VARIABILITY IN ATMOSPHERIC CIRCULATION AND MOISTURE FLUX OVER THE ARCTIC

Mean characteristics and variability in the spatio-temporal distributi on of Arctic water vapour and vapour fluxes are examined using several different rawinsonde-derived databases. Precipitable water averaged o ver the polar cap, 70-90 degrees N, peaks in July at 14.0 mm. Large po leward fluxes near the prime meridian reflect transport associated wit h north Atlantic cyclones and, for most months, a local maximum in ava ilable water vapour. The mean vapour flux convergence averaged for the polar cap peaks in September. There is a mean annual excess of precip itation minus evaporation (P - E) of 163 mm, with a 78 mm range betwee n extreme years. High P - E is favoured by a meridional circulation ac companied by a more dominant North Atlantic cyclone track. No trend in annual P - E is apparent over the 1974-1991 period.