MJO - A KEY COMPONENT IN THE ATMOSPHERE FOR TRIGGERING ENSO
Tetsuo Nakazawa
Meteorological Research Institute, Ibaraki, Tsukuba, Japan
By using the outgoing longwave radiation (OLR) data from NOAA polar-orbiting satellite and the sea level height (SLH) anomaly dataset from TOPEX/POSEIDON sea surface wind data, the atmospheric signals related with the Madden-Julian Oscillation (MJO) are examined during the period from Oct. 1992 through the present.
We found that the onset of 1997/98 ENSO was closely related to the atmospheric intraseasonal oscillation with a period of 1 to 2 months. The MJO appeared over the Indian Ocean in February 1997 and progressed into the western Pacific in March 1997. The onset MJO was characterized by the enhanced convective activity and low-level tropospheric westerlies. When the MJO came over the western Pacific, the low-level westerlies generated the oceanic Kelvin wave to initiate the 1997/98 ENSO. The following MJO signals in April and May also generated the Kelvin wave to enhance the magnitude of the positive SLH over the eastern equatorial Pacific.
There were other weak ENSO periods in 1993 and 1994. We would like to compare these periods with 1997/98 using these two datasets.
