Development of an acoustic transmitter for the high-time resolution measurements of tropospheric temperature structure with the MU radar-RASS

我们开发了一种高功率声发射系统，用于无线电声探测系统（RASS），这是一种遥感技术，用于获得对流层和平流层下层的温度分布，具有良好的精度和时间高度分辨率。首先，我们研究了平流层下层观测所需的MU雷达新型声发射系统的规格，并确定在MU雷达周围建立一个由20个电动喇叭扬声器组成的有源相控阵系统。电动喇叭扬声器的最大声输出达到140 dB，超出了所要求的声功率。我们还通过使用双曲喇叭获得了32%的高声学效率。通过使用新系统，我们成功地观测了1.5公里至18公里高度的温度和风速剖面。此外，我们控制了由几个扬声器组成的声束，并分析了信噪比（SNR）的概况。信噪比曲线表明，不同源声波散射后的RASS回波相相一致，并且在声波的射线追踪结果所期望的高度区域内增强了接收信号功率，证实了有源相控阵系统工作正常。利用本研究开发的RASS以高时高分辨率监测中尺度和微尺度现象的详细结构，我们期望获得现象机制的新的科学方面，以及它们所激发的各种大气波的特征。

We have been developed a high-power acoustic transmitter system for a RASS (Radio Acoustic Sounding System) which is a remote-sensing technique for obtaining temperature profiles in the troposphere and lower stratosphere with good accuracy and timeheight resolutions.First, we examined a specification of the new acoustic transmitter system of the MU radar required for the observations up to the lower stratosphere, and determined to build up an active phased-array system consisting of 20 electro-dynamic horn speakers surrounding the MU radar.Maximum acoustic output of an electro-dynamic horn speaker reached 140 dB exceeding the required acoustic power. We have also obtained a high acoustic efficiency of 32% by applying a hyperbolic horn. By using the new system, we were successful to observe temperature and wind velocity profiles from 1.5km to 18km altitudes.Further, we steered an acoustic beam formed by a few speakers and analyzed a profile of signal to noise ratios (SNR). The SNR profile indicated that RASS echoes scattered by the acoustic waves from different sources were in-phase and enhanced receiving signal power in a height region expected by the result of ray-tracing of the acoustic waves, which confirmed that the active phased-array system worked correctly.By monitoring detailed structures of meso-and micro-scale phenomena with high time-height resolutions by the RASS developed in this research, we expect to obtain new scientific aspects of mechanisms of the phenomena, and characteristics of various atmospheric waves excited by them.