Radiosonde humidity corrections and potential Atmospheric Infrared Sounder moisture accuracy

Abstract

[1] Although there are a number of sources of radiosonde data for validation of observations from other atmospheric sensors, routine operational sondes remain the main source for a large volume of data. In this study radiosonde moisture profiles are renormalized using Global Positioning System (GPS) Integrated Precipitable Water (IPW) vapor. The GPS-adjusted radiosonde humidity profiles are then compared to the Atmospheric Infrared Sounder (AIRS) measurements. As a check, AIRS measurements are also compared with unadjusted radiosonde moisture profiles. It is shown that the GPS-adjusted values are in better agreement with the AIRS measurements. On the basis of this result, the GPS-adjusted radiosondes are used to assess the AIRS potential accuracy. This is valid because the errors in the AIRS measurements and the adjustments are independent. The GPS-based renormalization of radiosonde humidity measurements produced a significant improvement in the agreement between AIRS and Vaisala RS 57 H type radiosondes in the lower troposphere, where much of the atmospheric water vapor resides. The adjustment also resulted in improved agreement between AIRS and radiosonde IPW estimates. The results showed a day/night bias in the radiosonde values as compared to the GPS and the AIRS values, demonstrating the potential use of the technique for evaluating and correcting this bias. Established corrections for humidity errors also have been applied to some operational radiosonde observations, specifically the published temperature correction developed for the Vaisala RS80 H type radiosonde. This correction produced a much smaller effect than the GPS adjustment.

Comparison of upper tropospheric water vapor observations from the Microwave Limb Sounder and Atmospheric Infrared Sounder

“…This shows that the larger the value of an observation, the higher the probability of MLS being wetter than AIRS, consistent with the findings of Read et al [2007]. A tendency toward the mean in AIRS is noted by McMillin et al [2007] in their comparison of AIRS total precipitable water vapor with ground‐based sensors; a similar effect may be occurring for AIRS UTWV observations. However, as argued by Read et al [2007], MLS tends to overestimate scenes wetter than 400 ppmv.…”

Validation of the Atmospheric Infrared Sounder Water Vapor Retrievals Using Global Positioning System: Case Study in South Korea

“…According to the results of previous studies, the AIRS TPW data showed that they are wetter at low altitudes (800 hPa) and drier at higher altitudes (300~600 hPa) when compared with the results of numerical models (Pierce et al 2006), and the accuracy was about 15% within the altitude rage of 2 km from the ground surface (Divakarla et al 2006). However, since the accuracy verification results from the previous studies are focused on the tropical region (Pierce et al 2006) or Europe and the USA (Fetzer et al 2003, McMillin et al 2007, there have been no sufficient verification researches conducted specifically for the observation environment in Korea.…”

“…There are a number of previous studies on the accuracy verification of AIRS TPW data using radiosondes and numerical models (Fetzer et al 2003, Divakarla et al 2006, Pierce et al 2006, McMillin et al 2007). According to the results of previous studies, the AIRS TPW data showed that they are wetter at low altitudes (800 hPa) and drier at higher altitudes (300~600 hPa) when compared with the results of numerical models (Pierce et al 2006), and the accuracy was about 15% within the altitude rage of 2 km from the ground surface (Divakarla et al 2006).…”

Analysis on Characteristics of Radiosonde Bias Using GPS Precipitable Water Vapor

“…It takes about 40 minutes to reach 16 km of altitude in this elevation speed and about 90 minute to reach 30 km of altitude (World Meterorological Organization 2008). Thus, after 30 minutes following the flying, the radiosonde reaches about 12 km of altitude where most of the water vapor in the atmosphere is contained (McMillin et al 2007).…”