Soil Moisture Influences on Summer Arctic Cyclones and their associated Poleward Moisture Transport

Abstract

Moisture transport into the Arctic is an important modulator for clouds, radiative forcing, and sea-ice change. Transport events, namely moist-air intrusions, are often associated with Arctic cyclones and, during the summer season, we find that the high-latitude land surface is a significant moisture source for intrusions. Summer Arctic cyclones typically originate from the surrounding continental interior and shorelines where, during the early stages of intensification, the warm sector experiences strong latent heat fluxes from the land surface. In this study, we use multiyear reanalysis data and back-trajectory calculations to quantify the linkages between key continental moisture source regions and water vapor within cyclone-induced intrusions. We also conduct regional soil moisture sensitivity experiments using the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) to diagnose the land-surface moisture contribution for an August 2016 Arctic cyclone case. Results from reanalysis show that land regions on average account for more than 30% of the total moist-air intrusion flux at 70° N during summer. COAMPS case-study experiments reaffirm this result showing that land-surface moisture flux on average accounts for 30% of the intrusion water vapor content. COAMPS experiments further reveal that land-surface moisture impacts cyclone intensification and moist-air intrusion cloud water vapor. When the regional soil moisture is reduced, intrusion cloud cover is also reduced resulting in an increase in the surface solar radiation >90 Wm-2. These results demonstrate that the high-latitude land surface plays an important role in the Arctic summer hydrological cycle, and may be increasingly impactful as traditionally cold or frozen soils warm.