Complementing regional ground GNSS-STEC computerized ionospheric tomography (CIT) with ionosonde data assimilation
Complementing regional ground GNSS-STEC computerized ionospheric tomography (CIT) with ionosonde data assimilation
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DOI：
10.1007/s10291-021-01133-y
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发表时间：
2021-04
期刊：
影响因子：
4.9
通讯作者：
Nicholas Ssessanga;M. Yamamoto;S. Saito;A. Saito;M. Nishioka
中科院分区：
文献类型：
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作者：
Nicholas Ssessanga;M. Yamamoto;S. Saito;A. Saito;M. Nishioka
在东亚地区开发了一种近实时计算机电离层层析成像（CIT）技术，以确定三维电子密度场。该技术基于感兴趣区域内的大量全球导航卫星系统观测数据，该区域的水平边界为110°-160°E和10°-60°N，高度从80公里延伸到25,000公里。在部署之前，研究人员利用电离层探空仪、中高层大气雷达和掩星数据验证了CIT结果，并找到了充分重建区域电离层垂直结构的技术。然而，由于在估计峰高和避免最终溶液中物理上不切实际的负密度方面还有改进的空间，我们提出了一种技术的初步结果，该技术通过将CIT结果纳入数据同化（DA）技术来解决这些问题。DA技术在CIT结果中加入了离子探空井底测量，从而提高了重建井底三维结构的精度。更具体地说，CIT NmF2和hmF2平均提高了60%以上。此外，在分析过程中，假设电离层电子密度可以用概率对数正态分布更好地描述，这引入了电离层成像中必需的正性约束。
A near-real-time computerized ionospheric tomography (CIT) technique was developed over the East Asian sector to specify the 3-D electron density field. The technique is based on a plethora of Global Navigation Satellite System observables within the region of interest which is bounded horizontally 110°–160°E and 10°–60°N and extending from 80 to 25,000 km in altitude. Prior to deployment, studies validated the CIT results using ionosonde, middle-upper atmosphere radar and occultation data and found the technique to adequately reconstruct the regional ionosphere vertical structure. However, with room for improvement in estimating the peak height and avoiding physically unrealistic negative densities in the final solution, we present preliminary results from a technique that addresses these issues by incorporating CIT results into a data assimilation (DA) technique. The DA technique adds ionosonde bottomside measurements into CIT results, thereby improving the accuracy of the reconstructed bottomside 3-D structure. More specifically, on average CIT NmF2 and hmF2 improve by more than 60%. Further, during analysis, ionospheric electron densities are assumed to be better described by probability log-normal distribution, which introduces the positivity constraint that is mandatory in ionospheric imaging.