Status: this preprint was under review for the journal AMT. A revision for further review has not been submitted.
Validation of COSMIC water vapor data in the upper troposphere
and lower stratosphere using MLS, MERRA and ERA-Interim
Ming Shangguan,Katja Matthes,Wuke Wang,and Tae-Kwon Wee
Abstract. Water vapor is the most important greenhouse gas in the atmosphere with important implications not only for the Earth’s radiation and energy budget but also for various chemical, physical and dynamical processes in the stratosphere. The Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Radio Occultation (RO) dataset from 2007 through 2013 is used for the first time to study the distribution and variability water vapor in the upper troposphere and lower stratosphere (UTLS). The COSMIC data are compared to the Microwave Limb Sounder (MLS) data, and to two global reanalyses: The Modern-Era Retrospective analysis for Research and Application (MERRA) of the National Aeronautics and Space Administration (NASA); and, the latest reanalysis of the European Center for Medium-range Weather Forecast (ECMWF), the ERA-Interim. The MLS data have been assimilated into the MERRA, whereas the COSMIC data are used for the ERA-Interim. As a result, the MERRA agrees well with the MLS data and so does the ERA-Interim with the COSMIC data. While the monthly zonal mean distributions of water vapor from the four datasets show good agreements in northern mid-latitudes, large discrepancies exist in high southern latitudes and tropics. The MERRA shows overall a consistent seasonal cycle with MLS, but has too strong winter dehydration over the Antarctic, and is very weak in the interannual variations. The ERA-Interim fails to properly represent the winter dehydration over the Antarctic, and shows an unrealistic seasonal cycle in the tropical upper troposphere. The COSMIC data shows a good agreement with the MLS data except for the tropical "taper recorder" signal, where the COSMIC data suggest a faster upward motion than the MLS data. The COSMIC data are able to represent the moisture variabilities associated with the Quasi-Biennial Oscillation and the El Niño-Southern Oscillation.
How to cite. Shangguan, M., Matthes, K., Wang, W., and Wee, T.-K.: Validation of COSMIC water vapor data in the upper troposphere
and lower stratosphere using MLS, MERRA and ERA-Interim, Atmos. Meas. Tech. Discuss. [preprint], https://doi.org/10.5194/amt-2016-248, in review, 2016.
A first validation of the COSMIC Radio Occultation (RO) water vapor data in the upper troposphere and lower stratosphere (UTLS) are presented in this paper. The COSMIC water vapor shows a good agreement with the Microwave limb Sounder (MLS) in both the spatial distribution and the seasonal to interannual variations. It is very valuable for studying the water vapor in the UTLS, thanks to its global coverage, all- weather aptitude and high vertical resolution.
A first validation of the COSMIC Radio Occultation (RO) water vapor data in the upper...