Atmospheric Responses of Gill-Type and Lindzen–Nigam Models to Global Warming

Abstract

Abstract The equatorial Pacific atmosphere responds differently to global warming in the Gill-type and Lindzen–Nigam models. Under an assumption of no change in the zonal sea surface temperature (SST) gradient in the Gill-type model, the Walker circulation is intensified in a warmer climate relative to current climatic conditions, while slightly weakened in the Lindzen–Nigam model. Furthermore, for more accurate derivation of the surface wind, the free atmosphere in the Gill-type model is combined with the atmospheric boundary layer. This modified Gill-type model actually produces weaker surface wind than the Gill-type model would, but the sensitivity of the Walker circulation to the warmer climate is similar to that obtained from the Gill-type model. These results may explain why the zonal gradient of equatorial Pacific SST during the twentieth century is observed to strengthen while the Walker circulation is not, even though they are dynamically linked.