Comment on the paper “Mars Express radio occultation data: A novel analysis approach” by Grandin et al. (2014)

详细信息    查看全文

• 作者：M. Pätzold ; M. K. Bird ; B. Häusler ; K. Peter ; S. Tellmann ; G. L. Tyler
• 刊名：Journal of Geophysical Research: Space Physics
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：121
• 期：10
• 页码：10,578-10,591
• 全文大小：1.1MB
• ISSN：2169-9402

文摘

In their recent paper, Grandin et al. (2014) claim to have developed a novel approach, principally a ray tracing method, to analyze radio sounding data from occulted spacecraft signals by planetary atmospheres without the usual assumptions of the radio occultation inversion method of a stratified, layered, symmetric atmosphere. They apply their “new approach” to observations of the Mars Express Radio Science (MaRS) experiment and compare their resulting temperature, neutral number density, and electron density profiles with those from MaRS, claiming that there is good agreement with the observations. The fact is, however, that there are serious disagreements in the most important altitude ranges. Their temperature profile shows a 30 K shift or a 300σ (1σ standard deviation = 0.1 K for the MaRS profile near the surface) difference toward warmer temperatures at the surface when compared with MaRS, while the MaRS profile is in best agreement with the profile from the Mars Climate Data Base V5.0 (MCD V5.0). Their full temperature profile from the surface to 250 km altitude deviates significantly from the MCD V5.0 profile. Their ionospheric electron density profile is considerably different from that derived from the MaRs observations. Although Grandin et al. (2014) claim to derive the neutral number density and temperature profiles above 200 km, including the asymptotic exosphere temperature, it is simply not possible to derive this information from what is essentially noise.