FY 1997

Regional variation of winter temperatures in the Arctic

Overland, J.E., J.M. Adams, and N.A. Bond

J. Climate, 10(5), 821–837, doi: 10.1175/1520-0442(1997)010<0821:RVOWTI>2 (1997)

The surface temperature field in the Arctic winter is primarily controlled by downward longwave radiation, which is determined by local atmospheric temperature and humidity profiles and the presence of clouds. The authors show that regional differences in the atmospheric thermal energy budget are related to the tropospheric circulation in the Arctic. Data sources include several gridded meteorological data sets and surface and rawinsonde observational data. Four independent climatologies of mean January surface temperature show consistent spatial patterns: coldest temperatures in the western Arctic north of Canada and warmer regions in the Chukchi, Greenland, and Barents Seas. Data from five winters 1986-1990 illustrate the coupling between the surface temperature, the downward longwave radiative fields, and the tropospheric temperature and humidity fields, with monthly surface/upper air correlations of order 0.6. Upper level circulation patterns reveal features similar to the surface temperature fields, notably a persistent low center located over northern Canada; the cyclonic flow around the low is a tropospheric extension of the polar vortex. Colder and drier conditions are maintained within the vortex and communicated to the surface through radiative processes. The polar vortex also steers transient weather systems, the most important mechanism for horizontal heat transport, into the eastern Arctic, which results in as much as 25 W m^–2 more heat flux into the eastern than the western Arctic. A reason for the colder temperatures in the western Arctic is that the polar vortex tends to be situated downstream of the northern Rocky Mountains; this preferred location is related to orographic forcing of planetary waves. Monthly and interannual variability of winter temperatures are conditioned by the interaction of the Arctic and mid-latitude circulations through the strength and position of the polar vortex.