| ANALYSIS AND CASE STUDY ON THE GENERATION OF RADAR ECHO BRIGHT BAND |
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| 作者姓名： | 董慧杰 王振会 郭丽君 王 云 |
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| 作者单位： | Collaborative Innovation Center on Forecast and Evaluation Meteorological Disasters, Nanjing, 210044 China |
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| 摘 要： | In this study, the vertical profiles of radar refractive factor (Z) observed with an X-band Doppler radar in Jurong on July 13, 2012 in different periods of a stratiform cloud precipitation process were simulated using the SimRAD software, and the contributions of each impact resulting in the bright band were analyzed quantitatively. In the simulation, the parameters inputted into SimRAD were updated until the output Z profile was nearly consistent with the observation. The input parameters were then deemed to reflect real conditions of the cloud and precipitation. The results showed that a wider (narrower) and brighter (darker) bright band corresponded to a larger (smaller) amount, wider (narrower) vertical distribution, and larger (smaller) mean diameter of melting particles in the melting layer. Besides this, radar reflectivity factors under the wider (narrower) melting layer were lager (smaller). This may be contributed to the adequate growth of larger rain drops in the upper melting layer. Sensitivity experiments of the generation of the radar bright band showed that a drastic increasing of the complex refractive index due to melting led to the largest impact, making the radar reflectivity factor increase by about 15 dBZ. Fragmentation of large particles was the second most important influence, making the value decrease by 10 dBZ. The collision–coalescence between melting particles, volumetric shrinking due to melting, and the falling speed of raindrops made the radar reflectivity factor change by about 3–7 dBZ. Shape transformation from spheres to oblate ellipsoids resulted in only a slight increase in the radar reflectivity factors (about 0.2 dBZ), which might be due to the fact that there are few large particles in stratiform cloud.
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| 关 键 词： | bright band radar reflectivity factor cloud microphysical structure |
| 修稿时间： | 5/5/2015 12:00:00 AM |
ANALYSIS AND CASE STUDY ON THE GENERATION OF RADAR ECHO BRIGHT BAND |
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| DONG Hui-jie,WANG Zhen-hui,GUO Li-jun and WANG Yun.ANALYSIS AND CASE STUDY ON THE GENERATION OF RADAR ECHO BRIGHT BAND[J].Journal of Tropical Meteorology,2015,21(3):285-294. |
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| Authors: | DONG Hui-jie WANG Zhen-hui GUO Li-jun and WANG Yun |
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| Institution: | Collaborative Innovation Center on Forecast and Evaluation Meteorological Disasters, Nanjing, 210044 China |
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| Abstract: | In this study, the vertical profiles of radar refractive factor(Z) observed with an X-band Doppler radar in Jurong on July 13, 2012 in different periods of a stratiform cloud precipitation process were simulated using the Sim RAD software, and the contributions of each impact resulting in the bright band were analyzed quantitatively. In the simulation, the parameters inputted into Sim RAD were updated until the output Z profile was nearly consistent with the observation. The input parameters were then deemed to reflect real conditions of the cloud and precipitation. The results showed that a wider(narrower) and brighter(darker) bright band corresponded to a larger(smaller) amount, wider(narrower) vertical distribution, and larger(smaller) mean diameter of melting particles in the melting layer. Besides this,radar reflectivity factors under the wider(narrower) melting layer were larger(smaller). This may be contributed to the adequate growth of larger rain drops in the upper melting layer. Sensitivity experiments of the generation of the radar bright band showed that a drastic increasing of the complex refractive index due to melting led to the largest impact,making the radar reflectivity factor increase by about 15 d BZ. Fragmentation of large particles was the second most important influence, making the value decrease by 10 d BZ. The collision-coalescence between melting particles, volumetric shrinking due to melting, and the falling speed of raindrops made the radar reflectivity factor change by about 3-7d BZ. Shape transformation from spheres to oblate ellipsoids resulted in only a slight increase in the radar reflectivity factors(about 0.2 d BZ), which might be due to the fact that there are few large particles in stratiform cloud. |
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| Keywords: | bright band radar reflectivity factor cloud microphysical structure |
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