Ozone production and loss rate measurements in the middle stratosphere

Abstract

We present the first simultaneous measurements of HO x , NO x , and Cl x radicals in the middle stratosphere obtained during a balloon flight at 34 N in September 1989, along with calculations from a photochemical model, to show that NO x catalytic cycles dominate loss of ozone (O 3 ) for altitudes between 24 and 38 km; the observed abundance of ClO is lower than that expected for altitudes above 30 km on the basis of models using recommended rates and cross sections, reducing the relative importance of the Cl x catalytic cycles for loss of O 3 ; and removal rates of O 3 derived from observed concentrations of rate limiting HO x , NO x , and Cl x radicals balance computed production rates for altitudes between 32 and 38 km, a region where ozone is expected to be regulated primarily by photochemical processes.1

Evolution of stratospheric ozone and water vapour time series studied with satellite measurements

“…We find turn around times to range between 1994 and 1996, although we see no obvious relationship between the upper and lower stratosphere. By using this method on the all instrument average anomalies we can not conclude that a recovery is more likely to occur earlier in the upper stratosphere, as suggested by Jucks et al (1996).…”

“…It has been suggested that a turn around point for ozone occurred sometime between 1995 and 1999 as a result of recorded declines of HCl and HF concentrations (Waugh et al, 2001;Newchurch et al, 2003;WMO, 2006). It is most likely that we will see a turn around firstly in the upper stratosphere as it is here where halocarbons are photochemically broken down due to strong UV light (Jucks et al, 1996). Eventually in time, a turn around point in the lower stratosphere should become apparent as the halogen gases are slowly phased out.…”

“…Mismatches are thus possible in terms of time and space, but as each data set comprises a large number of measurements the stochastic error should be minimised when measurements are averaged. We have chosen these altitude ranges firstly because the first signs of ozone recovery are expected to be seen in the upper stratosphere (Jucks et al, 1996) and that this upper altitude range is also adopted by other analyses and hence the results found here can easily be compared (for example, Newchurch et al, 2003). Furthermore, analysis above 45 km would mean extra care would need to be taken to account for large non negligible diurnal variability in ozone (while in the upper mesosphere for water vapour).…”

Dynamics Study of the OH + O2Branching Atmospheric Reaction. 4. Influence of Vibrational Relaxation in Collisions Involving Highly Excited Species

“…In fact, most attempts to explain the discrepancy between the upper atmospheric model predictions of ozone concentration and satellite observations, known as the "ozone deficit problem", [11][12][13][14] have employed equilibrium concentrations of different atmospheric constituents and/or equilibrium rate constants. [15][16][17][18][19][20][21] The poor success of such models in resolving the above-mentioned "ozone deficit" leads to the necessity of introducing new ozone sources based on vibrationally excited molecules. 5,10,[22][23][24] Following this idea, other sources of ozone, considering LTD conditions, have been suggested.…”

Do vibrationally excited OH molecules affect middle and upper atmospheric chemistry?

“…For SPE conditions the effect on the OH sink can reach −12%. The effect of vibrational excitation of OH on reactions studied in this paper is, in comparison to total sources and sinks of the involved species, by far not large enough to explain the so-called "HO x -dilemma" (Conway et al, 2000;Summers et al, 1997), although, as already suggested by Varandas (2004b), non-local thermodynamic equilibrium effects might explain a different chemistry in the mesosphere compared to the stratosphere; nor is the effect large enough to solve the so-called "ozone deficit problem" (Jucks et al, 1996;Osterman et al, 1997;Canty et al, 2006), at least when these reactions are studied in an isolated manner without consideration of potential feedback effects.…”