Investigating Recent Changes in MJO Precipitation and Circulation in Multiple Reanalyses

Abstract

Recent work using CMIP5 models under RCP8.5 suggests that individual multimodel mean changes in precipitation and wind variability associated with the Madden-Julian oscillation (MJO) are not detectable until the end of the 21st century. However, a decrease in the ratio of MJO circulation to precipitation anomaly amplitude is detectable as early as 2021-2040, consistent with an increase in dry static stability as predicted by weak temperature gradient balance. Here, we examine MJO activity in multiple reanalyses (ERA5, MERRA-2, and ERA-20C) and find that MJO wind and precipitation anomaly amplitudes have a complicated time evolution over the record. However, a decrease in the ratio of MJO circulation to precipitation anomaly amplitude is detected over the observational period, consistent with the change in dry static stability. These results suggest that weak temperature gradient theory may be able to help explain changes in MJO activity in recent decades. Plain Language Summary A recent study examined future projected changes in precipitation and wind strength associated with the Madden-Julian oscillation (MJO) in a set of anthropogenically forced warming simulations. While they showed that changes in the amplitude of individual MJO-related variables are not detectable until the end of the 21st century, they also demonstrated that a decrease in the ratio of MJO wind to precipitation anomaly amplitude is detectable as early as 2021-2040. To examine whether these MJO changes found in climate models are realistic, changes to MJO variability are assessed in three observational products, and we find that a similar decrease in the ratio of MJO wind to precipitation strength is detectable over 1901-2018. The change in MJO activity is consistent with that expected under climate warming.

Strengthened Causal Connections Between the MJO and the North Atlantic With Climate Warming

“…source and propagation of the Rossby waves into midlatitudes. Focusing first on changes to the MJO itself, Bui and Maloney (2019) show that ratio of MJO-induced circulation to precipitation in CMIP5 climate models decreases as the climate warms, and Hsiao et al (2020) provide evidence that these changes may already be detectable in the observations. These results are important as they suggest that MJO teleconnections, which are directly excited by the MJO divergent circulation, may weaken as the climate warms (Maloney et al, 2019;Wolding et al, 2017).…”

Emergence of Madden-Julian oscillation precipitation and wind amplitude changes in a warming climate

“…3a-f). As previous studies mostly focused on the absolute changes of the MJO [9][10][11][12][13][14][15][16][17][18] (for example, MJO precipitation amplitude change from −10% to +20% relative to the current climate, while MJO circulation anomalies increase at a slower rate or weaken), the result here suggests that uncertainties in MJO prediction and its teleconnection impacts may be higher because both absolute changes and emergence time need to be considered.…”

“…Jenney et al (2021) added that multi-model uncertainty, which may come from the uncertainty in the parameterized moist physics in the model as mentioned by Rushley et al (2019), also contributes to the uncertainty in future detection of the MJO characteristics 19,20 . In addition to the model results above, observational evidence also suggest that detecting MJO changes is complicated by interannual-to-multidecadal climate variations in the past few decades 16,21 .…”

“…In contrast, the change in MJO circulation amplitude is projected to weaken or increase at a slower rate than MJO precipitation amplitude 10 . Increases in MJO precipitation amplitude have been found in aquaplanet models 11 , single climate models 12,13 , multimodel analyses from the Coupled Model Intercomparison Project (CMIP) phase 3/5/6 10,14,15 , and also observations 16 . Projected increases in MJO precipitation and weakening or slower increases of MJO wind anomaly amplitude with warming are consistent with increases in dry tropical static stability, which are proportional to increases in tropical sea surface temperature (SST) 17 .…”

Climate Change Effect on Water Use Efficiency under Selected Soil and Water Conservation Practices in the Ruzizi Catchment, Eastern D.R. Congo

“…The relative change (∆) was the main matrix for defining the changes in rainfall or temperature in this study. According to Hsiao et al [43], for any quantity X, the relative change (%) compared to its reference state (Xref ) is defined by Equation (1):…”