JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Poster

A (Atmospheric and Hydrospheric Sciences) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS09] [EE] Stratosphere - Troposphere Interaction

Wed. May 24, 2017 10:45 AM - 12:15 PM Poster Hall (International Exhibition Hall HALL7)

convener:Nawo Eguchi(Kyushu University), Rei Ueyama(NASA Ames Research Center), Sean M Davis(NOAA Boulder), Seok Woo Son(Seoul National University)

[AAS09-P17] Assessment of upper tropospheric and stratospheric water vapour and ozone in reanalyses as part of S-RIP

*Sean M Davis1,2, Michaela Hegglin3, Masatomo Fujiwara4, Rossana Dragani5, Yayoi Harada6, Chiaki Kobayashi7, Craig Long8, Gloria Manney9,10, Eric Nash11, Susann Tegtmeier12, Tao Wang13, Krzysztof Wargan14, Jonathon Wright15 (1.NOAA Earth System Research Laboratory, 2.Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado at Boulder, 3.University of Reading, 4.Hokkaido University, 5.European Centre for Medium-Range Weather Forecasts, 6.Japan Meteorological Agency, 7.Meteorological Research Institute, Japan Meteorological Agency, 8.NOAA Climate Prediction Center, 9.NorthWest Research Associates, 10.New Mexico Institute of Mining and Technology, 11.Science Systems and Applications, Inc., Lanham, 12.GEOMAR Helmholtz Centre for Ocean Research , 13.NASA Jet Propulsion Laboratory/California Institute of Technology, 14.NASA Global Modeling and Assimilation Office, 15.Tsinghua University)

Keywords:ozone, water vapor, stratosphere, reanalyses, SPARC Reanalysis Intercomparison Project

Reanalysis datasets are widely used to understand atmospheric processes and past variability, and are often used as “observations” for comparison with climate model output. Because of the central role of water vapour (WV) and ozone (O3) in climate change, it is important to understand how accurately these species are represented in the existing global reanalyses, and whether or not significant differences exist amongst them. We present results from the WV and O3 intercomparisons that were performed as part of the SPARC (Stratosphere-troposphere Processes and their Role in Climate) Reanalysis Intercomparison Project (S-RIP). Comparisons are made over a range of timescales between the different reanalyses, and between reanalyses and observational datasets.
In addition to the intercomparisons, we discuss the treatment of WV and O3 in reanalyses to aid future research and guide the interpretation of differences between the reanalysis fields. Because total column ozone (TCO) is assimilated in the newer reanalyses, these reanalyses generally reproduce TCO well except when data coverage is lacking, such as during polar night. We find that the vertical distribution of ozone is relatively well represented in reanalyses, particularly given that for most reanalyses there are only weak constraints on the vertical profile of ozone from observations, and that most have a simplistic representation of ozone photochemical processes.
In contrast to O3, stratospheric WV data are not currently assimilated, with humidity observations typically used only in the troposphere below a specified vertical level at or near the tropopause. Thus, the fidelity of reanalysis stratospheric WV is sensitive to how accurately the fundamental drivers of stratospheric WV such as tropical tropopause layer temperatures, methane oxidation, and the stratospheric overturning circulation are represented. Because of these issues and the known deficiencies in the representation of stratospheric transport in reanalyses, we find much poorer agreement both amongst reanalyses and between reanalyses and independent observations. For these reasons, stratospheric WV from the current generation of reanalyses should not be used in scientific studies.