A rain-type adaptive optical flow method and its application in tropical cyclone rainfall nowcasting

Abstract

A rain-type adaptive pyramid Kanade–Lucas–Tomasi (A-PKLT) optical flow method for radar echo extrapolation is proposed. This method introduces a rain-type classification algorithm that can classify radar echoes into six types: convective, stratiform, surrounding convective, isolated convective core, isolated convective fringe, and weak echoes. Then, new schemes are designed to optimize specific parameters of the PKLT optical flow based on the rain type of the echo. At the same time, the gradients of radar reflectivity in the fringe positions corresponding to all types of rain echoes are increased. As a result, corner points that are characteristic points used for PKLT optical flow tracking in the surrounding area will be increased. Therefore, more motion vectors are purposefully obtained in the whole radar echo area. This helps to describe the motion characteristics of the precipitation more precisely. Then, the motion vectors corresponding to each type of rain echo are merged, and a denser motion vector field is generated by an interpolation algorithm on the basis of merged motion vectors. Finally, the dense motion vectors are used to extrapolate rain echoes into 0–60-min nowcasts by a semi-Lagrangian scheme. Compared with other nowcasting methods for four landfalling typhoons in or near Shanghai, the new optical flow method is found to be more accurate than the traditional cross-correlation and optical flow methods, particularly showing a clear improvement in the nowcasting of convective echoes on the spiral rainbands of typhoons.

Keywords

optical flow method / radar echo classification / adaptive / typhoon / nowcasting

References

[1] Bechini R, Chandrasekar V (2017). An enhanced optical flow technique for radar nowcasting of precipitation and winds. J Atmos Ocean Technol, 34(12): 2637–2658

[2] Bouguet J Y (2000). Pyramidal Implementation of the Lucas Kanade Feature Tracker description of the algorithm. Intel Corporation: 1–9

[3] Bowler N E H, Pierce C E, Seed A (2004). Development of a precipitation nowcasting algorithm based on optical flow techniques. J Hydrol (Amst), 288(1–2): 74–91

[4] Browning K A, Collier C G (1989). Nowcasting of precipitating systems. Rev Geophys, 27(3): 345–370

[5] Cao C Y, Chen Y Z, Liu D H, Li C, Li H, He J J (2015). The optical flow method and its application to nowcasting. Acta Meteorol Sin, 73(3): 471–480 (in Chinese)

[6] Chen L, Dai J H, Tao L (2009). Application of an improved TREC algorithm (CoTREC) for precipitation nowcast. J Trop Meteorol, 25(1): 117–122 (in Chinese)

[7] Chen L S, Li Y (2004). An overview on the study of the tropical cyclone rainfall. In: Proc. Inter. Conf. on Storms, Brisbane, Australian Meteorological and Oceanographic Society: 112–113

[8] Chen L S, Li Y, Cheng Z Q (2010). An overview of research and forecasting on rainfall associated with landfalling tropical cyclones. Adv Atmos Sci, 27(5): 967–976

[9] Chen P Y, Yu H, Xu M, Lei X T, Zeng F (2019). A simplified index to assess the combined impact of tropical cyclone precipitation and wind on China. Front Earth Sci, 13(4): 672–681

[10] Chen Y Z, Lan H P, Chen X L, Zhang W H (2017). A nowcasting technique based on application of the particle filter blending algorithm. J Meteorol Res, 31(5): 931–945

[11] Crane R K (1979). Automatic cell detection and tracking. IEEE Trans Geosci Electron, 17(4): 250–262

[12] Crum T, Ciardi E J, Boettcher J B, Istok M, Stern A (2013). How the wsr-88d and its new dual polarization capability can benefit the wind energy industry. In: 93rd American Meteorological Society Annual Meeting

[13] Dai J H (2013). Analysis of thunderstorm development and evolution features and mechanism study for the Yangtze River Delta region. Dissertation for the Doctoral Degree. Nanjing: Nanjing University (in Chinese)

[14] Dixon M, Wiener G (1993). TITAN: Thunderstorm identification, tracking, analysis, and nowcasting-A radar-based methodoloy. J Atmos Ocean Technol, 10(6): 785–797

[15] Dusan S Z, Valery M M, Alexander V R (2006). Correlation coefficients between horizontally and vertically polarized returns from ground clutter. J Atmos Ocean Technol, 23(3): 381–394

[16] Emanuel K, Center L (2018). 100 Years of progress in tropical cyclone research. Meteorol Monographs, 59: 15.1–15.68

[17] Fabry F (2015). Radar Meteorology: Principles and Practice. Cambridge: Cambridge University Press

[18] Germann U, Zawadzki I (2002). Scale-dependence of the predictability of precipitation from continental radar images. Part I: description of the methodology. Mon Weather Rev, 130(12): 2859–2873

[19] Gibson J J (1950). The Ecological Approach to Visual Perception. Boston: Houghton Mifflin

[20] Han L, Wang H Q, Lin Y J (2008). Application of optical flow method to nowcasting convective weather. Acta Scientiarum Naturalium Universitatis Pekinensis, 44(5): 751–755

[21] Houze R Jr (2010). Clouds in tropical cyclones. Mon Weather Rev, 138(2): 293–344

[22] Johnson J T, MacKeen P L, Witt A, Mitchell E D, Stumpf G J, Eilts M D, Thomas K W (1998). The storm cell identification and tracking (SCIT) algorithm: an enhanced WSR-88D algorithm. Weather Forecast, 13(2): 263–276

[23] Lucas B D, Kanade T (1981). An iterative image registration technique with an application to stereo vision. Proceedings of Imaging Understanding Workshop, 121–130

[24] Powell S W, Houze R A, Brodzik S R (2016). Rainfall-type categorization of radar echoes using polar coordinate reflectivity data. J Atmos Ocean Technol, 33(3): 523–538

[25] Rinehart R E, Garvey E T (1978). Three-dimensional storm motion detection by conventional weather radar. Nature, 273(5660): 287–289

[26] Schaefer J T (1990). The critical success index as an indicator of warning skill. Weather Forecast, 5(4): 570–575

[27] Shi J B, Tomasi C (1994). Good features to track. In: Proceedings IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR) Seattle: 593–600

[28] Steiner M, Houze R Jr, Yuter S E (1995). Climatological characterization of three-dimensional storm structure from operational radar and rain gauge data. J Appl Meteorol, 34(9): 1978–2007

[29] Sun M, Dai J H, Yuan Z H, Tao L (2015). An analysis of a back-propagating thunderstorm using the three-dimensional wind fields retrieved by the dual-Doppler radar data. Acta Meteorol Sin, 73(2): 247–262 (in Chinese)

[30] Tuttle J D, Foote G B (1990). Determination of the boundary layer airflow from a single Doppler radar. J Atmos Ocean Technol, 7(2): 218–232

[31] Wexler H (1945). The structure of the September, 1944, Hurricane when off Cape Henry, Virginia. Bull Am Meteorol Soc, 26(5): 156–159

[32] Wexler H (1947). Structure of hurricanes as determined by radar. Ann N Y Acad Sci, 48(8): 821–844

[33] Wilson J (2004). Precipitation nowcasting: past, present and future. In: Sixth Int. Symp. on Hydrological Applications of Weather Radar, Melbourne, VIC, Australia, Centre for Australian Weather and Climate Research, 8

[34] Woo W C, Wong W K (2017). Operational application of optical flow techniques to radar-based rainfall nowcasting. Atmosphere, 8(12): 48

[35] Yang L H, Liu X Y, Chen Y H (2017). Product analysis of correlation coefficient of dual polarization radar. Guangdong Meteorol, 39(3): 69–72 (in Chinese)

[36] Yu H, Chen L S (2019). Impact assessment of landfalling tropical cyclones: introduction to the special issue. Front Earth Sci, 13(4): 669–671

[37] Yu X D, Zheng Y G (2020). Advances in severe convective weather research and operational service in China. J Meteorol Res, 34(2): 189–217

[38] Yu X D, Zhou X G, Wang X M (2012). The advances in the nowcasting techniques on thunderstorms and severe convection. Acta Meteorol Sin, 70: 311–337 (in Chinese)

[39] Zhang L, Wei M, Li N, Zhou S H (2014). Improved optical flow method application to extrapolate radar echo. Sci Technol Engineering, 14(32): 133–137 (in Chinese)

[40] Zhang Q H, Wei Q, Chen L S (2010). Impact of landfalling tropical cyclones in Chinese mainland. Sci China Earth Sci, 53(10): 1559–1564

[41] Zheng Y G, Zhou K H, Sheng J, Lin Y J, Tian F Y, Tang W Y, Lan Y, Zhu W J (2015). Advances in techniques of monitoring, forecasting and warning of severe convective weather. J Applied Meteorol Sci, 26(6): 641–657 (in Chinese)

[42] Zhou G B, Gao S Z (2019). Analysis of the August 2019 atmospheric circulation and weather. Meteorol Mont, 45(11): 1621–1628 (in Chinese)

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