Numerical simulations of Greenland’s impact on the Northern Hemisphere winter circulation

The impact of Greenland’s orography on the general circulation is investigated. Two 10-yr simulations are conducted using the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) at T106 horizontal resolution (spectral truncation): a control simulation and a simulation where Greenland’s orography is set to sea level. A comparison of the simulations indicates that Greenland has a significant impact on the general circulation of the Northern Hemisphere at both lower and mid-tropospheric levels. The storm tracks over the North Atlantic are shifted southward in the presence of the mountain. There are significant differences between the two simulations over a large area in the Northern Hemisphere. It is argued that this difference pattern is linked to the damming of cold low-level air masses west of Greenland that result in a decrease in the 500-hPa geopotential height on the upstream side of the mountain. Thus, Greenland’s impact on the general circulation is fundamentally different from the impact of the Rocky Mountains and the Tibetan Plateau where westerlies impinging on a major mountain range create a trough downstream of the mountain.