GRAS误差对大气折射率廓线反演精度影响仿真研究

Refractivity retrieval deviation affected by GRAS error during the radio occultation atmospheric sounding process using simulation method

利用EGOPS软件仿真研究了多普勒偏差、多普勒频移、时钟稳定性/单差分、接收机噪声和局部多路径等GRAS误差对GNSS无线电掩星反演大气折射率廓线精度的影响.选择了一个上升掩星事件和一个下降掩星事件进行模拟分析,结果表明:误差最大值大部分出现在平流层顶附近,其中多普勒偏差引起的折射率相对误差最大值接近1%,多普勒频移引起的折射率相对误差最大值小于0.2%,时钟稳定性/单差分引起的折射率相对误差最大值接近0.8%,现实接收机噪声引起的折射率相对误差最大值超过了3%,局部多路径引起的折射率相对误差最大值小于1%.经讨论分析认为:对于高质量的无线电掩星大气廓线反演,仪器误差源中最主要的是接收机热噪声、时钟稳定性/单差分和多普勒偏差.

In this paper, the EGOPS simulation software was employed to evaluate the influences on the refractivity retrieval by GRAS error respectively, which include the doppler biases and drifts, clock stability/single-differencing, receiver thermal noise and multipath. The rising and setting occultation events are tested in the simulation. The results show that the maximum relative refractivity error is reached to 1% due to the influence of the Doppler bias, 0.2% due to the influence of the Doppler shift, 0.8% due to the influence of the Clock stability/single-differencing, less than 3% due to the influence of the receiver thermal noise and less than 1% due to the influence of the multipath respectively. It can be seen that the worst situation for refractivity retrieval is near the stratopause. The major error sources are the impact of the Receiver thermal noise, Clock stability/single differencing and POD-induced Doppler biases.