On the structure of the 30 to 50 day mode over the globe during FGGE

摘要: 6 vertical levels of the entire 365-day global FGGE Illb analysis for 5 variables are subjected to a time-series and frequency filter investigate structure 30- 50-day mode. This study isolates regions where amplitude these low-frequency oscillations large; structures across large also presented. The seasonal variation maximum 30–50 day filtered wind in lower troposphere is highlighted. major results year show that mode has its largest upper polar latitudes summer monsoon region. During northern winter, active located over equatorial belt central Pacific ocean. phase propagation on pressure surfaces examined simply from an time sequence weather maps. illustrated by pressure-time plots data sets at individual locations. suggests convective areas lack it most other regions. A highlight this phenomenon we have labelled as “low-frequency storms”. Here illustrate long-lasting, low-frequency, systems propagate meridionally (1) equator Himalayas (2) eastern ocean northwards during winter season. An example such long-lasting system traced 60° N; subsequently, appears move zonally gulf Alaska Canadian Arctic, north Atlantic, Europe prior dissipation Siberia. potential interactions between front cyclones another interesting aspect investigation. motions considered important since their (8 ms -1 ) they well-defined within scales motion (on order 4000 km or larger). DOI: 10.1111/j.1600-0870.1985.tb00432.x