Publication Date:
2013-01-17
Description:
[1] We analyse the relation between atmospheric temperature and water vapor - a fundamental component of the global climate system - for stratospheric water vapor (SWV). We compare measurements of SWV (and methane where available) over the period 1980–2011 from NOAA-FPH, SAGE II, HALOE, MLS/Aura, and ACE-FTS to model predictions based on troposphere-to-stratosphere transport from ERA-Interim, and temperatures from ERA-Interim, MERRA, CFSR, RATPAC, HadAT2 and RICHv1.5. All model predictions are dry biased. The interannual anomalies of the model predictions show periods of fairly regular oscillations, alternating with more quiescent periods and a few large-amplitude oscillations. They all agree well (correlation coefficients 0.9 and larger) with observations for higher-frequency variations (periods up to 2–3 years). Differences between SWV observations, and temperature data, respectively, render analysis of the model minus observation residual difficult. However, we find fairly well-defined periods of drifts in the residuals. For the 1980's model predictions differ most, and only the calculation with ERA-Interim temperatures is roughly within observational uncertainties. All model predictions show a drying relative to HALOE in the 1990's, followed by a moistening in the early 2000's. Drifts to NOAA-FPH are similar (but stronger), whereas no drift is present against SAGE II. As a result, the model calculations have a less pronounced drop in SWV in 2000 than HALOE. From the mid-2000's onwards, models and observations agree reasonably, and some differences can be traced to problems in the temperature data. These results indicate that both SWV and temperature data may still suffer from artefacts that need to be resolved in order to answer the question whether the large-scale flow and temperature field is sufficient to explain water entering the stratosphere.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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