Eastward propagating planetary waves with periods of 1-5 days in the winter Antarctic stratosphere as revealed by MERRA and lidar

Abstract

This study presents the first report of planetary wave (PW) influences on significant temperature perturbations (10-20 K) within a course of one day detected by an Fe lidar from 35 to 51 km in the austral winter of 2011 at McMurdo (77.8°S, 166.7°E), Antarctica. Such large temperature perturbations are captured in the Modern Era Retrospective-Analysis for Research and Applications (MERRA) data and correspond to various phases of eastward propagating PWs with periods of 1-5 days as revealed in MERRA. The strongest PW dominating the temperature perturbations has a period of 4-5 days with wavenumber -1. A 2-day wave with wavenumber -2 and a 1.25-day wave with wavenumber -3 also have significant influences. We find that these eastward propagating PWs are highly confined to winter high latitudes, likely because negative refractive indices equatorward of ~45°S result in evanescent wave characteristics and prevent the PWs from propagating to lower latitudes. The Eliassen-Palm flux divergence and instability analyses suggest that barotropic/baroclinic instability at 50°S-60°S induced by the stratospheric polar night jet and/or the "double-jet" structure is the most likely wave source. Such instability in the region poleward of 70°S is a complementary source for the 4-day wave, where we find that the heat flux of the 4-day wave is large and transported from ~70°S toward the pole above 40 km. This transport direction is likely linked to the meridional gradient of background temperature. The migrating diurnal tide near 78°S in the upper stratosphere is discernable, but significantly smaller than that of the dominant 4-day wave. Key Points First report of PW influences on lidar temperatures in polar stratosphere.The PWs are generated by the instability of the double-jet structure.Significant momentum and heat fluxes are linked with the dominating PWs. ©2013. American Geophysical Union. All Rights Reserved.