Response of the Intertropical Convergence Zone to Climate Change: Location, Width, and Strength

Michael P Byrne,Angeline G Pendergrass,Anita D Rapp,Kyle R Wodzicki

doi:10.1007/s40641-018-0110-5

Abstract

Purpose of ReviewThe intertropical convergence zone (ITCZ) is a planetary-scale band of heavy precipitation close to the equator. Here, we consider the response of the ITCZ structure to climate change using observations, simulations, and theory. We focus on the substantial yet underappreciated projected changes in ITCZ width and strength, and highlight an emerging conceptual framework for understanding these changes.Recent FindingsSatellite observations and reanalysis data show a narrowing and strengthening of precipitation in the ITCZ over recent decades in both the Atlantic and Pacific basins, but little change in ITCZ location. Consistent with observations, coupled climate models predict no robust change in the zonal-mean ITCZ location over the twenty-first century. However, the majority of models project a narrowing of the ITCZ and weakening mean ascent. Interestingly, changes in ITCZ width and strength are strongly anti-correlated across models.SummaryThe ITCZ has narrowed over recent decades yet its location has remained approximately constant. Climate models project further narrowing and a weakening of the average ascent within the ITCZ as the climate continues to warm. Following intense work over the last ten years, the physical mechanisms controlling the ITCZ location are now well understood. The development of complementary theories for ITCZ width and strength is a current research priority. Outstanding challenges include understanding the ITCZ response to past climate changes and over land versus ocean regions, and better constraining all aspects of the ITCZ structure in model projections.

Highlights

Earth’s deep-tropical climate is dominated by the intertropical convergence zone (ITCZ), a narrow band of risingThis article is part of the Topical Collection on Climate Change and Atmospheric CirculationElectronic Supplementary Material The online version of this article contains supplementary material, which is available to authorized users.air and intense precipitation (Fig. 1a)
Summary The ITCZ has narrowed over recent decades yet its location has remained approximately constant
Our analysis shows that climate models predict no robust change in ITCZ location over the twenty-first century (Fig. 3a)

Summary

Introduction

This article is part of the Topical Collection on Climate Change and Atmospheric Circulation. Precipitation in the ITCZ is driven by moisture convergence associated with the northerly and southerly trade winds that collide near the equator. It has been suggested that, through its influence on the global radiation budget, the ITCZ could influence global temperature and precipitation and their responses to climate change [2–5]. The ITCZ moves north and south across the equator following the seasonal cycle of solar insolation, and is intimately connected to seasonal monsoon circulations [6]. The ITCZ lies a few degrees north of the equator [7]. Considerable research has focused on why the ITCZ lies north of the equator, and how this meridional location responds to past and future climate change [8–11]. An energetic theory has been developed over the Climatology Project

Results

Discussion

Conclusion