The variability of H2O fluxes in the Earth's atmosphere

Water is the only substance that occurs not only in all three phases, gaseous, fluid, and solid in the Earth's atmosphere but also in transitions between them like in its "polymer forms" - clusters, clathrates, aerosols. Although the importance of the solid and fluid forms is popularly understood, there is less general understanding of the role of water vapor and especially for its polymer forms than for example. of carbon dioxide (CO2) or ozone (O-3)- The spatial and temporal distributions of the various phases of water in the atmosphere are in fact very important factors to climate, weather, the biosphere, the homogeneous and inhomogeneous chemistry of the atmosphere, as well as to the propagation of electromagnetic waves used in transatmospheric (global) navigation and communication systems and for relevant remote sensing measurements. In this context the atmosphere acts like a temporal and spatial variable, frequency dependent filter. Despite the fact that above the tropopause, i.e. in the stratosphere and mesosphere, there is less than 0.1 % of the total water vapor content of the Earth's atmosphere its influence is very significant for the physics and chemistry of the upper atmosphere and hence for the climate. The question is discussed: How variable is the total hydrogen budget of the Earth's atmosphere with time? (C) 2000 Elsevier Science Ltd. All rights reserved.