Impact of mountains on tropical circulation in two earth system models

Zachary Naiman, Paul J. Goodman, John P. Krasting, Sergey L. Malyshev, Joellen L. Russell, Ronald J. Stouffer, Andrew T. Wittenberg

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

Two state-of-the-art Earth system models (ESMs) were used in an idealized experiment to explore the role of mountains in shaping Earth's climate system. Similar to previous studies, removing mountains from both ESMs results in the winds becoming more zonal and weaker Indian and Asian monsoon circulations. However, there are also broad changes to the Walker circulation and El Niño-Southern Oscillation (ENSO). Without orography, convection moves across the entire equatorial Indo-Pacific basin on interannual time scales. ENSO has a stronger amplitude, lower frequency, and increased regularity. A wider equatorial wind zone and changes to equatorial wind stress curl result in a colder cold tongue and a steeper equatorial thermocline across the Pacific basin during La Niña years. Anomalies associated with ENSO warm events are larger without mountains and have greater impact on the mean tropical climate than when mountains are present. Without mountains, the centennial-mean Pacific Walker circulation weakens in both models by approximately 45%, but the strength of the mean Hadley circulation changes by less than 2%. Changes in the Walker circulation in these experiments can be explained by the large spatial excursions of atmospheric deep convection on interannual time scales. These results suggest that mountains are an important control on the large-scale tropical circulation, impacting ENSO dynamics and the Walker circulation, but have little impact on the strength of the Hadley circulation.

Original languageEnglish (US)
Pages (from-to)4149-4163
Number of pages15
JournalJournal of Climate
Volume30
Issue number11
DOIs
StatePublished - Jun 1 2017

Keywords

  • Climate classification/regimes
  • Climate models
  • Climate variability
  • Paleoclimate

ASJC Scopus subject areas

  • Atmospheric Science

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    Naiman, Z., Goodman, P. J., Krasting, J. P., Malyshev, S. L., Russell, J. L., Stouffer, R. J., & Wittenberg, A. T. (2017). Impact of mountains on tropical circulation in two earth system models. Journal of Climate, 30(11), 4149-4163. https://doi.org/10.1175/JCLI-D-16-0512.1