The Retrieval of Atmospheric Temperature and Humidity Using Radio Occultation Refractivity and Hyperspectral Infrared Radiances

• Main Authors: Kai-Wei Chang, 張凱威
• Other Authors: Hsuan Ren
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/60547538389334406826

碩士 === 國立中央大學 === 遙測科技碩士學位學程 === 101 === Hyperspectral infrared spectrometers and the radio occultation (RO) technique have become crucial for observing the atmosphere, and past studies showed that these two types of observations have complementary characteristics. Temperature retrievals from infrared sounders, such as the Atmospheric InfraRed Sounder (AIRS), tend to have higher error in the upper troposphere. In contrast, radio occultation measurements have a high vertical resolution, are highly accurate for temperature estimates in the upper troposphere and lower stratosphere, and can potentially be used to improve radiance-based temperature estimates. This study presents a physical-statistical algorithm which uses RO-derived refractivity and spectrometer radiances simultaneously to estimate temperature and humidity vertical profiles, demonstrated with measurements from FORMOSAT-3/COSMIC and AIRS. Comparison of simultaneously derived profiles and AIRS-alone derived profiles showed that the impact of RO observations to be most apparent in the upper troposphere between 100 hPa and 300hPa, where it reduced the root-mean-square difference of estimated temperature with a minimum reduction of 24\% (0.36 K) and a maximum of 35\% (0.66 K). In addition to having improved temperature profile retrievals in the upper troposphere, the humidity retrievals were also improved; the average root-mean-square difference below 100 hPa was reduced up to 43\% (0.57 g/kg) in comparison to radiosondes. In comparison to different reanalysis datasets and radiosonde soundings, the humidity profiles retrieved using the proposed algorithm were overall better than the infrared-only retrievals in all of the comparisons, and the temperature profiles improved upon the infrared-only most notably in the upper troposphere.