Spatial and temporal variability of Arctic Basin precipitation

Spatial and temporal variability of Arctic Basin precipitation is examined using NCEP/NCAR Reanalysis data for the years 1949-1999. P-E calculated from moisture flux convergence is compared with the North Atlantic Oscillation and the Arctic Oscillation (NAO and AO respectively). The impact of these large scale oscillations is found to be marked, with a winter P-E/NAO correlation of 0.49 (0.56 for the AO). On an annual basis, Arctic Basin P-E is much more closely correlated with the NAO (0.69) than with the AO (0.49), consistent with the Atlantic Ocean domination of the northward poleward moisture across 70°N. Regional analysis confirms that the NAO impact on P-E is concentrated around the periphery of the North Atlantic Ocean and extends north into the Arctic Ocean during winter. The NAO and AO differ in their P-E modulation over the northern Eurasia sector with the AO being much more important for all seasons except summer (winter AO/P-E correlation 0.53, NAO/P-E correlation 0.16), consistent with its much stronger impact on the atmospheric circulation in that area.

Principal component analysis (PCA) of the annual moisture flux convergence shows a prominent center of action over the Arctic Basin extending from Greenland across the North Pole to Siberia. A spectral analysis performed on the score of the first PCA shows a periodicity of approximately 6.7 years, significant at greater than the 90% confidence interval. The circulation patterns based on the 5 years with the largest positive score and the 5 years with the largest negative score are compared to show the difference between the opposite phases of the first PCA pattern. Anticyclonic moisture circulation is much more prominent over the Beaufort Sea for the negative phases than positive phases, with cyclonic moisture circulation over the rest of the Arctic Basin for both phases.