Effects of the acoustic and radar pulse length ratio on the accuracy of radio acoustic sounding system (RASS) temperature measurements with monochromatic acoustic pulses
Effects of the acoustic and radar pulse length ratio on the accuracy of radio acoustic sounding system (RASS) temperature measurements with monochromatic acoustic pulses
复制标题
声波和雷达脉冲长度比对使用单色声脉冲的无线电声学探测系统 (RASS) 温度测量精度的影响
DOI：
10.1029/93rs00359
复制
发表时间：
1993
期刊：
影响因子：
1.6
通讯作者：
S. Fukao
中科院分区：
文献类型：
--
作者：
T. Adachi;T. Tsuda;Y. Masuda;T. Takami;S. Kato;S. Fukao
本文研究了由脉冲多普勒雷达和声源组成的无线电声学探测系统（RASS）的温度测量精度。通过数值模拟和中高层大气雷达实验，我们发现声学和雷达脉冲长度比对精度有显著影响。当不严格满足布拉格条件时，数值模型预测在对应于声速fs的多普勒频移频率和发送声频fa之间检测到RASS回波谱的平均频移fm。当比值接近或大于1时，fm变得几乎与fa相同，而随着比值减小，fm接近fs。RASS实验涉及MU雷达工作在46.5兆赫（6.45米波长）和频率约为100赫兹的声学发射机表明，各种声学脉冲长度的RASS回波的观测特性与模型预测相当吻合。虽然数值模型表明，小值的比率是最好的精确测量的温度与RASS，该比率的最小值被确定为约0.2，通过考虑MU雷达的系统灵敏度，因为RASS回波强度降低，随着声脉冲长度变得更短。当声波脉冲和雷达脉冲的长度分别设置为约60 m（18个声波周期）和300 m（脉冲持续时间为1 μs）时，声波脉冲长度与雷达脉冲长度之比约为0.2，我们能够每3分钟获得5至9 km处的温度分布，精度约为0.5°C。
This paper is concerned with the accuracy of temperature measurements with radio acoustic sounding system (RASS) consisting of a pulsed Doppler radar and an acoustic source, where the latter excites short monochromatic pulses. Through the use of a numerical model and middle and upper atmosphere (MU) radar experiments, we found that the accuracy is significantly affected by the acoustic and radar pulse length ratio. When the Bragg condition is not strictly satisfied, a numerical model predicted that the mean frequency shift fm of a RASS echo spectrum is detected between the Doppler-shifted frequency corresponding to the sound speed fs and the transmitted acoustic frequency fa. When the ratio is close to or larger than unity, fm becomes almost identical with fa, while fm approaches fs as the ratio decreases. RASS experiments involving the MU radar operating at 46.5 MHz (6.45-m wavelength) and an acoustic transmitter with a frequency of about 100 Hz showed that the observed characteristics of RASS echoes for various acoustic pulse lengths agreed quite well with model predictions. Although the numerical model suggested that a small value of the ratio is preferable for accurate measurement of temperature with RASS, the minimum value of the ratio was determined to be about 0.2 by taking into account the system sensitivity of the MU radar, since the RASS echo intensity decreases as the acoustic pulse length becomes shorter. When the lengths of the acoustic and radar pulses were set equal to about 60 m (18 acoustic wave cycles) and 300 m (l μs in pulse duration), respectively, which gives a ratio of the acoustic pulse length to the radar pulse length of approximately 0.2, we were able to obtain temperature profiles at 5 to 9 km every 3 min with an accuracy of about 0.5°C.