Feasibility analysis of optimal terahertz (THz) bands for passive limb sounding of middle and upper atmospheric wind

Abstract

As of now, direct measurements of middle and upper atmospheric wind are still scarce, and the observation method is limited, especially for the upper stratosphere and lower mesosphere. This paper presents a study of band selection to derive line-of-sight wind from 30gkm to more than 120gkm using a high-spectral-resolution terahertz (THz) radiometer, which can fill the measurement gap between lidar and interferometer data. Simulations from 0.1-5gTHz for evaluating the feasibility of the spaceborne THz limb sounder are described in this study. The results show that high-precision wind (better than 5gms-1) can be obtained from 40 to 70gkm by covering a cluster of strong O3 lines. By choosing strong O2 or H2O lines, the high-quality measurement can be extended to 105gkm. The O atom (OI) lines can provide wind signals in the higher atmosphere. In addition, performance of different instrument parameters, including spectral resolution, bandwidth, and measurement noise, was analyzed, and, lastly, four different band combinations are suggested.