Using Semicircular Sampling to Increase Sea-Wind Retrieval Altitude with a High-Altitude UAV Scatterometer

Nekrasov, Alexey; Khachaturian, Alena B.; Fidge, Colin

doi:10.3390/drones6090223

Cited by 2 publications

(5 citation statements)

References 29 publications

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“…The maximum altitude limitations for semicircular observations are about 34.6, 20, and 11.54 km at the incidence angles of 30°, 45°, and 60°, respectively. In contrast to this advantage of semicircular observations, the maximum altitude limitations for circular observations were only 17.3, 10, and 5.77 km at incidence angles of 30°, 45°, and 60° [26,27].…”

Section: -3-results Summarymentioning

confidence: 89%

“…In previous work, to verify a wind vector retrieval procedure in the case of a semicircular observation scheme, we performed simulations considering the right-side NRCS semicircle with azimuths from 0° to 180° presented by N = 37 azimuth sectors with a 5° width, generating 261 "measured" NRCSs and integrating them for each azimuth sector [26,27]. A Rayleigh Power (Exponential) distribution and a sea water GMF by Equations 2 and 3 with an assumption of 0.2 dB instrument noise (currently considered the upper threshold for wind scatterometers) were used.…”

Section: -Results and Discussionmentioning

confidence: 99%

“…Recently, we have shown that a semicircular observation scheme allows doubling the maximum altitude of sea wind retrieval compared to a circular observation scheme [26,27]. Therefore, since sea wind retrieval is an integral part of the sea water/ice discrimination procedure, a semicircular observation scheme also doubles the maximum altitude of the sea water/ice discrimination method for a high-altitude conical scanning radar.…”

Section: -3-results Summarymentioning

confidence: 99%

“…Taking into consideration that the maximum altitude of the wind retrieval method with a typical circular observation scheme is about 17.3 km at an incidence angle of 30° and decreases with the incidence angle decrease to 5.77 km at an incidence angle of 60°, here we consider the possibility of sea water/ice discrimination by an airborne high-altitude conical scanning radar with the semicircular observation scheme (the right or left semicircle in Figure 1) to increase the maximum altitude of the method's applicability. As the maximum altitude of the sea wind retrieval method's applicability is doubled when a semicircular observation scheme is applied [26,27], we expected that this scheme will also be advantageous for sea water/ice discrimination as it will similarly allow an increase in the maximum altitude of the discrimination method when using a high-altitude conical scanning radar.…”

Section: -5-assumption Of Maximum Altitude Increasementioning

confidence: 99%

“…In this connection, we recently considered how to use a semicircular measurement scheme instead of typical circular observations for sea wind measurements with a conical scanning radar to increase the maximum altitude of its applicability. We demonstrated the potential to double the maximum altitude of the wind recovery method using a semicircular measurement scheme compared to a circular measurement scheme [26,27]. As sea wind retrieval is an integral part of the sea water/ice discrimination procedure, we therefore conjectured that a semicircular observation scheme should also significantly increase the maximum possible altitude of sea water/ice discrimination.…”

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confidence: 92%

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Using Semicircular Sampling to Increase Sea Water/Ice Discrimination Altitude

Nekrasov,

Khachaturian,

Fidge

2024

Emerg Sci J

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The rapid development of aircraft and unmanned aerial vehicles (UAV) increases their use, including in polar areas, which are characterized by their remoteness and rather harsh conditions. The dominant trends in airborne radar development are expanding their functionality and increasing the altitude of their applicability. Our study focuses on the functionality enhancement of airborne high-altitude conical scanning radars currently used for circular clouds and precipitation observations as well as for sea wind measurements. Recently, we showed how a semicircular observation scheme, instead of a circular one, can double the maximum applicable altitude of sea wind measurements made with such radars. Here we apply this approach to show how an airborne high-altitude conical scanning radar’s functionality can also be expanded for sea water/ice discrimination within a semicircular observation scheme, again doubling the maximum discrimination altitude compared to circular observations. The discrimination is performed in scatterometer mode using the minimum statistical distance of the measured normalized radar cross sections (NRCSs) to the geophysical model functions (GMFs) of the sea water and ice underlying surfaces. However, as no sea ice GMF is available for the considered horizontal transmit and receive polarization at the Ku band, we instead used a substitute sea ice GMF having the same azimuth isotropic property setting for its NRCSs as the averaged value of the measured azimuth NRCSs within the semicircular observations scheme. Our analysis found that incidence angles of 30°, 45°, and 60° are well suited to our sea water/ice discrimination method, and that incidence angles higher than 30° are preferable as they provide a higher difference in the statistical distance of the measured NRCSs to the sea ice and water GMFs, whereas an incidence angle of 30° provides the highest applicable altitude for sea water/ice discrimination and wind retrieval. We also demonstrated the ability of the sea water/ice discrimination procedure’s implementation for any airborne wind scatterometer or multimode radar operated in scatterometer mode over freezing seas to avoid entirely erroneous sea wind measurement results when a sea ice surface is observed. The obtained results can also be used for enhancing aircraft and UAV radars and for developing new remote sensing systems. Doi: 10.28991/ESJ-2024-08-02-07 Full Text: PDF

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Section: -3-results Summarymentioning

confidence: 89%

Section: -Results and Discussionmentioning

confidence: 99%

Section: -3-results Summarymentioning

confidence: 99%

Section: -5-assumption Of Maximum Altitude Increasementioning

confidence: 99%

mentioning

confidence: 92%

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Using Semicircular Sampling to Increase Sea Water/Ice Discrimination Altitude

Nekrasov,

Khachaturian,

Fidge

2024

Emerg Sci J

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Optimization of Airborne Scatterometer NRCS Semicircular Sampling for Sea Wind Retrieval

2023

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Airborne scatterometer capability depends on not only the device’s technical characteristics but also the scheme used for surface observations. Typically, a rotating-beam scatterometer uses a circular scheme for sampling normalized radar cross-sections (NRCS) at wind measurements over the sea. Here, we investigate wind retrieval using an updated semicircular scheme, providing the NRCS sampling at various combinations of incidence angles within the range 30° to 60°. The effectiveness of the wind retrieval using our semicircular sampling scheme was evaluated using Monte Carlo simulations, and we then developed corresponding wind algorithms that used a geophysical model function (GMF). As a result of the study, we found that a semicircular sampling scheme is well suited for wind retrieval over the sea using a rotating-beam scatterometer. We showed that a semicircular scheme can provide wind retrieval accuracies similar to those achievable with a conventional circular scheme, although the semicircular scheme requires approximately three times the number of NRCS samples integrated in each azimuth sector. Most importantly, however, the semicircular scheme enabled a maximum altitude for wind retrieval of twice the height possible with a circular scheme. In this study, we also demonstrate that the wind speed accuracy tends to increase with an increase in the incidence angle and similarly for the wind direction accuracy. Nonetheless, we then show that the simultaneous use of the NRCS sampling scheme at several incidence angles can increase the wind retrieval accuracy, especially when three or four incidence angles are used. The obtained results can be used to enhance airborne scatterometers and multimode radars operated in a scatterometer mode, including airborne high-altitude conical scanning radars, and can be applied to new remote sensing systems’ development.

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Using Semicircular Sampling to Increase Sea-Wind Retrieval Altitude with a High-Altitude UAV Scatterometer

Cited by 2 publications

References 29 publications

Using Semicircular Sampling to Increase Sea Water/Ice Discrimination Altitude

Using Semicircular Sampling to Increase Sea Water/Ice Discrimination Altitude

Optimization of Airborne Scatterometer NRCS Semicircular Sampling for Sea Wind Retrieval

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