The Influence of the MJO on the Intraseasonal Variability of Northern Hemisphere Spring Snow Depth

Intraseasonal variability in springtime Northern Hemisphere daily snow depth change (Delta SD) by phase of the MJO was explored in this study. Principal findings of the relationship between Delta SD and the MJO included the following: 1) Statistically significant regions of lagged Delta SD anomalies for multiple phases of the MJO were found in March, April, and May in both North America and Eurasia. 2) In each month, lagged Delta SD anomalies were physically supported by corresponding lagged anomalies of 500-hPa height (Z500) and surface air temperature (SAT). Spearman rank correlation coefficients indicated a moderate to strong relationship between both Z500 and Delta SD and SAT and Delta SD in both Eurasia and North America for phases 5 and 7 in March. In April, a moderately strong relationship between Z500 and Delta SD was found over Eurasia for phase 5, but the relationship between SAT and Delta SD was weak. In May, correlations between Delta SD and both Z500 and SAT over a hemisphere-wide latitude band from 60 degrees to 75 degrees N were close to -0.5 and -0.4, respectively. Given the strength of these statistical relationships, the following physical pathway is proposed for intraseasonal variability of spring snow depth changes: poleward-propagating Rossby waves in response to tropical MJO convection interact with Northern Hemisphere background flow, leading to anomalous troughing and ridging. These anomalous circulation centers then impact daily snow depth change via precipitation processes and anomalies in surface air temperature.