Stephen Foskey - September 15

Weather and Climate Systems

The impact of the Madden-Julian Oscillation on extreme winter weather over the United States

Stephen Foskey

Wednesday, September 15

3:00pm

Google Meet

This project seeks to understand how the MJO impacts extreme winter weather across the contiguous United States using both the Outgoing Longwave Radiation MJO Index (OMI) and the Real-Time MJO Monitoring Index (RMM). A number of studies have examined how the Madden-Julian Oscillation (MJO) affects temperature and precipitation over the United States, but less work has been done on how the MJO affects extreme winter weather events such as ice storms and heavy snow storms. The outcome of this study will help enable people to predict the possibility of winter weather several days to a few weeks in advance, which would allow individuals and institutions to prepare more effectively. The primary source for winter storm data used in this project is the National Centers for Environmental Information (NCEI) Storm Events Database, while further data will come from the Global Historical Climatology Network (GHCN), also produced by NCEI. Our results show that MJO phases 1, 2 and 4 tend to significantly increase the chance of winter weather over the eastern two thirds of the United States while it decreases during phases 5, 6, and 8. Generally, the composites from both the RMM and OMI have similar areas of increased and decreased winter weather activity. These modulations of winter weather by the MJO cannot be simply explained by its known impacts on temperature over the United States. Therefore, we use ERA5 reanalysis data to understand how the MJO modulates the observed frequency of winter weather events. The current hypothesis is that amplified Rossby waves generated by the MJO impact winter weather by modulating temperature, moisture, and jet locations over the United States.