Role of the Atmosphere in Climate Variability of the Tropical Atlantic

Abstract

Abstract This paper explores climate variability of the lower troposphere and boundary layer in the tropical Atlantic sector through a series of modeling simulations with a diagnostic primitive equation model. The focus is on the role that realistic diabatic heating and its vertical placement as well as surface temperature have in inducing/reinforcing the local monthly wind circulation, the role that thermal and momentum transients play in the Tropics, the potential for feedbacks, and the way through which other basins influence the tropical Atlantic region. NCEP–NCAR reanalysis data for the period 1958–93 are used to provide forcing and model verification. In the first part of the paper local effects are considered. It is found that the most important terms controlling anomalous surface winds over the ocean are boundary layer temperature gradients and diabatic heating anomalies at low levels (below 780 mb). Anomalous diabatic heating at mid- and upper levels (430–690 mb) contributes to the near-surface c...