Received: 17 Jun 2017 – Discussion started: 25 Jul 2017
Abstract. The quasi-two day wave (QTDW) during austral summer period usually coincides with sudden stratospheric warming (SSW) event in the winter hemisphere, while the influences of SSW on QTDW are not totally understood. In this work, the anomalous QTDW activities during the major SSW period of January 2006 are further investigated on the basis of hourly Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) reanalysis dataset. Strong westward QTDW with zonal wave number 2 (W2) is identified besides the conventionally dominant mode of zonal wave number 3 (W3). Meanwhile, the W3 peaks with an extremely short period of ~ 42 hours. Compared with January 2005 with no evident SSW, we found that the zonal mean zonal wind in the summer mesosphere is enhanced during 2006. The enhanced summer easterly sustains critical layers for W2 and short-period W3 QTDWs with larger phase speed, which facilitate their amplification through wave-mean flow interaction. The stronger summer easterly also provides stronger barotropic/baroclinic instabilities and thus larger forcing for the amplification of QTDW. The inter-hemispheric coupling induced by strong winter stratospheric planetary wave activities during SSW period is most likely responsible for the enhancement of summer easterly. Besides, we found that the nonlinear interaction between W3 QTDW and the wave number 1 stationary planetary wave (SPW1) may also contribute to the source of W2 at middle and low latitudes in the mesosphere.
How to cite. Gu, S.-Y., Dou, X., and Pancheva, D.: Investigation on the abnormal quasi-two day wave activities during sudden stratospheric warming period of January 2006, Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2017-563, 2017.
We used the NOGAPS-ALPHA reanalysis datasets upto mesopause region to investigate the anomalous Quasi-Two-Day Wave (QTDW) activities during the major Sudden Stratospheric Warming period of January 2006. We found that the SSW in the winter stratosphere could have significant influence on the QTDWs in the summer mesosphere through inter-hemispheric couplings. Our finding sheds new light on the coulings during SSW period.
We used the NOGAPS-ALPHA reanalysis datasets upto mesopause region to investigate the anomalous...