Estimating Tropical Cyclone Wind Structure and Intensity From Spaceborne Radiometer and Synthetic Aperture Radar

Abstract

We present a relatively simple method to estimate tropical cyclone (TC) surface wind structure (34-, 50-and 64-kt wind radii) and intensity (maximum wind speed, MWS) from wind fields acquired from the L-band SMAP radiometer and C-band Sentinel-1A/B and RADARSAT-2 synthetic aperture radar (SAR) between 2015 and 2020. The radiometer and SAR-derived wind radii and MWS are systematically compared with the best-track estimates. The root-mean-square errors (RMSEs) of R34, R50 and R64 are 31.2, 21.8 and 17.0 n mi (1 n mi =1.852 km) for radiometer, and 21.7, 16.5 and 16.3 n mi for SAR, respectively. These error values are smaller than the averaged best-track uncertainty estimates for the three wind radii. Compared to best-track reports, the bias and RMSE for the MWS estimates are-0.2 m/s and 5.8 m/s for radiometer, and 4.4 m/s and 9.1 m/s for SAR, respectively. These results are for the wind speeds in the range of 17-80 m/s. For the two typical TCs (Lionrock and Noru) in the Northwest Pacific Ocean, our results show that a combination of the radiometer and SAR wind data acquired within a very short time interval has the potential to simultaneously obtain reasonable measurements of the wind radii and intensity parameters. Moreover, for a TC with long lifecycle, such as Typhoon Noru, we demonstrate that high-resolution and multi-temporal synergistic observations from SAR and radiometer are valuable for studying fine-scale features of the wind field and characteristics of wind asymmetry associated with intensity change, as well as the evolution of TC surface wind structure and intensity.

Development of a New Tropical Cyclone Strip Segment Retrieval Model for C-Band Cross-Polarized SAR Data

“…It has a strip width of 1000 km and can cover the global sea in 2-3 days [41,42]. The SMAP radiometer is derived from brightness temperature retrieval and has been proven to be an efficient microwave sensor for observing ocean surface winds [3,4,[43][44][45]. The SMAP radiometer can accurately estimate hurricane intensity (70 m/s) and wind radius, and the wavelength of the L-band is much larger than the radius of a raindrop, so high wind speed can be measured even under heavy rainfall conditions [43].…”

“…Tropical cyclones (TCs) produce strong winds, heavy rain, and high sea states in the sea, which pose a serious threat to marine navigation and the lives of coastal residents. The observation of TC wind speed is of major importance for TC monitoring and forecasting [1][2][3]. In recent years, the retrieval algorithms for the high wind speed of TCs have attracted extensive attention in the satellite oceanic remote sensing field.…”

“…In recent years, the retrieval algorithms for the high wind speed of TCs have attracted extensive attention in the satellite oceanic remote sensing field. At present, because of the cloud-penetrating ability, microwave sensors such as radiometers [3,4], scatterometers [5,6], altimeters [7,8], and synthetic aperture radar (SAR) are used for sea surface wind retrieval. The superior high spatial resolution of SAR is advantageous for imaging sea surface changes caused by mesoscale atmospheric processes.…”

Observed Ocean Surface Winds and Mixed Layer Currents Under Tropical Cyclones: Asymmetric Characteristics

“…Statistical comparisons between SMAP-derived TC surface wind speeds and SFMR along-track measurements, have shown that a standard deviation of wind speed of 3.11 m/s for wind speeds between 10 and 70 m/s (Meissner et al, 2017). Compared with the best-track reports, the RMSE of SMAP-derived maximum TC wind speed is 5.8 m/s, for the wind speeds in the range of 17∼80 m/s (Zhang et al, 2021). Moreover, a previous study has demonstrated that the combination of L-and C-band satellite radiometer observations has capability to provide valuable information about the TC surface wind structure (Reul et al, 2017).…”

“…The RMSE of SAR-derived winds is about 5 m/s, for wind speeds up to 75 m/s (Mouche et al, 2019). Ocean surface wind fields from SARs and scatterometers have been widely used to analyze the characteristics of TC structure (Chavas & Emanuel, 2010;Zhang et al, 2020Zhang et al, , 2021.…”