Numerical simulation of a rainfall event in Greenland during 10–13 July 2012 using Non-hydrostatic Regional Model

Abstract:

On 12 July 2012, extensive surface melt occurred across much of the Greenland ice sheet. During this event, the expeditionary team of Snow Impurity and Glacial Microbe effects on the Arctic (SIGMA) project experienced unexpectedly heavy rainfall at their campsite on the northwestern Greenland ice sheet. We tried to reproduce the rainfall event by using the Japan Meteorological Agency Non-Hydrostatic Model (JMA-NHM) with 5-km horizontal resolution to characterize the temporal and spatial variation of the types of precipitation. The simulated results well agreed with observational data from surface stations and space-borne radar. According to the simulated results, the areas where the 1-h rainfall exceeded 0.1 mm at least once during the event accounted for 48% of the entire area of the Greenland ice sheet. In the coastal regions of western Greenland, precipitation during the event was composed of liquid hydrometeors, whereas in high-elevation regions, it was composed mainly of solid hydrometeors. Over intermediate regions, the phase of the precipitation changed temporally and spatially among liquid, solid, and a mixture of both. These phase transitions of the precipitation are very likely to affect the surface radiative properties of the ice sheet as well as the heat and mass balance at the surface of the ice sheet during the study period and afterward.