Meridional and temporal variations of lower-stratospheric gravity-wave activity over Japan, West Pacific ocean and East Indian ocean Original Research Article

Characteristics of gravity waves in the lower stratosphere were investigated based on rawinsonde and ozonesonde data accumulated over Japan, and West Pacific and East Indian oceans, with attention to the meridional and temporal variations of wave activity. Symmetrical distributions, with maxima near the equator, and anti-symmetrical distributions, with larger values in the northern (winter) hemisphere, were found in the gravity wave activities. Based on the long period of data over Japan, it was further shown that the gravity wave activity and background fields in wintertime had both clear interannual variations, and that active gravity waves were mainly due to quasi-periodically enhanced zonal wind passing over the mountain ranges.