Effects Of ~27-Day Solar Ultraviolet Variations On Tropical Precipitation And The Madden-Julian Oscillation
Presenter: Charles Hoopes P101
Co-Author(s): Lon Hood, Thomas Galarneau
Advisor(s): Lon Hood & Chris Castro
1Hydrology & Atmospheric Sciences
Composite analyses of NOAA satellite-based outgoing longwave radiation data and ERA5 reanalysis data for nearly six solar maximum periods confirm the existence of a response of tropical convection and precipitation to short-term (mainly 27-day) solar ultraviolet variations, which has been suggested by previous research. After a solar UV peak, 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. Support for this response appears via a phase count of individual phases, which show an increased occurrence rate of early MJO phases, associated with increased convection over the Indian Ocean, and a decreased rate of later MJO phases, associated with increased convection over the Pacific Ocean, following short-term solar peaks. The overall behavior appears to be consistent between individual solar cycles, and is detectable at least as far back as 1959. Additionally, the phases which appear to be influenced by solar activity have been found in previous work to affect the position of the storm track and jet stream over the Northern Pacific, presenting an intriguing possibility for future work in this area.