the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Jan 2022
A scheme to detect sand/dust weather applying meteorological radars
Abstract. Sandy dust weather occur frequently in arid and semi-arid areas. It is important to actually detect the sandy dust grain concentration or the visibility of the sandy dust weather for weather forecasting. In this paper, based on numerical calculation of the effective detection distance of different radar detecting the sandy-dust weather with different strength, a scheme to detect sand/dust weather applying existed meteorological radar stations is proposed in this paper. The scheme can be efficient to detect sandy dust weather, for it makes a good supplement to the current deficiencies in detecting sandy dust weather and it’s a cost-saving detection way by using the existed meteorological radars. In addition, the effect of charges carried by sand/dust grains and the relative humidity on the effective detection distance of radar is also investigated, and it shows that these effects will not change the proposed scheme. It will be promising to detect the sandy dust weather in the way of disastrous weather precaution by using this scheme.
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RC1: 'Comment on amt-2021-349', Anonymous Referee #1, 28 Feb 2022
The paper presents results of simulated detection capability for dust storms by using various radar types and lidar. The simulation considers various dust concentrations mostly expressed as visibility by human eye, and includes effects of relative humidity and electric charge for fixed particle concentrations. Based on the simulation results, the authors propose to use radar of different wavelength and lidar to detect dust storms.
The paper does not attempt to calculate the influence of polarization diversity of radar and lidar to distinguish dust storm returns from other returns; this is reasonably not scope of the paper. All calculations are based on spherical particles.
The English language is fair to poor which makes it sometimes difficult to follow the authors' argument. The authors should try to seek for support from a native English speaking person or someone being firm with English language.
Specific comments:
- Table 1 (and general): Why is C-band radar not considered? It is one of the most common types of meteorological services.
- Table 1: Lidar characteristics given indicate a device transmitting visible light with a pulse power of 4 kW. Such lidar is far from being eye-safe and thus not very likely to be used as a scanning device.
- Fig.2 (and others): The analysis is limited to a range of 10 km. Most ground based precipitation radar can detect dust storms at much larger distances; observations beyond 100 km have been reported. The authors should extend the analyses, at least for figures 2 and 3, to at least 50 km (better 100 km) range. Detection ranges below 100 meters need not to be considered.
- Section 2.3, manuscript lines 172ff: "centimeter-band radar has not yet been used to detect sandy dust weather" and "for sandstorms that occur in desert areas, it is impossible to detect them from such a long distance." Both is not correct. Centimeter wavelength radar is used since decades for dust storm detection, see e.g. Hannesen and Weipert, 2003, and Saeed at al 2014.
- Fig. 2 b and c: According to the authors' calculation, the detection range of centimeter-wavelength radar is limited to about 10 km for visibilities of several hundred meters. But in Saeed at al 2014 (e.g. figs 6 and 7), detection range of the Kuwait C-band radar is about 100 km for similar visibilities. The authors need to revise their calculation and should comment on such huge discrepancy.
- Fig. 2 f and discussion in the text: The authors should compare their derived detection ranges with those according to ISO 28902-2:2017
- Fig. 3: This figure should be given also for a visibility of 100 meters (not only for 10 and 1,000 meters)
- Section 4 (manuscript lines 228-308): The authors describe the influence of electric particle charge and relative humidity in many sentences, with the data given being of limited value. For the reader, e.g. "considering the influence of relative humidity, when detecting severe sandstorms, the effective detection range is reduced by 502 m and increased by 201 m, respectively" means that he has to figure out to which original data such reduction refers to. A reduction by 502 m is significant if it means e.g. from 2,000 down to 1,498 meters, but it is marginal if it means e.g. from 20,000 down to 19,498 meters. Instead of many such sentences, the authors should present a few tables with all these data and should summarize the tables in the text.
References:
- Hannesen, R., A. Weipert (2003): Detection of Dust Storms with a C-Band Doppler Radar. Preprints, 31st Int. Conf. on Radar Meteorology, AMS, Seattle (USA).
- T. M. Saeed, H. Al-Dashti, C. Spyrou (2014): Aerosol’s optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study. Atmos. Chem. Phys., 14, 3751–3769, 2014. doi:10.5194/acp-14-3751-2014
- ISO 28902-2:2017: Air quality — Environmental meteorology — Part 2: Ground-based remote sensing of wind by heterodyne pulsed Doppler lidar
Citation: https://doi.org/10.5194/amt-2021-349-RC1 - AC1: 'Reply on RC1', Xuebang Gao, 15 Apr 2022
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RC2: 'Comment on amt-2021-349', Anonymous Referee #2, 04 Mar 2022
The paper presents results from radiative transfer simulations on the attenuated backscatter received from sand particles by different kinds of radar and a lidar. The simulations cover different concentrations of sand dust representing different levels of visibility. The goal of the simulations is to estimate the maximum detection range for different levels of visibility given the characteristics of five radar and one lidar systems. In addition, the influence of surface charge of the sand particles and the relative humidity within the sand storm are investigated. The proposed scheme for the detection of sand storms over a wide range of conditions and over a large area consists of a W-band radar and a 535 nm lidar.
It is challenging to follow the manuscript due to poor use of English language. I would suggest the authors to have their manuscript checked by a native English speaker or somebody with fine English proficiency prior to the initial submission. The manuscript in its current form strains the voluntary review process.
Specific comments
-
Please give more details on the chosen parameters for the particle size distributions in section 2.1. How much does the maximum detection range depend on the number of very small particles in relation to fewer larger particles? How are \bar{r} and \sigma_r related to V?
-
Based on your simulations you should also discuss whether special specifications could be proposed for different radar wavelengths to be better suited for sand detection. This could in include the possibilities of increasing the radar sensitivity by increasing the pulse lengths or integration time. Can spatial resolution be exchanged with sensitivity?
-
You should elaborate more on the elements shown in Fig. 5 or leave it out.
-
In Section 4 it would aid the understanding to discuss the increased backscatter and increased attenuation/scattering due to the surface charge and relative humidity. The assumptions on the vertical distribution of humidity remained unclear to me. Furthermore, the water vapor concentration or at least the assumed air temperature should be give. I would have expected an signal attenuation due the water vapor at least in the W-band by a few dB. I might have missed it in an earlier part, but it is unclear to me if the sand storm is horizontally homogeneous over the whole plane or if it just starts a certain range.
-
Overall I am missing a comment on the effect of gaseous attenuation for the simulations.
-
Besides the effect of particle charge and humidity, the authors should also discuss the following
-
How does the beam broadening and Earth’s curvature affect the detectability of (shallow) dust storms?
-
How good is the assumption of spheres for sand particles?
-
Minor comments
- L 45: Check if Elsheikh et al. (2017) is the correct reference for moisture inversions in sand storms.
- L 64: “Meteorological radars are usually used to detect the sandy dust weather”. This sentence should be reconsidered. At least in my field of work, meteorological radars are primarily used to observe hydrometeors.
- From my understanding, the term “radar” stands for “radio detection and ranging” and is therefore different to a “light detection and ranging” system. Thus I am confused by the term “lidar radar”. Instead, I would personally prefer the simple term “lidar”.
- Fig. 1: As the yellow background does add nothing to the understanding of the figure, I would make it white.
- Figures 2 and 8 should use one color bar each for all six panels. This makes the panels more comprehensible.
I would like to encourage the authors to re-submit after a thorough revision.
Citation: https://doi.org/10.5194/amt-2021-349-RC2 - AC2: 'Reply on RC2', Xuebang Gao, 15 Apr 2022
-
-
RC3: 'Comment on amt-2021-349', Anonymous Referee #3, 05 Mar 2022
This manuscript presents theoretical calculations of radar sensitivity to dust particles for radar operating frequencies from L- to W-band. Radar detection thresholds are estimated as a function of range and dust storm intensity quantified by a visibility index. It appears that detecting sand and dust storms with currently deployed weather radars would be a good use of those radars to help protect cities and urban environments.
While the manuscript presents theoretical calculations, the manuscript does not show any radar observations of sand or dust that validate the theoretical calculations. Also, contrary to the manuscript title, the manuscript does not present a method or ‘scheme’ to detect sand or dust with weather radars that discriminates sand or dust radar measurements from backscattered energy from raindrops.The manuscript needs a review for English grammar and word usage.
Specific Comments
1. Abstract. The abstract does not present the results of the study. Also, the abstract states (line 10) that ‘The scheme can be efficient to detect sandy dust weather…” A scheme is not presented in this manuscript, just radar calculations to determine whether simulated radars have the sensitivity to detect sand or dust populations. Rewrite the abstract to describe the purpose of the study, methods of the study, results from the study, and potential impacts from the study.2. The manuscript presents scattering calculations of sand and dust particles to determine range detection curves. But, the study does not repeat the calculations for raindrops which would show whether the simulated radars are capable of detecting raindrops. Do the simulated radars have the same sensitivity as operational weather radars? Can the simulated radars detect raindrops at 100 km, or 200 km? Please extend the calculations to raindrops.
3. Section 2.2.2, line 74, and line 118. The maximum sand or dust particle is limited to diameters of 80 microns (line 74). The shortest radar wavelength is about 3 mm from W-band radar. The size parameter (line 118) is given as x = 2pi a /lambda. Using a = 40 microns and lambda = 3 mm, the size parameter is approximately 0.15. This maximum size dust particle is still within the Rayleigh scattering regime for W-band radar wavelengths. The Mie scattering approximations (equations 8 and 9) are superfluous and will revert to the Rayleigh approximation for these small size parameters. Section 2.2.2 is making the calculations more complicated than necessary.
4. Line 158. I do not know of a civilian scanning weather radar operating at L-band. Most scanning weather radars have antenna beamwidths no larger than 1 degree. An L-band antenna would have to be large to produce a 1 degree beamwidth. If the authors know of an L-band scanning weather radar, it would be interesting to see details of that radar.
5. Lines 118 to 194. The manuscript presents effective detection ranges with 1-meter resolution. For example, line 159, the detection range is 2671 m. Given the assumptions in the calculations, this is a false sense of accuracy. What are the simulation uncertainties for detection range? Asked another way, given a 3 dB uncertainty in signal-to-noise ratio, what is the uncertainty of the detection range?
6. Figure 2. Why do the detection ranges only go out to 10 km when weather radars typically have ranges out to 100 to 300 km?
7. Section 2 presented theoretical calculations of radar detection. Are there any radar observations of sand or dust storms that can validate these calculations? Without showing any real radar observations, the simulations have not been validated or put into real-life context.
8. Section 3 “The scheme of using meteorological radar to detect sand and dust weather”. This section does not present a “scheme” or method of detecting sand or dust weather. It appears that some thresholds have been set and shown in Fig. 4, but no flow diagram showing the decision logic is presented in the manuscript. Also, it does not present a method to discriminate scattering from sand or dust from scattering from raindrops. How does the method determine whether sand or dust is being detected rather than raindrops?
Citation: https://doi.org/10.5194/amt-2021-349-RC3 - AC3: 'Reply on RC3', Xuebang Gao, 15 Apr 2022
Status: closed
-
RC1: 'Comment on amt-2021-349', Anonymous Referee #1, 28 Feb 2022
The paper presents results of simulated detection capability for dust storms by using various radar types and lidar. The simulation considers various dust concentrations mostly expressed as visibility by human eye, and includes effects of relative humidity and electric charge for fixed particle concentrations. Based on the simulation results, the authors propose to use radar of different wavelength and lidar to detect dust storms.
The paper does not attempt to calculate the influence of polarization diversity of radar and lidar to distinguish dust storm returns from other returns; this is reasonably not scope of the paper. All calculations are based on spherical particles.
The English language is fair to poor which makes it sometimes difficult to follow the authors' argument. The authors should try to seek for support from a native English speaking person or someone being firm with English language.
Specific comments:
- Table 1 (and general): Why is C-band radar not considered? It is one of the most common types of meteorological services.
- Table 1: Lidar characteristics given indicate a device transmitting visible light with a pulse power of 4 kW. Such lidar is far from being eye-safe and thus not very likely to be used as a scanning device.
- Fig.2 (and others): The analysis is limited to a range of 10 km. Most ground based precipitation radar can detect dust storms at much larger distances; observations beyond 100 km have been reported. The authors should extend the analyses, at least for figures 2 and 3, to at least 50 km (better 100 km) range. Detection ranges below 100 meters need not to be considered.
- Section 2.3, manuscript lines 172ff: "centimeter-band radar has not yet been used to detect sandy dust weather" and "for sandstorms that occur in desert areas, it is impossible to detect them from such a long distance." Both is not correct. Centimeter wavelength radar is used since decades for dust storm detection, see e.g. Hannesen and Weipert, 2003, and Saeed at al 2014.
- Fig. 2 b and c: According to the authors' calculation, the detection range of centimeter-wavelength radar is limited to about 10 km for visibilities of several hundred meters. But in Saeed at al 2014 (e.g. figs 6 and 7), detection range of the Kuwait C-band radar is about 100 km for similar visibilities. The authors need to revise their calculation and should comment on such huge discrepancy.
- Fig. 2 f and discussion in the text: The authors should compare their derived detection ranges with those according to ISO 28902-2:2017
- Fig. 3: This figure should be given also for a visibility of 100 meters (not only for 10 and 1,000 meters)
- Section 4 (manuscript lines 228-308): The authors describe the influence of electric particle charge and relative humidity in many sentences, with the data given being of limited value. For the reader, e.g. "considering the influence of relative humidity, when detecting severe sandstorms, the effective detection range is reduced by 502 m and increased by 201 m, respectively" means that he has to figure out to which original data such reduction refers to. A reduction by 502 m is significant if it means e.g. from 2,000 down to 1,498 meters, but it is marginal if it means e.g. from 20,000 down to 19,498 meters. Instead of many such sentences, the authors should present a few tables with all these data and should summarize the tables in the text.
References:
- Hannesen, R., A. Weipert (2003): Detection of Dust Storms with a C-Band Doppler Radar. Preprints, 31st Int. Conf. on Radar Meteorology, AMS, Seattle (USA).
- T. M. Saeed, H. Al-Dashti, C. Spyrou (2014): Aerosol’s optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study. Atmos. Chem. Phys., 14, 3751–3769, 2014. doi:10.5194/acp-14-3751-2014
- ISO 28902-2:2017: Air quality — Environmental meteorology — Part 2: Ground-based remote sensing of wind by heterodyne pulsed Doppler lidar
Citation: https://doi.org/10.5194/amt-2021-349-RC1 - AC1: 'Reply on RC1', Xuebang Gao, 15 Apr 2022
-
RC2: 'Comment on amt-2021-349', Anonymous Referee #2, 04 Mar 2022
The paper presents results from radiative transfer simulations on the attenuated backscatter received from sand particles by different kinds of radar and a lidar. The simulations cover different concentrations of sand dust representing different levels of visibility. The goal of the simulations is to estimate the maximum detection range for different levels of visibility given the characteristics of five radar and one lidar systems. In addition, the influence of surface charge of the sand particles and the relative humidity within the sand storm are investigated. The proposed scheme for the detection of sand storms over a wide range of conditions and over a large area consists of a W-band radar and a 535 nm lidar.
It is challenging to follow the manuscript due to poor use of English language. I would suggest the authors to have their manuscript checked by a native English speaker or somebody with fine English proficiency prior to the initial submission. The manuscript in its current form strains the voluntary review process.
Specific comments
-
Please give more details on the chosen parameters for the particle size distributions in section 2.1. How much does the maximum detection range depend on the number of very small particles in relation to fewer larger particles? How are \bar{r} and \sigma_r related to V?
-
Based on your simulations you should also discuss whether special specifications could be proposed for different radar wavelengths to be better suited for sand detection. This could in include the possibilities of increasing the radar sensitivity by increasing the pulse lengths or integration time. Can spatial resolution be exchanged with sensitivity?
-
You should elaborate more on the elements shown in Fig. 5 or leave it out.
-
In Section 4 it would aid the understanding to discuss the increased backscatter and increased attenuation/scattering due to the surface charge and relative humidity. The assumptions on the vertical distribution of humidity remained unclear to me. Furthermore, the water vapor concentration or at least the assumed air temperature should be give. I would have expected an signal attenuation due the water vapor at least in the W-band by a few dB. I might have missed it in an earlier part, but it is unclear to me if the sand storm is horizontally homogeneous over the whole plane or if it just starts a certain range.
-
Overall I am missing a comment on the effect of gaseous attenuation for the simulations.
-
Besides the effect of particle charge and humidity, the authors should also discuss the following
-
How does the beam broadening and Earth’s curvature affect the detectability of (shallow) dust storms?
-
How good is the assumption of spheres for sand particles?
-
Minor comments
- L 45: Check if Elsheikh et al. (2017) is the correct reference for moisture inversions in sand storms.
- L 64: “Meteorological radars are usually used to detect the sandy dust weather”. This sentence should be reconsidered. At least in my field of work, meteorological radars are primarily used to observe hydrometeors.
- From my understanding, the term “radar” stands for “radio detection and ranging” and is therefore different to a “light detection and ranging” system. Thus I am confused by the term “lidar radar”. Instead, I would personally prefer the simple term “lidar”.
- Fig. 1: As the yellow background does add nothing to the understanding of the figure, I would make it white.
- Figures 2 and 8 should use one color bar each for all six panels. This makes the panels more comprehensible.
I would like to encourage the authors to re-submit after a thorough revision.
Citation: https://doi.org/10.5194/amt-2021-349-RC2 - AC2: 'Reply on RC2', Xuebang Gao, 15 Apr 2022
-
-
RC3: 'Comment on amt-2021-349', Anonymous Referee #3, 05 Mar 2022
This manuscript presents theoretical calculations of radar sensitivity to dust particles for radar operating frequencies from L- to W-band. Radar detection thresholds are estimated as a function of range and dust storm intensity quantified by a visibility index. It appears that detecting sand and dust storms with currently deployed weather radars would be a good use of those radars to help protect cities and urban environments.
While the manuscript presents theoretical calculations, the manuscript does not show any radar observations of sand or dust that validate the theoretical calculations. Also, contrary to the manuscript title, the manuscript does not present a method or ‘scheme’ to detect sand or dust with weather radars that discriminates sand or dust radar measurements from backscattered energy from raindrops.The manuscript needs a review for English grammar and word usage.
Specific Comments
1. Abstract. The abstract does not present the results of the study. Also, the abstract states (line 10) that ‘The scheme can be efficient to detect sandy dust weather…” A scheme is not presented in this manuscript, just radar calculations to determine whether simulated radars have the sensitivity to detect sand or dust populations. Rewrite the abstract to describe the purpose of the study, methods of the study, results from the study, and potential impacts from the study.2. The manuscript presents scattering calculations of sand and dust particles to determine range detection curves. But, the study does not repeat the calculations for raindrops which would show whether the simulated radars are capable of detecting raindrops. Do the simulated radars have the same sensitivity as operational weather radars? Can the simulated radars detect raindrops at 100 km, or 200 km? Please extend the calculations to raindrops.
3. Section 2.2.2, line 74, and line 118. The maximum sand or dust particle is limited to diameters of 80 microns (line 74). The shortest radar wavelength is about 3 mm from W-band radar. The size parameter (line 118) is given as x = 2pi a /lambda. Using a = 40 microns and lambda = 3 mm, the size parameter is approximately 0.15. This maximum size dust particle is still within the Rayleigh scattering regime for W-band radar wavelengths. The Mie scattering approximations (equations 8 and 9) are superfluous and will revert to the Rayleigh approximation for these small size parameters. Section 2.2.2 is making the calculations more complicated than necessary.
4. Line 158. I do not know of a civilian scanning weather radar operating at L-band. Most scanning weather radars have antenna beamwidths no larger than 1 degree. An L-band antenna would have to be large to produce a 1 degree beamwidth. If the authors know of an L-band scanning weather radar, it would be interesting to see details of that radar.
5. Lines 118 to 194. The manuscript presents effective detection ranges with 1-meter resolution. For example, line 159, the detection range is 2671 m. Given the assumptions in the calculations, this is a false sense of accuracy. What are the simulation uncertainties for detection range? Asked another way, given a 3 dB uncertainty in signal-to-noise ratio, what is the uncertainty of the detection range?
6. Figure 2. Why do the detection ranges only go out to 10 km when weather radars typically have ranges out to 100 to 300 km?
7. Section 2 presented theoretical calculations of radar detection. Are there any radar observations of sand or dust storms that can validate these calculations? Without showing any real radar observations, the simulations have not been validated or put into real-life context.
8. Section 3 “The scheme of using meteorological radar to detect sand and dust weather”. This section does not present a “scheme” or method of detecting sand or dust weather. It appears that some thresholds have been set and shown in Fig. 4, but no flow diagram showing the decision logic is presented in the manuscript. Also, it does not present a method to discriminate scattering from sand or dust from scattering from raindrops. How does the method determine whether sand or dust is being detected rather than raindrops?
Citation: https://doi.org/10.5194/amt-2021-349-RC3 - AC3: 'Reply on RC3', Xuebang Gao, 15 Apr 2022
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