The leading correlation of the winter Aleutian Low with surface air temperature during the subsequent summer over the Arctic and its possible mechanism

Abstract

The variations of surface air temperature (SAT) over the Arctic are closely related to global climate change. Based on reanalysis datasets and a newly defined Aleutian Low intensity index, we found a good correlation between intensity of winter Aleutian Low and the SAT over the Arctic during the subsequent summer. Explanations were given using correlation analysis, composite analysis, and singular value decomposition methods. When intensity of winter Aleutian Low was weaker, sea surface temperature appeared higher in the North Pacific in the subsequent spring and summer, resulting in mean meridional circulation anomalies and 500 hPa geopotential height anomalies in spring and summer. Anomalous upward motion in mid-latitudes and downward motion in high latitudes (Ferrel cell weakening) transported the warmer air to the north from lower layer to the upper layer followed by increases in the SAT over the Arctic. Anomalous downward motion over about 75°N also caused consequent adiabatic warming and contributed to inhibit the heat transportation from surface to upper layer. Negative 500 hPa geopotential height anomalies existed in mid-latitudes and positive anomalies existed in high latitudes. The pattern (low-in-south and high-in-north) benefited from increasing the inflow volume flux of the Bering Strait, which also made the SAT over the Arctic increase. The results of this study reveal the process that the summer SAT over the Arctic was modulated by interannual variability of intensity of winter Aleutian Low.