Numerical simulations of the atmospheric response to a sea surface temperature anomaly over the equatorial eastern Pacific Ocean

Abstract

In the tropics, the SSTA enhances precipitation over the central and eastern equatorial Pacific, while it decreases precipitation over the adjacent regions. The anomalous precipitation is predominantly balanced by the anomalous moisture flux convergence, which has comparable magnitude in the planetary boundary layer (PBL), and in the free atmosphere with quite different geographical distribution. In the midlatitudes, it is found that the SSTA results in a more zonal flow over the Pacific with an intensification of the upper-tropospheric westerlies. Associated with this intensification, synoptic-scale transient baroclinic waves become more active. This is consistent with interannual differences in observed spectral distributions of transients for five winters, two of which were El Nino winters. Geographically, the increase in barocline wave activity occurs in a zonal belt extending from the northeastern Pacific to the northern Atlantic. -from Authors