| The atmospheric hydrologic cycle of high northern latitudes is of significant importance in part because (1) coarse resolution global climate models have identified the region as being particularly sensitive to potential anthropogenic climate forcing and (2) even small changes in the freshwater budget of the Arctic Basin have the potential for profound consequences on global oceanic circulation, which is in turn closely linked to climate change. The current challenge is in data validation, identification of the processes responsible for producing the observed spatial distributions of the surface moisture flux, understanding how these mechanisms evolve on various time scales, and establishing the linkages with other hydrologic components. Using gridded atmospheric data supplemented by Arctic Ocean Buoy Program fields and in situ observations, a generalized depiction of the annual cycle of pressure fields over the Arctic is constructed. Along the periphery of northern Greenland and extending to the North Pole, a weak semiannual cycle is found in surface pressure with maxima in May and November. On interannual timescales, atmospheric mass over the central Arctic is exchanged with the storm track centers of action in the North Atlantic and North Pacific. In particular, the large decrease in central Arctic Basin sea level pressure during the late 1980s is due to a large transfer of atmospheric mass into the North Pacific. Estimates of convective available potential energy (CAPE) and the energy of convective inhibition have been made for available Arctic sounding data. On interannual time scales, computations suggest the atmosphere over the Siberian Arctic has become more stable in winter and less stable in summer. Using an array of precipitation data sets including historical estimates and remote-sensing-based methods, areal averaged estimates over major northern watersheds have been constructed. A mechanism of current interest over terrestrial land surfaces surrounding the Arctic Basin is known as precipitation recycling, defined as that fraction of moisture that precipitates on a specified region that had previously precipitated in situ. A new bulk diagnostic method is presented for estimating recycling that addresses fundamental concerns with the application of previous methods in the Arctic. |
