This paper analyzes behavior of annual period equatorial waves and the
ir role in oceanic variations, namely, the sea level displacement, zon
al current, and sea surface temperature (SST) along the equator in the
Pacific. Using; a linear model forced by observed wind stress, the am
plitudes and phases of the annual equatorial waves are calculated. The
model equatorial waves are compared with the waves decomposed from Le
vitus' (1982) climatological density data. The modeled and decomposed
first-meridional-mode Rossby waves of the two gravest vertical modes i
ndicate common features that those waves are forced in the eastern Pac
ific and propagate to the central Pacific. These first-meridional-mode
Rossby waves play a dominant role in the model sea level displacement
and cause the westward propagating feature in the model surface zonal
current in the central Pacific. The analysis suggests that the propag
ation of the surface zonal current is significantly responsible for th
e well-known westward propagation of annual SST variation in this regi
on. The modeled and decomposed Kelvin waves are significantly differen
t, but the model suggests that the role of the annual Kelvin waves in
the equatorial oceanic variations is smaller than that of the first-me
ridional-mode Rossby waves.