Leading modes of interannual soil moisture variability in European Russia and their relation to regional climate during the summer season

Abstract

Soil moisture (SM) data from the Global Land Evaporation Amsterdam Model dataset for 1980–2014 are used to investigate interannual variability of SM in European Russia during the summer season. An Empirical Orthogonal Function (EOF) analysis performed on monthly-mean data (i.e., separately for June, July and August) revealed three leading modes of SM variability, characterized by monopole (EOF-1), zonal dipole (EOF-2) and meridional dipole (EOF-3) patterns. Together these modes explain more than half of the total SM variability in each summer month. Analysis of correlations between the leading PCs (principal components) of SM in European Russia and indices of regional teleconnections suggests that the monopole pattern is associated with the Polar—Eurasia teleconnection, whereas the zonal and meridional dipole patterns are linked respectively to the East Atlantic—West Russia and Scandinavian teleconnections. These links are subject to change over the summer season. The leading PCs broadly capture the large SM anomalies associated with regional climate extremes (such as the Russian summer heat wave in 2010). Correlation analysis revealed generally consistent patterns in which positive (negative) SM anomalies are linked to cyclonic (anti-cyclonic) anomalies of sea level pressure, above (below) normal precipitation and negative (positive) anomalies of air temperature. Locally we find differing roles of air temperature and precipitation in land-atmosphere interaction. Specifically, while precipitation is the dominant driver of interannual SM variability in early summer, air temperature plays a larger role in late-summer land-atmosphere interaction (at some time scales) over the southern part of European Russia, where moisture availability is limited.