The Madden‐Julian Oscillation in a warmer world

Abstract

Global warming's impact on the Madden‐Julian Oscillation (MJO) is assessed using one of the few models capable in reproducing its key features. In a warmer climate predicted for the end of the century, the MJO increases in amplitude (by ~30%) and frequency, showing a more circumglobal propagation tendency. The MJO spatial extent becomes enhanced, deeper, and more zonally extended but meridionally confined. A stronger vertical tilting structure in diabatic heating, moisture, and convergence fields is seen. Our findings indicate that these changes result from an intensification of the frictional wave‐conditional instability of the second kind mechanism via the coupling of dynamical and thermodynamic response to the warming. The warming and moistening of the mean state contribute to the enhanced deep convective heating, driving a stronger‐forced Kelvin wave‐like perturbation. This reinforces the frictional low‐level convergence, leading to larger shallow convective heating and therefore to a faster development and enhancement of the deep convection in the MJO.

Changes in Madden‐Julian Oscillation Precipitation and Wind Variance Under Global Warming

“…A similar result was found in the Goddard Institute for Space Studies model (Adames et al, ). Chang et al () analyzed historical and Representative Concentration Pathway 8.5 (RCP8.5) simulations of the ECHAM5‐SIT model and showed that the amplitude of MJO precipitation variability increases by about 17% in the future while zonal wind variability changes insignificantly. The studies above were conducted with a limited set of models, and there has not yet been a detailed mechanistic study using a multimodel data set to investigate the covariability in global warming‐induced MJO precipitation and wind variance changes.…”

A Cautionary Note on the Long‐term Trend in Activity of the Madden‐Julian Oscillation During the Past Decades

“…Both observational (Lee & Seo, 2011;Slingo et al, 1999) and modelling studies (e.g., Adames et al, 2017;Arnold et al, 2015;Chang et al, 2015;Liu et al, 2013;Maloney et al, 2019) suggest that the MJO precipitation variations tend to enhance in a warming climate, along with weak increase or even decrease of MJO wind variability and teleconnections due to increase of tropical static stability (Bui & Maloney, 2018;Maloney et al, 2019;Wolding et al, 2017). Both observational (Lee & Seo, 2011;Slingo et al, 1999) and modelling studies (e.g., Adames et al, 2017;Arnold et al, 2015;Chang et al, 2015;Liu et al, 2013;Maloney et al, 2019) suggest that the MJO precipitation variations tend to enhance in a warming climate, along with weak increase or even decrease of MJO wind variability and teleconnections due to increase of tropical static stability (Bui & Maloney, 2018;Maloney et al, 2019;Wolding et al, 2017).…”

Characterization of Moist Processes Associated With Changes in the Propagation of the MJO With Increasing CO2

“…GCMs with various degrees of MJO simulation fidelity have been used to examine the response of the MJO to warming. While an accurate simulation of the MJO is a challenging task for many contemporary GCMs (Ahn et al, ; Jiang et al, ), many of these modeling studies have suggested an amplification of MJO variability and an increase in the frequency of the MJO in a warmer climate (Arnold et al, ; Carlson & Caballero, ; Chang et al, ; Liu, ; Liu et al, ; Song & Seo, ; Subramanian et al, ; Pritchard & Yang, ). With an atmosphere‐only GCM, Arnold et al () found MJO variability more than tripled as a response to an imposed 9°C SST increase.…”

“…With an atmosphere‐only GCM, Arnold et al () found MJO variability more than tripled as a response to an imposed 9°C SST increase. Using a coupled GCM, Chang et al () found that the period of the MJO changes from ∼50 days in a 20th century simulation to ∼30 days in a 21st.…”