Control of interannual and longer‐term variability of stratospheric water vapor

Abstract

[1] We use trajectory calculations based on 40-year European Reanalysis (ERA-40) data to predict the water mixing ratio of air entering the stratosphere in the tropics ( [1995][1996][1997][1998][1999][2000][2001][2002], the correlation between model predictions and HALOE water vapor anomalies in the tropical lower stratosphere is r = 0.81, as high as that between HALOE and SAGE II (r = 0.8).The model predictions suggest that the stratospheric quasi-biennial oscillation, El Niño-Southern Oscillation, and possibly volcanic eruptions all play a significant role in modulating [H 2 O] e , leading to interannual anomalies of order 0.5 ppmv with timescales of several months to years. Although the Lagrangian calculations show substantial interannual variability of transport pathways into the stratosphere, the results show that the interannual anomalies of [H 2 O] e are dominated by anomalies of the zonal mean temperature rather than by transport changes or localized temperature anomalies. This reinforces the paradox of apparently increasing stratospheric water vapor concentrations alongside, if anything, slightly decreasing temperatures at the tropical tropopause. The combination of measurement uncertainties and relatively strong interannual variability with periods of several months to years, on the one hand, limits our ability to detect, attribute, and verify long-term trends and, on the other hand, raises the question as to whether the previously published estimates of long-term trends are too large.Citation: Fueglistaler, S., and P. H. Haynes (2005), Control of interannual and longer-term variability of stratospheric water vapor,

The Tropical Tropopause Layer 1960–2100

“…The correlation is a tropical mean, so reflects transport processes as well. Three dimensional transport affects H 2 O Fueglistaler and Haynes, 2005), but we do expect a broad correlation with mean temperatures (Randel et al, 2004). Two models (MRI, CCSRNIES) lie above this line, which may indicate differences in transport, such that air has bypassed the tropical tropopause.…”

“…Gettelman and Forster (2002) described a climatology of the TTL, and looked at changes over the observed record from radiosondes, also finding decreases in tropopause pressure (increasing height) with little significant change in the bottom of the TTL (see below). Fueglistaler and Haynes (2005) showed that TTL trajectory analyses could reproduce changes in stratospheric entry water vapor. Santer et al (2003) examined simulated changes in thermal tropopause height and found that they could only explain observations if anthropogenic forcings were included.…”

“…Changes in the thermal structure of the TTL may alter clouds, affecting global climate through water vapor and cloud feedbacks (Bony et al, 2006). Changes to TTL structure may alter transport (Fueglistaler and Haynes, 2005) and water vapor . TTL water vapor in turn may affect stratospheric chemistry, ozone (Gettelman and Kinnison, 2007) and water vapor, as well as surface climate (Forster and Shine, 2002).…”

On the quality of the Nimbus 7 LIMS Version 6 water vapor profiles and distributions

“…Figure 2b is a plot of MLS V2.2 stratospheric H 2 O for 15 November 2004, based on data that were accessed from the MLS Website (http://mls.jpl.nasa.gov/). The period of 2004/05 of the MLS data was selected for comparison because the distribution of H 2 O is affected somewhat by the QBO-induced circulations of the lower stratosphere and the tropical winds were changing from a westerly to an easterly QBO phase, as was the case for the LIMS period (Fueglistaler and Haynes, 2005). Although MLS H 2 O extends to near the mesopause, Fig.…”

Investigating the yield of H<sub>2</sub>O and H<sub>2</sub> from methane oxidation in the stratosphere

“…SWV, for example, induces a reduction of stratospheric ozone concentration (Stenke and Grewe, 2005;Revell et al, 2016), cools the stratosphere (Revell et al, 2012;Forster and Shine, 1999;Maycock et al, 2014) and produces a positive radiative forcing (Solomon et al, 2010). Changes in SWV are mainly driven by tropospherestratosphere exchange (e.g., through deep convection in the tropics; Fueglistaler and Haynes, 2005). However, there is also a chemical contribution to SWV, mostly by oxidation of methane (CH 4 ) and hydrogen gas (H 2 ).…”