Lagged Response of MJO Convection and Precipitation to Solar Ultraviolet Variations on Intraseasonal Time Scales.

Composite analyses of NOAA satellite‐based outgoing longwave radiation data and ERA5 reanalysis data for nearly six solar maximum periods support the existence of a response of tropical convection and precipitation to short‐term (∼27‐day) solar ultraviolet variations. Following solar UV peaks, the response consists of an increase in average convection and precipitation in the equatorial Indian Ocean and a decrease in the western and central tropical Pacific, with maximum amplitude at a lag of 4 to 8 days. The opposite occurs following short‐term solar UV minima. The observed responses are most detectable when the Madden‐Julian oscillation (MJO) is active and appear to be related to a reduced ability of the MJO to propagate across the Maritime Continent barrier following solar UV peaks relative to UV minima. A similar behavior has previously been found when the stratospheric quasi‐biennial oscillation is in its westerly phase relative to its easterly phase. Plain Language Summary: Under solar maximum conditions, active regions on the sun produce strong variations of solar ultraviolet radiation on the solar rotational time scale (∼27 days). We have analyzed data from NOAA satellites and ERA5 reanalysis for almost six solar maximum periods. The results indicate that these short‐term solar ultraviolet variations affect tropical convection and precipitation. Following a peak in solar UV radiation, there is an increase in convection and precipitation in the equatorial Indian Ocean, and a decrease in the western and central tropical Pacific, with the most significant changes occurring 4 to 8 days later. The opposite happens after solar UV minima. These effects are most noticeable when the Madden‐Julian Oscillation is active and seem linked to its inability to move across the Maritime Continent barrier after solar peaks compared to solar minima. Similar patterns have been observed with the stratospheric quasi‐biennial oscillation in its westerly phase versus its easterly phase. Key Points: Evidence of lagged responses of tropical convection and precipitation to short‐term solar UV variations is found over six solar cyclesThe responses are due to solar effects on eastward propagation of the Madden‐Julian oscillation across the Maritime Continent barrierAverage precipitation rate differences following solar peaks and minima can be more than 20% of mean daily rates [ABSTRACT FROM AUTHOR]