Diagnostics of the large‐scale mixing properties from stratospheric analyses

Abstract

We present diagnostics of the large‐scale mixing of stratospheric flows for January 2000 using meteorological analyses produced by the GEOS‐3 system of the Data Assimilation Office (DAO) at NASA Goddard Space Flight Center (GSFC), the European Centre for Medium‐Range Weather Forecasts (ECMWF), and the Met Office (METO). To characterize the mixing properties of these numerical weather prediction (NWP) systems we calculate diffusion coefficients, contour lengthening rates, and equivalent mixing lengths. Qualitatively, our results show relatively good agreement between the mixing parameters in the upper troposphere and lower stratosphere and reveal similar zones of weak and strong mixing in the middle and upper stratosphere. These parameters, however, exhibit substantial quantitative differences in the middle and upper stratosphere. For January 2000, averaged values for the northern hemisphere (NH) show that the GEOS‐3 and ECMWF flows have strong mixing capabilities while the METO winds result in relatively weak mixing and strong transport polar barriers.