Tropical teleconnection and local response to SST anomalies during the 1997-1998 El Nino

The quasi-equilibrium tropical circulation model (QTCM) is used to examine the response to various sea surface temperature (SST) anomalies in the trop ical oceans during the 1997-1998 El Nino. Both local and remote responses a re noted. The negative precipitation anomalies to the north and south of th e El Nino - Southern Oscillation (ENSO) enhanced precipitation region are l argely a response to the warm SST anomalies in the central and eastern Paci fic. However, in the western Pacific and maritime continent, reduction of r ainfall is mainly caused by local cold SST anomalies. In the winter of the 1997-1998 El Nino, strong warm SST anomalies in the Indian Ocean contribute d to the local enhanced rainfall. They affect precipitation anomalies in ce ntral, eastern, and southern Africa. The drought in northern South America is clearly a remote response to ENSO warm SST anomalies in the Pacific, whi le the SST anomalies in the Atlantic also impact the drought. The tropical Pacific cold SST anomalies surrounding the ENSO warm anomalies appear not t o be caused by surface flux changes associated with atmospheric teleconnect ion (in simulations with specified SST in the ENSO warm region and a mixed- layer ocean model elsewhere). Atmospheric circulation tends to spread the w arm anomalies, but ocean dynamics appears also to be important for both col d and warm SST anomalies outside the equatorial upwelling region. In both t he regional specified SST experiments and mixed-layer experiments, relative subsidence tends to occur within convective zones, and it is generally loc alized. On the other hand, tropospheric temperature and wind anomalies spre ad much farther. The typical spatial scale of the remote response in temper ature and wind fields tends to be larger than the dominant scale of the pre cipitation response. The remote response in precipitation anomalies does no t appear to be related to temperature and wind anomalies in a simple manner .