Secular Changes of the Decadal Relationship Between the Northern Hemisphere Land Monsoon Rainfall and Sea Surface Temperature Over the Past Millennium in Climate Model Simulations. Issue 23 (9th December 2022)

• Record Type: Journal Article
• Authors: Shen, Tianyin; Sun, Weiyi; Liu, Jian; Wang, Bin; Chen, Deliang; Ning, Liang; Chen, Kefan
• Is Part Of: Journal of geophysical research. Volume 127:Issue 23(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-09
• Subjects: Northern Hemisphere land monsoon rainfall -- decadal variability -- extended ENSO -- North Atlantic–south Indian Ocean dipole -- volcanic eruptions -- CESM‐LME; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2022JD037065
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Understanding the decadal variability of Northern Hemisphere land monsoon rainfall (NHLMR) is crucial to social‐economic development. However, due to the temporal limitation of instrumental data, the decadal relationship between NHLMR and sea surface temperature (SST) remains uncertain. The extended El Niño–Southern Oscillation (XEN) SST index and the North Atlantic–south Indian Ocean dipole (NAID) SST index can be the predictors to help us understand the decadal relationship between NHLMR and SST. In this study, using the Community Earth System Model‐Last Millennium Ensemble (CESM‐LME) simulations, we find a significant and stable decadal correlation between the NHLMR and XEN in the all‐forcing (AF) (with natural and anthropogenic forcings, AF), control (internal variability only), and other external forcings run over the past millennium, which means that this simulated NHLMR‐XEN relationship is caused by internal variability. The AF experiments show that the decadal relationship between NHLMR and NAID is practically non‐existent until an abrupt and significant increase in volcanic eruptions at about 1700, which is also indicated by the Paleoclimate Modeling Intercomparison Project Phase 3 (Paleoclimate Modeling Intercomparison Project Phase 3) simulations. Using the volcanic forcing sensitivity experiments, we find that the successive strong volcanic eruptions in the Northern Hemisphere (NH) significantly strengthen the synchronous changes of NHLMR and NAID after 1700, with a periodicity of 20–40‐year for NHLMR and NAID. Specifically, successive NH eruptions weaken the north‐south hemispheric thermal contrast, contributing to the weakened NAID index. The cross‐equator flow is thus weakened, decreasing the NHLMR, which cause a resonant behavior of NHLMR and NAID. Plain Language Summary: Understanding the decadal variability of Northern Hemisphere land monsoon rainfall (NHLMR) is significant for climate predictions, infrastructure construction, food security, water resources planning, and disaster reduction in the monsoon region. However, the secular changes in the decadal relationship between NHLMR and sea surface temperature (SST) over the past millennium are unknown, due to the temporal limitation of observational data. This study explores the decadal relationship between NHLMR and SST in the past millennium through the Community Earth System Model‐Last Millennium Ensemble (CESM‐LME) simulation data. We use two SST indexes, including the extended El Niño–Southern Oscillation (XEN) SST index and North Atlantic–south Indian Ocean dipole (NAID) SST index. The decadal relationship between NHLMR and XEN has been stable and significant in the past millennium, which is caused by internal variability. However, the decadal relationship between NHLMR and NAID is only significant after 1700. The volcanic forcing experiments show that the successive strong volcanic eruptions in the NH induce the synchronous changes of NHLMR and NAID. Key Points: Decadal relationship between the Northern Hemisphere land monsoon rainfall (NHLMR) and extended El Niño/Southern Oscillation is robust over the past millennium A decadal relationship between NHLMR and North Atlantic–south Indian Ocean dipole (NAID) emerged about 1700 under volcanic eruptions Successive northern volcanic eruptions reduce thermal contrast between the two hemispheres, causing a resonant NHLMR‐NAID behavior