Interactive comment on “Trends and variability in stratospheric mixing: 1979–2005” by H. Garny

Anonymous Referee #1 Received and published: 14 June 2007 This paper analyzes the mixing properties of the stratosphere for 1979-2005 using the finite-time Lyapunov exponents computed from the NCEP/NCAR reanalysis winds. The length of the dataset allows the authors to perform a meaningful multiple regression analysis, which includes the climatology, linear trend, QBO, solar cycle, and ENSO. The climatology and the QBO signals agree reasonably well with the previous studies based on shorter datasets. The trends in the Lyapunov exponents and in the zonal mean winds are new, which reveal interesting features such as increased mixing in summertime southern surf zone in the lower stratosphere. Although the paper does not contain substantive results on the solar cycle and ENSO signals, the overall treatment is thorough and the paper is publishable with minor revisions. I do have a few comments/questions con-