HIGH-RESOLUTION STRATOSPHERIC TRACER FIELDS ESTIMATED FROM SATELLITE-OBSERVATIONS USING LAGRANGIAN TRAJECTORY CALCULATIONS

A technique is introduced by which high-resolution tracer fields may b e constructed from low-resolution satellite observations. The techniqu e relies upon the continual cascade of tracer variance from large to s mall scales and make use of wind fields generated by a data assimilati on scheme. To demonstrate its usefulness, the technique has been appli ed in a study of isentropic distributions of nitrous oxide in the wint er midstratosphere, using measurements made by the Improved Stratosphe ric and Mesospheric Sounder instrument on the Upper Atmosphere Researc h Satellite. The results show that the high-resolution fields signific antly increase the amount of information that is available from the sa tellite observations. The fields give insights into the characteristic structure and evolution of tracer distributions at scales that are no rmally obscured from view. Two results are particularly noteworthy. Fi rst, at the interface between low and middle latitudes there is eviden ce of active mixing. This mixing occurs on the eastern, equatorward si de of air that is being drawn toward high latitudes around the polar v ortex. Second, in the anticyclone, a complex pattern of transport is r evealed. 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.