No abstract

In this study we reexamine nearly four decades of in situ balloon-based stratospheric observations of SF 6 and CO 2 with an idealized model and reanalysis products. We use new techniques to account for the spatial and temporal inhomogeneity of the sparse balloon profiles and to calculate stratospheric mean ages of air more consistently from the observations with the idealized model. By doing so we are able to more clearly show and account for the variability of mean age of air throughout the bulk of the depth of the stratosphere. From an idealized model guided by the observations, we identify variability in the mean age due to the seasonal cycle of stratospheric transport, the quasi-biennial oscillation in tropical zonal winds, major volcanic eruptions, and linear trends that vary significantly with altitude. We calculate a negative mean age trend in the lowest 5 km of the stratosphere that agrees within uncertainties with a trend calculated from a set of chemistry climate model mean ages in this layer. The mean age trends reverse sign in the middle and upper stratosphere and are in agreement with a previous positive trend estimate using the same observational data set, although we have substantially reduced the uncertainty on the trend. Our analysis shows that a long time series of in situ profile measurements of trace gases such as SF 6 and CO 2 can be a unique and useful indicator of stratospheric circulation variability on a range of time scales and an important contributor to help validate the stratospheric portion of global chemistry climate models. However, with only SF 6 and CO 2 measurements, the competing effects on mean age between mean circulation and mixing (tropical entrainment) are not uniquely separable.

Histories of atmospheric N2O concentration and its δ15N and δ18O were reconstructed for the period 1952–2001 on the basis of the analyses of firn air collected at the North Greenland Ice Core Project (NGRIP), Greenland, and Dome Fuji and H72, Antarctica. The N2O concentration increased from 290 ppbv in 1952 to 316 ppbv in 2001, which agrees well with the results from atmospheric observations and polar ice core analyses. The δ15N and δ18O showed a secular decrease, the respective values being 8.9 and 21.5‰ in 1952 and 7.0 and 20.5‰ in 2001. Their rates of change also varied, from about −0.02‰ yr−1 in the 1950s to about −0.04‰ yr−1 in 1960–2001 for δ15N, and from about 0‰ yr−1 to −0.02‰ yr−1 for δ18O. The isotopic budgetary calculations using a two‐box model indicated that anthropogenic N2O emission from soils played a main role in the atmospheric N2O increase after industrialization, as well as that the average isotopic ratio of anthropogenic N2O has potentially been changed temporally.

Abstract. The vertical distribution of isotoporners ofN20 (14NISNI60, 15NI4NI60, and 14NI4NI80) in the lower and middle stratosphere was observed over Japan (39øN, 142øE) in 1999 using a balloon-borne cryogenic sampler and ground-based mass spectrometry. The abundance of the heavier isotoporners relative to 14NI4NI60 increased with altitude, while the mixing ratio of N20 decreased due to photochemical depletion. Maximum fractionation was observed at the highest altitude, 34.5 km, where (515NC•ai r (isotoporner ratio of center nitrogen), (515N13ai r (end nitrogen), and (•I8OsMow were 144.1%o, 42.4%0, and 119.0%o, respectively. The observed distribution is mostly accounted for by isotopic fractionation during consumption processes, which is in accordance with reported simulation experiments and theoretical prediction for photolytic fractionation of N20 isotopolners. However, the apparent fi'actionation factors in the lower (< •24 kin) and higher regions are different, which suggests that (1) the fractionation factor for stratospheric photolysis may depend on altitude or latitude, (2) transport and mixing processes in the stratosphere can aft•ct the vertical profile, and (3) the relative contribution of photolysis and photo-oxidation to total N20 sink is possibly dependent on altitude.

Combination EPA/PTV therapy significantly reduced coronary plaque volume compared to PTV therapy alone. Plaque stabilization was also reinforced by EPA/PTV therapy in particular SAP patients. The addition of EPA is a promising option to reduce residual CHD risk under intensive statin therapy.