Grabner ◽  
Vojtěch Bareš
Keyword(s):  
Water Vapor ◽  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Distribution Data ◽  
Vapor Sensing ◽  
Challenges And Opportunities ◽  
Atmospheric Observations ◽  
Microwave Link ◽  
Distribution Water

Abstract. Opportunistic sensing of rainfall and water vapor using commercial microwave links operated within cellular networks was conceived more than a decade ago. It has since been further investigated in numerous studies, predominantly concentrating on the frequency region of 15–40 GHz. This article provides the first evaluation of rainfall and water vapor sensing with microwave links operating at E-band frequencies (specifically 71–76 and 81–86 GHz). These microwave links are increasingly being updated (and are frequently replacing) older communication infrastructure. Attenuation–rainfall relations are investigated theoretically on drop size distribution data. Furthermore, quantitative rainfall estimates from six microwave links, operated within cellular backhaul, are compared with observed rainfall intensities. Finally, the capability to detect water vapor is demonstrated on the longest microwave link measuring 4.86 km in path length. The results show that E-band microwave links are markedly more sensitive to rainfall than devices operating in the 15–40 GHz range and can observe even light rainfalls, a feat practically impossible to achieve previously. The E-band links are, however, substantially more affected by errors related to variable drop size distribution. Water vapor retrieval might be possible from long E-band microwave links; nevertheless, the efficient separation of gaseous attenuation from other signal losses will be challenging in practice.

Drop-Size Distributions of Newtonian Liquid Sprays Produced by Fan-Jet Pressure Nozzles

1979 ◽  
Vol 101 (2) ◽  
pp. 171-177 ◽  
Author(s):  
W. S. Janna ◽  
J. E. A. John
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Newtonian Liquid ◽  
Distribution Data ◽  
Collection Device ◽  
Median Diameter ◽  
Spray Distribution ◽  
Liquid Sprays ◽  
Drop Size Distributions

The drop size distribution was measured by Newtonian liquid sprays produced by fan-jet pressure nozzles, operating in the pressure range 500 to nearly 3000 psig (3 450 to 20 680 kPa). The fluids used were water and a water-glycerin mixture. A collection device was constructed and droplets were captured on soot coated microscope slides. Subsequent sizing of the impacted particles with a microscope yielded drop size distribution data of accumulated volume per cent versus diameter. An experimental analysis was performed to relate the nozzle wall shear to the volume median diameter of the spray distribution. A linear correlation was found to exist on a semilog graph; for the Newtonian liquid sprays, it was determined that the volume median diameter could be predicted with: Dd=+8.5183−1.1113logτρQμσ

Drop-Size Distributions of Newtonian and Bingham Liquid Sprays Produced by Fan-Jet Pressure Nozzles With and Without the Preorifice

1981 ◽  
Vol 103 (4) ◽  
pp. 402-408
Author(s):  
William S. Janna ◽  
James E. A. John
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Distribution Data ◽  
Size Distributions ◽  
Volume Percent ◽  
Collection Device ◽  
Drop Size Distributions ◽  
Microscope Slides ◽  
Pressure Nozzle

Measurements were made of the drop-size distributions of water and of paint sprays produced by fan-jet pressure nozzles, operating in the pressure range 900 to nearly 3000 psi (6200–20,680 kPa). A collection device was constructed and droplets were captured on soot-coated and on plain microscope slides. Subsequent sizing of the impacted particles with a microscope yielded drop-size distribution data of accumulated volume percent versus diameter. Data were gathered of water and of paint sprays produced by a fan-jet pressure nozzle-preorifice combination. The effect of the preorifice on drop-size distribution was evaluated.

Effect of drop size distribution on microwave link rainfall retrieval at E-band

2020 ◽  
Author(s):  
Martin Fencl ◽  
Vojtech Bares
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Rainfall Variability ◽  
Frequency Region ◽  
Drop Size Distribution ◽  
Rainfall Model ◽  
One Year ◽  
Microwave Link ◽  
Rainfall Retrieval ◽  
Rainfall Estimates

<p>Rainfall retrieval with commercial microwave links (CMLs) relies on the relation between radiowave attenuation and rainfall intensity. The CMLs used to operate predominantly at 15-40 GHz frequency region where the relation between rainfall and attenuation was close-to-linear and only slightly dependent on drop size distribution (DSD) (Berne and Uijlenhoet, 2007). New generation of CMLs operated within cellular backhaul utilizes increasingly the E-band frequencies, specifically frequency region 71 - 86 GHz. The attenuation-rainfall relation at this region is, however, substantially more dependent on DSD.</p><p>One year of DSD data retrieved from Parsivel OTT disdrometer is used to simulate theoretical attenuation and quantify the effect of DSD on CML rainfall estimates. The results show that E-band CMLs are highly sensitive to DSD. The relative error related to DSD variability reaches up to 40%, which is about two to three times higher value compared to errors by CMLs operated at 15-40 GHz. These errors can be, however, reduced to approx. 20% when distinguishing between stratiform and convective rainfalls and introducing two different parameter sets for attenuation-rainfall relation, accordingly.  The improvement of CML rainfall estimates when adapting parameters of attenuation-rainfall relation is demonstrated on real attenuation data acquired from 4.8 km long E-band CML operated within cellular backhaul in Prague (CZ).</p><p>Variable drop size distribution represents a significant source of uncertainty in rainfall estimates retrieved from E-band CMLs. This uncertainty can be substantially reduced by adapting parameters of attenuation-rainfall model to rainfall type (DSD).</p><p> </p><p>References:</p><p>Berne, A., Uijlenhoet, R., 2007. Path-averaged rainfall estimation using microwave links: Uncertainty due to spatial rainfall variability. <em>Geophys. Res. Lett. 34</em>, L07403. https://doi.org/10.1029/2007GL029409</p>

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