On the Measurement of Precipitation Intensity by Radar

Twomey, S.

doi:10.1175/1520-0469(1953)010<0066:otmopi>2.0.co;2

Cited by 21 publications

(11 citation statements)

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“…Recent drop-size observations within Great Plains thunderstorms by Martner (1975) and Carbone and Nelson (1978) show high coefficients and low exponents during growth (updraft) phases of the thunderstorm and low coefficients and high exponents during declining (downdraft) phases. The large scatter in drop spectra over short time periods (5-10 min) and the wide disparity among Z-R relationships reported by others prompted Twomey (1953) to conclude that radar rainfall estimates derived with average Z-R relationship were only approximate at best (a factor of 2 high or low).…”

Section: ) Variations In the Z-r Relationshipsmentioning

confidence: 99%

Radar Measurement of Rainfall—A Summary

Wilson

Brandes

1979

Bull. Amer. Meteor. Soc.

453

255

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Radar can produce detailed precipitation information for large areas from a single location in real time. Although radar has been used experimentally for nearly 30 years to measure rainfall, operational implementation has been slow. Today we find that data are underutilized and both confusion and misunderstanding exist about the inherent ability of radar to measure rainfall, about factors that contribute to errors, and about the importance of careful calibration and signal processing. Areal and point rainfall estimates are often in error by a factor of two or more. Error sources reside in measurement of radar reflectivity factor, evaporation and advection of precipitation before reaching the ground, and variations in the drop-size distribution and vertical air motions. Nevertheless, radar can be of lifesaving usefulness by alerting forecasters to the potential for flash flooding. The most successful technique for improving the radar rainfall estimates has been to "calibrate" the radar with rain gages. Simple techniques that combine sparse gage reports (one gage per 1000-2000 km 2) with radar produce smaller measurement errors (10-30%) than either system alone. When high accuracy rainfall measurements are needed (average error less than about 10-20%) the advantage of radar is diminished, since the number of gages required for calibration is itself sufficient to provide the desired accuracy.

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Section: ) Variations In the Z-r Relationshipsmentioning

confidence: 99%

Radar Measurement of Rainfall—A Summary

Wilson

Brandes

1979

Bull. Amer. Meteor. Soc.

453

255

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“…In the early studies, the parameters were estimated by considering the fact that the DSD varies according to the storm type [16,[20][21][22][23]. It is also possible that both convective and stratiform clouds coexist, and that raindrops evaporate or collide while they are falling to the ground [24].…”

Section: Z-r Relationsmentioning

confidence: 99%

Calibrating Radar Data in an Orographic Setting: A Case Study for the Typhoon Nakri in the Hallasan Mountain, Korea

Yoo

2017

Atmosphere

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Abstract:The Typhoon Nakri passed the Jeju Island in Korea (1-3 August 2014) and recorded one-day rainfall of 1182 mm at Witse-Oreum (a place name where a small volcanic cone is) of the Hallasan Mountain, Korea. This one-day rainfall amount was the highest rainfall that was ever recorded in Korea. As the altitude of Witse-Oreum is 1673 m, it was believed that the orographic effect enhanced the rainfall depth significantly. It was also argued that the maximum rainfall could be recorded in some other locations in the Hallasan Mountain. In this study, the rainfall event due to the Typhoon Nakri in the Jeju Island was analyzed using the radar and rain gauge data that were collected during this rainfall event. Fortunately, two radars are available on the eastern and western side of the Jeju Island. The entire Hallasan Mountain is covered by these two radars. A total of 23 rain gauges are also available in the Jeju Island. As a first step, independent ground-level Z-R relations were derived for every 250 m interval from the sea-level. Each Z-R relation was then applied to the corresponding-altitude radar reflectivity data to generate the rain rate field over the Jeju Island. Finally, the generated radar rain rate data were examined fully to evaluate the orographic effect in the Hallasan Mountain, also to locate the point where the maximum rain rate was recorded. This result shows that the maximum one-day rainfall amount could be up to 1500 mm, which was about 30% higher than the rain gauge measurement.

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“…Important early papers include those on rain drop size distributions (Marshall & Palmer, 1948) and shapes (Browne & Robinson, 1952;Hunter, 1954;Newell et al, 1955), the measurement of precipitation (Ryde, 1946;Byers, 1948;Bowen, 1951;Twomey, 1953;Battan, 1953;Stout & Neill, 1953), its vertical structure (Langille & Gunn, 1948) and associated estimation errors (Hitschfeld & Bordan, 1954), and those on thunderstorm identification, behaviour and dynamics (Wexler & Swingle, 1947;Byers & Braham, 1949;Wexler, 1951;Ligda, 1951;Battan, 1953).…”

Section: Origins Of Weather Radar and Early Researchmentioning

confidence: 99%