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.