Water vapour over the western maritime Arctic: surface inversions, intrusions and total column



A composite year of hourly microwave radiometric water vapour (WV) density profiles from November 2007 to July 2008 and August to November 2009 over the unconsolidated sea-ice surface of the southeastern Beaufort Sea–Amundsen Gulf region was analysed. The annual cycle of monthly median total column precipitable water (PW) ranged from 1.4 mm in January to 16.8 mm in August. For all months, greater than 92% of the PW was below 5000 m. Peak PW in WV intrusions ranged from 3.4 mm in November to 37.3 mm in August. An L-shaped relationship was found between the monthly percentages of PW in near surface WV inversions and the median total column PW. This suggested that WV inversions have a greater impact on atmospheric downwelling longwave radiation, and in turn on the climate of the western maritime Arctic, in the winter early spring and late autumn when the median PW is low than in warmer months when it is relatively high. This result, consistent with the results of others, was supported by an analysis of hourly profiles for January (low PW month), and July (high PW month); 89% of the variability in the percentage of PW in near surface inversions was explained by the height of the top of the highest inversion which was generally much higher in the January than in July. In addition, near surface WV inversions occurred more frequently in the lower PW month than in the higher PW month. Copyright © 2012 Royal Meteorological Society