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The local water management has suffered from the shortage of accurate areal rainfall data collection in use of automatic rain gauge with partial pixel of 200 cm2 caused by the lack of the device installation in the area and the extreme complication of natural phenomenon involving precipitation. In response to that, the adoption of remote sensing technology in weather radar has been introduced to rainfall measurement for the past 50 years. When interacting with raindrop particles, the weather radar can detect radar reflectivity which varies depending on rainfall drop size distribution. This reflectivity subsequently becomes applicable as a support method to the conventional rainfall estimation after translated into rainfall intensity (R (mm/cm)) by using relationship Z-R (Z=aRb). This study had begun and concluded the data collecting process during August 25, 2018 to August 31, 2020 and accumulated 230 rainfall event data, including hourly rainfall data from 174 automatic rain gauges and radar reflectivity from Takhli radar operating under its measuring radius of 240 km, in analysis of altered Z-R relationship correspondingly to periodical rainfall drop size distributions to compare with the result by the use of Climatological Z-R relationship, Z=200R1.6 and Z=300R1.4. The result shows the improvements in accuracy of radar measurements of rainfall by incorporating the altered Z-R relationship correspondingly to periodical rainfall drop size distribution, raising up to [9.05%,10.68%,12.42%], [18.96%,22.50,26.39%], [18.59%,21.60%,25.78%] and [512.14%,580.58,621.36%] when considering from RMSE (Root Mean Squared Error), MSE (Mean Squared Error), MAE (Mean Absolute Error) and BIAS respectively, in comparison to that of Climatological Z-R relationship, Z=200R1.6 and Z=300R1.4.
Morin E, Gabella M. Radar-based quantitative precipitation estimation over Mediterranean and dry climate regimes. J Geophys Res. 2007; 112: D20108.
Marshall J S, and Palmer W M K. The Distribution of Raindrops with Size. Journal of Meteorology. 1984; 5(4): 165-166.
Mapiam P P, Sriwongsitanon N. Climatological Z-R relationship for radar rainfall estimation in the upper Ping river basin. ScienceAsia. 2008; 34: 215-222.
Hanchoowong R, Weesakul U, Chumchean S. Bias correction of radar rainfall estimates based on a geostatistical technique. ScienceAsia. 2012; 38: 373-385.
Chantraket P, Detyothin C, Pankaew S, Kirtsaeng S. An Operational Weather Radar-Based Calibration of Z–R Relationship over Central Region of Thailand. Int J Eng. 2016; 2: 92–100.
Ramli S, Tahir W. Radar Hydrology: New Z/R Relationships for Quantitative Precipitation Estimation in Klang River Basin, Malaysia, International Journal of Environmental Science and Development. 2011; 2(3).
Ayat H, Kaviaanpour M R, Moazami S,Hong Y, Ghaemi E. Calibration of weather radar using region probability matching method (RPMM), Theor Appl Climatol. DOI 10.1007/s00704-017-2266-7.
Richards W G, Crozier C L. Precipitation measurement with a C-band weather radar in Southern Ontario. Atmos Ocean. 1983; 21: 2505–2514.
Smith J A, Krajewski W F. A modeling study of rainfall rate reflectivity relationships. Water Resour Res. 1993; 29: 2505–2514.
Tokay A, Short D A. Evidence from tropical raindrop spectra of the origin of rain from stratiform versus convective clouds. J Appl Meteorol. 1996; 35: 355–371.
Bringi V, Chandrasekar V, Hubbert J, Gorgucci E, Randeu W, Schoenhuber M. Raindrop size distribution in different climatic regimes from disdrometer and dual-polarized radar analysis. J Atmos Sci. 2003; 60: 354–365.
Lee G W, Zawadzki I. Variability of drop size distributions: time-scale dependence of the variability and its effects on rain estimation. J Appl Meteorol. 2005; 44: 241–255.
Seo D J, Breidenbach J P. Real-time correction of spatially nonuniform bias in radar rainfall data using rain gauge measurements. J Hydrometeorol. 2002; 3: 93–111.
Chumchean S, Seed A. Sharma A. Correcting of real-time radar rainfall bias using a Kalman filtering approach. J Hydrol. 2006; 317: 123–137.
Chiang Y M, Chang F J, Jou B J D, Lin P F. Dynamic ANN for precipitation estimation and forecasting from radar observations. J Hydrol. 334, 250–261, 2007
รัชเวช หาญชูวงศ์, วลัยรัตน์ บุญไทย, ศิริลักษณ์ ชุ่มชื่น. การวิเคราะห์หาค่าปรับแก้ตามเวลารายชั่วโมงโดยประยุกต์ใช้วิธี Inverse Distance Weighting เพื่อเพิ่มความถูกต้องในการประเมินฝนเรดาร์อมก๋อย. 2564; 14: 61-73.
Michelson D, Einfalt T, Holleman I, Gjertsen U, Friedrich K, Haase G, Lindskog M, Sztuc J. Weather radar data quality in Europe: Quality control and characterization, COST 717 Working Document WDF_20_200204_1. 2004.
Hydro & meteo GmbH&Co. KG. SCOUT Documentation Version 3.32. Hydro & meteo GmbH & Co. KG. Germany: 2016.
Futon RA, Breidenbach JP, Seo DJ, Miller DA, O’Brannon T. The WSD–88D rainfall algorithm. Weather Forecasting. 1998; 13: 377 -395.
Doelling I G, Joss J, Riedl J. Systematic variations of Z-R relationships from drop size distributions measured in northern Germany during seven years. Atmospheric Research. 1998; 47-48: 635- 649.
Steiner M, Smith J A. Reflectivity, rain rate, and kinetic energy flux relationships based on raindrop spectra. American Meteorological Society. 2000; 39 : 1923-1940.
Hagen M, Yuter S E. Relations between radar reflectivity, liquid water content, and rainfall rate during the MAP-SOP. Atmospheric Sciences. 2003; 128 : 477-494.
Germann U, Galli G, Boscacci M, Bolliger M. Radar precipitation measurement in a mountainous region, Quarterly Journal of the Royal Meteorological Society. 2006; 132: 1669-1692.
กรมฝนหลวงและการบินเกษตร. โครงการประเมินปริมาณน้า ฝนดว้ยเรดาร์ภาคตะวนัออก. กรมฝนหลวงและการบินเกษตร. 2557.
Mapiam P P, Methaprayum M, Bogaard T A, Schoups G, Veldhuis MC T. Citizen rain gauge improves hourly radar rainfall bias correction using a two-step Kalman filter, Hydrol Earth Syst Sci. 2022; 26: 775–794.
Seed A, Sirivarden L, Sun X, Jordan P, Elliot J. On the calibration of Australian weather radars. Technical report 02/7. 2002; 40.
Woodley W, & Herndon A. A raingage evaluation of the Miami reflectivity-rainfall rate relation. Journal of Applied Meteorology.1970; 9(2): 258-264.