ATMOSPHERIC COMPONENTS OF THE ARCTIC OCEAN FRESHWATER BALANCE AND THEIR INTERANNUAL VARIABILITY

摘要

The atmospheric components of the hydrological cycle comprise the following: total precipitation (rainfall, snowfall and other hydrometeors deposited on the Earth's surface), evapo-sublimation, the horizontal advection of water vapour and of water in the liquid or solid phase. The information available on each of these variables is reviewed and assessed. For the Arctic Ocean, the conventional approach to moisture-balance assessment, using data on precipitation and evaporation, is severely constrained by the paucity of direct observations and their severe biases. There are even fewer direct evapo-sublimation measurements, and most rely on bulk aerodynamic formulations. The preferable alternative for the Arctic basin as a whole is to use indirect aerological computations of the net moisture balance. This approach can be supplemented by observations and model-derived data in order to obtain the spatial patterns of moisture balance variations. The data required to calculate atmospheric moisture flux divergence are acquired from atmospheric balloon soundings (rawinsonde ascents) of upper air winds and moisture content and from analyzed atmospheric fields. Calculations of the poleward flux of moisture from rawinsonde data indicate an annual flux convergence of 161 mm across 70°N with a 23-year range from 212 to 106 mm. The net (P-E) over the Arctic Ocean is about half of the calculated runoff into the Arctic and 20 percent of the total input. The potential variability in the atmospheric component, including its spatial characteristics, is assessed relative to that associated with the other components of the freshwater balance.