High-Resolution Stratospheric Tracer Fields Estimated from Satellite Observations Using Lagrangian Trajectory Calculations

Abstract

A technique is introduced by which high-resolution tracer fields may be constructed from low-resolution satellite observations. The technique relies upon the continual cascade of tracer variance from large to small scales and makes use of wind fields generated by a data assimilation scheme. To demonstrate its usefulness, the technique has been applied in a study of isentropic distributions of nitrous oxide in the winter midstratosphere, using measurements made by the Improved Stratospheric and Mesospheric Sounder instrument on the Upper Atmosphere Research Satellite. The results show that the high-resolution fields significantly increase the amount of information that is available from the satellite observations. The fields give insights into the characteristic structure and evolution of tracer distributions at scales that are normally obscured from view. Two results are particularly noteworthy. First, at the interface between low and middle latitudes there is evidence of active mixing. This mixing occurs on the eastern, equatorward side of air that is being drawn toward high latitudes around the polar vortex. Second, in the anticyclone, a complex pattern of transport is revealed. Air drawn in from low latitudes spirals together with ambient midlatitude air. Small scales are generated relatively slowly in the organized flow, and persistent filamentary structures, with transverse scales of hundreds of kilometers or greater, are seen.