Re-examining the Influence of Snow Cover Extent on Monsoon Precipitation

            This study examines the proposed teleconnection between the North American Monsoon and snow cover extent across northwestern North America, originally documented by Ellis and Hawkins (a.k.a. E&H, 2001). In the first phase, precipitation and snow water equivalent (SWE) were obtained from the ERA5 reanalysis dataset. In the second phase, we obtained precipitation from the PRISM model and snow cover extent from NOAA NESDIS satellite data. Both analyses examined roughly the same regions for SWE or snow cover (northwestern North America) and monsoon precipitation (Arizona and New Mexico) using data from 1967–2024 to evaluate E&H's original findings and identify current trends. After applying linear regression, no consistent correlation could be established between the two variables across modified methods and different time frames. Four time frames were studied: 1967–1972 (Pre-E&H), 1972–1997 (E&H period), 1967–2024 (full record), and 1997–2024 (Post-E&H). All displayed poor correlation, with the PRISM data analyzed within the E&H timeframe having the highest correlation (R² = 0.22). For the ERA5 analysis, poor correlation is attributed to ERA5 reporting snow as SWE rather than aerial extent. The lack of correlation between NESDIS snow cover and PRISM precipitation may reflect data handling errors or differences between the modern reanalysis approach and the rain gauge point averages used by E&H. These results may also suggest the teleconnection is not evident at a longer climatological scale, which would decrease its forecasting relevance. Future research could examine albedo rather than extent or continue refining the analysis code to verify integrity.