Annual and interannual variations in global 6.5DWs from 20 to 110km during 2002-2016 observed by TIMED/SABER

摘要

Using version 2.0 of the TIMED/SABER kinetic temperature data, we have conducted a study on the annual and interannual variations of 6.5DWs at 20-110km, from 52 degrees S to 52 degrees N for 2002-2016. First, we obtained global annual variations in the spectral power and amplitudes of 6.5DWs. We found that strong wave amplitudes emerged from 25 degrees S/N to 52 degrees S/N and peaked in the altitudes of the stratosphere, mesosphere, and the lower thermosphere. The annual variations in the 6.5DWs are similar in both hemispheres but different at various altitudes. At 40-50km, the annual maxima emerge mostly in winters. In the MLT, annual peaks occurred twice every half year. At 80-90km, 6.5DWs appeared mainly in equinoctial seasons and winters. At 100-110km, 6.5DWs emerged mainly in equinoctial seasons. Second, we continued the study of the interannual variations in 6.5DW amplitudes from 2002 to 2016. Frequency spectra of the monthly mean amplitudes showed that main dynamics in the long-term variations of 6.5DWs were AO and SAO in both hemispheres. In addition, 4month period signals were noticed in the MLT of the NH. The amplitudes of SAO and AO were obtained using a band-pass filter and were found to increase with altitude, as do the 6.5DW amplitudes. In both hemispheres, the relative importance of SAO and AO changes with altitude. At 40-50 and 100-110km, AO play a dominant role, while at 80-90km, they are weaker than SAO. Our results show that both the annual and interannual variations in 6.5DWs are mainly caused by the combined action of SAO and AO.