Global ocean surface vector winds (OSVW) have been produced in near real-time using conventional Advanced Scatterometer (ASCAT) processing at 12.5 and 25 km grid resolution. Additionally, a wind product tailored specifically for tropical cyclones (TCs) is generated from ASCAT using Ultra-High-Resolution (UHR) processing [1, 2]. Recently, the UHR ASCAT processing was further developed into a new coastal wind product [3] by implementing normalized radar cross section (NRCS) correction and applying the high wind CMOD5.H GMF [4]. This coastal UHR ASCAT wind product has the potential to measure high and extreme winds under TC conditions. Since the CMOD5.H GMF was developed based on NRCS with much lower spatial resolution, the resulting UHR ASCAT wind couldn’t capture the small-scale high and extreme wind conditions correctly. Thus, in order to leverage the benefits of the ultra-high-resolution measurements in TC environment, it was necessary to rescale the UHR winds with respect to a comparable resolution wind reference, such as wind measurements from the stepped-frequency microwave radiometer (SFMR) and the imaging wind and rain airborne profiler (IWRAP). The rescaling methodology follows a similar approach proposed by [5-7], where the original wind retrievals – in our case, the UHR ASCAT wind speeds from coastal processing – are modified at wind speed of 15 m/s to capture wind speed trends and storm structure, as measured by the airborne sensors. To validate the result of the rescaled UHR high winds, we use several passes of ASCAT over TCs and compare them with SFMR measurements when there is collocation within 30 minutes. In addition, we qualitatively compare the storm structure with TC wind measurements from Synthetic Aperture Radar (SAR), SMAP and AMSR-2. The initial results show that the updated UHR wind speed standard deviation with respect to SFMR is approximately 15% of wind speeds > 30 m/s. An example of the rescaled UHR ASCAT wind speeds with respect to SFMR wind speeds and a storm structure before and after wind speed adjustment are presented in Fig. 1. Figure 2 depicts a rescaled UHR ASCAT pass over Hurricane Lee in 2023 collocated with SFMR measurements within 30 minutes time difference.
In addition, we will show how the UHR ASCAT NRCS measurements can be used in novel way to identify the storm center as well as provide additional information about the storm wind radii (34-, 50, and 64-knots) and the radius of maximum winds.
[1] R. D. Lindsley and D. G. Long, "Enhanced-Resolution Reconstruction of ASCAT Backscatter Measurements," IEEE Transactions on Geoscience and Remote Sensing, Vol. 54, No. 5, pp. 2589-2601, doi:10.1109/TGRS.2015.2503762, 2016.
[2] R. D. Lindsley, J. R. Blodgett, and D. G. Long, "Analysis and Validation of High-Resolution Wind from ASCAT," IEEE Transactions on Geoscience and Remote Sensing, Vol. 54, No. 10, pp. 5699-5711, doi:10.1109/TGRS.2016.2570245, 2016.
[3]. S. Soisuvarn, Z. Jelenak, P. S. Chang, Q. Zhu and C. G. Shoup, "High-Resolution Coastal Winds From the NOAA Near Real-Time ASCAT Processor," in IEEE Transactions on Geoscience and Remote Sensing, vol. 61, pp. 1-12, 2023, Art no. 5208612, doi: 10.1109/TGRS.2023.3279764.
[4]. S. Soisuvarn, Z. Jelenak, P. S. Chang, S. O. Alsweiss and Q. Zhu, "CMOD5.H—A High Wind Geophysical Model Function for C-Band Vertically Polarized Satellite Scatterometer Measurements," IEEE Transactions on Geoscience and Remote Sensing, vol. 51, no. 6, pp. 3744-3760, 2013.
[5]. Polverari, F.; Portabella, M.; Lin,W.; Sapp, J.W.; Stoffelen, A.; Jelenak, Z.; Chang, P.S. On High and ExtremeWind Calibration
Using ASCAT. IEEE Trans. Geosci. Remote Sens. 2021, 60, 4202210.
[6]. F. Polverari, J. W. Sapp, M. Portabella, A. Stoffelen, Z. Jelenak and P. S. Chang, "On Dropsonde Surface-Adjusted Winds and Their Use for the Stepped Frequency Microwave Radiometer Wind Speed Calibration," in IEEE Transactions on Geoscience and Remote Sensing, vol. 60, pp. 1-8, 2022, Art no. 4208308, doi: 10.1109/TGRS.2022.3189310.
[7]. Ni, W.; Stoffelen, A.; Ren, K.; Yang, X.; Vogelzang, J. SAR and ASCAT Tropical Cyclone Wind Speed Reconciliation. Remote Sens. 2022, 14, 5535. https://doi.org/10.3390/rs14215535
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